/**
 * Cloudflare API 客户端:真实调用 api.cloudflare.com / dash.cloudflare.com。
 *
 * OAuth access token 来自 Cloudflare OAuth 授权(docs/02),Console 用它完成
 * 账号/域名发现、Email Worker 部署与 Email Routing 配置。
 *
 * OAuth 客户端凭据(client id / secret)有两个来源,settings 表优先、env 兜底:
 *   1. settings 表 —— 在「设置 → Cloudflare 接入」里填写;secret 用 AES-GCM 加密存储
 *      (cf_oauth_client_secret_enc),只回 last4。保存后立即生效,无需重新部署。
 *   2. env 变量 CF_OAUTH_CLIENT_ID / CF_OAUTH_CLIENT_SECRET —— 部署时注入的兜底。
 * 两者都没有时不提供任何降级通道,接入接口直接返回 503,避免出现"看似接入成功"的假数据。
 */

import { renderEmailWorkerScript } from "../../../shared/src/index.ts";
import type { Env } from "../env.ts";
import { decryptSecret, encryptSecret, getSetting, setSetting } from "../db.ts";

/** # 成员变量: OAuth 授权端点 **/
export const CF_OAUTH_AUTHORIZE_URL = "https://dash.cloudflare.com/oauth2/auth";

/** # 成员变量: OAuth token 端点 **/
export const CF_OAUTH_TOKEN_URL = "https://dash.cloudflare.com/oauth2/token";

/** # 成员变量: Cloudflare API 基址 **/
export const CF_API_BASE = "https://api.cloudflare.com/client/v4";

/** # 成员变量: 授权回调路径 **/
export const CF_OAUTH_CALLBACK_PATH = "/api/oauth/cloudflare/callback";

/** # 成员变量: 本应用实际需要的 scope(点号分隔;与 Cloudflare OAuth App 里勾选的权限对应)
 *
 *  重要背景(实测结论):
 *  - Cloudflare 第三方 OAuth 客户端的 scope 是 **点号分隔** 的 `<group>.<verb>`;
 *    `account:read` 这种冒号写法是 **wrangler 的第一方简写**,第三方客户端请求会被直接拒。
 *  - 「账号」不是 `account.read` 而是 `account-settings.read`(选择器里叫 Account Settings Read);
    它只用来取账号名,**默认不请求** —— 缺它时 discover() 会从 zone 的 account_id 反推账户。
 *  - Email Routing 在选择器里是 **四个独立权限**,其中改 catch-all 规则对应
 *    `email-routing-rule.write`(选择器里叫 Email Routing Rules Edit)。
 *  - 客户端注册的 scope 是「上限」而不是「默认值」:请求里没写的 scope 不会自动生效。
 *  以上名称可用 /cloudflare/preflight 的 scope 探测功能现场核对(见 discoverAllowedScopes)。
 **/
export const CF_OAUTH_SCOPES_DEFAULT = [
  "zone.read",
  "workers-scripts.write",
  "email-routing-rule.write",
].join(" ");

/** # 成员变量: scope 探测候选集(本应用所需 + 常见备选)
 *  探测时逐个试:被 Cloudflare 点名拒绝的剔除,剩下的即为 App 已授权的集合。 **/
export const CF_OAUTH_SCOPE_CANDIDATES = [
  "account-settings.read",
  "zone.read",
  "workers-scripts.write",
  "email-routing-rule.write",
  "email-routing-account-rule.read",
  "email-routing-address.write",
  "email-routing-suppression.write",
  "zone-settings.read",
];

/** # 成员变量: settings 表中保存 OAuth 客户端凭据的 key **/
export const CF_OAUTH_SETTING_KEYS = {
  clientId: "cf_oauth_client_id",
  secretEnc: "cf_oauth_client_secret_enc",
  secretLast4: "cf_oauth_client_secret_last4",
  scopes: "cf_oauth_scopes",
} as const;

