Function arrayDiff

src/lib/compare/myers.ts:18–75

(
  lvals: T[],
  rvals: T[],
  options?: DiffOptions,
)

 * @returns An array of differences.
 */
export function arrayDiff<T extends number | string | boolean | null>(
  lvals: T[],
  rvals: T[],
  options?: DiffOptions,
): Diff[] {
  const lineArray = [""];
  const lineHash: Record<string, number> = {};
  let n = lineArray.length;

  // Maps an array of lines to a string of unicode characters, then performs a text compare.
  const lines2chars = (lines: string[]) => {
    const baseChar = "0".charCodeAt(0);
    let chars = "";

    for (const line of lines) {
      if (lineHash.hasOwnProperty(line)) {
        chars += String.fromCharCode(baseChar + lineHash[line]);
      } else {
        chars += String.fromCharCode(baseChar + n);
        lineHash[line] = n;
        lineArray[n++] = line;
      }
    }

    return chars;
  };

  // Each line is an array element.
  const llines = lvals.map(String);
  const rlines = rvals.map(String);
  // Each character is an array element.
  const lchars = lines2chars(llines);
  const rchars = lines2chars(rlines);
  let lpos = 0;
  let rpos = 0;
  const diffs: Diff[] = [];

  diff(lchars, rchars, { ...options, isArrayDiff: true }).forEach((d) => {
    const n = d.value?.length!;

    if (d.removed) {
      for (let i = 0; i < n; i++) {
        diffs.push(newDiff(lpos, 1, "del"));
        lpos++;
      }
    } else if (d.added) {
      for (let i = 0; i < n; i++) {
        diffs.push(newDiff(rpos, 1, "ins"));
        rpos++;
      }
    } else {
      lpos += n;
      rpos += n;
    }
  });

  return diffs;
}