feat: add visual-diff package with syntax highlighting

packages/visual-diff/README.md

@@ -0,0 +1,204 @@
+# @interweb/visual-diff
+
+Beautiful visual diff with syntax highlighting for terminal and HTML output.
+
+## Features
+
+- Line-by-line diff computation with LCS algorithm
+- Syntax highlighting for 15+ languages (JavaScript, TypeScript, Python, SQL, Go, Rust, and more)
+- Beautiful terminal output with ANSI colors
+- HTML output with dark/light mode support
+- 6 built-in themes (default, github, monokai, dracula, nord, minimal)
+- Customizable themes and styling
+- Side-by-side and unified diff views
+- Parse and create unified diff format
+
+## Installation
+
+```bash
+npm install @interweb/visual-diff
+# or
+pnpm add @interweb/visual-diff
+# or
+yarn add @interweb/visual-diff
+```
+
+## Quick Start
+
+```typescript
+import { diff, renderTerminal, renderHtml } from '@interweb/visual-diff';
+
+const oldCode = `function hello() {
+  console.log("Hello");
+}`;
+
+const newCode = `function hello() {
+  console.log("Hello, World!");
+}`;
+
+// Compute the diff
+const result = diff(oldCode, newCode);
+
+// Render to terminal with syntax highlighting
+console.log(renderTerminal(result, { 
+  language: 'javascript',
+  theme: 'dracula'
+}));
+
+// Render to HTML
+const html = renderHtml(result, {
+  language: 'javascript',
+  darkMode: true
+});
+```
+
+## API
+
+### Diff Functions
+
+#### `diff(oldContent, newContent, options?)`
+
+Computes the diff between two strings.
+
+```typescript
+const result = diff(oldContent, newContent, {
+  context: 3,           // Number of context lines (default: 3)
+  ignoreWhitespace: false,  // Ignore whitespace differences
+  ignoreCase: false     // Ignore case differences
+});
+```
+
+#### `diffFiles(oldContent, newContent, oldFile, newFile, options?)`
+
+Computes diff with file metadata and auto-detected language.
+
+```typescript
+const result = diffFiles(
+  oldContent,
+  newContent,
+  'src/old.ts',
+  'src/new.ts'
+);
+// result.language will be 'typescript'
+```
+
+### Render Functions
+
+#### `renderTerminal(result, options?)`
+
+Renders diff to terminal with ANSI colors.
+
+```typescript
+const output = renderTerminal(result, {
+  theme: 'github',        // Theme name or custom theme
+  showLineNumbers: true,  // Show line numbers
+  syntaxHighlight: true,  // Enable syntax highlighting
+  language: 'typescript', // Override language detection
+  colorize: true          // Enable ANSI colors
+});
+```
+
+#### `renderHtml(result, options?)`
+
+Renders diff to HTML.
+
+```typescript
+const html = renderHtml(result, {
+  theme: 'monokai',
+  darkMode: true,
+  className: 'my-diff',
+  inlineStyles: true,
+  syntaxHighlight: true
+});
+```
+
+#### `renderHtmlDocument(result, options?)`
+
+Renders a complete HTML document with the diff.
+
+#### `renderHtmlSideBySide(result, options?)`
+
+Renders diff in side-by-side layout.
+
+### Themes
+
+Built-in themes:
+- `default` - Clean default theme
+- `github` - GitHub-style colors
+- `monokai` - Monokai editor theme
+- `dracula` - Dracula theme
+- `nord` - Nord color palette
+- `minimal` - Minimal styling
+
+#### Custom Themes
+
+```typescript
+import { createTheme } from '@interweb/visual-diff';
+
+const myTheme = createTheme('custom', {
+  added: { fg: 'cyan', bold: true },
+  removed: { fg: 'yellow' },
+  syntax: {
+    keyword: { fg: 'magenta', bold: true },
+    string: { fg: 'green' }
+  }
+});
+
+renderTerminal(result, { theme: myTheme });
+```
+
+### Syntax Highlighting
+
+Supported languages:
+- JavaScript / TypeScript
+- Python
+- JSON
+- HTML / XML
+- CSS / SCSS
+- SQL
+- YAML
+- Markdown
+- Go
+- Rust
+- Java
+- C / C++
+- Shell / Bash
+
+#### Language Detection
+
+```typescript
+import { detectLanguage } from '@interweb/visual-diff';
+
+detectLanguage('file.ts');  // 'typescript'
+detectLanguage('file.py');  // 'python'
+detectLanguage('file.sql'); // 'sql'
+```
+
+### Unified Diff Format
+
+```typescript
+import { createUnifiedDiff, parseUnifiedDiff } from '@interweb/visual-diff';
+
+// Create unified diff string
+const unified = createUnifiedDiff(result);
+
+// Parse unified diff string
+const parsed = parseUnifiedDiff(unifiedDiffString);
+```
+
+### Utilities
+
+```typescript
+import { hasDifferences, countChanges } from '@interweb/visual-diff';
+
+// Check if there are any differences
+if (hasDifferences(result)) {
+  // Get counts
+  const { additions, deletions } = countChanges(result);
+  console.log(`+${additions} -${deletions}`);
+}
+```
+
+## License
+
+MIT