import { useEffect, useState } from 'react';

import { Link, Navigate, useNavigate } from 'react-router-dom';

import { Icon } from '@/app/Icon';
import { Agreement } from '@/features/auth/components/Agreement';
import { PasswordInput } from '@/features/auth/components/PasswordInput';
import { VerificationCodeButton } from '@/features/auth/components/VerificationCodeButton';
import { verifyRegisterCode } from '@/lib/api/auth';
import { ImApiError } from '@/lib/api/client';
import { getTinode, registerAccount } from '@/lib/tinode/connection';
import { registerErrorMessage, validateCredentialsMessage } from '@/lib/tinode/errors';
import { subscribeMeTopic } from '@/lib/tinode/topics';
import { useSessionStore } from '@/stores/session';

const USERNAME_RE = /^[a-z0-9]{1,10}$/;
const PHONE_RE = /^\d{11}$/;
const INVITE_RE = /^[A-Za-z]{5}$/;

interface FormErrors {
  username?: string;
  phone?: string;
  code?: string;
  password?: string;
  invite?: string;
}

export function RegisterPage() {
  const navigate = useNavigate();
  const tenant = useSessionStore((s) => s.tenant);
  const setMyUserId = useSessionStore((s) => s.setMyUserId);

  const [username, setUsername] = useState('');
  const [phone, setPhone] = useState('');
  const [code, setCode] = useState('');
  const [password, setPassword] = useState('');
  const [invite, setInvite] = useState('');
  const [challengeId, setChallengeId] = useState('');
  const [agreed, setAgreed] = useState(false);
  const [errors, setErrors] = useState<FormErrors>({});
  const [formError, setFormError] = useState('');
  const [submitting, setSubmitting] = useState(false);

  // A challengeId/code pair is only valid for the phone number it was issued for -- without this,
  // editing the phone after requesting a code (typo fix) leaves a stale challengeId in place that
  // verifyRegisterCode() has no way to cross-check against the NEW phone in the field.
  useEffect(() => {
    setChallengeId('');
    setCode('');
  }, [phone]);

  if (!tenant) return <Navigate to="/tenant" replace />;

  const usingPhone = !!phone;

  const submit = async (e: React.FormEvent) => {
    e.preventDefault();
    const next: FormErrors = {};
    if (!username && !phone) next.username = '用户名和手机号至少填写一项';
    if (username && !USERNAME_RE.test(username)) next.username = '用户名仅支持 1-10 位小写字母或数字';
    if (usingPhone) {
      if (!PHONE_RE.test(phone)) next.phone = '请输入 11 位手机号';
      if (!challengeId) next.code = '请先获取验证码';
      else if (!/^\d{6}$/.test(code)) next.code = '请输入 6 位验证码';
    } else if (!INVITE_RE.test(invite)) {
      next.invite = '用户名注册需填写 5 位字母邀请码';
    }
    if (password.length < 8) next.password = '密码至少 8 位';
    setErrors(next);
    setFormError('');
    if (Object.keys(next).length || !agreed || submitting) return;

    setSubmitting(true);
    let verificationToken: string | undefined;
    try {
      if (usingPhone) {
        const verified = await verifyRegisterCode(challengeId, code);
        verificationToken = verified.verification_token;
      }
    } catch (err) {
      setErrors((e) => ({ ...e, code: err instanceof ImApiError ? err.message : '验证码错误或已过期' }));
      setSubmitting(false);
      return;
    }
    try {
      const ctrl = await registerAccount({
        username,
        phone,
        password,
        inviteCode: invite,
        verificationToken,
        challengeId: usingPhone ? challengeId : undefined,
      });
      if (ctrl.code >= 300 && ctrl.text === 'validate credentials') {
        setFormError(validateCredentialsMessage(ctrl.params as { reason?: string; cred?: string[] } | undefined));
        return;
      }
      const authToken = getTinode().getAuthToken();
      sessionStorage.setItem('im-session-token', authToken ? authToken.token : '');
      setMyUserId((ctrl.params?.user as string | undefined) ?? null);
      subscribeMeTopic().catch(() => {});
      navigate('/messages');
    } catch (err) {
      setFormError(registerErrorMessage(err));
    } finally {
      setSubmitting(false);
    }
  };

  return (
    <div className="flex h-dvh w-full flex-col overflow-y-auto bg-surface-page">
      <div className="flex h-12 flex-none items-center px-2 min-[900px]:hidden">
        <Link to="/login" className="grid h-9 w-9 place-items-center text-text-heading no-underline">
          <Icon name="arrow_back_ios_new" className="text-[20px]" />
        </Link>
        <strong className="flex-1 -ml-9 text-center text-[17px] font-semibold text-text-heading">注册</strong>
      </div>
      <div className="flex flex-1 items-center justify-center px-6 py-8">
        <form onSubmit={submit} className="flex w-full max-w-[380px] flex-col gap-4">
          <h1 className="m-0 text-[22px] font-bold text-text-title">创建账号</h1>
          {formError ? (
            <div className="flex items-center gap-1.5 rounded-lg bg-error-strip-bg px-3 py-2.5 text-sm text-error-strip-text">
              <Icon name="error_outline" className="text-[18px]" />
              {formError}
            </div>
          ) : null}

