/**
 * Class representation of ini-like file.
 * Authors:
 *  $(LINK2 https://github.com/FreeSlave, Roman Chistokhodov)
 * Copyright:
 *  Roman Chistokhodov, 2015-2017
 * License:
 *  $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
 * See_Also:
 *  $(LINK2 http://standards.freedesktop.org/desktop-entry-spec/latest/index.html, Desktop Entry Specification)
 */

module inilike.file;

private {
    import std.exception;
    import std.algorithm.iteration : map, filter;
    import std.algorithm.searching : canFind;
    import inilike.common;
}

public import inilike.range;
public import inilike.exception;
import inilike.read;

private @trusted string makeComment(string line) pure nothrow
{
    if (line.length && line[$-1] == '\n') {
        line = line[0..$-1];
    }
    if (!line.isComment && line.length) {
        line = '#' ~ line;
    }
    line = line.replace("\n", " ");
    return line;
}

private @trusted IniLikeLine makeCommentLine(string line) pure nothrow
{
    return IniLikeLine.fromComment(makeComment(line));
}

/**
 * Container used internally by $(D IniLikeFile) and $(D IniLikeGroup).
 * Technically this is a list with optional value access by key.
 */
struct ListMap(K,V, size_t chunkSize = 32)
{
    ///
    @disable this(this);

    /**
     * Insert key-value pair to the front of list.
     * Returns: Inserted node.
     */
    Node* insertFront(K key, V value) {
        Node* newNode = givePlace(key, value);
        putToFront(newNode);
        return newNode;
    }

    /**
     * Insert key-value pair to the back of list.
     * Returns: Inserted node.
     */
    Node* insertBack(K key, V value) {
        Node* newNode = givePlace(key, value);
        putToBack(newNode);
        return newNode;
    }

    /**
     * Insert key-value pair before some node in the list.
     * Returns: Inserted node.
     */
    Node* insertBefore(Node* node, K key, V value) {
        Node* newNode = givePlace(key, value);
        putBefore(node, newNode);
        return newNode;
    }

    /**
     * Insert key-value pair after some node in the list.
     * Returns: Inserted node.
     */
    Node* insertAfter(Node* node, K key, V value) {
        Node* newNode = givePlace(key, value);
        putAfter(node, newNode);
        return newNode;
    }

    /**
     * Add value at the start of list.
     * Returns: Inserted node.
     */
    Node* prepend(V value) {
        Node* newNode = givePlace(value);
        putToFront(newNode);
        return newNode;
    }

    /**
     * Add value at the end of list.
     * Returns: Inserted node.
     */
    Node* append(V value) {
        Node* newNode = givePlace(value);
        putToBack(newNode);
        return newNode;
    }

    /**
     * Add value before some node in the list.
     * Returns: Inserted node.
     */
    Node* addBefore(Node* node, V value) {
        Node* newNode = givePlace(value);
        putBefore(node, newNode);
        return newNode;
    }

    /**
     * Add value after some node in the list.
     * Returns: Inserted node.
     */
    Node* addAfter(Node* node, V value) {
        Node* newNode = givePlace(value);
        putAfter(node, newNode);
        return newNode;
    }

    /**
     * Move node to the front of list.
     */
    void moveToFront(Node* toMove)
    {
        if (_head is toMove) {
            return;
        }

        pullOut(toMove);
        putToFront(toMove);
    }

    /**
     * Move node to the back of list.
     */
    void moveToBack(Node* toMove)
    {
        if (_tail is toMove) {
            return;
        }

        pullOut(toMove);
        putToBack(toMove);
    }

    /**
     * Move node to the location before other node.
     */
    void moveBefore(Node* other, Node* toMove) {
        if (other is toMove) {
            return;
        }

        pullOut(toMove);
        putBefore(other, toMove);
    }

    /**
     * Move node to the location after other node.
     */
    void moveAfter(Node* other, Node* toMove) {
        if (other is toMove) {
            return;
        }

        pullOut(toMove);
        putAfter(other, toMove);
    }

    /**
     * Remove node from list. It also becomes unaccessible via key lookup.
     */
    void remove(Node* toRemove)
    {
        pullOut(toRemove);

        if (toRemove.hasKey()) {
            _dict.remove(toRemove.key);
        }

        if (_lastEmpty) {
            _lastEmpty.next = toRemove;
        }
        toRemove.prev = _lastEmpty;
        _lastEmpty = toRemove;
    }

    /**
     * Remove value by key.
     * Returns: true if node with such key was found and removed. False otherwise.
     */
    bool remove(K key) {
        Node** toRemove = key in _dict;
        if (toRemove) {
            remove(*toRemove);
            return true;
        }
        return false;
    }

    /**
     * Remove the first node.
     */
    void removeFront() {
        remove(_head);
    }

    /**
     * Remove the last node.
     */
    void removeBack() {
        remove(_tail);
    }

    /**
     * Get list node by key.
     * Returns: Found Node or null if container does not have node associated with key.
     */
    inout(Node)* getNode(K key) inout {
        auto toReturn = key in _dict;
        if (toReturn) {
            return *toReturn;
        }
        return null;
    }

    private static struct ByNode(NodeType)
    {
    private:
        NodeType* _begin;
        NodeType* _end;

    public:
        bool empty() const {
            return _begin is null || _end is null || _begin.prev is _end || _end.next is _begin;
        }

        auto front() {
            return _begin;
        }

        auto back() {
            return _end;
        }

        void popFront() {
            _begin = _begin.next;
        }

        void popBack() {
            _end = _end.prev;
        }

        @property auto save() {
            return this;
        }
    }

    /**
     * Iterate over list nodes.
     * See_Also: $(D byEntry)
     */
    auto byNode()
    {
        return ByNode!Node(_head, _tail);
    }

    ///ditto
    auto byNode() const
    {
        return ByNode!(const(Node))(_head, _tail);
    }

    /**
     * Iterate over nodes mapped to Entry elements (useful for testing).
     */
    auto byEntry() const {
        return byNode().map!(node => node.toEntry());
    }

    /**
     * Represenation of list node.
     */
    static struct Node {
    private:
        K _key;
        V _value;
        bool _hasKey;
        Node* _prev;
        Node* _next;

        @trusted this(K key, V value) pure nothrow {
            _key = key;
            _value = value;
            _hasKey = true;
        }

        @trusted this(V value) pure nothrow {
            _value = value;
            _hasKey = false;
        }

        @trusted void prev(Node* newPrev) pure nothrow {
            _prev = newPrev;
        }

        @trusted void next(Node* newNext) pure nothrow {
            _next = newNext;
        }

    public:
        /**
         * Get stored value.
         */
        @trusted inout(V) value() inout pure nothrow {
            return _value;
        }

        /**
         * Set stored value.
         */
        @trusted void value(V newValue) pure nothrow {
            _value = newValue;
        }

        /**
         * Tell whether this node is a key-value node.
         */
        @trusted bool hasKey() const pure nothrow {
            return _hasKey;
        }

        /**
         * Key in key-value node.
         */
        @trusted auto key() const pure nothrow {
            return _key;
        }

        /**
         * Access previous node in the list.
         */
        @trusted inout(Node)* prev() inout pure nothrow {
            return _prev;
        }

        /**
         * Access next node in the list.
         */
        @trusted inout(Node)* next() inout pure nothrow {
            return _next;
        }

        ///
        auto toEntry() const {
            static if (is(V == class)) {
                alias Rebindable!(const(V)) T;
                if (hasKey()) {
                    return Entry!T(_key, rebindable(_value));
                } else {
                    return Entry!T(rebindable(_value));
                }

            } else {
                alias V T;

                if (hasKey()) {
                    return Entry!T(_key, _value);
                } else {
                    return Entry!T(_value);
                }
            }
        }
    }

    /// Mapping of Node to structure.
    static struct Entry(T = V)
    {
    private:
        K _key;
        T _value;
        bool _hasKey;

    public:
        ///
        this(T value) {
            _value = value;
            _hasKey = false;
        }

        ///
        this(K key, T value) {
            _key = key;
            _value = value;
            _hasKey = true;
        }

        ///
        auto value() inout {
            return _value;
        }

        ///
        auto key() const {
            return _key;
        }

        ///
        bool hasKey() const {
            return _hasKey;
        }
    }

private:
    void putToFront(Node* toPut)
    in {
        assert(toPut !is null);
    }
    do {
        if (_head) {
            _head.prev = toPut;
            toPut.next = _head;
            _head = toPut;
        } else {
            _head = toPut;
            _tail = toPut;
        }
    }

    void putToBack(Node* toPut)
    in {
        assert(toPut !is null);
    }
    do {
        if (_tail) {
            _tail.next = toPut;
            toPut.prev = _tail;
            _tail = toPut;
        } else {
            _tail = toPut;
            _head = toPut;
        }
    }

    void putBefore(Node* node, Node* toPut)
    in {
        assert(toPut !is null);
        assert(node !is null);
    }
    do {
        toPut.prev = node.prev;
        if (toPut.prev) {
            toPut.prev.next = toPut;
        }
        toPut.next = node;
        node.prev = toPut;

        if (node is _head) {
            _head = toPut;
        }
    }

    void putAfter(Node* node, Node* toPut)
    in {
        assert(toPut !is null);
        assert(node !is null);
    }
    do {
        toPut.next = node.next;
        if (toPut.next) {
            toPut.next.prev = toPut;
        }
        toPut.prev = node;
        node.next = toPut;

        if (node is _tail) {
            _tail = toPut;
        }
    }

    void pullOut(Node* node)
    in {
        assert(node !is null);
    }
    do {
        if (node.next) {
            node.next.prev = node.prev;
        }
        if (node.prev) {
            node.prev.next = node.next;
        }

        if (node is _head) {
            _head = node.next;
        }
        if (node is _tail) {
            _tail = node.prev;
        }

        node.next = null;
        node.prev = null;
    }

    Node* givePlace(K key, V value) {
        auto newNode = Node(key, value);
        return givePlace(newNode);
    }

