/**
 * OpenCode Zen short-window rate-limit guidance (#1145 / OCX-56).
 *
 * OpenCode's keyed and keyless Zen chat endpoints share `https://opencode.ai/zen/v1`.
 * Free-model traffic can hit a short-window burst ceiling around 15–20 RPM
 * (community-measured). Zen often answers with opaque `429 Rate limit exceeded`
 * bodies and may omit `Retry-After` / `X-RateLimit-*`; when those headers are
 * present they still take precedence. Distinct from the keyless desktop
 * ~200 requests / 5h quota documented on `opencode-free`.
 */
import { validateClientRetryAfterHeader } from "../lib/retry-after";
import { registryEntryForProviderDestination } from "./registry";

const OPENCODE_ZEN_PROVIDER_IDS = new Set(["opencode-zen", "opencode-free"]);

/** Observed free-model burst ceiling on Zen (not an official OpenCode figure). */
export const OPENCODE_ZEN_OBSERVED_RPM_HINT = "roughly 15-20 requests per minute";

/**
 * Synthetic client backoff when Zen omits Retry-After after a rate-limit 429.
 * Longer than the generic 2s default so Codex-shaped clients do not immediately
 * re-hammer a ~15-20 RPM window.
 */
export const OPENCODE_ZEN_SYNTHETIC_RETRY_AFTER_SEC = 15;

const ENRICHMENT_MARKER = "15-20 requests per minute";

export function isOpenCodeZenRateLimitProvider(opts: {
  providerName?: string;
  baseUrl?: string;
  adapter?: string;
}): boolean {
  const name = opts.providerName?.trim();
  if (name && OPENCODE_ZEN_PROVIDER_IDS.has(name)) return true;
  const baseUrl = opts.baseUrl?.trim();
  if (!baseUrl) return false;
  const entry = registryEntryForProviderDestination({
    baseUrl,
    adapter: opts.adapter?.trim() || "openai-chat",
    authMode: "key",
  });
  return entry !== undefined && OPENCODE_ZEN_PROVIDER_IDS.has(entry.id);
}

/**
 * Same-key `retryOn429` only applies on key-authenticated HTTP paths — not
 * keyless `opencode-free` traffic and not custom `runTurn` transports.
 */
export function supportsOpenCodeZenRetryOn429Guidance(opts: {
  authMode?: string;
  hasApiKey?: boolean;
  supportsHttpSameKeyRetry?: boolean;
}): boolean {
  if (opts.supportsHttpSameKeyRetry === false) return false;
  if (opts.authMode !== undefined && opts.authMode !== "key") return false;
  return opts.hasApiKey === true;
}

/**
 * Append actionable Zen rate-limit context to a generic upstream 429 message and
 * embed a parseable `try again in Ns` hint so {@link resolveClientRetryAfter}
 * surfaces a useful Retry-After when the gateway sent none.
 */
export function enrichOpenCodeZenRateLimitMessage(
  message: string,
  opts: {
    status: number;
    providerName?: string;
    baseUrl?: string;
    adapter?: string;
    authMode?: string;
    hasApiKey?: boolean;
    /** Upstream Retry-After header; when valid, skip the synthetic 15s text hint. */
    upstreamRetryAfter?: string | null;
    /** False for custom `runTurn` transports outside the HTTP retry loop. */
    supportsHttpSameKeyRetry?: boolean;
    now?: number;
  },
): string {
  if (opts.status !== 429) return message;
  if (!isOpenCodeZenRateLimitProvider(opts)) return message;
  if (!/rate\s*limit/i.test(message)) return message;
  if (message.includes(ENRICHMENT_MARKER)) return message;

  const upstreamRetry = validateClientRetryAfterHeader(
    opts.upstreamRetryAfter,
    opts.now ?? Date.now(),
  );
  const retryHint = upstreamRetry || /try again in \d/i.test(message)
    ? ""
    : ` Try again in ${OPENCODE_ZEN_SYNTHETIC_RETRY_AFTER_SEC}s.`;
  const paceHint = supportsOpenCodeZenRetryOn429Guidance(opts)
    ? " Slow the request pace, or set providers.opencode-zen.retryOn429 for same-key backoff."
    : " Slow the request pace.";
  return (
    `${message}`
    + ` OpenCode Zen free-model traffic is often limited to ${OPENCODE_ZEN_OBSERVED_RPM_HINT}`
    + ` (observed; OpenCode does not publish this RPM, and may omit rate-limit headers).`
    + `${retryHint}`
    + paceHint
  );
}