Function iterFormatUnifiedDiffHunkUnified

src/iterFormatHunkUnified.ts:10–97

(
    context: Context,
    hunkParts: HunkPart[],
    lineChanges: (Change[] | null)[]
)

 * Formats a "unified diff" hunk i.e. a hunk from a traditional diff.
 */
export async function* iterFormatUnifiedDiffHunkUnified(
    context: Context,
    hunkParts: HunkPart[],
    lineChanges: (Change[] | null)[]
): AsyncIterable<FormattedString> {
    const lineWidth = context.SCREEN_WIDTH;

    const [
        { fileName: fileNameA, lines: hunkLinesA },
        { fileName: fileNameB, lines: hunkLinesB },
    ] = hunkParts;
    let [{ startLineNo: lineNoA }, { startLineNo: lineNoB }] = hunkParts;

    let indexA = 0,
        indexB = 0;
    while (indexA < hunkLinesA.length) {
        const hunkLineA = hunkLinesA[indexA];
        const prefixA = hunkLineA?.slice(0, 1) ?? null;

        switch (prefixA) {
            case null:
                // Ignore the missing lines we insert to match up indexes
                break;
            case '-':
                yield* formatAndFitHunkLine(
                    context,
                    lineWidth,
                    fileNameA,
                    lineNoA,
                    hunkLineA,
                    lineChanges[indexA]
                );
                lineNoA++;
                break;
            default:
                // indexA is pointing to an unmodified line, so yield all the
                // inserted lines from indexB up to this line
                while (indexB < indexA) {
                    const hunkLineB = hunkLinesB[indexB];
                    if (hunkLineB !== null) {
                        yield* formatAndFitHunkLine(
                            context,
                            lineWidth,
                            fileNameB,
                            lineNoB,
                            hunkLineB,
                            lineChanges[indexB]
                        );
                        lineNoB++;
                    }
                    indexB++;
                }

                // now yield the unmodified line, which should be present in both
                yield* formatAndFitHunkLine(
                    context,
                    lineWidth,
                    fileNameA,