    Node* givePlace(V value) {
        auto newNode = Node(value);
        return givePlace(newNode);
    }

    Node* givePlace(ref Node node) {
        Node* toReturn;
        if (_lastEmpty is null) {
            if (_storageSize < _storage.length) {
                toReturn = &_storage[_storageSize];
            } else {
                size_t storageIndex = (_storageSize - chunkSize) / chunkSize;
                if (storageIndex >= _additonalStorages.length) {
                    _additonalStorages ~= (Node[chunkSize]).init;
                }

                size_t index = (_storageSize - chunkSize) % chunkSize;
                toReturn = &_additonalStorages[storageIndex][index];
            }

            _storageSize++;
        } else {
            toReturn = _lastEmpty;
            _lastEmpty = _lastEmpty.prev;
            if (_lastEmpty) {
                _lastEmpty.next = null;
            }
            toReturn.next = null;
            toReturn.prev = null;
        }

        toReturn._hasKey = node._hasKey;
        toReturn._key = node._key;
        toReturn._value = node._value;

        if (toReturn.hasKey()) {
            _dict[toReturn.key] = toReturn;
        }
        return toReturn;
    }

    Node[chunkSize] _storage;
    Node[chunkSize][] _additonalStorages;
    size_t _storageSize;

    Node* _tail;
    Node* _head;
    Node* _lastEmpty;
    Node*[K] _dict;
}

unittest
{
    import std.range : isBidirectionalRange;
    ListMap!(string, string) listMap;
    static assert(isBidirectionalRange!(typeof(listMap.byNode())));
}

unittest
{
    import std.algorithm : equal;
    import std.range : ElementType;

    alias ListMap!(string, string, 2) TestListMap;

    TestListMap listMap;
    alias typeof(listMap).Node Node;
    alias ElementType!(typeof(listMap.byEntry())) Entry;

    assert(listMap.byEntry().empty);
    assert(listMap.getNode("Nonexistent") is null);

    listMap.insertFront("Start", "Fast");
    assert(listMap.getNode("Start") !is null);
    assert(listMap.getNode("Start").key() == "Start");
    assert(listMap.getNode("Start").value() == "Fast");
    assert(listMap.getNode("Start").hasKey());
    assert(listMap.byEntry().equal([Entry("Start", "Fast")]));
    assert(listMap.remove("Start"));
    assert(listMap.byEntry().empty);
    assert(listMap.getNode("Start") is null);

    listMap.insertBack("Finish", "Bad");
    assert(listMap.byEntry().equal([Entry("Finish", "Bad")]));
    assert(listMap.getNode("Finish").value() == "Bad");

    listMap.insertFront("Begin", "Good");
    assert(listMap.byEntry().equal([Entry("Begin", "Good"), Entry("Finish", "Bad")]));
    assert(listMap.getNode("Begin").value() == "Good");

    listMap.insertFront("Start", "Slow");
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Finish", "Bad")]));

    listMap.insertAfter(listMap.getNode("Begin"), "Middle", "Person");
    assert(listMap.getNode("Middle").value() == "Person");
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Middle", "Person"), Entry("Finish", "Bad")]));

    listMap.insertBefore(listMap.getNode("Middle"), "Mean", "Man");
    assert(listMap.getNode("Mean").value() == "Man");
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Mean", "Man"), Entry("Middle", "Person"), Entry("Finish", "Bad")]));

    assert(listMap.remove("Mean"));
    assert(listMap.remove("Middle"));

    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Finish", "Bad")]));

    listMap.insertFront("New", "Era");
    assert(listMap.byEntry().equal([Entry("New", "Era"), Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Finish", "Bad")]));

    listMap.insertBack("Old", "Epoch");
    assert(listMap.byEntry().equal([Entry("New", "Era"), Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Finish", "Bad"), Entry("Old", "Epoch")]));

    listMap.moveToBack(listMap.getNode("New"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Finish", "Bad"), Entry("Old", "Epoch"), Entry("New", "Era")]));

    listMap.moveToFront(listMap.getNode("Begin"));
    assert(listMap.byEntry().equal([Entry("Begin", "Good"), Entry("Start", "Slow"), Entry("Finish", "Bad"), Entry("Old", "Epoch"), Entry("New", "Era")]));

    listMap.moveAfter(listMap.getNode("Finish"), listMap.getNode("Start"));
    assert(listMap.byEntry().equal([Entry("Begin", "Good"), Entry("Finish", "Bad"), Entry("Start", "Slow"), Entry("Old", "Epoch"), Entry("New", "Era")]));

    listMap.moveBefore(listMap.getNode("Finish"), listMap.getNode("Old"));
    assert(listMap.byEntry().equal([Entry("Begin", "Good"), Entry("Old", "Epoch"), Entry("Finish", "Bad"), Entry("Start", "Slow"), Entry("New", "Era")]));

    listMap.moveBefore(listMap.getNode("Begin"), listMap.getNode("Start"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Old", "Epoch"), Entry("Finish", "Bad"), Entry("New", "Era")]));

    listMap.moveAfter(listMap.getNode("New"), listMap.getNode("Finish"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Begin", "Good"), Entry("Old", "Epoch"), Entry("New", "Era"), Entry("Finish", "Bad")]));

    listMap.getNode("Begin").value = "Evil";
    assert(listMap.getNode("Begin").value() == "Evil");

    listMap.remove("Begin");
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Old", "Epoch"), Entry("New", "Era"), Entry("Finish", "Bad")]));
    listMap.remove("Old");
    listMap.remove("New");
    assert(!listMap.remove("Begin"));

    Node* shebang = listMap.prepend("Shebang");
    Node* endOfStory = listMap.append("End of story");

    assert(listMap.byEntry().equal([Entry("Shebang"), Entry("Start", "Slow"), Entry("Finish", "Bad"), Entry("End of story")]));

    Node* mid = listMap.addAfter(listMap.getNode("Start"), "Mid");
    Node* average = listMap.addBefore(listMap.getNode("Finish"), "Average");
    assert(listMap.byEntry().equal([Entry("Shebang"), Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad"), Entry("End of story")]));

    listMap.remove(shebang);
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad"), Entry("End of story")]));

    listMap.remove(endOfStory);
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad")]));

    listMap.moveToFront(listMap.getNode("Start"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad")]));
    listMap.moveToBack(listMap.getNode("Finish"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad")]));

    listMap.moveBefore(listMap.getNode("Start"), listMap.getNode("Start"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad")]));
    listMap.moveAfter(listMap.getNode("Finish"), listMap.getNode("Finish"));
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Average"), Entry("Finish", "Bad")]));

    listMap.insertAfter(mid, "Center", "Universe");
    listMap.insertBefore(average, "Focus", "Cosmos");
    assert(listMap.byEntry().equal([Entry("Start", "Slow"), Entry("Mid"), Entry("Center", "Universe"), Entry("Focus", "Cosmos"), Entry("Average"), Entry("Finish", "Bad")]));

    listMap.removeFront();
    assert(listMap.byEntry().equal([Entry("Mid"), Entry("Center", "Universe"), Entry("Focus", "Cosmos"), Entry("Average"), Entry("Finish", "Bad")]));
    listMap.removeBack();

    assert(listMap.byEntry().equal([Entry("Mid"), Entry("Center", "Universe"), Entry("Focus", "Cosmos"), Entry("Average")]));

    assert(listMap.byEntry().retro.equal([Entry("Average"), Entry("Focus", "Cosmos"), Entry("Center", "Universe"), Entry("Mid")]));

    auto byEntry = listMap.byEntry();
    Entry entry = byEntry.front;
    assert(entry.value == "Mid");
    assert(!entry.hasKey());

    byEntry.popFront();
    assert(byEntry.equal([Entry("Center", "Universe"), Entry("Focus", "Cosmos"), Entry("Average")]));
    byEntry.popBack();
    assert(byEntry.equal([Entry("Center", "Universe"), Entry("Focus", "Cosmos")]));

    entry = byEntry.back;
    assert(entry.key == "Focus");
    assert(entry.value == "Cosmos");
    assert(entry.hasKey());

    auto saved = byEntry.save;

    byEntry.popFront();
    assert(byEntry.equal([Entry("Focus", "Cosmos")]));
    byEntry.popBack();
    assert(byEntry.empty);

    assert(saved.equal([Entry("Center", "Universe"), Entry("Focus", "Cosmos")]));
    saved.popBack();
    assert(saved.equal([Entry("Center", "Universe")]));
    saved.popFront();
    assert(saved.empty);

    static void checkConst(ref const TestListMap listMap)
    {
        assert(listMap.byEntry().equal([Entry("Mid"), Entry("Center", "Universe"), Entry("Focus", "Cosmos"), Entry("Average")]));
    }
    checkConst(listMap);

    static class Class
    {
        this(string name) {
            _name = name;
        }

        string name() const {
            return _name;
        }
    private:
        string _name;
    }

    alias ListMap!(string, Class) TestClassListMap;
    TestClassListMap classListMap;
    classListMap.insertFront("name", new Class("Name"));
    classListMap.append(new Class("Value"));
    auto byClass = classListMap.byEntry();
    assert(byClass.front.value.name == "Name");
    assert(byClass.front.key == "name");
    assert(byClass.back.value.name == "Value");
}

/**
 * Line in group.
 */
struct IniLikeLine
{
    /**
     * Type of line.
     */
    enum Type
    {
        None = 0,   /// deleted or invalid line
        Comment = 1, /// a comment or empty line
        KeyValue = 2 /// key-value pair
    }

