import { useEffect, useState } from "react";
import { Link, useNavigate } from "react-router-dom";
import { useAuth } from "../App";
import { Logo } from "../components/icons";
import { Button, Field, InlineAlert } from "../components/ui";
import { ApiError, api, session, type Tokens } from "../lib/client";
import type { User } from "../lib/types";

const EMAIL_RE = /^[^@\s]{1,64}@[^@\s]{1,190}\.[A-Za-z]{2,}$/;

/** 跟后端 `password_problem` 同一套规则；本地只做"别白跑一趟"的提示，真判定在服务端。 */
function passwordHint(password: string): string | null {
  if (password.length < 8) return "至少 8 位";
  if (password.length > 64) return "最多 64 位";
  if (!/[A-Za-z]/.test(password) || !/\d/.test(password)) return "要同时有字母和数字";
  return null;
}

/**
 * 注册：邮箱 + 验证码 + 密码。
 *
 * 为什么必须先验一次邮箱：短信登录关掉以后，邮箱是账号名也是唯一联系方式，
 * "随手填一个" 会让账号变成没人能找回的孤岛。
 */
export function RegisterPage() {
  const { reload } = useAuth();
  const navigate = useNavigate();
  const [email, setEmail] = useState("");
  const [code, setCode] = useState("");
  const [password, setPassword] = useState("");
  const [confirm, setConfirm] = useState("");
  const [nickname, setNickname] = useState("");
  const [countdown, setCountdown] = useState(0);
  const [sent, setSent] = useState(false);
  const [devCode, setDevCode] = useState<string | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [busy, setBusy] = useState(false);
  const [open, setOpen] = useState(true);

  useEffect(() => {
    let alive = true;
    api
      .get<{ email_register: boolean }>("/auth/methods")
      .then((data) => {
        if (alive) setOpen(data.email_register);
      })
      .catch(() => {
        /* 拿不到就按开着渲染，提交时服务端会给出真答案 */
      });
    return () => {
      alive = false;
    };
  }, []);

  useEffect(() => {
    if (countdown <= 0) return;
    const timer = setTimeout(() => setCountdown((v) => v - 1), 1000);
    return () => clearTimeout(timer);
  }, [countdown]);

  const emailValid = EMAIL_RE.test(email.trim());
  const weak = password ? passwordHint(password) : null;
  const mismatch = confirm.length > 0 && confirm !== password;
  const canSubmit =
    !busy && emailValid && code.length >= 4 && !weak && password.length > 0 && confirm === password;

  async function sendCode() {
    setError(null);
    setBusy(true);
    try {
      const data = await api.post<{ dev_code?: string }>("/auth/email/code", {
        email: email.trim(),
      });
      setDevCode(data.dev_code ?? null);
      setSent(true);
      setCountdown(60);
    } catch (err) {
      setError(err instanceof ApiError ? err.message : "发送失败");
    } finally {
      setBusy(false);
    }
  }

  async function submit(event: React.FormEvent) {
    event.preventDefault();
    if (!canSubmit) return;
    setError(null);
    setBusy(true);
    try {
      const data = await api.post<{ user: User; tokens: Tokens }>("/auth/register", {
        email: email.trim(),
        code,
        password,
        ...(nickname.trim() ? { nickname: nickname.trim() } : {}),
      });
      session.save(data.tokens);
      await reload();
      navigate("/", { replace: true });
    } catch (err) {
      setError(err instanceof ApiError ? err.message : "注册失败");
    } finally {
      setBusy(false);
    }
  }

  return (
    <main className="flex min-h-full items-center justify-center bg-paper-100 px-5 py-12">
      <div className="w-full max-w-sm">
        <div className="mb-8 flex items-center gap-2.5">
          <Logo size={30} />
          <div className="leading-tight">
            <div className="text-sm font-semibold text-ink-900">达道Task</div>
            <div className="text-2xs text-ink-400">任务 · 工单 · 知识</div>
          </div>
        </div>

        <h1 className="text-2xl font-semibold">创建账号</h1>
        <p className="mt-1.5 text-sm text-ink-500">
          用邮箱注册：先收一个验证码，再设一个密码。邮箱就是你的登录账号。
        </p>

        {!open && (
          <div className="mt-5">
            <InlineAlert>这台服务暂未开放自助注册，请联系管理员开通账号。</InlineAlert>
          </div>
        )}

        <form className="mt-5 space-y-4" onSubmit={submit}>
          <Field label="邮箱">
            <input
              id="email"
              className="input h-11"
              type="email"
              inputMode="email"
              autoComplete="email"
              placeholder="you@example.com"
              value={email}
              onChange={(e) => setEmail(e.target.value)}
              maxLength={255}
              disabled={!open}
            />
          </Field>

          <Field label="验证码">
            <div className="flex gap-2">
              <input
                id="code"
                className="input h-11 tracking-[0.3em]"
                inputMode="numeric"
                autoComplete="one-time-code"
                placeholder="6 位数字"
                value={code}
                onChange={(e) => setCode(e.target.value.trim())}
                maxLength={6}
                disabled={!open}
              />
              <Button
                type="button"
                variant="ghost"
                className="h-11 shrink-0 px-3.5"
                disabled={!open || !emailValid || busy || countdown > 0}
                onClick={sendCode}
              >
                {countdown > 0 ? `${countdown}s` : sent ? "重新发送" : "获取验证码"}
              </Button>
            </div>
          </Field>

          <Field label="密码">
            <input
              id="password"
              type="password"
              className="input h-11"
              autoComplete="new-password"
              placeholder="至少 8 位，字母 + 数字"
              value={password}
              onChange={(e) => setPassword(e.target.value)}
              maxLength={64}
              disabled={!open}
            />
            {weak && <span className="mt-1 block text-2xs text-clay-600">{weak}</span>}
          </Field>

          <Field label="确认密码">
            <input
              id="confirm"
              type="password"
              className="input h-11"
              autoComplete="new-password"
              placeholder="再输一次"
              value={confirm}
              onChange={(e) => setConfirm(e.target.value)}
              maxLength={64}
              disabled={!open}
            />
            {mismatch && <span className="mt-1 block text-2xs text-clay-600">两次输入不一致</span>}
          </Field>

          <Field label="昵称（可不填）">
            <input
              id="nickname"
              className="input h-11"
              autoComplete="nickname"
              placeholder="留空就用邮箱前缀"
              value={nickname}
              onChange={(e) => setNickname(e.target.value)}
              maxLength={32}
              disabled={!open}
            />
          </Field>

          {devCode && (
            <div className="flex items-start gap-2 rounded-lg border border-clay-500/20 bg-clay-50 px-3 py-2 text-xs text-clay-700">
              <span className="mt-px text-clay-500">开发环境验证码：{devCode}</span>
              <span className="text-clay-600/70">（生产环境只发到邮箱，不回显）</span>
            </div>
          )}
          {error && <InlineAlert>{error}</InlineAlert>}

          <Button
            type="submit"
            variant="primary"
            size="lg"
            className="mt-2 w-full"
            disabled={!open || !canSubmit}
          >
            {busy ? "处理中…" : "注册并登录"}
          </Button>
        </form>

        <p className="mt-6 text-sm text-ink-500">
          已经有账号了？
          <Link className="ml-1 font-medium text-primary-700 hover:underline" to="/login">
            去登录
          </Link>
        </p>
      </div>
    </main>
  );
}