/** # 成员变量: 已解析的 Cloudflare OAuth 客户端凭据 **/
export interface CFOAuthClient {
  clientId: string;
  clientSecret: string;
  /** 凭据来源:settings(后台设置)优先,env(部署变量)兜底 */
  source: "settings" | "env";
}

/** # 函数
 * 解析当前生效的 Cloudflare OAuth 客户端凭据(settings 优先,env 兜底)
 * 返回值: 未配置时 null
 */
export async function getOAuthClient(env: Env): Promise<CFOAuthClient | null> {
  const [clientId, secretEnc] = await Promise.all([
    getSetting(env, CF_OAUTH_SETTING_KEYS.clientId),
    getSetting(env, CF_OAUTH_SETTING_KEYS.secretEnc),
  ]);
  if (clientId && secretEnc) {
    try {
      const secret = await decryptSecret(env, secretEnc);
      if (secret) return { clientId, clientSecret: secret, source: "settings" };
    } catch {
      // 密文损坏(主密钥变更等)时继续尝试 env 兜底
    }
  }
  if (env.CF_OAUTH_CLIENT_ID && env.CF_OAUTH_CLIENT_SECRET) {
    return { clientId: env.CF_OAUTH_CLIENT_ID, clientSecret: env.CF_OAUTH_CLIENT_SECRET, source: "env" };
  }
  return null;
}

/** # 函数
 * Cloudflare OAuth 是否已配置(settings 或 env 任一来源可用)
 */
export async function isOAuthConfigured(env: Env): Promise<boolean> {
  return (await getOAuthClient(env)) !== null;
}

/** # 函数
 * OAuth 客户端凭据的展示用元信息(不含明文 secret)
 */
export async function oauthClientMeta(
  env: Env,
): Promise<{ client_id: string; has_secret: boolean; secret_last4: string; source: "settings" | "env" | "none" }> {
  const client = await getOAuthClient(env);
  if (!client) return { client_id: "", has_secret: false, secret_last4: "", source: "none" };
  const last4 = await getSetting(env, CF_OAUTH_SETTING_KEYS.secretLast4);
  return {
    client_id: client.clientId,
    has_secret: true,
    secret_last4: client.source === "settings" ? (last4 ?? "") : client.clientSecret.slice(-4),
    source: client.source,
  };
}

/** # 函数
 * 保存 OAuth 客户端凭据到 settings(secret 加密存储,只留 last4 供展示)
 */
export async function saveOAuthClient(env: Env, clientId: string, secret: string): Promise<void> {
  await setSetting(env, CF_OAUTH_SETTING_KEYS.clientId, clientId);
  await setSetting(env, CF_OAUTH_SETTING_KEYS.secretEnc, await encryptSecret(env, secret));
  await setSetting(env, CF_OAUTH_SETTING_KEYS.secretLast4, secret.slice(-4));
}

/** # 函数
 * 清除 settings 中的 OAuth 客户端凭据(env 兜底不受影响)
 */
export async function clearOAuthClient(env: Env): Promise<void> {
  for (const key of Object.values(CF_OAUTH_SETTING_KEYS)) {
    await env.DB.prepare("DELETE FROM settings WHERE key = ?").bind(key).run();
  }
}

/** # 函数
 * 解析实际请求的 scope 列表(settings 覆盖默认值;空白回退默认)
 */
export async function getOAuthScopes(env: Env): Promise<string> {
  const custom = (await getSetting(env, CF_OAUTH_SETTING_KEYS.scopes))?.trim();
  return custom || CF_OAUTH_SCOPES_DEFAULT;
}

/** # 函数
 * 拼出 Cloudflare 授权页 URL
 */
export function buildAuthorizeUrl(opts: { clientId: string; redirectUri: string; scopes: string; state: string }): string {
  return (
    `${CF_OAUTH_AUTHORIZE_URL}?response_type=code` +
    `&client_id=${encodeURIComponent(opts.clientId)}` +
    `&redirect_uri=${encodeURIComponent(opts.redirectUri)}` +
    `&scope=${encodeURIComponent(opts.scopes)}` +
    `&state=${encodeURIComponent(opts.state)}`
  );
}

