"use client"

import type React from "react"
import { useEffect, useRef, useState } from "react"
import { Mail, ArrowLeft, CheckCircle2 } from "lucide-react"
import { Button } from "@/components/ui/button"
import { Input } from "@/components/ui/input"
import { Label } from "@/components/ui/label"

const RESEND_COOLDOWN = 30 // seconds

function isValidEmail(value: string) {
  return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(value.trim())
}

export function LoginForm() {
  const [email, setEmail] = useState("")
  const [touched, setTouched] = useState(false)
  const [sent, setSent] = useState(false)
  const [sending, setSending] = useState(false)
  const [cooldown, setCooldown] = useState(0)
  const [error, setError] = useState<string | null>(null)

  const emailValid = isValidEmail(email)
  const showError = touched && email.length > 0 && !emailValid

  // Countdown timer for the resend cooldown.
  useEffect(() => {
    if (cooldown <= 0) return
    const id = setInterval(() => {
      setCooldown((c) => (c <= 1 ? 0 : c - 1))
    }, 1000)
    return () => clearInterval(id)
  }, [cooldown])

  async function sendLink() {
    setSending(true)
    setError(null)
    try {
      // Alltid samme suksess-respons uansett om e-posten finnes (anti-
      // enumerering, se ADR-009) -- kun nettverks-/serverfeil havner i catch.
      const res = await fetch("/auth/request-link", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        credentials: "include",
        body: JSON.stringify({ email: email.trim(), locale: "nb" }),
      })
      if (!res.ok) throw new Error(`request-link: ${res.status}`)
      setSent(true)
      setCooldown(RESEND_COOLDOWN)
    } catch {
      setError("Klarte ikke å sende lenken. Sjekk tilkoblingen og prøv igjen.")
    } finally {
      setSending(false)
    }
  }

  function handleSubmit(e: React.FormEvent) {
    e.preventDefault()
    setTouched(true)
    if (!emailValid || sending) return
    void sendLink()
  }

  function handleResend() {
    if (cooldown > 0 || sending) return
    void sendLink()
  }

  function handleReset() {
    setSent(false)
    setTouched(false)
  }

  return (
    <div className="w-full rounded-3xl border border-border bg-card p-6 shadow-lg shadow-black/5 sm:p-8">
      {sent ? (
        <ConfirmationState
          email={email}
          cooldown={cooldown}
          sending={sending}
          error={error}
          onResend={handleResend}
          onReset={handleReset}
        />
      ) : (
        <form onSubmit={handleSubmit} className="flex flex-col gap-6" noValidate>
          <div className="flex flex-col gap-2">
            <Label htmlFor="email" className="text-sm font-semibold">
              E-post
            </Label>
            <div className="relative">
              <Mail
                aria-hidden="true"
                className="pointer-events-none absolute left-3.5 top-1/2 size-5 -translate-y-1/2 text-muted-foreground"
              />
              <Input
                id="email"
                type="email"
                inputMode="email"
                autoComplete="email"
                autoFocus
                placeholder="deg@epost.no"
                value={email}
                onChange={(e) => setEmail(e.target.value)}
                onBlur={() => setTouched(true)}
                aria-invalid={showError}
                aria-describedby={showError ? "email-error" : undefined}
                className="h-14 rounded-2xl pl-11 text-base"
              />
            </div>
            {showError && (
              <p id="email-error" className="text-sm font-medium text-destructive">
                Skriv inn en gyldig e-postadresse.
              </p>
            )}
          </div>

          {error && (
            <p role="alert" className="text-center text-sm font-medium text-destructive">
              {error}
            </p>
          )}

          <Button
            type="submit"
            disabled={sending}
            className="h-14 rounded-2xl text-base font-bold shadow-sm"
          >
            {sending ? "Sender …" : "Send innloggingslenke"}
          </Button>

          <p className="text-center text-sm leading-relaxed text-muted-foreground text-pretty">
            Ingen passord. Vi sender deg en sikker lenke på e-post.
          </p>
        </form>
      )}
    </div>
  )
}

function ConfirmationState({
  email,
  cooldown,
  sending,
  error,
  onResend,
  onReset,
}: {
  email: string
  cooldown: number
  sending: boolean
  error: string | null
  onResend: () => void
  onReset: () => void
}) {
  const liveRef = useRef<HTMLHeadingElement>(null)

  useEffect(() => {
    liveRef.current?.focus()
  }, [])

  return (
    <div className="flex flex-col items-center gap-5 text-center">
      <div className="flex size-16 items-center justify-center rounded-2xl bg-primary/15">
        <CheckCircle2 aria-hidden="true" className="size-8 text-primary" />
      </div>

      <div className="flex flex-col gap-2">
        <h2
          ref={liveRef}
          tabIndex={-1}
          className="text-2xl font-extrabold tracking-tight outline-none text-balance"
        >
          Sjekk innboksen din
        </h2>
        <p className="text-sm leading-relaxed text-muted-foreground text-pretty">
          Vi har sendt en innloggingslenke til{" "}
          <span className="font-semibold text-foreground">{email}</span>. Åpne den på denne enheten for å logge inn.
        </p>
      </div>

      {error && (
        <p role="alert" className="text-sm font-medium text-destructive">
          {error}
        </p>
      )}

      <div className="mt-1 w-full">
        {cooldown > 0 ? (
          <p className="text-sm text-muted-foreground" aria-live="polite">
            Fikk du ingen e-post? Send på nytt om{" "}
            <span className="font-semibold text-foreground tabular-nums">{cooldown}s</span>
          </p>
        ) : (
          <Button
            type="button"
            variant="ghost"
            onClick={onResend}
            disabled={sending}
            className="h-11 rounded-xl font-semibold text-primary hover:bg-primary/10 hover:text-primary"
          >
            {sending ? "Sender …" : "Send lenken på nytt"}
          </Button>
        )}
      </div>

      <button
        type="button"
        onClick={onReset}
        className="mt-1 inline-flex items-center gap-1.5 text-sm font-semibold text-muted-foreground transition-colors hover:text-foreground"
      >
        <ArrowLeft aria-hidden="true" className="size-4" />
        Bruk en annen e-post
      </button>
    </div>
  )
}