    /**
     * Contruct from comment.
     */
    @nogc @safe static IniLikeLine fromComment(string comment) nothrow pure {
        return IniLikeLine(comment, null, Type.Comment);
    }

    /**
     * Construct from key and value. Value must be provided as it's written in a file, i.e in the escaped form.
     */
    @nogc @safe static IniLikeLine fromKeyValue(string key, string value) nothrow pure {
        return IniLikeLine(key, value, Type.KeyValue);
    }

    /**
     * Get comment.
     * Returns: Comment or empty string if type is not Type.Comment.
     */
    @nogc @safe string comment() const nothrow pure {
        return _type == Type.Comment ? _first : null;
    }

    /**
     * Get key.
     * Returns: Key or empty string if type is not Type.KeyValue
     */
    @nogc @safe string key() const nothrow pure {
        return _type == Type.KeyValue ? _first : null;
    }

    /**
     * Get value.
     * Returns: Value in the escaped form or empty string if type is not Type.KeyValue
     */
    @nogc @safe string value() const nothrow pure {
        return _type == Type.KeyValue ? _second : null;
    }

    /**
     * Get type of line.
     */
    @nogc @safe Type type() const nothrow pure {
        return _type;
    }
private:
    string _first;
    string _second;
    Type _type = Type.None;
}


/**
 * This class represents the group (section) of key-value entries in the ini-like file.
 * Instances of this class can be created only in the context of $(D IniLikeFile) or its derivatives.
 * Values are stored in the escaped form, but the interface allows to set and get values in both escaped and unescaped forms.
 * Note: Keys are case-sensitive.
 */
class IniLikeGroup
{
private:
    alias ListMap!(string, IniLikeLine) LineListMap;

public:
    ///
    enum InvalidKeyPolicy : ubyte {
        ///Throw error on invalid key
        throwError,
        ///Skip invalid key
        skip,
        ///Save entry with invalid key.
        save
    }

    /**
     * Create $(D IniLikeGroup) instance with given name.
     */
    protected @nogc @safe this(string groupName) nothrow {
        _name = groupName;
    }

    private @safe final string setKeyValueImpl(string key, string value)
    in {
        assert(!value.needEscaping);
    }
    do {
        import std.stdio;
        auto node = _listMap.getNode(key);
        if (node) {
            node.value = IniLikeLine.fromKeyValue(key, value);
        } else {
            _listMap.insertBack(key, IniLikeLine.fromKeyValue(key, value));
        }
        return value;
    }

    /**
     * Check if the group contains a value associated with the key.
     */
    @nogc @safe final bool contains(string key) const nothrow pure {
        return _listMap.getNode(key) !is null;
    }

    /**
     * Get value by key in escaped form.
     * Returns: The escaped value associated with the key, or empty string if group does not contain such item.
     * See_Also: $(D setEscapedValue), $(D unescapedValue)
     */
    @nogc @safe final string escapedValue(string key) const nothrow pure {
        auto node = _listMap.getNode(key);
        if (node) {
            return node.value.value;
        } else {
            return null;
        }
    }

    /**
     * Perform locale matching lookup as described in $(LINK2 https://specifications.freedesktop.org/desktop-entry-spec/latest/ar01s05.html, Localized values for keys).
     * Params:
     *  key = Non-localized key.
     *  locale = Locale in intereset.
     *  nonLocaleFallback = Allow fallback to non-localized version.
     * Returns:
     *  The escaped localized value associated with key and locale,
     *  or the value associated with non-localized key if group does not contain localized value and nonLocaleFallback is true.
     * See_Also: $(D setEscapedValue), $(D unescapedValue)
     */
    @safe final string escapedValue(string key, string locale, Flag!"nonLocaleFallback" nonLocaleFallback = Yes.nonLocaleFallback) const nothrow pure {
        //Any ideas how to get rid of this boilerplate and make less allocations?
        const t = parseLocaleName(locale);
        auto lang = t.lang;
        auto country = t.country;
        auto modifier = t.modifier;

        if (lang.length) {
            string pick;
            if (country.length && modifier.length) {
                pick = escapedValue(localizedKey(key, locale));
                if (pick !is null) {
                    return pick;
                }
            }
            if (country.length) {
                pick = escapedValue(localizedKey(key, lang, country));
                if (pick !is null) {
                    return pick;
                }
            }
            if (modifier.length) {
                pick = escapedValue(localizedKey(key, lang, string.init, modifier));
                if (pick !is null) {
                    return pick;
                }
            }
            pick = escapedValue(localizedKey(key, lang, string.init));
            if (pick !is null) {
                return pick;
            }
        }

        if (nonLocaleFallback) {
            return escapedValue(key);
        } else {
            return null;
        }
    }

    ///
    unittest
    {
        auto lilf = new IniLikeFile;
        lilf.addGenericGroup("Entry");
        auto group = lilf.group("Entry");
        assert(group.groupName == "Entry");
        group.setEscapedValue("Name", "Programmer");
        group.setEscapedValue("Name[ru_RU]", "Разработчик");
        group.setEscapedValue("Name[ru@jargon]", "Кодер");
        group.setEscapedValue("Name[ru]", "Программист");
        group.setEscapedValue("Name[de_DE@dialect]", "Programmierer"); //just example
        group.setEscapedValue("Name[fr_FR]", "Programmeur");
        group.setEscapedValue("GenericName", "Program");
        group.setEscapedValue("GenericName[ru]", "Программа");
        assert(group.escapedValue("Name") == "Programmer");
        assert(group.escapedValue("Name", "ru@jargon") == "Кодер");
        assert(group.escapedValue("Name", "ru_RU@jargon") == "Разработчик");
        assert(group.escapedValue("Name", "ru") == "Программист");
        assert(group.escapedValue("Name", "ru_RU.UTF-8") == "Разработчик");
        assert(group.escapedValue("Name", "nonexistent locale") == "Programmer");
        assert(group.escapedValue("Name", "de_DE@dialect") == "Programmierer");
        assert(group.escapedValue("Name", "fr_FR.UTF-8") == "Programmeur");
        assert(group.escapedValue("GenericName", "ru_RU") == "Программа");
        assert(group.escapedValue("GenericName", "fr_FR") == "Program");
        assert(group.escapedValue("GenericName", "fr_FR", No.nonLocaleFallback) is null);
    }

    private @trusted final bool validateKeyValue(string key, string value, InvalidKeyPolicy invalidKeyPolicy)
    {
        validateValue(key, value);

        try {
            validateKey(key, value);
            return true;
        } catch(IniLikeEntryException e) {
            final switch(invalidKeyPolicy) {
                case InvalidKeyPolicy.throwError:
                    throw e;
                case InvalidKeyPolicy.save:
                    validateKeyImpl(key, value, _name);
                    return true;
                case InvalidKeyPolicy.skip:
                    validateKeyImpl(key, value, _name);
                    return false;
            }
        }
    }

    /**
     * Set value associated with key.
     * Params:
     *  key = Key to associate value with.
     *  value = Value to set. Must be in escaped form.
     *  invalidKeyPolicy = Policy about invalid keys.
     * Throws: $(D inilike.exception.IniLikeEntryException) if key or value is not valid or value needs to be escaped.
     * See_Also: $(D escapedValue), $(D setUnescapedValue)
     */
    @safe final string setEscapedValue(string key, string value, InvalidKeyPolicy invalidKeyPolicy = InvalidKeyPolicy.throwError)
    {
        if (validateKeyValue(key, value, invalidKeyPolicy)) {
            return setKeyValueImpl(key, value);
        }
        return null;
    }

    /**
     * Set value associated with key and locale.
     * Throws: $(D inilike.exception.IniLikeEntryException) if key or value is not valid or value needs to be escaped.
     * See_Also: $(D escapedValue), $(D setUnescapedValue)
     */
    @safe final string setEscapedValue(string key, string locale, string value, InvalidKeyPolicy invalidKeyPolicy = InvalidKeyPolicy.throwError) {
        return setEscapedValue(localizedKey(key, locale), value, invalidKeyPolicy);
    }

    /**
     * Get value by key.
     * Params:
     *  key = Key of value.
     *  locale = Optional locale to use in localized lookup if not empty.
     *  nonLocaleFallback = Allow fallback to non-localized version.
     * Returns: The unescaped value associated with key or null if not found.
     * See_Also: $(D escapedValue), $(D setUnescapedValue)
     */
    @safe final string unescapedValue(string key, string locale = null, Flag!"nonLocaleFallback" nonLocaleFallback = Yes.nonLocaleFallback) const nothrow pure {
        if (locale.length) {
            return escapedValue(key, locale, nonLocaleFallback).unescapeValue();
        } else {
            return escapedValue(key).unescapeValue();
        }
    }

    /**
     * Set value by key. The value is considered to be in the unescaped form.
     * Throws: $(D inilike.exception.IniLikeEntryException) if key or value is not valid.
     * See_Also: $(D unescapedValue), $(D setEscapedValue)
     */
    @safe final string setUnescapedValue(string key, string value, InvalidKeyPolicy invalidKeyPolicy = InvalidKeyPolicy.throwError) {
        value = value.escapeValue();
        return setEscapedValue(key, value, invalidKeyPolicy);
    }

    ///ditto, localized version
    @safe final string setUnescapedValue(string key, string locale, string value, InvalidKeyPolicy invalidKeyPolicy = InvalidKeyPolicy.throwError) {
        value = value.escapeValue();
        return setEscapedValue(key, locale, value, invalidKeyPolicy);
    }

    /**
     * Removes entry by key. Do nothing if no value associated with key found.
     * Returns: true if entry was removed, false otherwise.
     */
    @safe final bool removeEntry(string key) nothrow pure {
        return _listMap.remove(key);
    }