/** # 成员变量: 授权配置自检结果 **/
export interface OAuthPreflight {
  /** 授权端点是否接受当前 client_id / redirect_uri / scope 组合 */
  ok: boolean;
  /** Cloudflare 返回的 Location 指向(登录同意页 = 配置正确) */
  location: string;
  /** 错误码(invalid_scope / invalid_request / access_denied ...) */
  error: string | null;
  /** 错误描述原文 */
  description: string | null;
  /** 给用户的处置建议 */
  hint: string | null;
  /** 本次自检使用的参数 */
  used: { client_id: string; redirect_uri: string; scope: string };
  /** scope 探测结果:App 已授权 / 尚未授权 */
  scopes: { allowed: string[]; denied: string[]; probed: boolean; note: string | null };
}

/** # 函数
 * 授权配置自检:用当前配置请求 Cloudflare 授权端点但**不跟随跳转**,
 * 据跳转目标判断 OAuth App 是否配置正确(纯只读探测,不会产生授权)。
 * 这样不用开浏览器就能验证 Client URI 校验、是否已 promote to public、scope 是否已授权。
 */
export async function preflightOAuth(env: Env, requestOrigin: string): Promise<OAuthPreflight> {
  const client = await getOAuthClient(env);
  const redirectUri = oauthRedirectUri(env, requestOrigin);
  const scope = await getOAuthScopes(env);
  const used = { client_id: client?.clientId ?? "", redirect_uri: redirectUri, scope };
  const noScopes = { allowed: [], denied: [], probed: false, note: null };
  if (!client) {
    return {
      ok: false,
      location: "",
      error: "not_configured",
      description: "尚未配置 Cloudflare OAuth 客户端",
      hint: "先在下方填入 Client ID 与 Client Secret 并保存",
      used,
      scopes: noScopes,
    };
  }
  let resp: Response;
  try {
    resp = await fetch(
      buildAuthorizeUrl({ clientId: client.clientId, redirectUri, scopes: scope, state: "wmh_preflight" }),
      { redirect: "manual" },
    );
  } catch (err) {
    return {
      ok: false,
      location: "",
      error: "network",
      description: err instanceof Error ? err.message : String(err),
      hint: "Console 无法访问 dash.cloudflare.com,请检查出网",
      used,
      scopes: noScopes,
    };
  }
  const location = resp.headers.get("location") ?? "";
  if (resp.status >= 300 && resp.status < 400 && location) {
    const target = new URL(location, redirectUri);
    const callbackBase = redirectUri.split("?")[0];
    // Cloudflare 拒绝授权时有两种落点:弹回我们登记的回调地址,或跳它自己的 /oauth/error 页
    const isCallbackBounce = location.startsWith(callbackBase);
    const isCfErrorPage = target.origin === "https://dash.cloudflare.com" && target.pathname.startsWith("/oauth/");
    if (isCallbackBounce || isCfErrorPage) {
      const error = target.searchParams.get("error");
      const description = target.searchParams.get("error_description");
      // 被拒的是 scope 时顺便探测出「已授权 / 待勾选」,省得用户猜选择器里该勾哪几项
      const scopes =
        error === "invalid_scope"
          ? await discoverAllowedScopes(client.clientId, redirectUri)
          : { allowed: [], denied: [], probed: false, note: null };
      return { ok: false, location, error, description, hint: hintForOAuthError(error), used, scopes };
    }
    // 跳到登录/同意页 = client_id、redirect_uri、scope 全部被接受
    return { ok: true, location, error: null, description: null, hint: null, used, scopes: noScopes };
  }
  return {
    ok: false,
    location,
    error: `http_${resp.status}`,
    description: `授权端点返回 HTTP ${resp.status}`,
    hint: "检查 Client ID 是否正确",
    used,
    scopes: noScopes,
  };
}

