// Surgical line-level update for JSON5 files that preserves comments and
// formatting. Used by saveClientTranslations so that the Nitro localization
// files keep their headers and section markers when an admin edits a value.
//
// Assumptions (true for every Nitro `.json5` file in the repo):
//   * one entry per line, formatted as `<key>: <value>,`
//   * keys are simple strings (single- or double-quoted, or bare)
//   * values are strings (single- or double-quoted)
// If a changed key cannot be located via this contract, we report it back so
// the caller can decide whether to fall back to a full re-serialization.

export interface PatchResult {
  /** The new file content, with surgical edits applied. */
  content: string
  /** Keys that we could not patch surgically (missing or unusual format). */
  unpatchedKeys: string[]
}

function escapeRegExp(s: string): string {
  return s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
}

function escapeForQuote(value: string, quote: '"' | "'"): string {
  // Escape backslashes first, then the chosen quote. Newlines/tabs are
  // preserved as escape sequences so we don't break the JSON5 parser.
  let out = value.replace(/\\/g, '\\\\')
  out = out.replace(new RegExp(quote, 'g'), `\\${quote}`)
  out = out.replace(/\n/g, '\\n').replace(/\r/g, '\\r').replace(/\t/g, '\\t')
  return out
}

/**
 * Apply per-key value updates to a JSON5 source string while preserving
 * comments and formatting. Only keys present in `original` (and with a
 * different value in `updated`) are touched.
 */
export function patchJson5(
  raw: string,
  original: Record<string, string>,
  updated: Record<string, string>,
): PatchResult {
  let result = raw
  const unpatchedKeys: string[] = []

  for (const [key, newVal] of Object.entries(updated)) {
    if (!(key in original)) {
      // Key did not exist on disk — append/merge logic is the caller's job.
      unpatchedKeys.push(key)
      continue
    }
    if (original[key] === newVal) continue

    const keyPattern = `(['"]?)${escapeRegExp(key)}\\1\\s*:\\s*(["'])((?:\\\\.|(?!\\2).)*)\\2`
    const re = new RegExp(keyPattern)
    const idx = result.search(re)
    if (idx < 0) {
      unpatchedKeys.push(key)
      continue
    }
    const match = re.exec(result)
    if (!match) {
      unpatchedKeys.push(key)
      continue
    }

    const valueQuote = match[2] as '"' | "'"
    const oldValueLen = match[3].length
    const fullLen = match[0].length
    // prefix keeps everything up to and including the opening value quote
    const prefix = match[0].slice(0, fullLen - oldValueLen - 1)
    const escaped = escapeForQuote(newVal, valueQuote)
    const replacement = prefix + escaped + valueQuote

    result = result.slice(0, idx) + replacement + result.slice(idx + fullLen)
  }

  return { content: result, unpatchedKeys }
}