// Friendly copy for WebAuthn ceremony failures — pure and DOM-free so it's
// unit-testable in Node (home/test/ceremony-errors.test.mjs) and shared by the
// home pages (home.js, enroll.js, restore.js).
//
// The browser's ceremony errors are famously opaque (NotAllowedError is the
// catch-all for "cancelled", "timed out", "blocked", and "no credential"), so
// members read a specific, human sentence instead of an exception name. The
// technical detail (error name + the phase tag backup-core.js attaches) is
// deliberately kept — parenthesised after the sentence — because it's the only
// signal we have when debugging a member's report.

// friendlyCeremonyError maps a ceremony failure to member-facing copy.
// `ceremony` is the intent the user pressed: "signin" (credentials.get) or
// "create" (credentials.create). Returns { message, detail }: message is the
// friendly sentence, detail the technical crumb (e.g. "NotAllowedError [create]").
export function friendlyCeremonyError(err, ceremony) {
  const name = (err && err.name) || "";
  const phase = err && err.phase ? " [" + err.phase + "]" : "";
  const detail = (name || "Error") + phase;
  const creating = ceremony === "create";
  switch (name) {
    case "NotAllowedError":
      // Cancelled, timed out, or the browser refused — indistinguishable by
      // design, so the copy covers both the deliberate and the accidental read.
      return {
        message: creating
          ? "Creating your sign-in was cancelled. If you didn't cancel, try again."
          : "Sign in was cancelled. If you didn't cancel, try again.",
        detail,
      };
    case "InvalidStateError":
      // Duplicate registration: the device already holds a matching sign-in.
      if (creating) return { message: "That's already set up. Try signing in instead.", detail };
      break;
    case "ConstraintError":
    case "NotSupportedError":
      // In practice: user verification is required but the device has nothing
      // to verify with — no screen lock set up.
      return {
        message: "This device needs a screen lock, PIN, fingerprint, or face unlock before it can sign in this way.",
        detail,
      };
    case "SecurityError":
      // RP id / origin mismatch — a deployment problem, not the member's.
      return { message: "Sign-in isn't configured for this website address.", detail };
    case "AbortError":
      return { message: "Sign-in was interrupted. Try again.", detail };
  }
  // Anything else (network errors, our own thrown Errors) already carries a
  // human message — pass it through under the same shape.
  return { message: (err && err.message) || String(err), detail };
}

// formatCeremonyError composes the one-line status string every caller renders:
// the friendly sentence plus the kept-on-purpose technical detail.
export function formatCeremonyError(err, ceremony) {
  const { message, detail } = friendlyCeremonyError(err, ceremony);
  return message + " (" + detail + ")";
}