# text-diff-patch

> Zero-dependency Myers line diff producing unified-diff hunks, with fuzzy patch application, reject reporting, and word-level highlighting.

text-diff-patch computes an O(ND) Myers diff between two texts, formats it as

unified-diff hunks, and can apply those hunks back to a (possibly slightly

shifted) base text — reporting exactly which hunks couldn't be placed rather

than throwing. It also exposes a word-level diff for intra-line highlighting.

Built for agents that generate, store, and re-apply edits against files that

may have drifted since the diff was made.

## API

- `myersDiff(a: string[], b: string[]): DiffOp[]` — `DiffOp = { type: "equal"|"delete"|"insert", value: string }`.

- `toLines(text: string): string[]`

- `buildHunks(ops: DiffOp[], context?: number): Hunk[]` — `Hunk = { oldStart, oldLines, newStart, newLines, lines: string[] }`.

- `createPatch(oldText: string, newText: string, options?: { context?: number; oldFile?: string; newFile?: string }): string`

- `parsePatch(patchText: string): Hunk[]`

- `applyPatch(text: string, patch: string | Hunk[], options?: { fuzz?: number }): { result: string; applied: number; rejects: RejectedHunk[] }` — `RejectedHunk = { hunk: Hunk; reason: string }`.

- `tokenizeWords(line: string): string[]`

- `diffWords(a: string, b: string): DiffOp[]`

- `highlightWordDiff(a: string, b: string, options?: { insertOpen?; insertClose?; deleteOpen?; deleteClose? }): string`

## Install

```bash

npm install @ferrow/text-diff-patch

```

Part of the Ferrow open-source toolkit: https://github.com/FerrowAI/ferrow-toolkit — sponsored by https://ferrow.ai