Install UV

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...v8)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.forgejo/workflows/check.yml

@@ -0,0 +1,74 @@
+name: Check
+
+on:
+  push:
+    branches: ['main']
+  pull_request:
+    branches: ['main']
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: '-Dwarnings'
+
+jobs:
+  build:
+    runs-on: docker
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          check-latest: true
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            reconcile-js/node_modules
+            examples/website/node_modules
+            ~/.npm
+          key: >-
+            ${{ runner.os }}-npm-${{
+            hashFiles(
+              'reconcile-js/package-lock.json',
+              'examples/website/package-lock.json'
+            )
+            }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Install uv
+        run: |
+          curl --proto '=https' --tlsv1.2 -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Lint
+        run: scripts/lint.sh
+
+      - name: Test
+        run: scripts/test.sh
+
+      - name: Build website
+        run: scripts/build-website.sh

.forgejo/workflows/publish.yml

@@ -0,0 +1,172 @@
+name: Publish
+
+on:
+  push:
+    branches: ['main']
+    tags: ['*']
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: '-Dwarnings'
+
+concurrency:
+  group: 'pages'
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: docker
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          check-latest: true
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            reconcile-js/node_modules
+            examples/website/node_modules
+            ~/.npm
+          key: >-
+            ${{ runner.os }}-npm-${{
+            hashFiles(
+              'reconcile-js/package-lock.json',
+              'examples/website/package-lock.json'
+            )
+            }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Install uv
+        run: |
+          curl --proto '=https' --tlsv1.2 -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Lint
+        run: scripts/lint.sh
+
+      - name: Test
+        run: scripts/test.sh
+
+      - name: Build website
+        run: scripts/build-website.sh
+
+      - name: Deploy to pages mount
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          apt-get update && apt-get install -y rsync
+          rsync -a --delete examples/website/dist/ /pages/reconcile
+
+  publish-crate:
+    needs: build
+    runs-on: docker
+    if: startsWith(github.ref, 'refs/tags/')
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Publish to crates.io
+        run: cargo publish --token ${{ secrets.CRATES_IO_TOKEN }}
+
+  publish-npm:
+    needs: build
+    runs-on: docker
+    if: startsWith(github.ref, 'refs/tags/')
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          check-latest: true
+          registry-url: 'https://registry.npmjs.org'
+
+      - name: Cache Rust dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            reconcile-js/node_modules
+            ~/.npm
+          key: >-
+            ${{ runner.os }}-npm-${{
+            hashFiles('reconcile-js/package-lock.json')
+            }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
+      - name: Install Rust toolchain
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+            | sh -s -- -y --default-toolchain none --profile minimal
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+
+      - name: Build website
+        run: scripts/build-website.sh
+
+      - name: Publish reconcile-js to NPM
+        run: |
+          cd reconcile-js
+          cp ../README.md .
+          npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}

.github/dependabot.yml

@@ -1,26 +0,0 @@
-# To get started with Dependabot version updates, you'll need to specify which
-# package ecosystems to update and where the package manifests are located.
-# Please see the documentation for all configuration options:
-# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
-
-version: 2
-updates:
-  - package-ecosystem: 'cargo'
-    directories: ['**']
-    schedule:
-      interval: 'daily'
-
-  - package-ecosystem: 'github-actions'
-    directories: ['**']
-    schedule:
-      interval: 'daily'
-
-  - package-ecosystem: 'npm'
-    directories: ['/reconcile-js', '/examples/website']
-    schedule:
-      interval: 'daily'
-
-  - package-ecosystem: 'pip'
-    directories: ['/reconcile-python']
-    schedule:
-      interval: 'daily'

.github/workflows/check.yml

@@ -1,198 +0,0 @@
-name: Check & publish
-
-on:
-  push:
-    branches: ['main']
-    tags: ['*']
-  pull_request:
-    branches: ['main']
-
-env:
-  CARGO_TERM_COLOR: always
-  RUSTFLAGS: '-Dwarnings'
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Setup Node.js environment
-        uses: actions/setup-node@v6.3.0
-        with:
-          node-version: '22.x'
-          check-latest: true
-
-      - name: Install uv
-        uses: astral-sh/setup-uv@v6
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Lint
-        run: scripts/lint.sh
-
-      - name: Test
-        run: scripts/test.sh
-
-  publish-crate:
-    needs: build
-    runs-on: ubuntu-latest
-    if: startsWith(github.ref, 'refs/tags/')
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Publish to crates.io
-        run: cargo publish --token ${{ secrets.CRATES_IO_TOKEN }}
-
-  publish-npm:
-    needs: build
-    runs-on: ubuntu-latest
-    if: startsWith(github.ref, 'refs/tags/')
-    permissions:
-      contents: read
-      id-token: write
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Setup Node.js environment
-        uses: actions/setup-node@v6.3.0
-        with:
-          node-version: '22.x'
-          check-latest: true
-          registry-url: 'https://registry.npmjs.org'
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Cache npm dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            reconcile-js/node_modules
-            ~/.npm
-          key: ${{ runner.os }}-npm-${{ hashFiles('reconcile-js/package-lock.json') }}
-          restore-keys: |
-            ${{ runner.os }}-npm-
-
-      - name: Build website
-        run: scripts/build-website.sh
-
-      - name: Publish reconcile-js to NPM
-        run: |
-          cd reconcile-js
-          cp ../README.md .
-          npm publish --provenance --access public
-
-  build-python-wheels:
-    needs: build
-    if: startsWith(github.ref, 'refs/tags/')
-    strategy:
-      matrix:
-        include:
-          - os: ubuntu-latest
-            target: x86_64
-          - os: ubuntu-latest
-            target: aarch64
-          - os: macos-latest
-            target: x86_64
-          - os: macos-latest
-            target: aarch64
-          - os: windows-latest
-            target: x86_64
-    runs-on: ${{ matrix.os }}
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - uses: actions/setup-python@v6
-        with:
-          python-version: '3.x'
-
-      - name: Copy README
-        run: cp README.md reconcile-python/
-
-      - uses: PyO3/maturin-action@v1
-        with:
-          target: ${{ matrix.target }}
-          args: --release --out dist --find-interpreter
-          manylinux: auto
-          working-directory: reconcile-python
-
-      - uses: actions/upload-artifact@v4
-        with:
-          name: wheels-${{ matrix.os }}-${{ matrix.target }}
-          path: reconcile-python/dist/*.whl
-
-  build-python-sdist:
-    needs: build
-    if: startsWith(github.ref, 'refs/tags/')
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v6
-
-      - name: Copy README
-        run: cp README.md reconcile-python/
-
-      - uses: PyO3/maturin-action@v1
-        with:
-          command: sdist
-          args: --out dist
-          working-directory: reconcile-python
-
-      - uses: actions/upload-artifact@v4
-        with:
-          name: sdist
-          path: reconcile-python/dist/*.tar.gz
-
-  publish-pypi:
-    needs: [build-python-wheels, build-python-sdist]
-    runs-on: ubuntu-latest
-    permissions:
-      id-token: write
-
-    steps:
-      - uses: actions/download-artifact@v4
-        with:
-          pattern: '{wheels-*,sdist}'
-          merge-multiple: true
-          path: dist
-
-      - uses: pypa/gh-action-pypi-publish@release/v1