    ///ditto, but remove entry by localized key.
    @safe final bool removeEntry(string key, string locale) nothrow pure {
        return removeEntry(localizedKey(key, locale));
    }

    ///ditto, but remove entry by node.
    @safe final void removeEntry(LineNode node) nothrow pure {
        _listMap.remove(node.node);
    }

    private @nogc @safe static auto staticByKeyValue(Range)(Range nodes) nothrow {
        return nodes.map!(node => node.value).filter!(v => v.type == IniLikeLine.Type.KeyValue).map!(v => keyValueTuple(v.key, v.value));
    }

    /**
     * Iterate by Key-Value pairs. Values are left in escaped form.
     * Returns: Range of Tuple!(string, "key", string, "value").
     * See_Also: $(D escapedValue), $(D byIniLine)
     */
    @nogc @safe final auto byKeyValue() const nothrow {
        return staticByKeyValue(_listMap.byNode);
    }

    /**
     * Empty range of the same type as $(D byKeyValue). Can be used in derived classes if it's needed to have an empty range.
     * Returns: Empty range of Tuple!(string, "key", string, "value").
     */
    @nogc @safe static auto emptyByKeyValue() nothrow {
        const ListMap!(string, IniLikeLine) listMap;
        return staticByKeyValue(listMap.byNode);
    }

    ///
    unittest
    {
        assert(emptyByKeyValue().empty);
        auto group = new IniLikeGroup("Group name");
        static assert(is(typeof(emptyByKeyValue()) == typeof(group.byKeyValue()) ));
    }

    /**
     * Get name of this group.
     * Returns: The name of this group.
     */
    @nogc @safe final string groupName() const nothrow pure {
        return _name;
    }

    /**
     * Returns: Range of $(D IniLikeLine)s included in this group.
     * See_Also: $(D byNode), $(D byKeyValue)
     */
    @trusted final auto byIniLine() const {
        return _listMap.byNode.map!(node => node.value);
    }

    /**
     * Wrapper for internal ListMap node.
     */
    static struct LineNode
    {
    private:
        LineListMap.Node* node;
        string groupName;
    public:
        /**
         * Get key of node.
         */
        @nogc @trusted string key() const pure nothrow {
            if (node) {
                return node.key;
            } else {
                return null;
            }
        }

        /**
         * Get $(D IniLikeLine) pointed by node.
         */
        @nogc @trusted IniLikeLine line() const pure nothrow {
            if (node) {
                return node.value;
            } else {
                return IniLikeLine.init;
            }
        }

        /**
         * Set value for line. If underline line is comment, than newValue is set as comment.
         * Prerequisites: Node must be non-null.
         */
        @trusted void setEscapedValue(string newValue) pure {
            auto type = node.value.type;
            if (type == IniLikeLine.Type.KeyValue) {
                node.value = IniLikeLine.fromKeyValue(node.value.key, newValue);
            } else if (type == IniLikeLine.Type.Comment) {
                node.value = makeCommentLine(newValue);
            }
        }

        /**
         * Check if underlined node is null.
         */
        @nogc @safe bool isNull() const pure nothrow {
            return node is null;
        }
    }

    private @trusted auto lineNode(LineListMap.Node* node) pure nothrow {
        return LineNode(node, groupName());
    }

    /**
     * Iterate over nodes of internal list.
     * See_Also: $(D getNode), $(D byIniLine)
     */
    @trusted auto byNode() {
        return _listMap.byNode().map!(node => lineNode(node));
    }

    /**
     * Get internal list node for key.
     * See_Also: $(D byNode)
     */
    @trusted final auto getNode(string key) {
        return lineNode(_listMap.getNode(key));
    }

    /**
     * Add key-value entry without diret association of the value with the key. Can be used to add duplicates.
     */
    final auto appendValue(string key, string value, InvalidKeyPolicy invalidKeyPolicy = InvalidKeyPolicy.throwError) {
        if (validateKeyValue(key, value, invalidKeyPolicy)) {
            return lineNode(_listMap.append(IniLikeLine.fromKeyValue(key, value)));
        } else {
            return lineNode(null);
        }
    }

    /**
     * Add comment line into the group.
     * Returns: Added $(D LineNode).
     * See_Also: $(D byIniLine), $(D prependComment), $(D addCommentBefore), $(D addCommentAfter)
     */
    @safe final auto appendComment(string comment) nothrow pure {
        return lineNode(_listMap.append(makeCommentLine(comment)));
    }

    /**
     * Add comment line at the start of group (after group header, before any key-value pairs).
     * Returns: Added $(D LineNode).
     * See_Also: $(D byIniLine), $(D appendComment), $(D addCommentBefore), $(D addCommentAfter)
     */
    @safe final auto prependComment(string comment) nothrow pure {
        return lineNode(_listMap.prepend(makeCommentLine(comment)));
    }

    /**
     * Add comment before some node.
     * Returns: Added $(D LineNode).
     * See_Also: $(D byIniLine), $(D appendComment), $(D prependComment), $(D getNode), $(D addCommentAfter)
     */
    @trusted final auto addCommentBefore(LineNode node, string comment) nothrow pure
    in {
        assert(!node.isNull());
    }
    do {
        return _listMap.addBefore(node.node, makeCommentLine(comment));
    }

    /**
     * Add comment after some node.
     * Returns: Added $(D LineNode).
     * See_Also: $(D byIniLine), $(D appendComment), $(D prependComment), $(D getNode), $(D addCommentBefore)
     */
    @trusted final auto addCommentAfter(LineNode node, string comment) nothrow pure
    in {
        assert(!node.isNull());
    }
    do {
        return _listMap.addAfter(node.node, makeCommentLine(comment));
    }

    /**
     * Move line to the start of group.
     * Prerequisites: $(D toMove) is not null and belongs to this group.
     * See_Also: $(D getNode)
     */
    @trusted final void moveLineToFront(LineNode toMove) nothrow pure {
        _listMap.moveToFront(toMove.node);
    }

    /**
     * Move line to the end of group.
     * Prerequisites: $(D toMove) is not null and belongs to this group.
     * See_Also: $(D getNode)
     */
    @trusted final void moveLineToBack(LineNode toMove) nothrow pure {
        _listMap.moveToBack(toMove.node);
    }

    /**
     * Move line before other line in the group.
     * Prerequisites: $(D toMove) and $(D other) are not null and belong to this group.
     * See_Also: $(D getNode)
     */
    @trusted final void moveLineBefore(LineNode other, LineNode toMove) nothrow pure {
        _listMap.moveBefore(other.node, toMove.node);
    }

    /**
     * Move line after other line in the group.
     * Prerequisites: $(D toMove) and $(D other) are not null and belong to this group.
     * See_Also: $(D getNode)
     */
    @trusted final void moveLineAfter(LineNode other, LineNode toMove) nothrow pure {
        _listMap.moveAfter(other.node, toMove.node);
    }

private:
    @trusted static void validateKeyImpl(string key, string value, string groupName)
    {
        if (key.empty || key.strip.empty) {
            throw new IniLikeEntryException("key must not be empty", groupName, key, value);
        }
        if (key.isComment()) {
            throw new IniLikeEntryException("key must not start with #", groupName, key, value);
        }
        if (key.canFind('=')) {
            throw new IniLikeEntryException("key must not have '=' character in it", groupName, key, value);
        }
        if (key.needEscaping()) {
            throw new IniLikeEntryException("key must not contain new line characters", groupName, key, value);
        }
    }

protected:
    /**
     * Validate key before setting value to key for this group and throw exception if not valid.
     * Can be reimplemented in derived classes.
     *
     * Default implementation checks if key is not empty string, does not look like comment and does not contain new line or carriage return characters.
     * Params:
     *  key = key to validate.
     *  value = value that is being set to key.
     * Throws: $(D inilike.exception.IniLikeEntryException) if either key is invalid.
     * See_Also: $(D validateValue)
     * Note:
     *  Implementer should ensure that their implementation still validates key for format consistency (i.e. no new line characters, etc.).
     *  If not sure, just call super.validateKey(key, value) in your implementation.
     */
    @trusted void validateKey(string key, string value) const {
        validateKeyImpl(key, value, _name);
    }

    ///
    unittest
    {
        auto ilf = new IniLikeFile();
        ilf.addGenericGroup("Group");

        auto entryException = collectException!IniLikeEntryException(ilf.group("Group").setEscapedValue("", "Value1"));
        assert(entryException !is null);
        assert(entryException.groupName == "Group");
        assert(entryException.key == "");
        assert(entryException.value == "Value1");

        entryException = collectException!IniLikeEntryException(ilf.group("Group").setEscapedValue("    ", "Value2"));
        assert(entryException !is null);
        assert(entryException.key == "    ");
        assert(entryException.value == "Value2");

        entryException = collectException!IniLikeEntryException(ilf.group("Group").setEscapedValue("New\nLine", "Value3"));
        assert(entryException !is null);
        assert(entryException.key == "New\nLine");
        assert(entryException.value == "Value3");

        entryException = collectException!IniLikeEntryException(ilf.group("Group").setEscapedValue("# Comment", "Value4"));
        assert(entryException !is null);
        assert(entryException.key == "# Comment");
        assert(entryException.value == "Value4");

        entryException = collectException!IniLikeEntryException(ilf.group("Group").setEscapedValue("Everyone=Is", "Equal"));
        assert(entryException !is null);
        assert(entryException.key == "Everyone=Is");
        assert(entryException.value == "Equal");
    }

