"use client"

import { useState } from "react"
import { signIn } from "next-auth/react"
import { useRouter } from "next/navigation"
import { zodResolver } from "@hookform/resolvers/zod"
import { useForm } from "react-hook-form"
import { Eye, EyeOff, Loader2 } from "lucide-react"
import Link from "next/link"

import { Button } from "@/components/ui/button"
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card"
import { Form, FormControl, FormField, FormItem, FormLabel, FormMessage } from "@/components/ui/form"
import { Input } from "@/components/ui/input"
import { Alert, AlertDescription } from "@/components/ui/alert"

import { loginSchema, type LoginInput } from "@/lib/validation"

export default function SignInPage() {
  const [showPassword, setShowPassword] = useState(false)
  const [isLoading, setIsLoading] = useState(false)
  const [error, setError] = useState("")
  const router = useRouter()

  const [showTwoFactor, setShowTwoFactor] = useState(false)

  const form = useForm<LoginInput>({
    resolver: zodResolver(loginSchema),
    defaultValues: {
      email: "",
      password: "",
      twoFactorCode: "",
    },
  })

  const onSubmit = async (data: LoginInput) => {
    setIsLoading(true)
    setError("")
    
    try {
      const result = await signIn("credentials", {
        email: data.email,
        password: data.password,
        twoFactorCode: data.twoFactorCode,
        redirect: false,
      })

      if (result?.error) {
        if (result.error === "2FA_REQUIRED") {
          setShowTwoFactor(true)
          // Don't clear password here so user can just enter code
        } else {
          setError(result.error)
        }
      } else if (result?.ok) {
        router.push("/")
        router.refresh()
      } else {
        setError("Something went wrong. Please try again.")
      }
    } catch {
      setError("An unexpected error occurred")
    } finally {
      setIsLoading(false)
    }
  }

  return (
    <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-background to-muted/20 p-4">
      <Card className="w-full max-w-md">
        <CardHeader className="space-y-1">
          <CardTitle className="text-2xl text-center">Sign In</CardTitle>
          <CardDescription className="text-center">
            {showTwoFactor 
              ? "Enter the code from your authenticator app"
              : "Enter your email and password to access your account"}
          </CardDescription>
        </CardHeader>
        <CardContent className="space-y-4">
          {error && (
            <Alert variant="destructive">
              <AlertDescription>{error}</AlertDescription>
            </Alert>
          )}

          <Form {...form}>
            <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
              {!showTwoFactor ? (
                <>
                  <FormField
                    control={form.control}
                    name="email"
                    render={({ field }) => (
                      <FormItem>
                        <FormLabel>Email</FormLabel>
                        <FormControl>
                          <Input
                            type="email"
                            placeholder="john@example.com"
                            autoComplete="email"
                            {...field}
                          />
                        </FormControl>
                        <FormMessage />
                      </FormItem>
                    )}
                  />
                  <FormField
                    control={form.control}
                    name="password"
                    render={({ field }) => (
                      <FormItem>
                        <FormLabel>Password</FormLabel>
                        <FormControl>
                          <div className="relative">
                            <Input
                              type={showPassword ? "text" : "password"}
                              placeholder="Enter your password"
                              autoComplete="current-password"
                              {...field}
                            />
                            <Button
                              type="button"
                              variant="ghost"
                              size="sm"
                              className="absolute right-0 top-0 h-full px-3 py-2 hover:bg-transparent"
                              onClick={() => setShowPassword(!showPassword)}
                            >
                              {showPassword ? (
                                <EyeOff className="h-4 w-4" />
                              ) : (
                                <Eye className="h-4 w-4" />
                              )}
                            </Button>
                          </div>
                        </FormControl>
                        <FormMessage />
                      </FormItem>
                    )}
                  />
                </>
              ) : (
                <FormField
                  control={form.control}
                  name="twoFactorCode"
                  render={({ field }) => (
                    <FormItem>
                      <FormLabel>Two-Factor Code</FormLabel>
                      <FormControl>
                        <Input
                          placeholder="000000"
                          autoComplete="one-time-code"
                          maxLength={6}
                          {...field}
                          autoFocus
                        />
                      </FormControl>
                      <FormMessage />
                    </FormItem>
                  )}
                />
              )}
              
              <Button type="submit" className="w-full" disabled={isLoading}>
                {isLoading && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
                {showTwoFactor ? "Verify" : "Sign In"}
              </Button>
            </form>
          </Form>

          {!showTwoFactor && (
            <>
              <div className="text-center text-sm">
                <span className="text-muted-foreground">Don&apos;t have an account? </span>
                <Link href="/signup" className="text-primary hover:underline font-medium">
                  Sign up
                </Link>
              </div>

              <div className="text-center">
                <Button variant="link" className="text-sm text-muted-foreground">
                  Forgot your password?
                </Button>
              </div>
            </>
          )}
          
          {showTwoFactor && (
             <div className="text-center">
                <Button 
                  variant="link" 
                  className="text-sm text-muted-foreground"
                  onClick={() => setShowTwoFactor(false)}
                >
                  Back to login
                </Button>
              </div>
          )}
        </CardContent>
      </Card>
    </div>
  )
}