// Copyright 2020 Garett Tok Ern Liang
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import 'package:source_span/source_span.dart';
import 'package:yaml/yaml.dart';

import 'editor.dart';

/// Determines if [string] is dangerous by checking if parsing the plain string can
/// return a result different from [string].
///
/// This function is also capable of detecting if non-printable characters are in
/// [string].
bool isDangerousString(String string) {
  ArgumentError.checkNotNull(string, 'string');

  try {
    if (loadYamlNode(string).value != string) {
      return true;
    }

    /// [string] should also not contain the `[`, `]`, `,`, `{` and `}` indicator characters.
    return string.contains(RegExp(r'\{|\[|\]|\}|,'));
  } catch (e) {
    /// This catch statement catches [ArgumentError] in `loadYamlNode` when
    /// a string can be interpreted as a URI tag, but catches for other
    /// [YamlException]s
    return true;
  }
}

/// Asserts that [value] is a valid scalar according to YAML.
///
/// A valid scalar is a number, String, boolean, or null.
void assertValidScalar(Object value) {
  if (value is num || value is String || value is bool || value == null) {
    return;
  }

  throw ArgumentError.value(value, 'value', 'Not a valid scalar type!');
}

/// Checks if [node] is a [YamlNode] with block styling.
///
/// [ScalarStyle.ANY] and [CollectionStyle.ANY] are considered to be block styling
/// by default for maximum flexibility.
bool isBlockNode(YamlNode node) {
  ArgumentError.checkNotNull(node, 'node');

  if (node is YamlScalar) {
    if (node.style == ScalarStyle.LITERAL ||
        node.style == ScalarStyle.FOLDED ||
        node.style == ScalarStyle.ANY) {
      return true;
    }
  }

  if (node is YamlList &&
      (node.style == CollectionStyle.BLOCK ||
          node.style == CollectionStyle.ANY)) return true;
  if (node is YamlMap &&
      (node.style == CollectionStyle.BLOCK ||
          node.style == CollectionStyle.ANY)) return true;

  return false;
}

/// Returns the content sensitive ending offset of [yamlNode] (i.e. where the last
/// meaningful content happens)
int getContentSensitiveEnd(YamlNode yamlNode) {
  ArgumentError.checkNotNull(yamlNode, 'yamlNode');

  if (yamlNode is YamlList) {
    if (yamlNode.style == CollectionStyle.FLOW) {
      return yamlNode.span.end.offset;
    } else {
      return getContentSensitiveEnd(yamlNode.nodes.last);
    }
  } else if (yamlNode is YamlMap) {
    if (yamlNode.style == CollectionStyle.FLOW) {
      return yamlNode.span.end.offset;
    } else {
      return getContentSensitiveEnd(yamlNode.nodes.values.last);
    }
  }

  return yamlNode.span.end.offset;
}

/// Checks if the item is a Map or a List
bool isCollection(Object item) => item is Map || item is List;

/// Checks if [index] is [int], >=0, < [length]
bool isValidIndex(Object index, int length) {
  return index is int && index >= 0 && index < length;
}

/// Checks if the item is empty, if it is a List or a Map.
///
/// Returns `false` if [item] is not a List or Map.
bool isEmpty(Object item) {
  if (item is Map) return item.isEmpty;
  if (item is List) return item.isEmpty;

  return false;
}

/// Creates a [SourceSpan] from [sourceUrl] with no meaningful location
/// information.
///
/// Mainly used with [wrapAsYamlNode] to allow for a reasonable
/// implementation of [SourceSpan.message].
SourceSpan shellSpan(Object sourceUrl) {
  final shellSourceLocation = SourceLocation(0, sourceUrl: sourceUrl);
  return SourceSpanBase(shellSourceLocation, shellSourceLocation, '');
}

/// Returns if [value] is a [YamlList] or [YamlMap] with [CollectionStyle.FLOW].
bool isFlowYamlCollectionNode(Object value) {
  if (value is YamlList || value is YamlMap) {
    return (value as dynamic).style == CollectionStyle.FLOW;
  }

  return false;
}

/// Determines the index where [newKey] will be inserted if the keys in [map] are in
/// alphabetical order when converted to strings.
///
/// Returns the length of [map] if the keys in [map] are not in alphabetical order.
int getMapInsertionIndex(YamlMap map, Object newKey) {
  ArgumentError.checkNotNull(map, 'map');

  final keys = map.nodes.keys.map((k) => k.toString()).toList();