    /**
     * Validate value for key before setting value to key for this group and throw exception if not valid.
     * Can be reimplemented in derived classes.
     * The key is provided because you may want to implement specific checks depending on the key name.
     *
     * Default implementation checks if value is escaped. It does not check the key in any way.
     * Params:
     *  key = key the value is being set to.
     *  value = value to validate. Considered to be escaped.
     * Throws: $(D inilike.exception.IniLikeEntryException) if value is invalid.
     * See_Also: $(D validateKey)
     */
    @trusted void validateValue(string key, string value) const {
        if (value.needEscaping()) {
            throw new IniLikeEntryException("The value needs to be escaped", _name, key, value);
        }
    }

    ///
    unittest
    {
        auto ilf = new IniLikeFile();
        ilf.addGenericGroup("Group");

        auto entryException = collectException!IniLikeEntryException(ilf.group("Group").setEscapedValue("Key", "New\nline"));
        assert(entryException !is null);
        assert(entryException.key == "Key");
        assert(entryException.value == "New\nline");
    }
private:
    LineListMap _listMap;
    string _name;
}

/**
 * Ini-like file.
 */
class IniLikeFile
{
private:
    alias ListMap!(string, IniLikeGroup, 8) GroupListMap;
public:
    ///Behavior on duplicate key in the group.
    enum DuplicateKeyPolicy : ubyte
    {
        ///Throw error on entry with duplicate key.
        throwError,
        ///Skip duplicate without error.
        skip,
        ///Preserve all duplicates in the list. The first found value remains accessible by key.
        preserve
    }

    ///Behavior on group with duplicate name in the file.
    enum DuplicateGroupPolicy : ubyte
    {
        ///Throw error on group with duplicate name.
        throwError,
        ///Skip duplicate without error.
        skip,
        ///Preserve all duplicates in the list. The first found group remains accessible by key.
        preserve
    }

    ///Behavior of ini-like file reading.
    static struct ReadOptions
    {
        ///Behavior on groups with duplicate names.
        DuplicateGroupPolicy duplicateGroupPolicy = DuplicateGroupPolicy.throwError;
        ///Behavior on duplicate keys.
        DuplicateKeyPolicy duplicateKeyPolicy = DuplicateKeyPolicy.throwError;

        ///Behavior on invalid keys.
        IniLikeGroup.InvalidKeyPolicy invalidKeyPolicy = IniLikeGroup.InvalidKeyPolicy.throwError;

        ///Whether to preserve comments on reading.
        Flag!"preserveComments" preserveComments = Yes.preserveComments;

        ///Setting parameters in any order, leaving not mentioned ones in default state.
        @nogc @safe this(Args...)(Args args) nothrow pure {
            foreach(arg; args) {
                assign(arg);
            }
        }

        ///
        unittest
        {
            ReadOptions readOptions;

            readOptions = ReadOptions(No.preserveComments);
            assert(readOptions.duplicateGroupPolicy == DuplicateGroupPolicy.throwError);
            assert(readOptions.duplicateKeyPolicy == DuplicateKeyPolicy.throwError);
            assert(!readOptions.preserveComments);

            readOptions = ReadOptions(DuplicateGroupPolicy.skip, DuplicateKeyPolicy.preserve);
            assert(readOptions.duplicateGroupPolicy == DuplicateGroupPolicy.skip);
            assert(readOptions.duplicateKeyPolicy == DuplicateKeyPolicy.preserve);
            assert(readOptions.preserveComments);

            const duplicateGroupPolicy = DuplicateGroupPolicy.preserve;
            immutable duplicateKeyPolicy = DuplicateKeyPolicy.skip;
            const preserveComments = No.preserveComments;
            readOptions = ReadOptions(duplicateGroupPolicy, IniLikeGroup.InvalidKeyPolicy.skip, preserveComments, duplicateKeyPolicy);
            assert(readOptions.duplicateGroupPolicy == DuplicateGroupPolicy.preserve);
            assert(readOptions.duplicateKeyPolicy == DuplicateKeyPolicy.skip);
            assert(readOptions.invalidKeyPolicy == IniLikeGroup.InvalidKeyPolicy.skip);
        }

        /**
         * Assign arg to the struct member of corresponding type.
         * Note:
         *  It's compile-time error to assign parameter of type which is not part of ReadOptions.
         */
        @nogc @safe void assign(T)(T arg) nothrow pure {
            alias Unqual!(T) ArgType;
            static if (is(ArgType == DuplicateKeyPolicy)) {
                duplicateKeyPolicy = arg;
            } else static if (is(ArgType == DuplicateGroupPolicy)) {
                duplicateGroupPolicy = arg;
            } else static if (is(ArgType == Flag!"preserveComments")) {
                preserveComments = arg;
            } else static if (is(ArgType == IniLikeGroup.InvalidKeyPolicy)) {
                invalidKeyPolicy = arg;
            } else {
                static assert(false, "Unknown argument type " ~ typeof(arg).stringof);
            }
        }
    }

    ///
    unittest
    {
        string contents = `# The first comment
[First Entry]
# Comment
GenericName=File manager
GenericName[ru]=Файловый менеджер
# Another comment
[Another Group]
Name=Commander
# The last comment`;

        alias IniLikeFile.ReadOptions ReadOptions;
        alias IniLikeFile.DuplicateKeyPolicy DuplicateKeyPolicy;
        alias IniLikeFile.DuplicateGroupPolicy DuplicateGroupPolicy;

        IniLikeFile ilf = new IniLikeFile(iniLikeStringReader(contents), null, ReadOptions(No.preserveComments));
        assert(!ilf.readOptions().preserveComments);
        assert(ilf.leadingComments().empty);
        assert(equal(
            ilf.group("First Entry").byIniLine(),
            [IniLikeLine.fromKeyValue("GenericName", "File manager"), IniLikeLine.fromKeyValue("GenericName[ru]", "Файловый менеджер")]
        ));
        assert(equal(
            ilf.group("Another Group").byIniLine(),
            [IniLikeLine.fromKeyValue("Name", "Commander")]
        ));

        contents = `[Group]
Duplicate=First
Key=Value
Duplicate=Second`;

        ilf = new IniLikeFile(iniLikeStringReader(contents), null, ReadOptions(DuplicateKeyPolicy.skip));
        assert(equal(
            ilf.group("Group").byIniLine(),
            [IniLikeLine.fromKeyValue("Duplicate", "First"), IniLikeLine.fromKeyValue("Key", "Value")]
        ));

        ilf = new IniLikeFile(iniLikeStringReader(contents), null, ReadOptions(DuplicateKeyPolicy.preserve));
        assert(equal(
            ilf.group("Group").byIniLine(),
            [IniLikeLine.fromKeyValue("Duplicate", "First"), IniLikeLine.fromKeyValue("Key", "Value"), IniLikeLine.fromKeyValue("Duplicate", "Second")]
        ));
        assert(ilf.group("Group").escapedValue("Duplicate") == "First");

        contents = `[Duplicate]
Key=First
[Group]
[Duplicate]
Key=Second`;

        ilf = new IniLikeFile(iniLikeStringReader(contents), null, ReadOptions(DuplicateGroupPolicy.preserve));
        auto byGroup = ilf.byGroup();
        assert(byGroup.front.escapedValue("Key") == "First");
        assert(byGroup.back.escapedValue("Key") == "Second");

        auto byNode = ilf.byNode();
        assert(byNode.front.group.groupName == "Duplicate");
        assert(byNode.front.key == "Duplicate");
        assert(byNode.back.key is null);

        contents = `[Duplicate]
Key=First
[Group]
[Duplicate]
Key=Second`;

        ilf = new IniLikeFile(iniLikeStringReader(contents), null, ReadOptions(DuplicateGroupPolicy.skip));
        auto byGroup2 = ilf.byGroup();
        assert(byGroup2.front.escapedValue("Key") == "First");
        assert(byGroup2.back.groupName == "Group");
    }

    /**
     * Behavior of ini-like file saving.
     * See_Also: $(D save)
     */
    static struct WriteOptions
    {
        ///Whether to preserve comments (lines that starts with '#') on saving.
        Flag!"preserveComments" preserveComments = Yes.preserveComments;
        ///Whether to preserve empty lines on saving.
        Flag!"preserveEmptyLines" preserveEmptyLines = Yes.preserveEmptyLines;
        /**
         * Whether to write empty line after each group except for the last.
         * New line is not written when it already exists before the next group.
         */
        Flag!"lineBetweenGroups" lineBetweenGroups = No.lineBetweenGroups;

        /**
         * Pretty mode. Save comments, skip existing new lines, add line before the next group.
         */
        @nogc @safe static auto pretty() nothrow pure {
            return WriteOptions(Yes.preserveComments, No.preserveEmptyLines, Yes.lineBetweenGroups);
        }

        /**
         * Exact mode. Save all comments and empty lines as is.
         */
        @nogc @safe static auto exact() nothrow pure {
            return WriteOptions(Yes.preserveComments, Yes.preserveEmptyLines, No.lineBetweenGroups);
        }

        @nogc @safe this(Args...)(Args args) nothrow pure {
            foreach(arg; args) {
                assign(arg);
            }
        }

        /**
         * Assign arg to the struct member of corresponding type.
         * Note:
         *  It's compile-time error to assign parameter of type which is not part of $(D WriteOptions).
         */
        @nogc @safe void assign(T)(T arg) nothrow pure {
            alias Unqual!(T) ArgType;
            static if (is(ArgType == Flag!"preserveEmptyLines")) {
                preserveEmptyLines = arg;
            } else static if (is(ArgType == Flag!"lineBetweenGroups")) {
                lineBetweenGroups = arg;
            } else static if (is(ArgType == Flag!"preserveComments")) {
                preserveComments = arg;
            } else {
                static assert(false, "Unknown argument type " ~ typeof(arg).stringof);
            }
        }
    }