.github/workflows/gh-pages.yml

@@ -1,72 +0,0 @@
-name: Deploy Website to GitHub Pages
-
-on:
-  push:
-    branches:
-      - main
-  workflow_dispatch:
-
-# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
-permissions:
-  contents: read
-  pages: write
-  id-token: write
-
-# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
-# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
-concurrency:
-  group: 'pages'
-  cancel-in-progress: false
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: write
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v6
-
-      - name: Cache Rust dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cargo/bin/
-            ~/.cargo/registry/index/
-            ~/.cargo/registry/cache/
-            ~/.cargo/git/db/
-            target/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-
-
-      - name: Cache npm dependencies
-        uses: actions/cache@v5
-        with:
-          path: |
-            reconcile-js/node_modules
-            ~/.npm
-          key: ${{ runner.os }}-npm-${{ hashFiles('reconcile-js/package-lock.json') }}
-          restore-keys: |
-            ${{ runner.os }}-npm-
-
-      - name: Build wasm
-        run: |
-          which wasm-pack || cargo install wasm-pack
-          scripts/build-website.sh
-
-      - name: Upload artifact
-        uses: actions/upload-pages-artifact@v4
-        with:
-          path: examples/website/dist
-
-  deploy:
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
-    needs: build
-    steps:
-      - name: Deploy to GitHub Pages
-        id: deployment
-        uses: actions/deploy-pages@v4

.vscode/settings.json

@@ -8,5 +8,8 @@
     },
     "rust-analyzer.cargo.features": [
         "all"
+    ],
+    "python.analysis.extraPaths": [
+        "./reconcile-python/python"
     ]
 }

Cargo.lock

@@ -428,7 +428,7 @@ checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf"
 
 [[package]]
 name = "reconcile-text"
-version = "0.9.3"
+version = "0.11.0"
 dependencies = [
  "console_error_panic_hook",
  "diff-match-patch-rs",

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "reconcile-text"
 description = "Intelligent 3-way text merging with automated conflict resolution"
-version = "0.9.3"
+version = "0.11.0"
 rust-version = "1.94"
 authors = ["Andras Schmelczer <andras@schmelczer.dev>"]
 edition = "2024"

docs/advanced-ts.md

@@ -2,40 +2,65 @@
 
 ## Edit Provenance
 
-Track which changes came from where using `reconcileWithHistory`:
+Track which changes came from where using `reconcileWithHistory`. The result's
+`history` field is typed as `SpanWithHistory[]`, and each span's `history` is a
+`History` string-literal union.
 
-```javascript
+```typescript
-const result = reconcileWithHistory(
+import { reconcileWithHistory, type History, type SpanWithHistory } from 'reconcile-text';
-  'Hello world',
-  'Hello beautiful world',
-  'Hi world'
-);
 