  for (var i = 1; i < keys.length; i++) {
    if (keys[i].compareTo(keys[i - 1]) < 0) {
      return map.length;
    }
  }

  final insertionIndex = keys.indexWhere((key) => key.compareTo(newKey) > 0);

  if (insertionIndex != -1) return insertionIndex;

  return map.length;
}

/// Returns the [style] property of [target], if it is a [YamlNode]. Otherwise return null.
Object getStyle(Object target) {
  if (target is YamlNode) {
    return (target as dynamic).style;
  }

  return null;
}

/// Returns the detected indentation step used in [yaml], or
/// defaults to a value of `2` if no indentation step can be detected.
///
/// Indentation step is determined by the difference in indentation of the
/// first block-styled yaml collection in the second level as compared to the
/// top-level elements. In the case where there are multiple possible
/// candidates, we choose the candidate closest to the start of [yaml].
int getIndentation(YamlEditor editor) {
  final node = editor.parseAt([]);
  Iterable<YamlNode> children;
  var indentation = 2;

  if (node is YamlMap && node.style == CollectionStyle.BLOCK) {
    children = node.nodes.values;
  } else if (node is YamlList && node.style == CollectionStyle.BLOCK) {
    children = node.nodes;
  }

  if (children != null) {
    for (final child in children) {
      var indent = 0;
      if (child is YamlList) {
        indent = getListIndentation(editor.toString(), child);
      } else if (child is YamlMap) {
        indent = getMapIndentation(editor.toString(), child);
      }

      if (indent != 0) indentation = indent;
    }
  }
  return indentation;
}

/// Gets the indentation level of [list]. This is 0 if it is a flow list,
/// but returns the number of spaces before the hyphen of elements for
/// block lists.
///
/// Throws [UnsupportedError] if an empty block map is passed in.
int getListIndentation(String yaml, YamlList list) {
  ArgumentError.checkNotNull(list, 'list');

  if (list.style == CollectionStyle.FLOW) return 0;

  /// An empty block map doesn't really exist.
  if (list.isEmpty) {
    throw UnsupportedError('Unable to get indentation for empty block list');
  }

  final lastSpanOffset = list.nodes.last.span.start.offset;
  final lastNewLine = yaml.lastIndexOf('\n', lastSpanOffset - 1);
  final lastHyphen = yaml.lastIndexOf('-', lastSpanOffset - 1);

  if (lastNewLine == -1) return lastHyphen;

  return lastHyphen - lastNewLine - 1;
}

/// Gets the indentation level of [map]. This is 0 if it is a flow map,
/// but returns the number of spaces before the keys for block maps.
int getMapIndentation(String yaml, YamlMap map) {
  ArgumentError.checkNotNull(map, 'map');

  if (map.style == CollectionStyle.FLOW) return 0;

  /// An empty block map doesn't really exist.
  if (map.isEmpty) {
    throw UnsupportedError('Unable to get indentation for empty block map');
  }

  /// Use the number of spaces between the last key and the newline as
  /// indentation.
  final lastKey = map.nodes.keys.last as YamlNode;
  final lastSpanOffset = lastKey.span.start.offset;
  final lastNewLine = yaml.lastIndexOf('\n', lastSpanOffset);
  final lastQuestionMark = yaml.lastIndexOf('?', lastSpanOffset);

  if (lastQuestionMark == -1) {
    if (lastNewLine == -1) return lastSpanOffset;
    return lastSpanOffset - lastNewLine - 1;
  }

  /// If there is a question mark, it might be a complex key. Check if it
  /// is on the same line as the key node to verify.
  if (lastNewLine == -1) return lastQuestionMark;
  if (lastQuestionMark > lastNewLine) {
    return lastQuestionMark - lastNewLine - 1;
  }

  return lastSpanOffset - lastNewLine - 1;
}

/// Returns the detected line ending used in [yaml], more specifically, whether
/// [yaml] appears to use Windows `\r\n` or Unix `\n` line endings.
///
/// The heuristic used is to count all `\n` in the text and if stricly more
/// than half of them are preceded by `\r` we report that windows line endings
/// are used.
String getLineEnding(String yaml) {
  var index = -1;
  var unixNewlines = 0;
  var windowsNewlines = 0;
  while ((index = yaml.indexOf('\n', index + 1)) != -1) {
    if (index != 0 && yaml[index - 1] == '\r') {
      windowsNewlines++;
    } else {
      unixNewlines++;
    }
  }

  return windowsNewlines > unixNewlines ? '\r\n' : '\n';
}