    /**
     * Wrapper for internal $(D ListMap) node.
     */
    static struct GroupNode
    {
    private:
        GroupListMap.Node* node;
    public:
        /**
         * Key the group associated with.
         * While every group has groupName, it might be added to the group list without association, therefore will not have key.
         */
        @nogc @trusted string key() const pure nothrow {
            if (node) {
                return node.key();
            } else {
                return null;
            }
        }

        /**
         * Access underlined group.
         */
        @nogc @trusted IniLikeGroup group() pure nothrow {
            if (node) {
                return node.value();
            } else {
                return null;
            }
        }

        /**
         * Check if underlined node is null.
         */
        @nogc @safe bool isNull() pure nothrow const {
            return node is null;
        }
    }

protected:
    /**
     * Insert group into $(D IniLikeFile) object and use its name as key.
     * Prerequisites: group must be non-null. It also should not be held by some other $(D IniLikeFile) object.
     */
    @trusted final auto insertGroup(IniLikeGroup group)
    in {
        assert(group !is null);
    }
    do {
        return GroupNode(_listMap.insertBack(group.groupName, group));
    }

    /**
     * Append group to group list without associating group name with it. Can be used to add groups with duplicated names.
     * Prerequisites: group must be non-null. It also should not be held by some other $(D IniLikeFile) object.
     */
    @trusted final auto putGroup(IniLikeGroup group)
    in {
        assert(group !is null);
    }
    do {
        return GroupNode(_listMap.append(group));
    }

    /**
     * Add comment before groups.
     * This function is called only in constructor and can be reimplemented in derived classes.
     * Params:
     *  comment = Comment line to add.
     */
    @trusted void onLeadingComment(string comment) {
        if (_readOptions.preserveComments) {
            appendLeadingComment(comment);
        }
    }

    /**
     * Add comment for group.
     * This function is called only in constructor and can be reimplemented in derived classes.
     * Params:
     *  comment = Comment line to add.
     *  currentGroup = The group returned recently by createGroup during parsing. Can be null (e.g. if discarded)
     *  groupName = The name of the currently parsed group. Set even if currentGroup is null.
     * See_Also: $(D createGroup), $(D IniLikeGroup.appendComment)
     */
    @trusted void onCommentInGroup(string comment, IniLikeGroup currentGroup, string groupName)
    {
        if (currentGroup && _readOptions.preserveComments) {
            currentGroup.appendComment(comment);
        }
    }

    /**
     * Add key/value pair for group.
     * This function is called only in constructor and can be reimplemented in derived classes.
     * Params:
     *  key = Key to insert or set.
     *  value = Value to set for key.
     *  currentGroup = The group returned recently by createGroup during parsing. Can be null (e.g. if discarded)
     *  groupName = The name of the currently parsed group. Set even if currentGroup is null.
     * See_Also: $(D createGroup)
     */
    @trusted void onKeyValue(string key, string value, IniLikeGroup currentGroup, string groupName)
    {
        if (currentGroup) {
            if (currentGroup.contains(key)) {
                final switch(_readOptions.duplicateKeyPolicy) {
                    case DuplicateKeyPolicy.throwError:
                        throw new IniLikeEntryException("key already exists", groupName, key, value);
                    case DuplicateKeyPolicy.skip:
                        break;
                    case DuplicateKeyPolicy.preserve:
                        currentGroup.appendValue(key, value, _readOptions.invalidKeyPolicy);
                        break;
                }
            } else {
                currentGroup.setEscapedValue(key, value, _readOptions.invalidKeyPolicy);
            }
        }
    }

    /**
     * Create $(D IniLikeGroup) by groupName during file parsing.
     *
     * This function can be reimplemented in derived classes, e.g. to insert additional checks.
     * Returned value is later passed to $(D onCommentInGroup) and $(D onKeyValue) methods as currentGroup.
     * Reimplemented method also is allowed to return null.
     * Default implementation just creates and returns empty $(D IniLikeGroup) with name set to groupName.
     *  If group already exists and $(D DuplicateGroupPolicy) is skip, then null is returned.
     * Throws:
     *  $(D inilike.exception.IniLikeGroupException) if group with such name already exists.
     *  $(D inilike.exception.IniLikeException) if groupName is empty.
     * See_Also:
     *  $(D onKeyValue), $(D onCommentInGroup)
     */
    @trusted IniLikeGroup onGroup(string groupName) {
        if (group(groupName) !is null) {
            final switch(_readOptions.duplicateGroupPolicy) {
                case DuplicateGroupPolicy.throwError:
                    throw new IniLikeGroupException("group with such name already exists", groupName);
                case DuplicateGroupPolicy.skip:
                    return null;
                case DuplicateGroupPolicy.preserve:
                    auto toPut = createGroupByName(groupName);
                    if (toPut) {
                        putGroup(toPut);
                    }
                    return toPut;
            }
        } else {
            auto toInsert = createGroupByName(groupName);
            if (toInsert) {
                insertGroup(toInsert);
            }
            return toInsert;
        }
    }

    /**
     * Reimplement in derive class.
     */
    @trusted IniLikeGroup createGroupByName(string groupName) {
        return createEmptyGroup(groupName);
    }

    /**
     * Can be used in derived classes to create instance of IniLikeGroup.
     * Throws: $(D inilike.exception.IniLikeException) if groupName is empty.
     */
    @safe static createEmptyGroup(string groupName) {
        if (groupName.length == 0) {
            throw new IniLikeException("empty group name");
        }
        return new IniLikeGroup(groupName);
    }
public:
    /**
     * Construct empty $(D IniLikeFile), i.e. without any groups or values
     */
    @nogc @safe this() nothrow {

    }

    /**
     * Read from file.
     * Throws:
     *  $(B ErrnoException) if file could not be opened.
     *  $(D inilike.exception.IniLikeReadException) if error occured while reading the file.
     */
    @trusted this(string fileName, ReadOptions readOptions = ReadOptions.init) {
        this(iniLikeFileReader(fileName), fileName, readOptions);
    }

    /**
     * Read from range of $(D inilike.range.IniLikeReader).
     * Note: All exceptions thrown within constructor are turning into $(D IniLikeReadException).
     * Throws:
     *  $(D inilike.exception.IniLikeReadException) if error occured while parsing.
     */
    this(IniLikeReader)(IniLikeReader reader, string fileName = null, ReadOptions readOptions = ReadOptions.init)
    {
        _readOptions = readOptions;
        IniLikeGroup currentGroup;

        auto onMyLeadingComment = delegate void(string line) {
            onLeadingComment(line);
        };
        auto onMyGroup = delegate ActionOnGroup(string groupName) {
            currentGroup = onGroup(groupName);
            return ActionOnGroup.proceed;
        };
        auto onMyKeyValue = delegate void(string key, string value, string groupName) {
            onKeyValue(key, value, currentGroup, groupName);
        };
        auto onMyCommentInGroup = delegate void(string line, string groupName) {
            onCommentInGroup(line, currentGroup, groupName);
        };

        readIniLike(reader, onMyLeadingComment, onMyGroup, onMyKeyValue, onMyCommentInGroup, fileName);
        _fileName = fileName;
    }

    /**
     * Get group by name.
     * Returns: $(D IniLikeGroup) instance associated with groupName or null if not found.
     * See_Also: $(D byGroup)
     */
    @nogc @safe final inout(IniLikeGroup) group(string groupName) nothrow inout pure {
        auto pick = _listMap.getNode(groupName);
        if (pick) {
            return pick.value;
        }
        return null;
    }

    /**
     * Get $(D GroupNode) by groupName.
     */
    @nogc @safe final auto getNode(string groupName) nothrow pure {
        return GroupNode(_listMap.getNode(groupName));
    }

    /**
     * Create new group using groupName.
     * Returns: Newly created instance of $(D IniLikeGroup).
     * Throws:
     *  $(D inilike.exception.IniLikeGroupException) if group with such name already exists.
     *  $(D inilike.exception.IniLikeException) if groupName is empty.
     * See_Also: $(D removeGroup), $(D group)
     */
    @safe final IniLikeGroup addGenericGroup(string groupName) {
        if (group(groupName) !is null) {
            throw new IniLikeGroupException("group already exists", groupName);
        }
        auto toReturn = createEmptyGroup(groupName);
        insertGroup(toReturn);
        return toReturn;
    }

    /**
     * Remove group by name. Do nothing if group with such name does not exist.
     * Returns: true if group was deleted, false otherwise.
     * See_Also: $(D addGenericGroup), $(D group)
     */
    @safe bool removeGroup(string groupName) nothrow {
        return _listMap.remove(groupName);
    }

    /**
     * Range of groups in order how they were defined in file.
     * See_Also: $(D group)
     */
    @nogc @safe final auto byGroup() inout nothrow {
        return _listMap.byNode().map!(node => node.value);
    }

    /**
     * Iterate over $(D GroupNode)s.
     */
    @nogc @safe final auto byNode() nothrow {
        return _listMap.byNode().map!(node => GroupNode(node));
    }

    /**
     * Save object to the file using .ini-like format.
     * Throws: $(D ErrnoException) if the file could not be opened or an error writing to the file occured.
     * See_Also: $(D saveToString), $(D save)
     */
    @trusted final void saveToFile(string fileName, const WriteOptions options = WriteOptions.exact) const {
        import std.stdio : File;

        auto f = File(fileName, "w");
        void dg(in string line) {
            f.writeln(line);
        }
        save(&dg, options);
    }

    /**
     * Save object to string using .ini like format.
     * Returns: A string that represents the contents of file.
     * Note: The resulting string differs from the contents that would be written to file via $(D saveToFile)
     * in the way it does not add new line character at the end of the last line.
     * See_Also: $(D saveToFile), $(D save)
     */
    @trusted final string saveToString(const WriteOptions options = WriteOptions.exact) const {
        auto a = appender!(string[])();
        save(a, options);
        return a.data.join("\n");
    }

