'use client'

import { useActionState } from 'react'
import { useFormStatus } from 'react-dom'
import { Button } from '@/components/ui/button'
import { Input } from '@/components/ui/input'

type ActionResult = { error: string | Record<string, string[]> } | undefined

function SubmitButton({ label }: { label: string }) {
  const { pending } = useFormStatus()
  return (
    <Button type="submit" className="w-full" disabled={pending}>
      {pending ? 'Even wachten…' : label}
    </Button>
  )
}

function getErrorMessage(error: ActionResult): string | null {
  if (!error) return null
  if (typeof error.error === 'string') return error.error
  // Field errors object — flatten to first message
  const first = Object.values(error.error).flat()[0]
  return first ?? null
}

interface AuthFormProps {
  action: (_prevState: unknown, formData: FormData) => Promise<ActionResult>
  submitLabel: string
}

export function AuthForm({ action, submitLabel }: AuthFormProps) {
  const [state, formAction] = useActionState(action, undefined)
  const errorMessage = getErrorMessage(state)

  return (
    <form action={formAction} className="space-y-4">
      <div className="space-y-2">
        <label htmlFor="username" className="text-sm font-medium text-foreground">
          Gebruikersnaam
        </label>
        <Input
          id="username"
          name="username"
          type="text"
          autoComplete="username"
          required
          minLength={3}
          placeholder="jouw-naam"
          className="bg-input-background border-border focus-visible:ring-primary"
        />
      </div>

      <div className="space-y-2">
        <label htmlFor="password" className="text-sm font-medium text-foreground">
          Wachtwoord
        </label>
        <Input
          id="password"
          name="password"
          type="password"
          autoComplete="current-password"
          required
          minLength={8}
          placeholder="••••••••"
          className="bg-input-background border-border focus-visible:ring-primary"
        />
      </div>

      {errorMessage && (
        <div className="bg-error-container text-error-container-foreground rounded-lg px-3 py-2 text-sm border-l-4 border-error">
          {errorMessage}
        </div>
      )}

      <SubmitButton label={submitLabel} />
    </form>
  )
}