/**
 * Copyright (c) 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule RichTextEditorUtil
 * @typechecks
 * 
 */

'use strict';

var DraftEntity = require('./DraftEntity');
var DraftModifier = require('./DraftModifier');
var EditorState = require('./EditorState');
var SelectionState = require('./SelectionState');

var adjustBlockDepthForContentState = require('./adjustBlockDepthForContentState');
var nullthrows = require('fbjs/lib/nullthrows');

var RichTextEditorUtil = {
  currentBlockContainsLink: function currentBlockContainsLink(editorState) {
    var selection = editorState.getSelection();
    return editorState.getCurrentContent().getBlockForKey(selection.getAnchorKey()).getCharacterList().slice(selection.getStartOffset(), selection.getEndOffset()).some(function (v) {
      var entity = v.getEntity();
      return !!entity && DraftEntity.get(entity).getType() === 'LINK';
    });
  },

  getCurrentBlockType: function getCurrentBlockType(editorState) {
    var selection = editorState.getSelection();
    return editorState.getCurrentContent().getBlockForKey(selection.getStartKey()).getType();
  },

  getDataObjectForLinkURL: function getDataObjectForLinkURL(uri) {
    return { url: uri.toString() };
  },

  handleKeyCommand: function handleKeyCommand(editorState, command) {
    switch (command) {
      case 'bold':
        return RichTextEditorUtil.toggleInlineStyle(editorState, 'BOLD');
      case 'italic':
        return RichTextEditorUtil.toggleInlineStyle(editorState, 'ITALIC');
      case 'underline':
        return RichTextEditorUtil.toggleInlineStyle(editorState, 'UNDERLINE');
      case 'code':
        return RichTextEditorUtil.toggleCode(editorState);
      case 'backspace':
      case 'backspace-word':
      case 'backspace-to-start-of-line':
        return RichTextEditorUtil.onBackspace(editorState);
      case 'delete':
      case 'delete-word':
      case 'delete-to-end-of-block':
        return RichTextEditorUtil.onDelete(editorState);
      default:
        return null;
    }
  },

  insertSoftNewline: function insertSoftNewline(editorState) {
    var contentState = DraftModifier.insertText(editorState.getCurrentContent(), editorState.getSelection(), '\n', editorState.getCurrentInlineStyle(), null);

    var newEditorState = EditorState.push(editorState, contentState, 'insert-characters');

    return EditorState.forceSelection(newEditorState, contentState.getSelectionAfter());
  },

  /**
   * For collapsed selections at the start of styled blocks, backspace should
   * just remove the existing style.
   */
  onBackspace: function onBackspace(editorState) {
    var selection = editorState.getSelection();
    if (!selection.isCollapsed() || selection.getAnchorOffset() || selection.getFocusOffset()) {
      return null;
    }

    // First, try to remove a preceding atomic block.
    var content = editorState.getCurrentContent();
    var startKey = selection.getStartKey();
    var blockBefore = content.getBlockBefore(startKey);

    if (blockBefore && blockBefore.getType() === 'atomic') {
      var atomicBlockTarget = selection.merge({
        anchorKey: blockBefore.getKey(),
        anchorOffset: 0
      });
      var asCurrentStyle = DraftModifier.setBlockType(content, atomicBlockTarget, content.getBlockForKey(startKey).getType());
      var withoutAtomicBlock = DraftModifier.removeRange(asCurrentStyle, atomicBlockTarget, 'backward');
      if (withoutAtomicBlock !== content) {
        return EditorState.push(editorState, withoutAtomicBlock, 'remove-range');
      }
    }

    // If that doesn't succeed, try to remove the current block style.
    var withoutBlockStyle = RichTextEditorUtil.tryToRemoveBlockStyle(editorState);

    if (withoutBlockStyle) {
      return EditorState.push(editorState, withoutBlockStyle, 'change-block-type');
    }

    return null;
  },

  onDelete: function onDelete(editorState) {
    var selection = editorState.getSelection();
    if (!selection.isCollapsed()) {
      return null;
    }

    var content = editorState.getCurrentContent();
    var startKey = selection.getStartKey();
    var block = content.getBlockForKey(startKey);
    var length = block.getLength();

    // The cursor is somewhere within the text. Behave normally.
    if (selection.getStartOffset() < length) {
      return null;
    }

    var blockAfter = content.getBlockAfter(startKey);

    if (!blockAfter || blockAfter.getType() !== 'atomic') {
      return null;
    }

    var atomicBlockTarget = selection.merge({
      focusKey: blockAfter.getKey(),
      focusOffset: blockAfter.getLength()
    });

    var withoutAtomicBlock = DraftModifier.removeRange(content, atomicBlockTarget, 'forward');

    if (withoutAtomicBlock !== content) {
      return EditorState.push(editorState, withoutAtomicBlock, 'remove-range');
    }

    return null;
  },

  onTab: function onTab(event, editorState, maxDepth) {
    var selection = editorState.getSelection();
    var key = selection.getAnchorKey();
    if (key !== selection.getFocusKey()) {
      return editorState;
    }

    var content = editorState.getCurrentContent();
    var block = content.getBlockForKey(key);
    var type = block.getType();
    if (type !== 'unordered-list-item' && type !== 'ordered-list-item') {
      return editorState;
    }

    event.preventDefault();

