Class DiffParser

app/src/lib/diff-parser.ts:63–461

 * See https://www.gnu.org/software/diffutils/manual/html_node/Detailed-Unified.html
 */
export class DiffParser {
  /**
   * Line start pointer.
   *
   * The offset into the text property where the current line starts (ie either zero
   * or one character ahead of the last newline character).
   */
  private ls!: number

  /**
   * Line end pointer.
   *
   * The offset into the text property where the current line ends (ie it points to
   * the newline character) or -1 if the line boundary hasn't been determined yet
   */
  private le!: number

  /**
   * The text buffer containing the raw, unified diff output to be parsed
   */
  private text!: string

  public constructor() {
    this.reset()
  }

  /**
   * Resets the internal parser state so that it can be reused.
   *
   * This is done automatically at the end of each parse run.
   */
  private reset() {
    this.ls = 0
    this.le = -1
    this.text = ''
  }

  /**
   * Aligns the internal character pointers at the boundaries of
   * the next line.
   *
   * Returns true if successful or false if the end of the diff
   * has been reached.
   */
  private nextLine(): boolean {
    this.ls = this.le + 1

    // We've reached the end of the diff
    if (this.ls >= this.text.length) {
      return false
    }

    this.le = this.text.indexOf('\n', this.ls)

    // If we can't find the next newline character we'll put our
    // end pointer at the end of the diff string
    if (this.le === -1) {
      this.le = this.text.length