// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'description.dart';
import 'equals_matcher.dart';
import 'feature_matcher.dart';
import 'interfaces.dart';
import 'util.dart';

/// Returns a matcher which matches [Iterable]s in which all elements
/// match the given [matcher].
Matcher everyElement(matcher) => _EveryElement(wrapMatcher(matcher));

class _EveryElement extends _IterableMatcher {
  final Matcher _matcher;

  _EveryElement(this._matcher);

  @override
  bool typedMatches(Iterable item, Map matchState) {
    var i = 0;
    for (var element in item) {
      if (!_matcher.matches(element, matchState)) {
        addStateInfo(matchState, {'index': i, 'element': element});
        return false;
      }
      ++i;
    }
    return true;
  }

  @override
  Description describe(Description description) =>
      description.add('every element(').addDescriptionOf(_matcher).add(')');

  @override
  Description describeTypedMismatch(
      item, Description mismatchDescription, Map matchState, bool verbose) {
    if (matchState['index'] != null) {
      var index = matchState['index'];
      var element = matchState['element'];
      mismatchDescription
          .add('has value ')
          .addDescriptionOf(element)
          .add(' which ');
      var subDescription = StringDescription();
      _matcher.describeMismatch(
          element, subDescription, matchState['state'] as Map, verbose);
      if (subDescription.length > 0) {
        mismatchDescription.add(subDescription.toString());
      } else {
        mismatchDescription.add("doesn't match ");
        _matcher.describe(mismatchDescription);
      }
      mismatchDescription.add(' at index $index');
      return mismatchDescription;
    }
    return super
        .describeMismatch(item, mismatchDescription, matchState, verbose);
  }
}

/// Returns a matcher which matches [Iterable]s in which at least one
/// element matches the given [matcher].
Matcher anyElement(matcher) => _AnyElement(wrapMatcher(matcher));

class _AnyElement extends _IterableMatcher {
  final Matcher _matcher;

  _AnyElement(this._matcher);

  @override
  bool typedMatches(Iterable item, Map matchState) =>
      item.any((e) => _matcher.matches(e, matchState));

  @override
  Description describe(Description description) =>
      description.add('some element ').addDescriptionOf(_matcher);
}

/// Returns a matcher which matches [Iterable]s that have the same
/// length and the same elements as [expected], in the same order.
///
/// This is equivalent to [equals] but does not recurse.
Matcher orderedEquals(Iterable expected) => _OrderedEquals(expected);

class _OrderedEquals extends _IterableMatcher {
  final Iterable _expected;
  final Matcher _matcher;

  _OrderedEquals(this._expected) : _matcher = equals(_expected, 1);

  @override
  bool typedMatches(Iterable item, Map matchState) =>
      _matcher.matches(item, matchState);

  @override
  Description describe(Description description) =>
      description.add('equals ').addDescriptionOf(_expected).add(' ordered');

  @override
  Description describeTypedMismatch(Iterable item,
      Description mismatchDescription, Map matchState, bool verbose) {
    return _matcher.describeMismatch(
        item, mismatchDescription, matchState, verbose);
  }
}

/// Returns a matcher which matches [Iterable]s that have the same length and
/// the same elements as [expected], but not necessarily in the same order.
///
/// Note that this is worst case O(n^2) runtime and memory usage so it should
/// only be used on small iterables.
Matcher unorderedEquals(Iterable expected) => _UnorderedEquals(expected);

class _UnorderedEquals extends _UnorderedMatches {
  final List _expectedValues;

  _UnorderedEquals(Iterable expected)
      : _expectedValues = expected.toList(),
        super(expected.map(equals));

  @override
  Description describe(Description description) => description
      .add('equals ')
      .addDescriptionOf(_expectedValues)
      .add(' unordered');
}

/// Iterable matchers match against [Iterable]s. We add this intermediate
/// class to give better mismatch error messages than the base Matcher class.
abstract class _IterableMatcher extends FeatureMatcher<Iterable> {
  const _IterableMatcher();
}

