react-native-devtools-frontend/front_end/source_frame/SourceCodeDiff.js

// Copyright 2016 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.

SourceFrame.SourceCodeDiff = class {
  /**
   * @param {!TextEditor.CodeMirrorTextEditor} textEditor
   */
  constructor(textEditor) {
    this._textEditor = textEditor;
    /** @type {!Array<!TextEditor.TextEditorPositionHandle>}*/
    this._animatedLines = [];
    /** @type {?number} */
    this._animationTimeout = null;
  }

  /**
   * @param {?string} oldContent
   * @param {?string} newContent
   */
  highlightModifiedLines(oldContent, newContent) {
    if (typeof oldContent !== 'string' || typeof newContent !== 'string') {
      return;
    }

    const diff =
        SourceFrame.SourceCodeDiff.computeDiff(Diff.Diff.lineDiff(oldContent.split('\n'), newContent.split('\n')));
    const changedLines = [];
    for (let i = 0; i < diff.length; ++i) {
      const diffEntry = diff[i];
      if (diffEntry.type === SourceFrame.SourceCodeDiff.EditType.Delete) {
        continue;
      }
      for (let lineNumber = diffEntry.from; lineNumber < diffEntry.to; ++lineNumber) {
        const position = this._textEditor.textEditorPositionHandle(lineNumber, 0);
        if (position) {
          changedLines.push(position);
        }
      }
    }
    this._updateHighlightedLines(changedLines);
    this._animationTimeout = setTimeout(
        this._updateHighlightedLines.bind(this, []), 400);  // // Keep this timeout in sync with sourcesView.css.
  }

  /**
   * @param {!Array<!TextEditor.TextEditorPositionHandle>} newLines
   */
  _updateHighlightedLines(newLines) {
    if (this._animationTimeout) {
      clearTimeout(this._animationTimeout);
    }
    this._animationTimeout = null;
    this._textEditor.operation(operation.bind(this));

    /**
     * @this {SourceFrame.SourceCodeDiff}
     */
    function operation() {
      toggleLines.call(this, false);
      this._animatedLines = newLines;
      toggleLines.call(this, true);
    }

    /**
     * @param {boolean} value
     * @this {SourceFrame.SourceCodeDiff}
     */
    function toggleLines(value) {
      for (let i = 0; i < this._animatedLines.length; ++i) {
        const location = this._animatedLines[i].resolve();
        if (location) {
          this._textEditor.toggleLineClass(location.lineNumber, 'highlight-line-modification', value);
        }
      }
    }
  }

  /**
   * @param {!Diff.Diff.DiffArray} diff
   * @return {!Array<!{type: !SourceFrame.SourceCodeDiff.EditType, from: number, to: number}>}
   */
  static computeDiff(diff) {
    const result = [];
    let hasAdded = false;
    let hasRemoved = false;
    let blockStartLineNumber = 0;
    let currentLineNumber = 0;
    let isInsideBlock = false;
    for (let i = 0; i < diff.length; ++i) {
      const token = diff[i];
      if (token[0] === Diff.Diff.Operation.Equal) {
        if (isInsideBlock) {
          flush();
        }
        currentLineNumber += token[1].length;
        continue;
      }

      if (!isInsideBlock) {
        isInsideBlock = true;
        blockStartLineNumber = currentLineNumber;
      }

      if (token[0] === Diff.Diff.Operation.Delete) {
        hasRemoved = true;
      } else {
        currentLineNumber += token[1].length;
        hasAdded = true;
      }
    }
    if (isInsideBlock) {
      flush();
    }
    if (result.length > 1 && result[0].from === 0 && result[1].from === 0) {
      const merged = {type: SourceFrame.SourceCodeDiff.EditType.Modify, from: 0, to: result[1].to};
      result.splice(0, 2, merged);
    }
    return result;

    function flush() {
      let type = SourceFrame.SourceCodeDiff.EditType.Insert;
      let from = blockStartLineNumber;
      let to = currentLineNumber;
      if (hasAdded && hasRemoved) {
        type = SourceFrame.SourceCodeDiff.EditType.Modify;
      } else if (!hasAdded && hasRemoved && from === 0 && to === 0) {
        type = SourceFrame.SourceCodeDiff.EditType.Modify;
        to = 1;
      } else if (!hasAdded && hasRemoved) {
        type = SourceFrame.SourceCodeDiff.EditType.Delete;
        from -= 1;
      }
      result.push({type: type, from: from, to: to});
      isInsideBlock = false;
      hasAdded = false;
      hasRemoved = false;
    }
  }
};

/** @enum {symbol} */
SourceFrame.SourceCodeDiff.EditType = {
  Insert: Symbol('Insert'),
  Delete: Symbol('Delete'),
  Modify: Symbol('Modify'),
};