-console.log(result.text);    // "Hi beautiful world"
+const result = reconcileWithHistory('Hello world', 'Hello beautiful world', 'Hi world');
-console.log(result.history); /*
+
-[
+console.log(result.text); // "Hi beautiful world"
-  {
+
-    "text": "Hello",
+const history: SpanWithHistory[] = result.history;
-    "history": "RemovedFromRight"
+console.log(history);
-  },
+// [
-  {
+//   { text: "Hello", history: "RemovedFromRight" },
-    "text": "Hi",
+//   { text: "Hi", history: "AddedFromRight" },
-    "history": "AddedFromRight"
+//   { text: " beautiful", history: "AddedFromLeft" },
-  },
+//   { text: " ", history: "Unchanged" },
-  {
+//   { text: "world", history: "Unchanged" },
-    "text": " beautiful",
+// ]
-    "history": "AddedFromLeft"
+
-  },
+const classByHistory = {
-  {
+  Unchanged: 'merge-unchanged',
-    "text": " ",
+  AddedFromLeft: 'merge-added-left',
-    "history": "Unchanged"
+  AddedFromRight: 'merge-added-right',
-  },
+  RemovedFromLeft: 'merge-removed-left',
-  {
+  RemovedFromRight: 'merge-removed-right',
-    "text": "world",
+} satisfies Record<History, string>;
-    "history": "Unchanged"
+```
+
+Using `satisfies Record<History, string>` keeps the object literal's values
+narrow while forcing every history case to be handled. If a future version adds
+another `History` value, TypeScript will point at this mapping.
+
+For control flow, use the same union as an exhaustiveness check:
+
+```typescript
+import type { History } from 'reconcile-text';
+
+function historyLabel(history: History): string {
+  switch (history) {
+    case 'Unchanged':
+      return 'unchanged';
+    case 'AddedFromLeft':
+      return 'added by left';
+    case 'AddedFromRight':
+      return 'added by right';
+    case 'RemovedFromLeft':
+      return 'removed from left';
+    case 'RemovedFromRight':
+      return 'removed from right';
+    default:
+      return assertNever(history);
   }
-]
+}
-*/
+
+function assertNever(value: never): never {
+  throw new Error(`Unhandled history value: ${value}`);
+}
 ```
 
 ## Tokenisation Strategies
@@ -45,26 +70,162 @@ console.log(result.history); /*
 - **Word tokeniser** (`"Word"`) - Splits on word boundaries (recommended for prose)
 - **Character tokeniser** (`"Character"`) - Individual characters (fine-grained control)
 - **Line tokeniser** (`"Line"`) - Line-by-line (similar to `git merge` or more precisely [`git merge-file`](https://git-scm.com/docs/git-merge-file))
+- **Markdown tokeniser** (`"Markdown"`) - Splits on Markdown structural boundaries (headings, list items, paragraphs)
+
+```typescript
+import { reconcile, type BuiltinTokenizer } from 'reconcile-text';
+
+const tokenizers = [
+  'Word',
+  'Character',
+  'Line',
+  'Markdown',
+] as const satisfies readonly BuiltinTokenizer[];
+
+const result = reconcile('abc', 'axc', 'abyc', 'Character');
+console.log(result.text); // "axyc"
+
+for (const tokenizer of tokenizers) {
+  const merged = reconcile(
+    '# Title\n\n- old item\n',
+    '# Title\n\n- old item\n- left item\n',
+    '# New title\n\n- old item\n',
+    tokenizer
+  );
+
+  console.log(tokenizer, merged.text);
+}
+```
 
 ## Cursor Tracking
 
-`reconcile-text` automatically tracks cursor positions through merges, which is useful for collaborative editors. Selections can be tracked by providing them as a pair of cursors.
+`reconcile-text` automatically tracks cursor positions through merges, which is
+useful for collaborative editors. Selections can be tracked by providing them as
+a pair of cursors.
 
-```javascript
+```typescript
-const result = reconcile(
+import { reconcile, type TextWithOptionalCursors } from 'reconcile-text';
-  'Hello world',
+
-  {
+const left = {
-    text: 'Hello beautiful world',
+  text: 'Hello beautiful world',
-    cursors: [{ id: 1, position: 6 }], // After "Hello "
+  cursors: [{ id: 1, position: 6 }], // After "Hello "
-  },
+} satisfies TextWithOptionalCursors;
-  {
+
-    text: 'Hi world',
+const right = {
-    cursors: [{ id: 2, position: 0 }], // At the beginning
+  text: 'Hi world',
-  }
+  cursors: [{ id: 2, position: 0 }], // At the beginning
-);
+} satisfies TextWithOptionalCursors;
+
+const result = reconcile('Hello world', left, right);
 
 // Result: "Hi beautiful world" with repositioned cursors
-console.log(result.text);    // "Hi beautiful world"
+console.log(result.text); // "Hi beautiful world"
 console.log(result.cursors); // [{ id: 2, position: 0 }, { id: 1, position: 3 }]
 ```
+
 > The `cursors` list is sorted by character position (not IDs).
+
+## Generic Helpers and Inference
+
+The exported merge functions are intentionally small: they merge strings, or
+strings plus cursor metadata. In TypeScript applications, keep domain-specific
+metadata in your own typed wrappers and let inference preserve the surrounding
+shape.
+
+```typescript
+import { reconcile, type BuiltinTokenizer } from 'reconcile-text';
+
+type ReconciledText<T extends { text: string }> = Omit<T, 'text'> & {
+  text: string;
+};
+
+function reconcileDraft<TDraft extends { text: string }>(
+  parent: TDraft,
+  left: TDraft,
+  right: TDraft,
+  tokenizer?: BuiltinTokenizer
+): ReconciledText<TDraft> {
+  return {
+    ...right,
+    text: reconcile(parent.text, left.text, right.text, tokenizer).text,
+  };
+}
+
+interface MarkdownDraft {
+  id: string;
+  text: string;
+  updatedAt: Date;
+}
+
+const parent: MarkdownDraft = {
+  id: 'intro',
+  text: '# Title\n\nOld text\n',
+  updatedAt: new Date('2026-01-01T00:00:00Z'),
+};
+
+const left: MarkdownDraft = {
+  ...parent,
+  text: '# Title\n\nOld text\n\n- left note\n',
+};
+
+const right: MarkdownDraft = {
+  ...parent,
+  text: '# New title\n\nOld text\n',
+};
+
+const merged = reconcileDraft(parent, left, right, 'Markdown');
+// merged is inferred as { id: string; updatedAt: Date; text: string }
+```
+
+Use `satisfies` for configuration objects and cursor payloads when you want
+compile-time checking without widening everything to the library interface.
+
+```typescript
+import type { BuiltinTokenizer, TextWithOptionalCursors } from 'reconcile-text';
+
+const mergeOptions = {
+  tokenizer: 'Markdown',
+  renderDeletedSpans: true,
+} satisfies {
+  tokenizer: BuiltinTokenizer;
+  renderDeletedSpans: boolean;
+};
+
+const documentWithSelection = {
+  text: 'Hello beautiful world',
+  cursors: [
+    { id: 1, position: 6 },
+    { id: 2, position: 15 },
+  ],
+} satisfies TextWithOptionalCursors;
+```
+
+## Compact Diffs
+
+Generate and apply compact diff representations. The TypeScript type is
+`Array<number | string>` for `diff()` and `Array<number | bigint | string>` for
+`undiff()`, because the underlying WebAssembly layer may represent integer
+entries as `bigint`.
+
+```typescript
+import { diff, undiff } from 'reconcile-text';
+
+const original = 'Hello world';
+const changed = 'Hello beautiful world';
+
+// Generate a compact diff
+const changes = diff(original, changed);
+console.log(changes); // [5, " beautiful world"]
+
+// Reconstruct the changed text from the diff
+const reconstructed = undiff(original, changes);
+console.assert(reconstructed === changed);
+```
+
+Diff entries are positive integers (retain N characters), negative integers
+(delete N characters), and strings (insert text).
+
+## Complete Example
+
+For a complete browser example that renders `SpanWithHistory` values and cursor
+selections, see the [example website source](../examples/website/src/index.ts).

