/**
 * Low-level RunPod transport. Every model runs as its own RunPod endpoint; this
 * handles the common request envelope, bearer auth, and both response modes:
 *
 *   - `/runsync` (preferred): the job runs synchronously and the body already
 *     contains `output` (or IS the output for a custom handler).
 *   - `/run`: returns `{ id, status }`; we poll `/status/{id}` until the job
 *     reaches a terminal state or the time budget (kept under the 60s serverless
 *     function cap) is exhausted.
 *
 * RUNPOD_API_KEY is read here so callers never handle the secret directly, and
 * it is NEVER echoed into an error message. Upstream error bodies are truncated
 * to 160 chars before being surfaced.
 *
 * PROVENANCE: a faithful port of
 * `advance-photo-gallery-web-sdk/apps/web/src/lib/runpod/client.ts` (same 55s
 * budget, same polling, same RunpodError.status mapping).
 *
 * SERVER-ONLY.
 */

export class RunpodError extends Error {
  status: number;
  constructor(message: string, status = 502) {
    super(message);
    this.name = "RunpodError";
    this.status = status;
  }
}

export interface RunpodCallOpts {
  /** Human label used in error messages, e.g. "sd-inpaint". */
  name: string;
  /** Full endpoint URL from the per-model env var (…/runsync or …/run). */
  url: string;
  input: Record<string, unknown>;
  /** Total budget for the whole call incl. polling. Default 55s (< the 60s cap). */
  timeoutMs?: number;
  pollIntervalMs?: number;
}

interface RunpodEnvelope {
  id?: string;
  status?: string;
  output?: unknown;
  error?: unknown;
}

export async function runpodCall<TOut = unknown>(opts: RunpodCallOpts): Promise<TOut> {
  const { name, url, input } = opts;
  const timeoutMs = opts.timeoutMs ?? 55_000;
  const pollIntervalMs = opts.pollIntervalMs ?? 1500;

  const key = process.env.RUNPOD_API_KEY;
  if (!key) throw new RunpodError("RUNPOD_API_KEY is not set.", 500);

  const deadline = Date.now() + timeoutMs;
  const authHeaders = { authorization: `Bearer ${key}` };

  let res: Response;
  try {
    res = await fetch(url, {
      method: "POST",
      headers: { "content-type": "application/json", ...authHeaders },
      body: JSON.stringify({ input }),
      signal: AbortSignal.timeout(timeoutMs),
      cache: "no-store",
    });
  } catch {
    throw new RunpodError(`Could not reach RunPod (${name}).`, 502);
  }
  if (!res.ok) {
    // Truncated on purpose — never surface a full upstream body to the client.
    const detail = (await res.text().catch(() => "")).slice(0, 160);
    throw new RunpodError(`RunPod ${name} error (${res.status}). ${detail}`.trim(), 502);
  }

  const data = (await res.json().catch(() => null)) as RunpodEnvelope | null;
  if (!data || typeof data !== "object") {
    throw new RunpodError(`RunPod ${name} returned an invalid response.`, 502);
  }

  // Terminal failure reported in a job envelope.
  if (data.status === "FAILED" || data.status === "CANCELLED") {
    throw new RunpodError(`RunPod ${name} job ${data.status.toLowerCase()}.`, 502);
  }
  // No job id → this is not an async envelope; the body itself is the output.
  // Covers custom /runsync handlers that return their result directly, even when
  // it carries a `status` field (e.g. "success").
  if (data.id === undefined) {
    return (data.output !== undefined ? data.output : data) as TOut;
  }
  // Job envelope that already carries a completed/inline output.
  if (data.output !== undefined && (data.status === undefined || data.status === "COMPLETED")) {
    return data.output as TOut;
  }

  // Async: poll /status/{id} until COMPLETED / FAILED / the time budget runs out.
  // Each wait + fetch is clamped to the remaining budget so the whole call stays
  // under `timeoutMs` (kept below the 60s function cap).
  const statusUrl = url.replace(/\/run(sync)?(\/?)$/, `/status/${data.id}`);
  for (;;) {
    const remaining = deadline - Date.now();
    if (remaining < 500) break; // not enough budget for another round
    await sleep(Math.min(pollIntervalMs, remaining));
    const left = deadline - Date.now();
    if (left <= 0) break;
    let sres: Response;
    try {
      sres = await fetch(statusUrl, {
        headers: authHeaders,
        signal: AbortSignal.timeout(Math.min(10_000, Math.max(1000, left))),
        cache: "no-store",
      });
    } catch {
      continue; // transient — keep polling until the deadline
    }
    if (!sres.ok) continue;
    const sdata = (await sres.json().catch(() => null)) as RunpodEnvelope | null;
    if (!sdata) continue;
    if (sdata.status === "COMPLETED") return sdata.output as TOut;
    if (sdata.status === "FAILED" || sdata.status === "CANCELLED") {
      throw new RunpodError(`RunPod ${name} job ${sdata.status.toLowerCase()}.`, 502);
    }
  }
  throw new RunpodError(
    `RunPod ${name} timed out (raise the endpoint's speed or use /runsync).`,
    504,
  );
}

function sleep(ms: number): Promise<void> {
  return new Promise((resolve) => setTimeout(resolve, ms));
}