/** # 函数
 * scope 探测:授权端点在**显示同意页之前**就会校验 scope,被拒时通过 error_description 点名是哪一个。
 *  于是可以逐轮「请求剩余候选 → 剔除被点名的那个」,收敛出该 App 实际已授权的集合。
 *  全程无需登录/同意,不产生任何授权;每轮一个未认证请求。
 *  返回值: allowed=已授权、denied=尚未授权(需在选择器里补勾)
 */
async function probeScopes(
  clientId: string,
  redirectUri: string,
): Promise<{ allowed: string[]; denied: string[]; error: string | null }> {
  const remaining = [...CF_OAUTH_SCOPE_CANDIDATES];
  const denied: string[] = [];
  for (let i = 0; i < CF_OAUTH_SCOPE_CANDIDATES.length + 1; i++) {
    if (remaining.length === 0) return { allowed: [], denied, error: null };
    let location = "";
    try {
      const resp = await fetch(
        buildAuthorizeUrl({ clientId, redirectUri, scopes: remaining.join(" "), state: "wmh_preflight" }),
        { redirect: "manual" },
      );
      location = resp.headers.get("location") ?? "";
    } catch {
      return { allowed: remaining, denied, error: "network" };
    }
    if (!location) return { allowed: remaining, denied, error: "no_redirect" };
    const target = new URL(location, redirectUri);
    const error = target.searchParams.get("error");
    if (error !== "invalid_scope") {
      // 其它错误(回调地址不匹配等)与 scope 无关,停止并把剩余当作"未知"
      return { allowed: remaining, denied, error };
    }
    const named = /scope '([^']+)'/.exec(target.searchParams.get("error_description") ?? "")?.[1];
    const rejected = named && remaining.includes(named) ? named : remaining[0];
    denied.push(rejected);
    remaining.splice(remaining.indexOf(rejected), 1);
  }
  return { allowed: remaining, denied, error: null };
}

/** # 函数
 * 对外包装的 scope 探测:返回可直接展示给用户的结果
 */
export async function discoverAllowedScopes(
  clientId: string,
  redirectUri: string,
): Promise<OAuthPreflight["scopes"]> {
  const res = await probeScopes(clientId, redirectUri);
  if (res.error) {
    return {
      allowed: res.allowed,
      denied: res.denied,
      probed: false,
      note: `scope 探测中断(${res.error});请在 Cloudflare App 里逐项核对权限`,
    };
  }
  return { allowed: res.allowed, denied: res.denied, probed: true, note: null };
}

/** # 函数
 * 把 Cloudflare 授权错误翻译成可执行的处置建议
 */
function hintForOAuthError(error: string | null): string | null {
  if (error === "invalid_scope") {
    return (
      "OAuth App 不允许请求本应用需要的某些 scope。到 Cloudflare Dashboard → My Profile → OAuth Applications " +
      "编辑该应用:Client URI 填 Console 域名(如 https://wmailhub.adx9.com)、按提示加 TXT 记录完成域名校验、" +
      "Promote to public,并在选择器里勾选下方「待勾选」列出的权限。客户端注册的 scope 是上限而非默认," +
      "没勾的权限即使账号有也不会生效。"
    );
  }
  if (error === "invalid_request") {
    return (
      "请求被拒:最常见是回调地址(Redirect URL)与应用里登记的不一致——请把本页显示的回调地址原样填进 " +
      "Cloudflare OAuth App 的 Redirect URL(本应用不会用其它地址回调)。"
    );
  }
  if (error === "access_denied") {
    return "授权被拒绝:请在 Cloudflare 页面确认同意授权。";
  }
  return null;
}