examples/website/package-lock.json

@@ -28,7 +28,7 @@
     },
     "../../reconcile-js": {
       "name": "reconcile-text",
-      "version": "0.9.3",
+      "version": "0.11.0",
       "dev": true,
       "license": "MIT",
       "devDependencies": {
@@ -651,16 +651,6 @@
         "node": ">=20.0.0"
       }
     },
-    "node_modules/@trysound/sax": {
-      "version": "0.2.0",
-      "resolved": "https://registry.npmjs.org/@trysound/sax/-/sax-0.2.0.tgz",
-      "integrity": "sha512-L7z9BgrNEcYyUYtF+HaEfiS5ebkh9jXqbszz7pC0hRBPaatV0XjSD3+eHrpqFemQfgwiFF0QPIarnIihIDn7OA==",
-      "dev": true,
-      "license": "ISC",
-      "engines": {
-        "node": ">=10.13.0"
-      }
-    },
     "node_modules/@types/body-parser": {
       "version": "1.19.6",
       "resolved": "https://registry.npmjs.org/@types/body-parser/-/body-parser-1.19.6.tgz",
@@ -1180,9 +1170,9 @@
       }
     },
     "node_modules/ajv": {
-      "version": "8.17.1",
+      "version": "8.18.0",
-      "resolved": "https://registry.npmjs.org/ajv/-/ajv-8.17.1.tgz",
+      "resolved": "https://registry.npmjs.org/ajv/-/ajv-8.18.0.tgz",
-      "integrity": "sha512-B/gBuNg5SiMTrPkC+A2+cW0RszwxYmn6VYxB/inlBStS5nx6xHIt/ehKRhIMhqusl7a8LjQoZnjCs5vhwxOQ1g==",
+      "integrity": "sha512-PlXPeEWMXMZ7sPYOHqmDyCJzcfNrUr3fGNKtezX14ykXOEIvyK81d+qydx89KY5O71FKMPaQ2vBfBFI5NHR63A==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -3396,9 +3386,9 @@
       }
     },
     "node_modules/lodash": {
-      "version": "4.17.21",
+      "version": "4.17.23",
-      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.23.tgz",
-      "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg==",
+      "integrity": "sha512-LgVTMpQtIopCi79SJeDiP0TfWi5CNEc/L/aRdTh3yIvmZXTnheWpKjSZhnvMl8iXbC1tFg9gdHHDMLoV7CnG+w==",
       "dev": true,
       "license": "MIT"
     },
@@ -4550,6 +4540,16 @@
         }
       }
     },
+    "node_modules/sax": {
+      "version": "1.5.0",
+      "resolved": "https://registry.npmjs.org/sax/-/sax-1.5.0.tgz",
+      "integrity": "sha512-21IYA3Q5cQf089Z6tgaUTr7lDAyzoTPx5HRtbhsME8Udispad8dC/+sziTNugOEx54ilvatQ9YCzl4KQLPcRHA==",
+      "dev": true,
+      "license": "BlueOak-1.0.0",
+      "engines": {
+        "node": ">=11.0.0"
+      }
+    },
     "node_modules/schema-utils": {
       "version": "4.3.3",
       "resolved": "https://registry.npmjs.org/schema-utils/-/schema-utils-4.3.3.tgz",
@@ -5098,19 +5098,19 @@
       }
     },
     "node_modules/svgo": {
-      "version": "3.3.2",
+      "version": "3.3.3",
-      "resolved": "https://registry.npmjs.org/svgo/-/svgo-3.3.2.tgz",
+      "resolved": "https://registry.npmjs.org/svgo/-/svgo-3.3.3.tgz",
-      "integrity": "sha512-OoohrmuUlBs8B8o6MB2Aevn+pRIH9zDALSR+6hhqVfa6fRwG/Qw9VUMSMW9VNg2CFc/MTIfabtdOVl9ODIJjpw==",
+      "integrity": "sha512-+wn7I4p7YgJhHs38k2TNjy1vCfPIfLIJWR5MnCStsN8WuuTcBnRKcMHQLMM2ijxGZmDoZwNv8ipl5aTTen62ng==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
-        "@trysound/sax": "0.2.0",
         "commander": "^7.2.0",
         "css-select": "^5.1.0",
         "css-tree": "^2.3.1",
         "css-what": "^6.1.0",
         "csso": "^5.0.5",
-        "picocolors": "^1.0.0"
+        "picocolors": "^1.0.0",
+        "sax": "^1.5.0"
       },
       "bin": {
         "svgo": "bin/svgo"

examples/website/src/index.html

@@ -198,6 +198,8 @@
           <div class="footer-links">
             <a
               href="https://www.npmjs.com/package/reconcile-text"
+              target="_blank"
+              rel="noopener noreferrer"
               aria-label="npm package"
             >
               <svg
@@ -212,6 +214,8 @@
             </a>
             <a
               href="https://pypi.org/project/reconcile-text/"
+              target="_blank"
+              rel="noopener noreferrer"
               aria-label="PyPI package"
             >
               <svg
@@ -226,6 +230,8 @@
             </a>
             <a
               href="https://crates.io/crates/reconcile-text"
+              target="_blank"
+              rel="noopener noreferrer"
               aria-label="crates.io crate"
             >
               <svg
@@ -240,6 +246,8 @@
             </a>
             <a
               href="https://github.com/schmelczer/reconcile"
+              target="_blank"
+              rel="noopener noreferrer"
               aria-label="GitHub repository"
             >
               <svg

examples/website/src/style.scss

@@ -479,27 +479,29 @@ $DOT_RADIUS: 4;
 }
 
 footer {
-  padding: 16px;
+  padding: 32px 16px;
   width: 100%;
-  position: relative;
   display: flex;
   justify-content: center;
   align-items: center;
+  gap: 24px;
   color: $text-secondary;
 }
 
