import { Change } from 'diff';

import { Context } from './context';

import { formatAndFitHunkLine } from './formatAndFitHunkLine';

import { FormattedString } from './formattedString';

import { HunkPart } from './iterFormatHunk';

/**

* 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,

lineNoA,

hunkLineA,

lineChanges[indexB]

);

lineNoA++;

lineNoB++;

indexB++;

}

indexA++;

}

// yield any remaining lines in hunk B, which can happen if there were more

// insertions at the end of the hunk

while (indexB < hunkLinesB.length) {

const hunkLineB = hunkLinesB[indexB];

if (hunkLineB !== null) {

yield* formatAndFitHunkLine(

context,

lineWidth,

fileNameB,

lineNoB,

hunkLineB,

lineChanges[indexB]

);

lineNoB++;

}

indexB++;

}

}

/**

* Formats a "combined diff" hunk i.e. a hunk from a combined diff, generated by

* --cc or --combined options, which are defaults for merge commits.

*/

export async function* iterFormatCombinedDiffHunkUnified(

context: Context,

hunkParts: HunkPart[],

lineChanges: (Change[] | null)[]

): AsyncIterable<FormattedString> {

const lineWidth = context.SCREEN_WIDTH;

// The final hunk part shows the current state of the file, so we just

// display that with additions and deletions highlighted.

const { fileName, lines, startLineNo } = hunkParts[hunkParts.length - 1];

let lineNo = startLineNo;

let numDeletes = 0;

for (let i = 0; i < lines.length; i++) {

const line = lines[i];

const prefix = line?.slice(0, 1) ?? null;

if (prefix == '-') {

numDeletes++;

} else {

lineNo -= numDeletes;

numDeletes = 0;

}

yield* formatAndFitHunkLine(

context,

lineWidth,

fileName,

lineNo,

line,

lineChanges[i]

);

lineNo++;

}

}