/** # 函数
 * 计算 OAuth 授权回调地址(优先 CF_OAUTH_REDIRECT_URI,其次 PUBLIC_BASE_URL,最后请求 origin)
 */
export function oauthRedirectUri(env: Env, requestOrigin: string): string {
  const base = env.CF_OAUTH_REDIRECT_URI ?? env.PUBLIC_BASE_URL ?? requestOrigin;
  return base.endsWith(CF_OAUTH_CALLBACK_PATH)
    ? base
    : `${base.replace(/\/$/, "")}${CF_OAUTH_CALLBACK_PATH}`;
}

/** # 成员变量: 邮件发现的 Cloudflare 资源描述 **/
export interface CFAccount {
  id: string;
  name: string;
}

export interface CFZone {
  id: string;
  name: string;
  account_id: string;
  status: string;
}

/** # 成员变量: 账号/域名发现结果 **/
export interface CFDiscovery {
  /** 目标 Cloudflare 账户(id + 展示名) */
  account: CFAccount;
  /** 该账户(或 token 可见)下的域名 Zone */
  zones: CFZone[];
  /** 账号来源:accounts 接口,或因缺少账号级读权限而从 zone 的 account_id 反推 */
  accountSource: "accounts" | "zones";
}

/** # 成员变量: Cloudflare API 客户端接口(自动安装所需操作) **/
export interface CFApi {
  /** 用 code 换 access token */
  exchangeToken(code: string, redirectUri: string): Promise<{ accessToken: string; expiresIn: number }>;
  /** 发现 token 可访问的账户 + 其下域名 */
  discover(accessToken: string): Promise<CFDiscovery>;
  /** 创建或更新账号级 Email Worker(幂等) */
  putEmailWorker(opts: {
    accessToken: string;
    accountId: string;
    scriptName: string;
    /** Console 对外地址(Worker -> Console) **/
    consoleUrl: string;
    /** Worker 身份(与 WorkerCredential.worker_id 一致) **/
    workerId: string;
    /** Worker credential secret(HMAC 签名密钥) **/
    workerSecret: string;
  }): Promise<{ id: string }>;
  /** 开启 Zone 的 Email Routing(幂等) */
  enableEmailRouting(opts: { accessToken: string; zoneId: string }): Promise<{ enabled: boolean }>;
  /** 配置 Zone catch-all 规则指向 Email Worker(幂等) */
  setCatchAllRule(opts: {
    accessToken: string;
    zoneId: string;
    workerName: string;
  }): Promise<{ ok: boolean }>;
}

/** # 函数
 * 构造 Cloudflare API 客户端(内部使用已解析的 OAuth 客户端凭据)
 * 返回值: 未配置 OAuth 客户端时抛错(调用方应先判断 isOAuthConfigured)
 */
export async function getCFApi(env: Env): Promise<CFApi> {
  const client = await getOAuthClient(env);
  if (!client) throw new Error("cloudflare oauth not configured");
  return new RealCFApi(client);
}

/** # 成员变量: Cloudflare API 实现 **/
export class RealCFApi implements CFApi {
  /** # 成员变量: OAuth 客户端凭据(settings 或 env) **/
  constructor(private client: CFOAuthClient) {}

  async exchangeToken(code: string, redirectUri: string) {
    const resp = await fetch(CF_OAUTH_TOKEN_URL, {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded" },
      body: new URLSearchParams({
        grant_type: "authorization_code",
        code,
        client_id: this.client.clientId,
        client_secret: this.client.clientSecret,
        redirect_uri: redirectUri,
      }),
    });
    if (!resp.ok) throw new Error(`cloudflare token exchange failed: ${resp.status}`);
    const data = (await resp.json()) as { access_token: string; expires_in?: number };
    return { accessToken: data.access_token, expiresIn: data.expires_in ?? 3600 };
  }

  private async api<T>(token: string, path: string, init?: RequestInit): Promise<T> {
    const resp = await fetch(`${CF_API_BASE}${path}`, {
      ...init,
      headers: {
        Authorization: `Bearer ${token}`,
        "Content-Type": "application/json",
        ...(init?.headers ?? {}),
      },
    });
    const data = (await resp.json()) as { success: boolean; errors?: { message: string }[]; result: T };
    if (!data.success) throw new Error(`cloudflare api ${path}: ${data.errors?.[0]?.message ?? resp.status}`);
    return data.result;
  }