-.github-link > svg {
+.footer-links {
-  position: absolute;
+  display: flex;
+  align-items: center;
+  gap: 16px;
+}
+
+.footer-links > a > svg {
   color: $text-secondary;
-  top: 50%;
+  width: 28px;
-  right: 36px;
+  height: 28px;
-  transform: translateY(-50%);
-  width: 32px;
-  height: 32px;
   transition: transform 0.2s;
 }
 
-.github-link > svg:hover {
+.footer-links > a > svg:hover {
   cursor: pointer;
-  transform: translateY(-50%) scale(1.15);
+  transform: scale(1.15);
 }

reconcile-js/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "reconcile-text",
-  "version": "0.9.3",
+  "version": "0.11.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "reconcile-text",
-      "version": "0.9.3",
+      "version": "0.11.0",
       "license": "MIT",
       "devDependencies": {
         "@types/jest": "^30.0.0",
@@ -24,7 +24,7 @@
     },
     "../pkg": {
       "name": "reconcile-text",
-      "version": "0.9.3",
+      "version": "0.11.0",
       "dev": true,
       "license": "MIT"
     },

reconcile-js/package.json

@@ -1,6 +1,6 @@
 {
   "name": "reconcile-text",
-  "version": "0.9.3",
+  "version": "0.11.0",
   "description": "Intelligent 3-way text merging with automated conflict resolution",
   "main": "dist/reconcile.node.js",
   "browser": "dist/reconcile.web.js",
@@ -18,7 +18,7 @@
   "homepage": "https://schmelczer.dev/reconcile/",
   "repository": {
     "type": "git",
-    "url": "https://github.com/schmelczer/reconcile.git"
+    "url": "git+https://github.com/schmelczer/reconcile.git"
   },
   "bugs": {
     "url": "https://github.com/schmelczer/reconcile/issues",

reconcile-python/Cargo.lock

@@ -104,14 +104,14 @@ dependencies = [
 
 [[package]]
 name = "reconcile-text"
-version = "0.9.3"
+version = "0.11.0"
 dependencies = [
  "thiserror",
 ]
 
 [[package]]
 name = "reconcile-text-python"
-version = "0.9.3"
+version = "0.11.0"
 dependencies = [
  "pyo3",
  "reconcile-text",

reconcile-python/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "reconcile-text-python"
-version = "0.9.3"
+version = "0.11.0"
 edition = "2024"
 rust-version = "1.94"
 authors = ["Andras Schmelczer <andras@schmelczer.dev>"]

reconcile-python/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "maturin"
 
 [project]
 name = "reconcile-text"
-version = "0.9.3"
+version = "0.11.0"
 description = "Intelligent 3-way text merging with automated conflict resolution"
 readme = "README.md"
 license = { text = "MIT" }

reconcile-python/uv.lock

@@ -168,7 +168,7 @@ wheels = [
 
 [[package]]
 name = "reconcile-text"
-version = "0.9.3"
+version = "0.11.0"
 source = { editable = "." }
 
 [package.dev-dependencies]

scripts/lint.sh

@@ -5,9 +5,6 @@ set -e
 which cargo-machete || cargo install cargo-machete
 cargo machete
 
-which lychee || cargo install lychee
-lychee --verbose --exclude npmjs.com README.md
-
 cargo clippy --all-targets --all-features --fix --allow-dirty --allow-staged
 cargo fmt --all
 
@@ -20,6 +17,7 @@ npm ci
 npm run format
 
 cd ../../reconcile-python
+cp ../README.md .
 uv run maturin develop -q
 uv run ruff check python/ tests/
 uv run ruff format python/ tests/

scripts/test.sh

@@ -28,6 +28,7 @@ npm run test
 cd -
 
 cd reconcile-python
+cp ../README.md .
 uv run maturin develop
 uv run pytest -v
 cd -

src/tokenizer/token.rs

@@ -1,4 +1,7 @@
-use std::fmt::Debug;
+use std::{
+    fmt::Debug,
+    hash::{Hash, Hasher},
+};
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -78,3 +81,14 @@ where
         self.normalized == other.normalized
     }
 }
+
+/// Hashes based on the `normalized` field only, consistent with the
+/// [`PartialEq`] implementation.
+impl<T> Hash for Token<T>
+where
+    T: PartialEq + Clone + Debug + Hash,
+{
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.normalized.hash(state);
+    }
+}

src/utils/myers_diff.rs

@@ -11,13 +11,11 @@
 //! The implementation of this algorithm is based on the implementation by
 //! Brandon Williams.
 //!
-//! # Heuristics
+//! # Complexity
 //!
-//! At present this implementation of Myers' does not implement any more
+//! The worst case (completely dissimilar inputs) is `O((N+M)²)` time. In
-//! advanced heuristics that would solve some pathological cases.  For instance
+//! practice the divide-and-conquer strategy with prefix/suffix stripping keeps
-//! passing two large and completely distinct sequences to the algorithm will
+//! subproblems small for typical text.
-//! make it spin without making reasonable progress.
-//! For potential improvements here see [similar#15](https://github.com/mitsuhiko/similar/issues/15).
 
