/**
 * lang-detect.ts — Map file paths to highlight.js language identifiers.
 *
 * Pure function, no DOM or hljs dependency — fully unit-testable.
 * Used by blob.ts and diff.ts for client-side syntax highlighting.
 */

const EXT_MAP: Record<string, string> = {
  py: 'python', pyw: 'python',
  ts: 'typescript', tsx: 'typescript',
  js: 'javascript', jsx: 'javascript', mjs: 'javascript', cjs: 'javascript',
  rs: 'rust',
  go: 'go',
  swift: 'swift',
  kt: 'kotlin', kts: 'kotlin',
  java: 'java',
  rb: 'ruby', rake: 'ruby',
  cpp: 'cpp', cc: 'cpp', cxx: 'cpp', c: 'cpp', h: 'cpp', hpp: 'cpp',
  hs: 'haskell',
  json: 'json', jsonc: 'json',
  yaml: 'yaml', yml: 'yaml',
  toml: 'toml',
  bats: 'bash',
  sh: 'bash', bash: 'bash', zsh: 'bash',
  html: 'xml', htm: 'xml', xml: 'xml', svg: 'xml',
  css: 'css', scss: 'css', sass: 'css',
  sql: 'sql',
  md: 'markdown', mdx: 'markdown',
  txt: 'plaintext',
};

/** Dotfiles with no extension, keyed by exact filename. */
const FILENAME_MAP: Record<string, string> = {
  '.museattributes': 'toml',
  '.museignore': 'toml',
};

/**
 * Return the highlight.js language identifier for a file path.
 * Falls back to `'plaintext'` for unknown extensions.
 */
export function extToLang(path: string): string {
  const filename = path.split('/').pop() ?? path;
  if (filename in FILENAME_MAP) return FILENAME_MAP[filename]!;
  // Zsh completion files: _<command> with no extension (e.g. completions/_muse)
  if (filename.startsWith('_') && !filename.includes('.')) return 'bash';
  const ext = filename.split('.').pop()?.toLowerCase() ?? '';
  return EXT_MAP[ext] ?? 'plaintext';
}