/// Returns a matcher which matches [Iterable]s whose elements match the
/// matchers in [expected], but not necessarily in the same order.
///
/// Note that this is worst case O(n^2) runtime and memory usage so it should
/// only be used on small iterables.
Matcher unorderedMatches(Iterable expected) => _UnorderedMatches(expected);

class _UnorderedMatches extends _IterableMatcher {
  final List<Matcher> _expected;
  final bool _allowUnmatchedValues;

  _UnorderedMatches(Iterable expected, {bool allowUnmatchedValues})
      : _expected = expected.map(wrapMatcher).toList(),
        _allowUnmatchedValues = allowUnmatchedValues ?? false;

  String _test(List values) {
    // Check the lengths are the same.
    if (_expected.length > values.length) {
      return 'has too few elements (${values.length} < ${_expected.length})';
    } else if (!_allowUnmatchedValues && _expected.length < values.length) {
      return 'has too many elements (${values.length} > ${_expected.length})';
    }

    var edges = List.generate(values.length, (_) => <int>[], growable: false);
    for (var v = 0; v < values.length; v++) {
      for (var m = 0; m < _expected.length; m++) {
        if (_expected[m].matches(values[v], {})) {
          edges[v].add(m);
        }
      }
    }
    // The index into `values` matched with each matcher or `null` if no value
    // has been matched yet.
    var matched = List<int>(_expected.length);
    for (var valueIndex = 0; valueIndex < values.length; valueIndex++) {
      _findPairing(edges, valueIndex, matched);
    }
    for (var matcherIndex = 0;
        matcherIndex < _expected.length;
        matcherIndex++) {
      if (matched[matcherIndex] == null) {
        final description = StringDescription()
            .add('has no match for ')
            .addDescriptionOf(_expected[matcherIndex])
            .add(' at index $matcherIndex');
        final remainingUnmatched =
            matched.sublist(matcherIndex + 1).where((m) => m == null).length;
        return remainingUnmatched == 0
            ? description.toString()
            : description
                .add(' along with $remainingUnmatched other unmatched')
                .toString();
      }
    }
    return null;
  }

  @override
  bool typedMatches(Iterable item, Map mismatchState) =>
      _test(item.toList()) == null;

  @override
  Description describe(Description description) => description
      .add('matches ')
      .addAll('[', ', ', ']', _expected)
      .add(' unordered');

  @override
  Description describeTypedMismatch(item, Description mismatchDescription,
          Map matchState, bool verbose) =>
      mismatchDescription.add(_test(item.toList()));

  /// Returns `true` if the value at [valueIndex] can be paired with some
  /// unmatched matcher and updates the state of [matched].
  ///
  /// If there is a conflict where multiple values may match the same matcher
  /// recursively looks for a new place to match the old value. [reserved]
  /// tracks the matchers that have been used _during_ this search.
  bool _findPairing(List<List<int>> edges, int valueIndex, List<int> matched,
      [Set<int> reserved]) {
    reserved ??= Set<int>();
    final possiblePairings =
        edges[valueIndex].where((m) => !reserved.contains(m));
    for (final matcherIndex in possiblePairings) {
      reserved.add(matcherIndex);
      final previouslyMatched = matched[matcherIndex];
      if (previouslyMatched == null ||
          // If the matcher isn't already free, check whether the existing value
          // occupying the matcher can be bumped to another one.
          _findPairing(edges, matched[matcherIndex], matched, reserved)) {
        matched[matcherIndex] = valueIndex;
        return true;
      }
    }
    return false;
  }
}

/// A pairwise matcher for [Iterable]s.
///
/// The [comparator] function, taking an expected and an actual argument, and
/// returning whether they match, will be applied to each pair in order.
/// [description] should be a meaningful name for the comparator.
Matcher pairwiseCompare<S, T>(
        Iterable<S> expected, bool comparator(S a, T b), String description) =>
    _PairwiseCompare(expected, comparator, description);

typedef _Comparator<S, T> = bool Function(S a, T b);

class _PairwiseCompare<S, T> extends _IterableMatcher {
  final Iterable<S> _expected;
  final _Comparator<S, T> _comparator;
  final String _description;