  listAccounts(token: string) {
    return this.api<CFAccount[]>(token, "/accounts");
  }

  async listZones(token: string, accountId?: string) {
    // 分页拉全 Zone(每页 50,最多 20 页);不给 accountId 时返回 token 可见的全部 Zone
    const out: CFZone[] = [];
    for (let page = 1; page <= 20; page++) {
      const query = new URLSearchParams({ per_page: "50", page: String(page) });
      if (accountId) query.set("account.id", accountId);
      const rows = await this.api<CFZone[]>(token, `/zones?${query.toString()}`);
      out.push(...rows);
      if (rows.length < 50) break;
    }
    return out;
  }

  /** 账号 + 域名发现。
   *  优先用 /accounts 拿账户名(需要账号级读权限);
   *  没有该权限时退而求其次:直接列 token 可见的 Zone,用 zone 自带的 account_id 反推账户,
   *  展示名用第一个域名代替 —— 这样只要授权了 zone.read 就能完成接入。 */
  async discover(token: string): Promise<CFDiscovery> {
    try {
      const accounts = await this.listAccounts(token);
      if (accounts.length > 0) {
        const account = accounts[0];
        return { account, zones: await this.listZones(token, account.id), accountSource: "accounts" };
      }
    } catch {
      // 缺少账号级读权限,走下面的反推路径
    }
    const zones = await this.listZones(token);
    if (zones.length === 0) throw new Error("no cloudflare zone accessible with this token");
    const accountId = zones[0].account_id;
    const more = zones.length > 1 ? ` 等 ${zones.length} 个域名` : "";
    return { account: { id: accountId, name: `${zones[0].name}${more}` }, zones, accountSource: "zones" };
  }

  async putEmailWorker(opts: {
    accessToken: string;
    accountId: string;
    scriptName: string;
    consoleUrl: string;
    workerId: string;
    workerSecret: string;
  }) {
    // Email Worker 即带 email handler 的 Worker 脚本;Console 地址与 Worker 凭据以明文常量打进脚本,
    // 避免给 Worker 配置额外的 secrets 绑定(docs/11 §8:凭据本身经 HMAC 保护 Console API)。
    const script = renderEmailWorkerScript(opts.consoleUrl, opts.workerId, opts.workerSecret);
    const form = new FormData();
    form.append(
      "metadata",
      new Blob([JSON.stringify({ main_module: "worker.js", bindings: [] })], { type: "application/json" }),
    );
    form.append("worker.js", new Blob([script], { type: "application/javascript+module" }));
    const resp = await fetch(
      `${CF_API_BASE}/accounts/${opts.accountId}/workers/scripts/${opts.scriptName}`,
      {
        method: "PUT",
        headers: { Authorization: `Bearer ${opts.accessToken}` },
        body: form,
      },
    );
    if (!resp.ok) throw new Error(`upload email worker failed: ${resp.status}`);
    return { id: opts.scriptName };
  }

  async enableEmailRouting(opts: { accessToken: string; zoneId: string }) {
    await this.api(opts.accessToken, `/zones/${opts.zoneId}/email/routing`, {
      method: "POST",
      body: JSON.stringify({ enabled: true, skip_wizard: true }),
    });
    return { enabled: true };
  }

  async setCatchAllRule(opts: { accessToken: string; zoneId: string; workerName: string }) {
    await this.api(opts.accessToken, `/zones/${opts.zoneId}/email/routing/rules/catch_all`, {
      method: "PUT",
      body: JSON.stringify({
        matchers: [{ type: "all" }],
        actions: [{ type: "worker", value: [opts.workerName] }],
        enabled: true,
        name: "wmailhub catch-all",
      }),
    });
    return { ok: true };
  }
}