'use client';

import { useEffect, useState } from 'react';
import { useRouter, useSearchParams } from 'next/navigation';
import Link from 'next/link';
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { z } from 'zod';
import { toast } from 'sonner';
import { cn } from '@/lib/utils';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { Label } from '@/components/ui/label';
import { BrandedAuthShell } from '@/components/shared/branded-auth-shell';
import { useAuthBranding } from '@/components/shared/auth-branding-provider';
import { FormErrorSummary } from '@/components/forms/form-error-summary';
import { useFormScrollToError } from '@/hooks/use-form-scroll-to-error';

// `identifier` accepts either an email address or a username (3–30 lowercase
// letters / digits / dot / underscore / hyphen). The server endpoint
// /api/auth/sign-in-by-identifier resolves the username server-side and
// forwards to better-auth in one round-trip - the canonical email is never
// returned to the browser, which closes the username-enumeration vector.
const loginSchema = z.object({
  identifier: z.string().min(1, 'Email or username is required'),
  password: z.string().min(1, 'Password is required'),
});

type LoginFormData = z.infer<typeof loginSchema>;

/**
 * H-02: Validate a redirect target before pushing the user to it. The
 * middleware appends `?redirect=<path>` when a session check fails on a
 * protected route; an unsanitized router.push of that value would let a
 * crafted URL bounce the user to an external host or protocol-relative
 * `//evil.com` after a successful sign-in. Only same-origin, single-leading-
 * slash paths pass.
 */
function safeRedirectTarget(raw: string | null): string {
  if (!raw) return '/dashboard';
  // Allow only paths starting with a single `/` (rules out `//evil.com`
  // protocol-relative URLs and `https://…` absolute ones).
  if (!raw.startsWith('/') || raw.startsWith('//')) return '/dashboard';
  return raw;
}

export default function LoginPage() {
  const router = useRouter();
  const branding = useAuthBranding();
  const appName = branding?.appName?.trim() || 'CRM';
  const searchParams = useSearchParams();
  const [isLoading, setIsLoading] = useState(false);

  // Fresh-DB bootstrap detection: if no super-admin exists yet, /setup
  // owns the first-run flow. Failure of the status endpoint is silent
  // (login still works for everyone else).
  useEffect(() => {
    let cancelled = false;
    fetch('/api/v1/bootstrap/status')
      .then((r) => (r.ok ? (r.json() as Promise<{ data?: { needsBootstrap?: boolean } }>) : null))
      .then((payload) => {
        if (cancelled || !payload) return;
        if (payload.data?.needsBootstrap) router.replace('/setup');
      })
      .catch(() => {
        /* silent - login UX must still work even if status check fails */
      });
    return () => {
      cancelled = true;
    };
  }, [router]);

  const {
    register,
    handleSubmit,
    formState: { errors },
  } = useForm<LoginFormData>({
    resolver: zodResolver(loginSchema),
  });
  const submitWithScroll = useFormScrollToError(handleSubmit, errors);

  async function onSubmit(data: LoginFormData) {
    setIsLoading(true);
    try {
      const res = await fetch('/api/auth/sign-in-by-identifier', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          identifier: data.identifier.trim(),
          password: data.password,
        }),
      });

      if (!res.ok) {
        const payload = (await res.json().catch(() => ({}))) as {
          error?: { message?: string };
        };
        toast.error(payload.error?.message ?? 'Invalid credentials');
        return;
      }

      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      router.push(safeRedirectTarget(searchParams.get('redirect')) as any);
    } catch {
      toast.error('Something went wrong. Please try again.');
    } finally {
      setIsLoading(false);
    }
  }

  return (
    <BrandedAuthShell>
      <div className="text-center mb-6">
        <h1 className="text-xl font-semibold text-gray-900">{appName}</h1>
        <p className="text-sm text-gray-500 mt-1">Sign in to continue</p>
      </div>

      <form onSubmit={submitWithScroll(onSubmit)} className="space-y-4" noValidate>
        <FormErrorSummary
          errors={errors}
          labels={{ identifier: 'Email or username', password: 'Password' }}
        />
        <div className="space-y-1.5">
          <Label htmlFor="identifier">Email or username</Label>
          <Input
            id="identifier"
            type="text"
            autoComplete="username"
            autoCapitalize="none"
            spellCheck={false}
            disabled={isLoading}
            className={cn(errors.identifier && 'border-destructive focus-visible:ring-destructive')}
            {...register('identifier')}
          />
          {errors.identifier && (
            <p className="text-sm text-destructive">{errors.identifier.message}</p>
          )}
        </div>

        <div className="space-y-1.5">
          <div className="flex items-center justify-between">
            <Label htmlFor="password">Password</Label>
            <Link
              href="/reset-password"
              className="text-xs text-[#0058b3] underline-offset-2 underline hover:no-underline"
            >
              Forgot password?
            </Link>
          </div>
          <Input
            id="password"
            type="password"
            autoComplete="current-password"
            disabled={isLoading}
            className={cn(errors.password && 'border-destructive focus-visible:ring-destructive')}
            {...register('password')}
          />
          {errors.password && <p className="text-sm text-destructive">{errors.password.message}</p>}
        </div>

        <Button
          type="submit"
          className="w-full bg-[#007bff] hover:bg-[#0069d9] text-white"
          disabled={isLoading}
        >
          {isLoading ? 'Signing in…' : 'Sign in'}
        </Button>
      </form>
    </BrandedAuthShell>
  );
}
