import { ensureSchema, getRawDb } from "../../../lib/mvp-db";
import { getRuntimeEnv } from "../../../lib/runtime-env";
import {
  buildWecomOAuthUrl,
  exchangeWecomOAuthCode,
  resolveWecomConfig,
  WecomClientError,
  type WecomBindings,
} from "../../../lib/wecom-client";
import { getRequestPrincipal } from "../../../lib/user-auth";
import {
  signWecomBindState,
  verifyWecomBindState,
} from "../../../lib/wecom-oauth-service";

const env = getRuntimeEnv();

function bindResultPage(
  title: string,
  message: string,
  options: { ok?: boolean; status?: number; redirectHome?: boolean } = {},
) {
  const ok = options.ok ?? false;
  const html = `<!doctype html>
<html lang="zh-CN">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>${title}</title>
<style>
  body { margin:0; min-height:100vh; display:flex; align-items:center; justify-content:center;
    background:#f4f6f5; font-family:-apple-system,"PingFang SC","Microsoft YaHei",sans-serif; color:#1f2a26; }
  .card { width:min(420px, calc(100% - 40px)); padding:32px 28px; border:1px solid #e3e8e5; border-radius:16px;
    background:#fff; text-align:center; }
  .icon { width:44px; height:44px; margin:0 auto 14px; border-radius:50%; display:flex; align-items:center;
    justify-content:center; font-size:22px; font-weight:700; color:#fff; }
  .ok .icon { background:#2f9e75; } .fail .icon { background:#c9503f; }
  h1 { margin:0 0 10px; font-size:17px; }
  p { margin:0 0 18px; font-size:13px; line-height:1.8; color:#5f6a65; word-break:break-all; }
  a { display:inline-block; padding:9px 22px; border-radius:10px; background:#2f9e75; color:#fff;
    font-size:13px; text-decoration:none; }
</style>
</head>
<body>
<div class="card ${ok ? "ok" : "fail"}">
  <div class="icon">${ok ? "✓" : "!"}</div>
  <h1>${title}</h1>
  <p>${message}</p>
  <a href="/">回到工作台</a>
</div>
${options.redirectHome ? "<script>setTimeout(function(){location.href = '/';},1500)</script>" : ""}
</body>
</html>`;
  return new Response(html, {
    status: options.status ?? 200,
    headers: {
      "content-type": "text/html; charset=utf-8",
      "cache-control": "private, no-store",
    },
  });
}

function appOrigin(requestUrl: URL) {
  const configured = String(env.APP_ORIGIN ?? "").trim().replace(/\/$/, "");
  return configured || requestUrl.origin;
}

async function handleStart(request: Request, requestUrl: URL) {
  const principal = await getRequestPrincipal(request);
  if (!principal || principal.kind !== "user") {
    return Response.redirect(new URL("/", requestUrl).toString(), 302);
  }
  const config = resolveWecomConfig(env as unknown as WecomBindings);
  if (!config.corpId || !config.agentId || !config.secret) {
    return bindResultPage(
      "暂不可用",
      "服务器未配置企业微信自建应用（WECOM_CORP_ID / WECOM_AGENT_ID / WECOM_SECRET），请联系管理员。",
      { status: 503 },
    );
  }
  const state = await signWecomBindState(principal.user.id);
  const redirectUri = `${appOrigin(requestUrl)}/api/wecom-bind`;
  return new Response(null, {
    status: 302,
    headers: {
      location: buildWecomOAuthUrl({
        corpId: config.corpId,
        agentId: config.agentId,
        redirectUri,
        state,
      }),
      "cache-control": "private, no-store",
    },
  });
}

async function handleCallback(request: Request, requestUrl: URL) {
  const code = String(requestUrl.searchParams.get("code") ?? "").trim();
  const state = String(requestUrl.searchParams.get("state") ?? "").trim();
  if (!code || !state) {
    return bindResultPage("绑定失败", "缺少企业微信授权参数，请回到工作台重新发起绑定。", {
      status: 400,
    });
  }
  const verified = await verifyWecomBindState(state);
  if (!verified) {
    return bindResultPage(
      "绑定链接已过期",
      "本次授权会话已失效（10 分钟内有效），请回到工作台重新点击「企业微信授权绑定」。",
      { status: 400 },
    );
  }
  const principal = await getRequestPrincipal(request);
  if (
    !principal ||
    principal.kind !== "user" ||
    principal.user.id !== verified.userId
  ) {
    return bindResultPage(
      "登录态校验失败",
      "请先在本浏览器登录发起绑定的那个后台账号，再重新完成企业微信授权。",
      { status: 403 },
    );
  }
  const config = resolveWecomConfig(env as unknown as WecomBindings);
  let identity: { userId?: string; externalUserId?: string };
  try {
    identity = await exchangeWecomOAuthCode(config, code);
  } catch (error) {
    const message =
      error instanceof WecomClientError
        ? error.message
        : "企业微信授权身份换取失败，请稍后重试。";
    return bindResultPage("绑定失败", message, { status: 502 });
  }
  if (!identity.userId) {
    return bindResultPage(
      "无法绑定",
      "当前企微身份不是企业内部成员（外部联系人不能绑定后台账号），请用企业内部成员身份授权。",
      { status: 400 },
    );
  }
  await ensureSchema();
  const db = getRawDb();
  const conflict = await db
    .prepare(
      "SELECT id, username FROM users WHERE wecom_userid = ? AND id <> ? LIMIT 1",
    )
    .bind(identity.userId, principal.user.id)
    .first<{ id: string; username: string }>();
  if (conflict) {
    return bindResultPage(
      "该企微账号已被绑定",
      `企微账号 ${identity.userId} 已绑定到后台账号「${conflict.username}」，如需换绑请联系管理员在「用户管理」中处理。`,
      { status: 409 },
    );
  }
  await db
    .prepare(
      "UPDATE users SET wecom_userid = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?",
    )
    .bind(identity.userId, principal.user.id)
    .run();
  return bindResultPage(
    "绑定成功",
    `已将企微账号 ${identity.userId} 绑定到当前后台账号，正在返回工作台…`,
    { ok: true, redirectHome: true },
  );
}

export async function GET(request: Request) {
  const requestUrl = new URL(request.url);
  if (requestUrl.searchParams.has("code")) {
    return handleCallback(request, requestUrl);
  }
  return handleStart(request, requestUrl);
}