 use std::{
     fmt::Debug,
@@ -41,26 +39,21 @@ pub fn myers_diff<T>(old: &[Token<T>], new: &[Token<T>]) -> Vec<RawOperation<T>>
 where
     T: PartialEq + Clone + Debug,
 {
-    let max_d = (old.len() + new.len()).div_ceil(2) + 1;
+    let max_edit_distance = (old.len() + new.len()).div_ceil(2) + 1;
-    let mut vb = V::new(max_d);
+    let mut backward_endpoints = FurthestEndpoints::new(max_edit_distance);
-    let mut vf = V::new(max_d);
+    let mut forward_endpoints = FurthestEndpoints::new(max_edit_distance);
-    let mut result = Vec::new();
+    let mut result = Vec::with_capacity(old.len() + new.len());
 
     conquer(
         old,
         0..old.len(),
         new,
         0..new.len(),
-        &mut vf,
+        &mut forward_endpoints,
-        &mut vb,
+        &mut backward_endpoints,
         &mut result,
     );
 
-    debug_assert!(
-        result.iter().all(|op| op.tokens().len() == 1),
-        "All operations must be of length 1"
-    );
-
     result
 }
 
@@ -68,50 +61,52 @@ where
 // edges. All D-paths consist of a (D - 1)-path followed by a non-diagonal edge
 // and then a possibly empty sequence of diagonal edges called a snake.
 
-/// `V` contains the endpoints of the furthest reaching `D-paths`. For each
+/// Contains the endpoints of the furthest reaching `D-paths`. For each
-/// recorded endpoint `(x,y)` in diagonal `k`, we only need to retain `x`
+/// recorded endpoint `(x, y)` on diagonal `k`, we only need to retain `x`
-/// because `y` can be computed from `x - k`. In other words, `V` is an array of
+/// because `y` can be computed from `x - k`. In other words, this is an array
-/// integers where `V[k]` contains the row index of the endpoint of the furthest
+/// of integers where `endpoints[k]` contains the row index of the endpoint of
-/// reaching path in diagonal `k`.
+/// the furthest reaching path on diagonal `k`.
 ///
-/// We can't use a traditional Vec to represent `V` since we use `k` as an index
+/// We can't use a traditional Vec since we use `k` as an index and it can take
-/// and it can take on negative values. So instead `V` is represented as a
+/// on negative values. So instead this is a light-weight wrapper around a Vec
-/// light-weight wrapper around a Vec plus an `offset` which is the maximum
+/// plus an `offset` which is the maximum value `k` can take on, used to map
-/// value `k` can take on to map negative `k`'s back to a value >= 0.
+/// negative `k`'s back to a value >= 0.
 #[derive(Debug)]
-struct V {
+struct FurthestEndpoints {
     offset: isize,
-    v: Vec<usize>,
+    endpoints: Vec<usize>,
 }
 
-impl V {
+impl FurthestEndpoints {
-    fn new(max_d: usize) -> Self {
+    fn new(max_edit_distance: usize) -> Self {
-        // max_d should fit in isize for the algorithm to work correctly
+        let offset =
-        let offset = isize::try_from(max_d).expect("max_d must fit in isize");
+            isize::try_from(max_edit_distance).expect("max_edit_distance must fit in isize");
         Self {
             offset,
-            v: vec![0; 2 * max_d + 1],
+            endpoints: vec![0; 2 * max_edit_distance + 1],
         }
     }
 
     fn len(&self) -> usize {
-        self.v.len()
+        self.endpoints.len()
     }
 }
 
-impl Index<isize> for V {
+impl Index<isize> for FurthestEndpoints {
     type Output = usize;
 
-    fn index(&self, index: isize) -> &Self::Output {
+    fn index(&self, diagonal: isize) -> &Self::Output {
-        let idx = usize::try_from(index + self.offset).expect("index + offset must fit in usize");
+        let idx =
-        &self.v[idx]
+            usize::try_from(diagonal + self.offset).expect("diagonal + offset must fit in usize");
+        &self.endpoints[idx]
     }
 }
 
-impl IndexMut<isize> for V {
+impl IndexMut<isize> for FurthestEndpoints {
-    fn index_mut(&mut self, index: isize) -> &mut Self::Output {
+    fn index_mut(&mut self, diagonal: isize) -> &mut Self::Output {
-        let idx = usize::try_from(index + self.offset).expect("index + offset must fit in usize");
+        let idx =
-        &mut self.v[idx]
+            usize::try_from(diagonal + self.offset).expect("diagonal + offset must fit in usize");
+        &mut self.endpoints[idx]
     }
 }
 
@@ -119,6 +114,26 @@ fn split_at(range: Range<usize>, at: usize) -> (Range<usize>, Range<usize>) {
     (range.start..at, at..range.end)
 }
 
+/// Adjust a lower diagonal bound so it has the same parity as `edit_distance`.
+/// Diagonals are visited in steps of 2, so `lower` must share `edit_distance`'s
+/// parity.
+fn align_lower_bound(lower: isize, edit_distance: isize) -> isize {
+    if (lower & 1) == (edit_distance & 1) {
+        lower
+    } else {
+        lower + 1
+    }
+}
+
+/// Adjust an upper diagonal bound so it has the same parity as `edit_distance`.
+fn align_upper_bound(upper: isize, edit_distance: isize) -> isize {
+    if (upper & 1) == (edit_distance & 1) {
+        upper
+    } else {
+        upper - 1
+    }
+}
+
 /// A `Snake` is a sequence of diagonal edges in the edit graph.  Normally
 /// a snake has a start end end point (and it is possible for a snake to have
 /// a length of zero, meaning the start and end points are the same) however
@@ -135,106 +150,143 @@ fn find_middle_snake<T>(
     old_range: Range<usize>,
     new: &[Token<T>],
     new_range: Range<usize>,
-    vf: &mut V,
+    forward_endpoints: &mut FurthestEndpoints,
-    vb: &mut V,
+    backward_endpoints: &mut FurthestEndpoints,
 ) -> Option<(usize, usize)>
 where
     T: PartialEq + Clone + Debug,
 {
-    let n = old_range.len();
+    let old_len = old_range.len();
-    let m = new_range.len();
+    let new_len = new_range.len();
+
+    let old_len_signed = isize::try_from(old_len).expect("old_len must fit in isize");
+    let new_len_signed = isize::try_from(new_len).expect("new_len must fit in isize");
 
