// In-memory cache of the most recent relay-reported credit balance + tier.
// Updated every time a relay provider call lands (success or 4xx error
// that includes the standard envelope). Exposed via /api/relay/status
// so the UI can render the "N credits remaining · Tier: X" banner
// without re-hitting the relay just for status.
//
// Not persisted to disk — the relay is the source of truth. We just cache
// the last response so the UI doesn't have to wait for the next request
// to refresh the display. On a fresh boot the cache is empty until the
// first /api/relay/status call, which can optionally probe the relay.

let lastSnapshot = {
  creditsRemaining: null,   // number | null
  tier: null,               // "core" | "pro" | "max" | null
  lastUpdated: null,        // ms-epoch | null
  lastError: null,          // string | null
};

// Called by the relay provider on every response (including error
// responses that the relay annotated with the standard envelope).
// `envelope` is the parsed JSON shape: { credits_remaining, tier, ... }.
export function updateRelayState(envelope) {
  if (!envelope || typeof envelope !== "object") return;
  if (typeof envelope.credits_remaining === "number") {
    lastSnapshot.creditsRemaining = envelope.credits_remaining;
  }
  if (typeof envelope.tier === "string") {
    lastSnapshot.tier = envelope.tier;
  }
  lastSnapshot.lastUpdated = Date.now();
  lastSnapshot.lastError = null;
}

// Record a relay error (network failure, 5xx with no envelope, etc.).
// Surfaced in the UI status so the user knows the balance display is stale.
export function recordRelayError(message) {
  lastSnapshot.lastError = (message || "Unknown relay error").slice(0, 300);
  lastSnapshot.lastUpdated = Date.now();
}

export function getRelayState() {
  return { ...lastSnapshot };
}

export function resetRelayState() {
  lastSnapshot = {
    creditsRemaining: null,
    tier: null,
    lastUpdated: null,
    lastError: null,
  };
}