import { redactText } from "../rss/redact.ts";
import { detectChallenge } from "./challenge.ts";
import type { SiteRateLimiter } from "./rate-limit.ts";
import { SiteError } from "./types.ts";

export interface SiteHttpContext {
  siteId: string;
  fetch: typeof globalThis.fetch;
  limiter: SiteRateLimiter;
  timeoutMs: number;
  userAgent?: string;
  now: () => Date;
}

function retryAfterMs(res: Response, now: Date): number | undefined {
  const v = res.headers.get("retry-after");
  if (!v) return undefined;
  if (/^\d+$/.test(v.trim())) return Number(v.trim()) * 1000;
  const t = Date.parse(v);
  return Number.isNaN(t) ? undefined : Math.max(0, t - now.getTime());
}

/**
 * 站点请求:先取站点令牌,再发请求;Cloudflare 挑战(`cf-mitigated: challenge`,或 403 / 503 / 429 的挑战页)→ `challenge`
 * (不是凭据错误,CF-2);其余 429/503 统一映射并顺延限流器。
 * 返回的 Response 由调用方消费。错误消息只含脱敏后的 URL。
 */
export async function siteFetch(
  ctx: SiteHttpContext,
  url: string,
  init: RequestInit & { signal?: AbortSignal } = {},
): Promise<Response> {
  await ctx.limiter.acquire(init.signal ?? undefined);
  const timeout = AbortSignal.timeout(ctx.timeoutMs);
  const signal = init.signal ? AbortSignal.any([init.signal, timeout]) : timeout;
  const headers = new Headers(init.headers);
  if (ctx.userAgent && !headers.has("user-agent")) headers.set("user-agent", ctx.userAgent);
  const safeUrl = redactText(url);
  let res: Response;
  try {
    res = await ctx.fetch(url, { ...init, headers, signal });
  } catch (e) {
    if (init.signal?.aborted) throw e;
    const reason = timeout.aborted ? "超时" : (e as Error).message;
    throw new SiteError(ctx.siteId, "network", redactText(`请求 ${safeUrl} 失败:${reason}`));
  }
  const ch = await detectChallenge(res);
  res = ch.res;
  if (ch.rule) {
    await res.body?.cancel().catch(() => {});
    throw new SiteError(ctx.siteId, "challenge", `请求 ${safeUrl}:站点要求人机验证(Cloudflare)`, {
      httpStatus: res.status,
      detail: { reason: "challenge", rule: ch.rule, httpStatus: res.status },
    });
  }
  if (res.status === 429 || res.status === 503) {
    const ra = retryAfterMs(res, ctx.now());
    await res.body?.cancel().catch(() => {});
    if (ra !== undefined) ctx.limiter.penalize(ra);
    throw new SiteError(
      ctx.siteId,
      res.status === 429 ? "rate_limited" : "site_maintenance",
      `请求 ${safeUrl} 返回 HTTP ${res.status}`,
      { httpStatus: res.status, ...(ra !== undefined ? { retryAfterMs: ra } : {}) },
    );
  }
  if (res.status >= 500) {
    await res.body?.cancel().catch(() => {});
    throw new SiteError(ctx.siteId, "site_maintenance", `请求 ${safeUrl} 返回 HTTP ${res.status}`, {
      httpStatus: res.status,
    });
  }
  return res;
}

/** 读取响应体并限制大小(默认 16 MiB,足够容纳 .torrent 与列表页)。 */
export async function readBody(ctx: SiteHttpContext, res: Response, maxBytes = 16 * 1024 * 1024): Promise<Uint8Array> {
  if (!res.body) return new Uint8Array();
  const reader = res.body.getReader();
  const chunks: Uint8Array[] = [];
  let total = 0;
  for (;;) {
    const { done, value } = await reader.read();
    if (done) break;
    total += value.byteLength;
    if (total > maxBytes) {
      await reader.cancel().catch(() => {});
      throw new SiteError(ctx.siteId, "parse_error", `响应超过 ${maxBytes} 字节上限`);
    }
    chunks.push(value);
  }
  const out = new Uint8Array(total);
  let off = 0;
  for (const c of chunks) {
    out.set(c, off);
    off += c.byteLength;
  }
  return out;
}

export async function readText(ctx: SiteHttpContext, res: Response): Promise<string> {
  return new TextDecoder("utf-8").decode(await readBody(ctx, res));
}