    // Only allow indenting one level beyond the block above, and only if
    // the block above is a list item as well.
    var blockAbove = content.getBlockBefore(key);
    if (!blockAbove) {
      return editorState;
    }

    var typeAbove = blockAbove.getType();
    if (typeAbove !== 'unordered-list-item' && typeAbove !== 'ordered-list-item') {
      return editorState;
    }

    var depth = block.getDepth();
    if (!event.shiftKey && depth === maxDepth) {
      return editorState;
    }

    maxDepth = Math.min(blockAbove.getDepth() + 1, maxDepth);

    var withAdjustment = adjustBlockDepthForContentState(content, selection, event.shiftKey ? -1 : 1, maxDepth);

    return EditorState.push(editorState, withAdjustment, 'adjust-depth');
  },

  toggleBlockType: function toggleBlockType(editorState, blockType) {
    var selection = editorState.getSelection();
    var startKey = selection.getStartKey();
    var endKey = selection.getEndKey();
    var content = editorState.getCurrentContent();
    var target = selection;

    // Triple-click can lead to a selection that includes offset 0 of the
    // following block. The `SelectionState` for this case is accurate, but
    // we should avoid toggling block type for the trailing block because it
    // is a confusing interaction.
    if (startKey !== endKey && selection.getEndOffset() === 0) {
      var blockBefore = nullthrows(content.getBlockBefore(endKey));
      endKey = blockBefore.getKey();
      target = target.merge({
        anchorKey: startKey,
        anchorOffset: selection.getStartOffset(),
        focusKey: endKey,
        focusOffset: blockBefore.getLength(),
        isBackward: false
      });
    }

    var hasAtomicBlock = content.getBlockMap().skipWhile(function (_, k) {
      return k !== startKey;
    }).reverse().skipWhile(function (_, k) {
      return k !== endKey;
    }).some(function (v) {
      return v.getType() === 'atomic';
    });

    if (hasAtomicBlock) {
      return editorState;
    }

    var typeToSet = content.getBlockForKey(startKey).getType() === blockType ? 'unstyled' : blockType;

    return EditorState.push(editorState, DraftModifier.setBlockType(content, target, typeToSet), 'change-block-type');
  },

  toggleCode: function toggleCode(editorState) {
    var selection = editorState.getSelection();
    var anchorKey = selection.getAnchorKey();
    var focusKey = selection.getFocusKey();

    if (selection.isCollapsed() || anchorKey !== focusKey) {
      return RichTextEditorUtil.toggleBlockType(editorState, 'code-block');
    }

    return RichTextEditorUtil.toggleInlineStyle(editorState, 'CODE');
  },

  /**
   * Toggle the specified inline style for the selection. If the
   * user's selection is collapsed, apply or remove the style for the
   * internal state. If it is not collapsed, apply the change directly
   * to the document state.
   */
  toggleInlineStyle: function toggleInlineStyle(editorState, inlineStyle) {
    var selection = editorState.getSelection();
    var currentStyle = editorState.getCurrentInlineStyle();

    // If the selection is collapsed, toggle the specified style on or off and
    // set the result as the new inline style override. This will then be
    // used as the inline style for the next character to be inserted.
    if (selection.isCollapsed()) {
      return EditorState.setInlineStyleOverride(editorState, currentStyle.has(inlineStyle) ? currentStyle.remove(inlineStyle) : currentStyle.add(inlineStyle));
    }

    // If characters are selected, immediately apply or remove the
    // inline style on the document state itself.
    var content = editorState.getCurrentContent();
    var newContent;

    // If the style is already present for the selection range, remove it.
    // Otherwise, apply it.
    if (currentStyle.has(inlineStyle)) {
      newContent = DraftModifier.removeInlineStyle(content, selection, inlineStyle);
    } else {
      newContent = DraftModifier.applyInlineStyle(content, selection, inlineStyle);
    }

    return EditorState.push(editorState, newContent, 'change-inline-style');
  },

  toggleLink: function toggleLink(editorState, targetSelection, entityKey) {
    var withoutLink = DraftModifier.applyEntity(editorState.getCurrentContent(), targetSelection, entityKey);

    return EditorState.push(editorState, withoutLink, 'apply-entity');
  },

  /**
   * When a collapsed cursor is at the start of an empty styled block, allow
   * certain key commands (newline, backspace) to simply change the
   * style of the block instead of the default behavior.
   */
  tryToRemoveBlockStyle: function tryToRemoveBlockStyle(editorState) {
    var selection = editorState.getSelection();
    var offset = selection.getAnchorOffset();
    if (selection.isCollapsed() && offset === 0) {
      var key = selection.getAnchorKey();
      var content = editorState.getCurrentContent();
      var block = content.getBlockForKey(key);
      if (block.getLength() > 0) {
        return null;
      }

      var type = block.getType();
      var blockBefore = content.getBlockBefore(key);
      if (type === 'code-block' && blockBefore && blockBefore.getType() === 'code-block') {
        return null;
      }

      if (type !== 'unstyled') {
        return DraftModifier.setBlockType(content, selection, 'unstyled');
      }
    }
    return null;
  }
};

module.exports = RichTextEditorUtil;