  _PairwiseCompare(this._expected, this._comparator, this._description);

  @override
  bool typedMatches(Iterable item, Map matchState) {
    if (item.length != _expected.length) return false;
    var iterator = item.iterator;
    var i = 0;
    for (var e in _expected) {
      iterator.moveNext();
      if (!_comparator(e, iterator.current as T)) {
        addStateInfo(matchState,
            {'index': i, 'expected': e, 'actual': iterator.current});
        return false;
      }
      i++;
    }
    return true;
  }

  @override
  Description describe(Description description) =>
      description.add('pairwise $_description ').addDescriptionOf(_expected);

  @override
  Description describeTypedMismatch(Iterable item,
      Description mismatchDescription, Map matchState, bool verbose) {
    if (item.length != _expected.length) {
      return mismatchDescription
          .add('has length ${item.length} instead of ${_expected.length}');
    } else {
      return mismatchDescription
          .add('has ')
          .addDescriptionOf(matchState["actual"])
          .add(' which is not $_description ')
          .addDescriptionOf(matchState["expected"])
          .add(' at index ${matchState["index"]}');
    }
  }
}

/// Matches [Iterable]s which contain an element matching every value in
/// [expected] in any order, and may contain additional values.
///
/// For example: `[0, 1, 0, 2, 0]` matches `containsAll([1, 2])` and
/// `containsAll([2, 1])` but not `containsAll([1, 2, 3])`.
///
/// Will only match values which implement [Iterable].
///
/// Each element in the value will only be considered a match for a single
/// matcher in [expected] even if it could satisfy more than one. For instance
/// `containsAll([greaterThan(1), greaterThan(2)])` will not be satisfied by
/// `[3]`. To check that all matchers are satisfied within an iterable and allow
/// the same element to satisfy multiple matchers use
/// `allOf(matchers.map(contains))`.
///
/// Note that this is worst case O(n^2) runtime and memory usage so it should
/// only be used on small iterables.
Matcher containsAll(Iterable expected) => _ContainsAll(expected);

class _ContainsAll extends _UnorderedMatches {
  final Iterable _unwrappedExpected;

  _ContainsAll(Iterable expected)
      : _unwrappedExpected = expected,
        super(expected.map(wrapMatcher), allowUnmatchedValues: true);
  @override
  Description describe(Description description) =>
      description.add('contains all of ').addDescriptionOf(_unwrappedExpected);
}

/// Matches [Iterable]s which contain an element matching every value in
/// [expected] in the same order, but may contain additional values interleaved
/// throughout.
///
/// For example: `[0, 1, 0, 2, 0]` matches `containsAllInOrder([1, 2])` but not
/// `containsAllInOrder([2, 1])` or `containsAllInOrder([1, 2, 3])`.
///
/// Will only match values which implement [Iterable].
Matcher containsAllInOrder(Iterable expected) => _ContainsAllInOrder(expected);

class _ContainsAllInOrder extends _IterableMatcher {
  final Iterable _expected;

  _ContainsAllInOrder(this._expected);

  String _test(Iterable item, Map matchState) {
    var matchers = _expected.map(wrapMatcher).toList();
    var matcherIndex = 0;
    for (var value in item) {
      if (matchers[matcherIndex].matches(value, matchState)) matcherIndex++;
      if (matcherIndex == matchers.length) return null;
    }
    return StringDescription()
        .add('did not find a value matching ')
        .addDescriptionOf(matchers[matcherIndex])
        .add(' following expected prior values')
        .toString();
  }

  @override
  bool typedMatches(Iterable item, Map matchState) =>
      _test(item, matchState) == null;

  @override
  Description describe(Description description) => description
      .add('contains in order(')
      .addDescriptionOf(_expected)
      .add(')');

  @override
  Description describeTypedMismatch(Iterable item,
          Description mismatchDescription, Map matchState, bool verbose) =>
      mismatchDescription.add(_test(item, matchState));
}