    ///
    unittest
    {
        string contents =
`
# Leading comment
[First group]
# Comment inside
Key=Value
[Second group]

Key=Value

[Third group]
Key=Value`;

        auto ilf = new IniLikeFile(iniLikeStringReader(contents));
        assert(ilf.saveToString(WriteOptions.exact) == contents);

        assert(ilf.saveToString(WriteOptions.pretty) ==
`# Leading comment
[First group]
# Comment inside
Key=Value

[Second group]
Key=Value

[Third group]
Key=Value`);

        assert(ilf.saveToString(WriteOptions(No.preserveComments, No.preserveEmptyLines)) ==
`[First group]
Key=Value
[Second group]
Key=Value
[Third group]
Key=Value`);

        assert(ilf.saveToString(WriteOptions(No.preserveComments, No.preserveEmptyLines, Yes.lineBetweenGroups)) ==
`[First group]
Key=Value

[Second group]
Key=Value

[Third group]
Key=Value`);
    }

    /**
     * Use Output range or delegate to retrieve strings line by line.
     * Those strings can be written to the file or be showed in text area.
     * Note: Output strings don't have trailing newline character.
     * See_Also: $(D saveToFile), $(D saveToString)
     */
    final void save(OutRange)(OutRange sink, const WriteOptions options = WriteOptions.exact) const if (isOutputRange!(OutRange, string)) {
        foreach(line; leadingComments()) {
            if (options.preserveComments) {
                if (line.empty && !options.preserveEmptyLines) {
                    continue;
                }
                put(sink, line);
            }
        }
        bool firstGroup = true;
        bool lastWasEmpty = false;

        foreach(group; byGroup()) {
            if (!firstGroup && !lastWasEmpty && options.lineBetweenGroups) {
                put(sink, "");
            }

            put(sink, "[" ~ group.groupName ~ "]");
            foreach(line; group.byIniLine()) {
                lastWasEmpty = false;
                if (line.type == IniLikeLine.Type.Comment) {
                    if (!options.preserveComments) {
                        continue;
                    }
                    if (line.comment.empty) {
                        if (!options.preserveEmptyLines) {
                            continue;
                        }
                        lastWasEmpty = true;
                    }
                    put(sink, line.comment);
                } else if (line.type == IniLikeLine.Type.KeyValue) {
                    put(sink, line.key ~ "=" ~ line.value);
                }
            }
            firstGroup = false;
        }
    }

    /**
     * File path where the object was loaded from.
     * Returns: File name as was specified on the object creation.
     */
    @nogc @safe final string fileName() nothrow const pure {
        return _fileName;
    }

    /**
     * Leading comments.
     * Returns: Range of leading comments (before any group)
     * See_Also: $(D appendLeadingComment), $(D prependLeadingComment), $(D clearLeadingComments)
     */
    @nogc @safe final auto leadingComments() const nothrow pure {
        return _leadingComments;
    }

    ///
    unittest
    {
        auto ilf = new IniLikeFile();
        assert(ilf.appendLeadingComment("First") == "#First");
        assert(ilf.appendLeadingComment("#Second") == "#Second");
        assert(ilf.appendLeadingComment("Sneaky\nKey=Value") == "#Sneaky Key=Value");
        assert(ilf.appendLeadingComment("# New Line\n") == "# New Line");
        assert(ilf.appendLeadingComment("") == "");
        assert(ilf.appendLeadingComment("\n") == "");
        assert(ilf.prependLeadingComment("Shebang") == "#Shebang");
        assert(ilf.leadingComments().equal(["#Shebang", "#First", "#Second", "#Sneaky Key=Value", "# New Line", "", ""]));
        ilf.clearLeadingComments();
        assert(ilf.leadingComments().empty);
    }

    /**
     * Add leading comment. This will be appended to the list of leadingComments.
     * Note: # will be prepended automatically if line is not empty and does not have # at the start.
     *  The last new line character will be removed if present. Others will be replaced with whitespaces.
     * Returns: Line that was added as comment.
     * See_Also: $(D leadingComments), $(D prependLeadingComment)
     */
    @safe final string appendLeadingComment(string line) nothrow pure {
        line = makeComment(line);
        _leadingComments ~= line;
        return line;
    }

    /**
     * Prepend leading comment (e.g. for setting shebang line).
     * Returns: Line that was added as comment.
     * See_Also: $(D leadingComments), $(D appendLeadingComment)
     */
    @safe final string prependLeadingComment(string line) nothrow pure {
        line = makeComment(line);
        _leadingComments = line ~ _leadingComments;
        return line;
    }

    /**
     * Remove all coments met before groups.
     * See_Also: $(D leadingComments)
     */
    @nogc final @safe void clearLeadingComments() nothrow {
        _leadingComments = null;
    }

    /**
     * Move the group to make it the first.
     */
    @trusted final void moveGroupToFront(GroupNode toMove) nothrow pure {
        _listMap.moveToFront(toMove.node);
    }

    /**
     * Move the group to make it the last.
     */
    @trusted final void moveGroupToBack(GroupNode toMove) nothrow pure {
        _listMap.moveToBack(toMove.node);
    }

    /**
     * Move group before other.
     */
    @trusted final void moveGroupBefore(GroupNode other, GroupNode toMove) nothrow pure {
        _listMap.moveBefore(other.node, toMove.node);
    }

    /**
     * Move group after other.
     */
    @trusted final void moveGroupAfter(GroupNode other, GroupNode toMove) nothrow pure {
        _listMap.moveAfter(other.node, toMove.node);
    }

    @safe final ReadOptions readOptions() nothrow const pure {
        return _readOptions;
    }

    /**
     * Shortcut to $(D IniLikeGroup.escapedValue) of given group.
     * Returns null if the group does not exist.
     */
    @nogc @safe final string escapedValue(string groupName, string key)
    {
        auto g = group(groupName);
        if (g) {
            return g.escapedValue(key);
        } else {
            return null;
        }
    }

    /// ditto, localized version
    @safe final string escapedValue(string groupName, string key, string locale, Flag!"nonLocaleFallback" nonLocaleFallback = Yes.nonLocaleFallback)
    {
        auto g = group(groupName);
        if (g) {
            return g.escapedValue(key, locale, nonLocaleFallback);
        } else {
            return null;
        }
    }

    /**
     * Shortcut to $(D IniLikeGroup.unescapedValue) of given group.
     * Returns null if the group does not exist.
     */
    @safe final string unescapedValue(string groupName, string key, string locale = null, Flag!"nonLocaleFallback" nonLocaleFallback = Yes.nonLocaleFallback)
    {
        auto g = group(groupName);
        if (g) {
            return g.unescapedValue(key, locale, nonLocaleFallback);
        } else {
            return null;
        }
    }

private:
    string _fileName;
    GroupListMap _listMap;
    string[] _leadingComments;
    ReadOptions _readOptions;
}

///
unittest
{
    import std.file;
    import std.path;
    import std.stdio;

    string contents =
`# The first comment
[First Entry]
# Comment
GenericName=File manager
GenericName[ru]=Файловый менеджер
NeedUnescape=yes\\i\tneed
NeedUnescape[ru]=да\\я\tнуждаюсь
# Another comment
[Another Group]
Name=Commander
Comment=Manage files
# The last comment`;

    auto ilf = new IniLikeFile(iniLikeStringReader(contents), "contents.ini");
    assert(ilf.fileName() == "contents.ini");
    assert(equal(ilf.leadingComments(), ["# The first comment"]));
    assert(ilf.group("First Entry"));
    assert(ilf.group("Another Group"));
    assert(ilf.getNode("Another Group").group is ilf.group("Another Group"));
    assert(ilf.group("NonExistent") is null);
    assert(ilf.getNode("NonExistent").isNull());
    assert(ilf.getNode("NonExistent").key() is null);
    assert(ilf.getNode("NonExistent").group() is null);
    assert(ilf.saveToString(IniLikeFile.WriteOptions.exact) == contents);

    version(inilikeFileTest)
    {
        string tempFile = buildPath(tempDir(), "inilike-unittest-tempfile");
        try {
            assertNotThrown!IniLikeReadException(ilf.saveToFile(tempFile));
            auto fileContents = cast(string)std.file.read(tempFile);
            assert(equal(fileContents.lineSplitter, contents.lineSplitter), "Contents should be preserved as is");