     // By Lemma 1 in the paper, the optimal edit script length is odd or even as
     // `delta` is odd or even.
-    let delta = isize::try_from(n).expect("n must fit in isize")
+    let delta = old_len_signed - new_len_signed;
-        - isize::try_from(m).expect("m must fit in isize");
+    let delta_is_odd = delta & 1 == 1;
-    let odd = delta & 1 == 1;
 
     // The initial point at (0, -1)
-    vf[1] = 0;
+    forward_endpoints[1] = 0;
     // The initial point at (N, M+1)
-    vb[1] = 0;
+    backward_endpoints[1] = 0;
 
-    let d_max = (n + m).div_ceil(2) + 1;
+    let max_edit_distance = (old_len + new_len).div_ceil(2) + 1;
-    assert!(vf.len() >= d_max);
+    assert!(forward_endpoints.len() >= max_edit_distance);
-    assert!(vb.len() >= d_max);
+    assert!(backward_endpoints.len() >= max_edit_distance);
+
+    let max_edit_distance_signed =
+        isize::try_from(max_edit_distance).expect("max_edit_distance must fit in isize");
+
+    for edit_distance in 0..max_edit_distance_signed {
+        // Tighter diagonal bounds: on diagonal k = x - y the constraints
+        // 0 <= x <= old_len and 0 <= y <= new_len give k in [-new_len, old_len].
+        // Intersect with the algorithm's [-edit_distance, edit_distance]
+        // range and snap to the correct parity (k advances in steps of 2).
+        let forward_diagonal_lo =
+            align_lower_bound((-edit_distance).max(-new_len_signed), edit_distance);
+        let forward_diagonal_hi =
+            align_upper_bound(edit_distance.min(old_len_signed), edit_distance);
 
-    let d_max_isize = isize::try_from(d_max).expect("d_max must fit in isize");
-    for d in 0..d_max_isize {
         // Forward path
-        for k in (-d..=d).rev().step_by(2) {
+        for diagonal in (forward_diagonal_lo..=forward_diagonal_hi).rev().step_by(2) {
-            let mut x = if k == -d || (k != d && vf[k - 1] < vf[k + 1]) {
+            let mut old_idx = if diagonal == -edit_distance
-                vf[k + 1]
+                || (diagonal != edit_distance
+                    && forward_endpoints[diagonal - 1] < forward_endpoints[diagonal + 1])
+            {
+                forward_endpoints[diagonal + 1]
             } else {
-                vf[k - 1] + 1
+                forward_endpoints[diagonal - 1] + 1
             };
-            let y = usize::try_from(isize::try_from(x).expect("x must fit in isize") - k)
+            let new_idx = usize::try_from(
-                .expect("x - k must be non-negative and fit in usize");
+                isize::try_from(old_idx).expect("old_idx must fit in isize") - diagonal,
+            )
+            .expect("old_idx - diagonal must be non-negative and fit in usize");
 
             // The coordinate of the start of a snake
-            let (x0, y0) = (x, y);
+            let (snake_start_old, snake_start_new) = (old_idx, new_idx);
-            //  While these sequences are identical, keep moving through the
+
-            //  graph with no cost
+            // While these sequences are identical, keep moving through the
-            if x < old_range.len() && y < new_range.len() {
+            // graph with no cost
+            if old_idx < old_range.len() && new_idx < new_range.len() {
                 let advance = common_prefix_len(
                     old,
-                    old_range.start + x..old_range.end,
+                    old_range.start + old_idx..old_range.end,
                     new,
-                    new_range.start + y..new_range.end,
+                    new_range.start + new_idx..new_range.end,
                 );
-                x += advance;
+                old_idx += advance;
             }
 
             // This is the new best x value
-            vf[k] = x;
+            forward_endpoints[diagonal] = old_idx;
 
             // Only check for connections from the forward search when N - M is
             // odd and when there is a reciprocal k line coming from the other
-            // direction.
+            // direction. Forward diagonal k maps to backward diagonal
-            if odd && (k - delta).abs() <= (d - 1) {
+            // (delta - k). Overlap occurs when the combined forward + backward
-                // TODO optimise this so we don't have to compare against n
+            // reach covers the full width:
-                if vf[k] + vb[-(k - delta)] >= n {
+            //   forward_endpoints[k] + backward_endpoints[delta - k] >= old_len.
-                    // Return the snake
+            if delta_is_odd
-                    return Some((x0 + old_range.start, y0 + new_range.start));
+                && (diagonal - delta).abs() <= (edit_distance - 1)
-                }
+                && forward_endpoints[diagonal] + backward_endpoints[-(diagonal - delta)] >= old_len
+            {
+                return Some((
+                    snake_start_old + old_range.start,
+                    snake_start_new + new_range.start,
+                ));
             }
         }
 
-        // Backward path
+        let backward_diagonal_lo =
-        for k in (-d..=d).rev().step_by(2) {
+            align_lower_bound((-edit_distance).max(-new_len_signed), edit_distance);
-            let mut x = if k == -d || (k != d && vb[k - 1] < vb[k + 1]) {
+        let backward_diagonal_hi =
-                vb[k + 1]
+            align_upper_bound(edit_distance.min(old_len_signed), edit_distance);
-            } else {
-                vb[k - 1] + 1
-            };
-            let mut y = usize::try_from(isize::try_from(x).expect("x must fit in isize") - k)
-                .expect("x - k must be non-negative and fit in usize");
 