          <div className="flex flex-col gap-1.5">
            <input
              value={username}
              onChange={(e) => setUsername(e.target.value.replace(/[^a-z0-9]/g, '').slice(0, 10))}
              placeholder="用户名（1-10位小写字母或数字）"
              autoComplete="username"
              className={`h-[50px] rounded-lg bg-surface-input px-3.5 text-[15px] outline-none focus:border focus:border-focus-border focus:shadow-focus-ring ${
                errors.username ? 'border border-danger-text' : ''
              }`}
            />
            {errors.username ? <div className="text-xs text-danger-border">{errors.username}</div> : null}
          </div>

          <div className="flex items-center gap-3 text-xs text-text-tertiary-3">
            <div className="h-px flex-1 bg-border-row" />
            或
            <div className="h-px flex-1 bg-border-row" />
          </div>

          <div className="flex flex-col gap-1.5">
            <label
              className={`flex h-[50px] items-center gap-2 rounded-lg bg-surface-input px-3.5 has-focus:border has-focus:shadow-focus-ring ${
                errors.phone ? 'border border-danger-text' : 'has-focus:border-focus-border'
              }`}
            >
              <span className="text-[15px] text-text-tertiary-2">+86</span>
              <input
                value={phone}
                onChange={(e) => setPhone(e.target.value.replace(/\D/g, '').slice(0, 11))}
                placeholder="请输入手机号"
                inputMode="numeric"
                className="w-full bg-transparent text-[15px] outline-none"
              />
            </label>
            {errors.phone ? <div className="text-xs text-danger-border">{errors.phone}</div> : null}
          </div>

          <div className="flex flex-col gap-1.5">
            <div className="flex gap-2">
              <input
                value={code}
                onChange={(e) => setCode(e.target.value.replace(/\D/g, '').slice(0, 6))}
                placeholder="短信验证码"
                inputMode="numeric"
                className={`h-[50px] flex-1 rounded-lg bg-surface-input px-3.5 text-[15px] outline-none ${
                  errors.code ? 'border border-danger-text' : ''
                }`}
              />
              <VerificationCodeButton
                phone={phone}
                scene="register"
                onChallenge={setChallengeId}
                onError={(msg) => setErrors((e) => ({ ...e, code: msg }))}
              />
            </div>
            {errors.code ? <div className="text-xs text-danger-border">{errors.code}</div> : null}
          </div>

          <PasswordInput value={password} onChange={setPassword} placeholder="设置密码" autoComplete="new-password" error={errors.password} />

          <div className="flex flex-col gap-1.5">
            {/* 邀请码大小写敏感（唯一索引按 ascii_bin 排序），不能像其它字段那样统一大小写 */}
            <input
              value={invite}
              onChange={(e) => setInvite(e.target.value.replace(/[^A-Za-z]/g, '').slice(0, 5))}
              placeholder="邀请码（5位英文字母，区分大小写）"
              autoCapitalize="off"
              autoCorrect="off"
              className={`h-[50px] rounded-lg bg-surface-input px-3.5 text-[15px] outline-none ${
                errors.invite ? 'border border-danger-text' : ''
              }`}
            />
            {errors.invite ? <div className="text-xs text-danger-border">{errors.invite}</div> : null}
          </div>

          {!usingPhone ? (
            <p className="m-0 text-xs text-text-tertiary-3">未绑定手机号无法自助找回密码，忘记密码后只能联系企业管理员重置</p>
          ) : null}

          <button
            type="submit"
            disabled={(!username && !phone) || !password || !agreed || submitting}
            className="h-[50px] rounded-lg bg-btn text-base font-medium text-white shadow-btn disabled:bg-btn-disabled disabled:shadow-none"
          >
            {submitting ? '注册中…' : '注册'}
          </button>
          <Link to="/login" className="text-center text-sm text-accent no-underline">
            已有账号？返回登录
          </Link>
          <Agreement checked={agreed} onChange={setAgreed} prefix="注册即认同MeetingIM" />
        </form>
      </div>
    </div>
  );
}