            IniLikeFile filf;
            assertNotThrown!IniLikeReadException(filf = new IniLikeFile(tempFile));
            assert(filf.fileName() == tempFile);
            remove(tempFile);
        } catch(Exception e) {
            //environmental error in unittests
        }
    }

    assert(ilf.escapedValue("NonExistent", "Key") is null);
    assert(ilf.escapedValue("NonExistent", "Key", "ru") is null);
    assert(ilf.unescapedValue("NonExistent", "Key") is null);

    auto firstEntry = ilf.group("First Entry");

    assert(!firstEntry.contains("NonExistent"));
    assert(firstEntry.contains("GenericName"));
    assert(firstEntry.contains("GenericName[ru]"));
    assert(firstEntry.byNode().filter!(node => node.isNull()).empty);
    assert(firstEntry.escapedValue("GenericName") == "File manager");
    assert(firstEntry.getNode("GenericName").key == "GenericName");
    assert(firstEntry.getNode("NonExistent").key is null);
    assert(firstEntry.getNode("NonExistent").line.type == IniLikeLine.Type.None);

    assert(firstEntry.escapedValue("NeedUnescape") == `yes\\i\tneed`);
    assert(ilf.escapedValue("First Entry", "NeedUnescape") == `yes\\i\tneed`);

    assert(firstEntry.unescapedValue("NeedUnescape") == "yes\\i\tneed");
    assert(ilf.unescapedValue("First Entry", "NeedUnescape") == "yes\\i\tneed");

    assert(firstEntry.escapedValue("NeedUnescape", "ru") == `да\\я\tнуждаюсь`);
    assert(ilf.escapedValue("First Entry", "NeedUnescape", "ru") == `да\\я\tнуждаюсь`);

    assert(firstEntry.unescapedValue("NeedUnescape", "ru") == "да\\я\tнуждаюсь");
    assert(ilf.unescapedValue("First Entry", "NeedUnescape", "ru") == "да\\я\tнуждаюсь");

    firstEntry.setUnescapedValue("NeedEscape", "i\rneed\nescape");
    assert(firstEntry.escapedValue("NeedEscape") == `i\rneed\nescape`);
    firstEntry.setUnescapedValue("NeedEscape", "ru", "мне\rнужно\nэкранирование");
    assert(firstEntry.escapedValue("NeedEscape", "ru") == `мне\rнужно\nэкранирование`);

    firstEntry.setEscapedValue("GenericName", "Manager of files");
    assert(firstEntry.escapedValue("GenericName") == "Manager of files");
    firstEntry.setEscapedValue("Authors", "Unknown");
    assert(firstEntry.escapedValue("Authors") == "Unknown");
    firstEntry.getNode("Authors").setEscapedValue("Known");
    assert(firstEntry.escapedValue("Authors") == "Known");

    assert(firstEntry.escapedValue("GenericName", "ru") == "Файловый менеджер");
    firstEntry.setEscapedValue("GenericName", "ru", "Менеджер файлов");
    assert(firstEntry.escapedValue("GenericName", "ru") == "Менеджер файлов");
    firstEntry.setEscapedValue("Authors", "ru", "Неизвестны");
    assert(firstEntry.escapedValue("Authors", "ru") == "Неизвестны");

    firstEntry.removeEntry("GenericName");
    assert(!firstEntry.contains("GenericName"));
    firstEntry.removeEntry("GenericName", "ru");
    assert(!firstEntry.contains("GenericName[ru]"));
    firstEntry.setEscapedValue("GenericName", "File Manager");
    assert(firstEntry.escapedValue("GenericName") == "File Manager");

    assert(ilf.group("Another Group").escapedValue("Name") == "Commander");
    assert(equal(ilf.group("Another Group").byKeyValue(), [ keyValueTuple("Name", "Commander"), keyValueTuple("Comment", "Manage files") ]));

    auto latestCommentNode = ilf.group("Another Group").appendComment("The lastest comment");
    assert(latestCommentNode.line.comment == "#The lastest comment");
    latestCommentNode.setEscapedValue("The latest comment");
    assert(latestCommentNode.line.comment == "#The latest comment");
    assert(ilf.group("Another Group").prependComment("The first comment").line.comment == "#The first comment");

    assert(equal(
        ilf.group("Another Group").byIniLine(),
        [IniLikeLine.fromComment("#The first comment"), IniLikeLine.fromKeyValue("Name", "Commander"), IniLikeLine.fromKeyValue("Comment", "Manage files"), IniLikeLine.fromComment("# The last comment"), IniLikeLine.fromComment("#The latest comment")]
    ));

    auto nameLineNode = ilf.group("Another Group").getNode("Name");
    assert(nameLineNode.line.value == "Commander");
    auto commentLineNode = ilf.group("Another Group").getNode("Comment");
    assert(commentLineNode.line.value == "Manage files");

    ilf.group("Another Group").addCommentAfter(nameLineNode, "Middle comment");
    ilf.group("Another Group").addCommentBefore(commentLineNode, "Average comment");

    assert(equal(
        ilf.group("Another Group").byIniLine(),
        [
            IniLikeLine.fromComment("#The first comment"), IniLikeLine.fromKeyValue("Name", "Commander"),
            IniLikeLine.fromComment("#Middle comment"), IniLikeLine.fromComment("#Average comment"),
            IniLikeLine.fromKeyValue("Comment", "Manage files"), IniLikeLine.fromComment("# The last comment"), IniLikeLine.fromComment("#The latest comment")
        ]
    ));

    ilf.group("Another Group").removeEntry(latestCommentNode);

    assert(equal(
        ilf.group("Another Group").byIniLine(),
        [
            IniLikeLine.fromComment("#The first comment"), IniLikeLine.fromKeyValue("Name", "Commander"),
            IniLikeLine.fromComment("#Middle comment"), IniLikeLine.fromComment("#Average comment"),
            IniLikeLine.fromKeyValue("Comment", "Manage files"), IniLikeLine.fromComment("# The last comment")
        ]
    ));

    assert(equal(ilf.byGroup().map!(g => g.groupName), ["First Entry", "Another Group"]));

    assert(!ilf.removeGroup("NonExistent Group"));

    assert(ilf.removeGroup("Another Group"));
    assert(!ilf.group("Another Group"));
    assert(equal(ilf.byGroup().map!(g => g.groupName), ["First Entry"]));

    ilf.addGenericGroup("Another Group");
    assert(ilf.group("Another Group"));
    assert(ilf.group("Another Group").byIniLine().empty);
    assert(ilf.group("Another Group").byKeyValue().empty);

    assertThrown(ilf.addGenericGroup("Another Group"));

    ilf.addGenericGroup("Other Group");
    assert(equal(ilf.byGroup().map!(g => g.groupName), ["First Entry", "Another Group", "Other Group"]));

    assertThrown!IniLikeException(ilf.addGenericGroup(""));

    import std.range : isForwardRange;

    const IniLikeFile cilf = ilf;
    static assert(isForwardRange!(typeof(cilf.byGroup())));
    static assert(isForwardRange!(typeof(cilf.group("First Entry").byKeyValue())));
    static assert(isForwardRange!(typeof(cilf.group("First Entry").byIniLine())));

    contents =
`[Group]
GenericName=File manager
[Group]
GenericName=Commander`;

    auto shouldThrow = collectException!IniLikeReadException(new IniLikeFile(iniLikeStringReader(contents), "config.ini"));
    assert(shouldThrow !is null, "Duplicate groups should throw");
    assert(shouldThrow.lineNumber == 3);
    assert(shouldThrow.lineIndex == 2);
    assert(shouldThrow.fileName == "config.ini");

    contents =
`[Group]
Key=Value1
Key=Value2`;

    shouldThrow = collectException!IniLikeReadException(new IniLikeFile(iniLikeStringReader(contents)));
    assert(shouldThrow !is null, "Duplicate key should throw");
    assert(shouldThrow.lineNumber == 3);

    contents =
`[Group]
Key=Value
=File manager`;

    shouldThrow = collectException!IniLikeReadException(new IniLikeFile(iniLikeStringReader(contents)));
    assert(shouldThrow !is null, "Empty key should throw");
    assert(shouldThrow.lineNumber == 3);

    contents =
`[Group]
#Comment
Valid=Key
NotKeyNotGroupNotComment`;

    shouldThrow = collectException!IniLikeReadException(new IniLikeFile(iniLikeStringReader(contents)));
    assert(shouldThrow !is null, "Invalid entry should throw");
    assert(shouldThrow.lineNumber == 4);

    contents =
`#Comment
NotComment
[Group]
Valid=Key`;
    shouldThrow = collectException!IniLikeReadException(new IniLikeFile(iniLikeStringReader(contents)));
    assert(shouldThrow !is null, "Invalid comment should throw");
    assert(shouldThrow.lineNumber == 2);


    contents = `# The leading comment
[One]
# Comment1
Key1=Value1
Key2=Value2
Key3=Value3
[Two]
Key1=Value1
Key2=Value2
Key3=Value3
# Comment2
[Three]
Key1=Value1
Key2=Value2
# Comment3
Key3=Value3`;

    ilf = new IniLikeFile(iniLikeStringReader(contents));

    ilf.moveGroupToFront(ilf.getNode("Two"));
    assert(ilf.byNode().map!(g => g.key).equal(["Two", "One", "Three"]));

    ilf.moveGroupToBack(ilf.getNode("One"));
    assert(ilf.byNode().map!(g => g.key).equal(["Two", "Three", "One"]));

    ilf.moveGroupBefore(ilf.getNode("Two"), ilf.getNode("Three"));
    assert(ilf.byGroup().map!(g => g.groupName).equal(["Three", "Two", "One"]));

    ilf.moveGroupAfter(ilf.getNode("Three"), ilf.getNode("One"));
    assert(ilf.byGroup().map!(g => g.groupName).equal(["Three", "One", "Two"]));

    auto groupOne = ilf.group("One");
    groupOne.moveLineToFront(groupOne.getNode("Key3"));
    groupOne.moveLineToBack(groupOne.getNode("Key1"));

    assert(groupOne.byIniLine().equal([
        IniLikeLine.fromKeyValue("Key3", "Value3"), IniLikeLine.fromComment("# Comment1"),
        IniLikeLine.fromKeyValue("Key2", "Value2"), IniLikeLine.fromKeyValue("Key1", "Value1")
    ]));

    auto groupTwo = ilf.group("Two");
    groupTwo.moveLineBefore(groupTwo.getNode("Key1"), groupTwo.getNode("Key3"));
    groupTwo.moveLineAfter(groupTwo.getNode("Key2"), groupTwo.getNode("Key1"));

    assert(groupTwo.byIniLine().equal([
        IniLikeLine.fromKeyValue("Key3", "Value3"), IniLikeLine.fromKeyValue("Key2", "Value2"),
         IniLikeLine.fromKeyValue("Key1", "Value1"), IniLikeLine.fromComment("# Comment2")
    ]));
}