// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/**
 * @param {!Object} config
 * @param {{diffRows: !Array<!Changes.ChangesView.Row>, baselineLines: !Array<string>, currentLines: !Array<string>, mimeType: string}} parserConfig
 * @return {{
 *  startState: function():!Changes.ChangesHighlighter.DiffState,
 *  token: function(!CodeMirror.StringStream, !Changes.ChangesHighlighter.DiffState):string,
 *  blankLine: function(!Changes.ChangesHighlighter.DiffState):string,
 *  copyState: function(!Changes.ChangesHighlighter.DiffState):Changes.ChangesHighlighter.DiffState
 * }}
 */
export default function ChangesHighlighter(config, parserConfig) {
  const diffRows = parserConfig.diffRows;
  const baselineLines = parserConfig.baselineLines;
  const currentLines = parserConfig.currentLines;
  const syntaxHighlightMode = CodeMirror.getMode({}, parserConfig.mimeType);

  /**
   * @param {!Changes.ChangesHighlighter.DiffState} state
   * @param {number} baselineLineNumber
   * @param {number} currentLineNumber
   */
  function fastForward(state, baselineLineNumber, currentLineNumber) {
    if (baselineLineNumber > state.baselineLineNumber) {
      fastForwardSyntaxHighlighter(state.baselineSyntaxState, state.baselineLineNumber, baselineLineNumber, baselineLines);
      state.baselineLineNumber = baselineLineNumber;
    }
    if (currentLineNumber > state.currentLineNumber) {
      fastForwardSyntaxHighlighter(state.currentSyntaxState, state.currentLineNumber, currentLineNumber, currentLines);
      state.currentLineNumber = currentLineNumber;
    }
  }

  /**
   * @param {!Object} syntaxState
   * @param {number} from
   * @param {number} to
   * @param {!Array<string>} lines
   */
  function fastForwardSyntaxHighlighter(syntaxState, from, to, lines) {
    let lineNumber = from;
    while (lineNumber < to && lineNumber < lines.length) {
      const stream = new CodeMirror.StringStream(lines[lineNumber]);
      if (stream.eol() && syntaxHighlightMode.blankLine) {
        syntaxHighlightMode.blankLine(syntaxState);
      }
      while (!stream.eol()) {
        syntaxHighlightMode.token(stream, syntaxState);
        stream.start = stream.pos;
      }
      lineNumber++;
    }
  }

  return {
    /**
     * @return {!Changes.ChangesHighlighter.DiffState}
     */
    startState: function() {
      return {
        rowNumber: 0,
        diffTokenIndex: 0,
        currentLineNumber: 0,
        baselineLineNumber: 0,
        currentSyntaxState: CodeMirror.startState(syntaxHighlightMode),
        baselineSyntaxState: CodeMirror.startState(syntaxHighlightMode),
        syntaxPosition: 0,
        diffPosition: 0,
        syntaxStyle: '',
        diffStyle: ''
      };
    },

    /**
     * @param {!CodeMirror.StringStream} stream
     * @param {!Changes.ChangesHighlighter.DiffState} state
     * @return {string}
     */
    token: function(stream, state) {
      const diffRow = diffRows[state.rowNumber];
      if (!diffRow) {
        stream.next();
        return '';
      }
      fastForward(state, diffRow.baselineLineNumber - 1, diffRow.currentLineNumber - 1);
      let classes = '';
      if (stream.pos === 0) {
        classes += ' line-background-' + diffRow.type + ' line-' + diffRow.type;
      }

      const syntaxHighlighterNeedsRefresh = state.diffPosition >= state.syntaxPosition;
      if (state.diffPosition <= state.syntaxPosition) {
        state.diffPosition += diffRow.tokens[state.diffTokenIndex].text.length;
        state.diffStyle = diffRow.tokens[state.diffTokenIndex].className;
        state.diffTokenIndex++;
      }

      if (syntaxHighlighterNeedsRefresh) {
        if (diffRow.type === Changes.ChangesView.RowType.Deletion || diffRow.type === Changes.ChangesView.RowType.Addition ||
            diffRow.type === Changes.ChangesView.RowType.Equal) {
          state.syntaxStyle = syntaxHighlightMode.token(
              stream, diffRow.type === Changes.ChangesView.RowType.Deletion ? state.baselineSyntaxState : state.currentSyntaxState);
          state.syntaxPosition = stream.pos;
        } else {
          state.syntaxStyle = '';
          state.syntaxPosition = Infinity;
        }
      }

      stream.pos = Math.min(state.syntaxPosition, state.diffPosition);
      classes += ' ' + state.syntaxStyle;
      classes += ' ' + state.diffStyle;

      if (stream.eol()) {
        state.rowNumber++;
        if (diffRow.type === Changes.ChangesView.RowType.Deletion) {
          state.baselineLineNumber++;
        } else {
          state.currentLineNumber++;
        }
        state.diffPosition = 0;
        state.syntaxPosition = 0;
        state.diffTokenIndex = 0;
      }
      return classes;
    },

    /**
     * @param {!Changes.ChangesHighlighter.DiffState} state
     * @return {string}
     */
    blankLine: function(state) {
      const diffRow = diffRows[state.rowNumber];
      state.rowNumber++;
      state.syntaxPosition = 0;
      state.diffPosition = 0;
      state.diffTokenIndex = 0;
      if (!diffRow) {
        return '';
      }

      let style = '';
      if (syntaxHighlightMode.blankLine) {
        if (diffRow.type === Changes.ChangesView.RowType.Equal || diffRow.type === Changes.ChangesView.RowType.Addition) {
          style = syntaxHighlightMode.blankLine(state.currentSyntaxState);
          state.currentLineNumber++;
        } else if (diffRow.type === Changes.ChangesView.RowType.Deletion) {
          style = syntaxHighlightMode.blankLine(state.baselineSyntaxState);
          state.baselineLineNumber++;
        }
      }
      return style + ' line-background-' + diffRow.type + ' line-' + diffRow.type;
    },

    /**
     * @param {!Changes.ChangesHighlighter.DiffState} state
     * @return {!Changes.ChangesHighlighter.DiffState}
     */
    copyState: function(state) {
      const newState = Object.assign({}, state);
      newState.currentSyntaxState = CodeMirror.copyState(syntaxHighlightMode, state.currentSyntaxState);
      newState.baselineSyntaxState = CodeMirror.copyState(syntaxHighlightMode, state.baselineSyntaxState);
      return /** @type {!Changes.ChangesHighlighter.DiffState} */ (newState);
    }
  };
}

CodeMirror.defineMode('devtools-diff', ChangesHighlighter);

/* Legacy exported object */
self.Changes = self.Changes || {};

/* Legacy exported object */
Changes = Changes || {};

Changes.ChangesHighlighter = ChangesHighlighter;

/**
 * @typedef {!{
  *  rowNumber: number,
  *  diffTokenIndex: number,
  *  currentLineNumber: number,
  *  baselineLineNumber: number,
  *  currentSyntaxState: !Object,
  *  baselineSyntaxState: !Object,
  *  syntaxPosition: number,
  *  diffPosition: number,
  *  syntaxStyle: string,
  *  diffStyle: string
  * }}
  */
Changes.ChangesHighlighter.DiffState;