-            // The coordinate of the start of a snake
+        // Backward path
-            if x < n && y < m {
+        for diagonal in (backward_diagonal_lo..=backward_diagonal_hi)
+            .rev()
+            .step_by(2)
+        {
+            let mut old_idx = if diagonal == -edit_distance
+                || (diagonal != edit_distance
+                    && backward_endpoints[diagonal - 1] < backward_endpoints[diagonal + 1])
+            {
+                backward_endpoints[diagonal + 1]
+            } else {
+                backward_endpoints[diagonal - 1] + 1
+            };
+            let mut new_idx = usize::try_from(
+                isize::try_from(old_idx).expect("old_idx must fit in isize") - diagonal,
+            )
+            .expect("old_idx - diagonal must be non-negative and fit in usize");
+
+            // Extend the snake backward (matching suffix)
+            if old_idx < old_len && new_idx < new_len {
                 let advance = common_suffix_len(
                     old,
-                    old_range.start..old_range.start + n - x,
+                    old_range.start..old_range.start + old_len - old_idx,
                     new,
-                    new_range.start..new_range.start + m - y,
+                    new_range.start..new_range.start + new_len - new_idx,
                 );
-                x += advance;
+                old_idx += advance;
-                y += advance;
+                new_idx += advance;
             }
 
             // This is the new best x value
-            vb[k] = x;
+            backward_endpoints[diagonal] = old_idx;
 
-            if !odd && (k - delta).abs() <= d {
+            if !delta_is_odd
-                // TODO optimise this so we don't have to compare against n
+                && (diagonal - delta).abs() <= edit_distance
-                if vb[k] + vf[-(k - delta)] >= n {
+                && backward_endpoints[diagonal] + forward_endpoints[-(diagonal - delta)] >= old_len
-                    // Return the snake
+            {
-                    return Some((n - x + old_range.start, m - y + new_range.start));
+                return Some((
-                }
+                    old_len - old_idx + old_range.start,
+                    new_len - new_idx + new_range.start,
+                ));
             }
         }
-
-        // TODO: Maybe there's an opportunity to optimise and bail early?
     }
 
     None
@@ -245,54 +297,72 @@ fn conquer<T>(
     mut old_range: Range<usize>,
     new: &[Token<T>],
     mut new_range: Range<usize>,
-    vf: &mut V,
+    forward_endpoints: &mut FurthestEndpoints,
-    vb: &mut V,
+    backward_endpoints: &mut FurthestEndpoints,
     result: &mut Vec<RawOperation<T>>,
 ) where
     T: PartialEq + Clone + Debug,
 {
     // Check for common prefix
-    let common_prefix_len = common_prefix_len(old, old_range.clone(), new, new_range.clone());
+    let prefix_len = common_prefix_len(old, old_range.clone(), new, new_range.clone());
-    if common_prefix_len > 0 {
+    if prefix_len > 0 {
         result.extend(
-            old[old_range.start..old_range.start + common_prefix_len]
+            old[old_range.start..old_range.start + prefix_len]
                 .iter()
                 .map(|token| RawOperation::Equal(vec![token.clone()])),
         );
     }
-    old_range.start += common_prefix_len;
+    old_range.start += prefix_len;
-    new_range.start += common_prefix_len;
+    new_range.start += prefix_len;
 
     // Check for common suffix
-    let common_suffix_len = common_suffix_len(old, old_range.clone(), new, new_range.clone());
+    let suffix_len = common_suffix_len(old, old_range.clone(), new, new_range.clone());
-    let common_suffix = (
+    let suffix_start = old_range.end - suffix_len;
-        old_range.end - common_suffix_len,
+    old_range.end -= suffix_len;
-        new_range.end - common_suffix_len,
+    new_range.end -= suffix_len;
-    );
-    old_range.end -= common_suffix_len;
-    new_range.end -= common_suffix_len;
 
     if old_range.is_empty() && new_range.is_empty() {
         // do nothing
     } else if new_range.is_empty() {
         result.extend(
-            old[old_range.start..old_range.start + old_range.len()]
+            old[old_range.start..old_range.end]
                 .iter()
                 .map(|token| RawOperation::Delete(vec![token.clone()])),
         );
     } else if old_range.is_empty() {
         result.extend(
-            new[new_range.start..new_range.start + new_range.len()]
+            new[new_range.start..new_range.end]
                 .iter()
                 .map(|token| RawOperation::Insert(vec![token.clone()])),
         );
-    } else if let Some((x_start, y_start)) =
+    } else if let Some((split_old, split_new)) = find_middle_snake(
-        find_middle_snake(old, old_range.clone(), new, new_range.clone(), vf, vb)
+        old,
-    {
+        old_range.clone(),
-        let (old_a, old_b) = split_at(old_range, x_start);
+        new,
-        let (new_a, new_b) = split_at(new_range, y_start);
+        new_range.clone(),
-        conquer(old, old_a, new, new_a, vf, vb, result);
+        forward_endpoints,
-        conquer(old, old_b, new, new_b, vf, vb, result);
+        backward_endpoints,
+    ) {
+        let (old_before, old_after) = split_at(old_range, split_old);
+        let (new_before, new_after) = split_at(new_range, split_new);
+        conquer(
+            old,
+            old_before,
+            new,
+            new_before,
+            forward_endpoints,
+            backward_endpoints,
+            result,
+        );
+        conquer(
+            old,
+            old_after,
+            new,
+            new_after,
+            forward_endpoints,
+            backward_endpoints,
+            result,
+        );
     } else {
         result.extend(
             old[old_range.start..old_range.end]
@@ -306,9 +376,9 @@ fn conquer<T>(
         );
     }
 
-    if common_suffix_len > 0 {
+    if suffix_len > 0 {
         result.extend(
-            old[common_suffix.0..common_suffix.0 + common_suffix_len]
+            old[suffix_start..suffix_start + suffix_len]
                 .iter()
                 .map(|token| RawOperation::Equal(vec![token.clone()])),
         );