'use client'

import { useState } from 'react'
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
import { Input } from '@/components/ui/input'
import { Button } from '@/components/ui/button'
import { Label } from '@/components/ui/label'
import { AlertCircle, CheckCircle2, Eye, EyeOff, Loader2, Mail, Lock, Monitor, Smartphone } from 'lucide-react'

type Step = 'verify' | 'change' | 'success'

const MAIL_DOMAIN = 'monaco-opc.com'
const MAIL_SERVER = 'mail.monaco-opc.com'

export default function ChangeEmailPasswordPage() {
  const [step, setStep] = useState<Step>('verify')
  const [email, setEmail] = useState('')
  const [currentPassword, setCurrentPassword] = useState('')
  const [newPassword, setNewPassword] = useState('')
  const [confirmPassword, setConfirmPassword] = useState('')
  const [showCurrentPassword, setShowCurrentPassword] = useState(false)
  const [showNewPassword, setShowNewPassword] = useState(false)
  const [showConfirmPassword, setShowConfirmPassword] = useState(false)
  const [error, setError] = useState('')
  const [loading, setLoading] = useState(false)

  async function handleVerify(e: React.FormEvent) {
    e.preventDefault()
    setError('')

    const emailLower = email.toLowerCase().trim()
    if (!emailLower.endsWith(`@${MAIL_DOMAIN}`)) {
      setError(`Email must be an @${MAIL_DOMAIN} address.`)
      return
    }

    setLoading(true)
    try {
      const res = await fetch('/api/email/verify-credentials', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ email: emailLower, password: currentPassword }),
      })

      const data = await res.json()

      if (res.status === 429) {
        setError(data.error || 'Too many attempts. Please try again later.')
        return
      }

      if (!data.valid) {
        setError(data.error || 'Invalid email or password.')
        return
      }

      setStep('change')
    } catch {
      setError('Connection error. Please try again.')
    } finally {
      setLoading(false)
    }
  }

  async function handleChangePassword(e: React.FormEvent) {
    e.preventDefault()
    setError('')

    if (newPassword.length < 8) {
      setError('Password must be at least 8 characters.')
      return
    }

    if (!/(?=.*[a-z])(?=.*[A-Z])(?=.*\d)/.test(newPassword)) {
      setError('Password must contain at least one uppercase letter, one lowercase letter, and one number.')
      return
    }

    if (newPassword !== confirmPassword) {
      setError('Passwords do not match.')
      return
    }

    setLoading(true)
    try {
      const res = await fetch('/api/email/change-password', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          email: email.toLowerCase().trim(),
          currentPassword,
          newPassword,
        }),
      })

      const data = await res.json()

      if (!res.ok) {
        setError(data.error || 'Failed to change password.')
        return
      }

      setStep('success')
    } catch {
      setError('Connection error. Please try again.')
    } finally {
      setLoading(false)
    }
  }

  return (
    <div className="mx-auto max-w-lg">
      <div className="mb-8 text-center">
        <Mail className="mx-auto h-12 w-12 text-[#053d57] mb-4" />
        <h1 className="text-heading font-semibold text-[#053d57]">Email Account</h1>
        <p className="text-muted-foreground mt-2">
          Change your @{MAIL_DOMAIN} email password
        </p>
      </div>

      {step === 'verify' && (
        <Card>
          <CardHeader>
            <CardTitle>Verify Your Identity</CardTitle>
            <CardDescription>
              Enter your email address and current password to continue.
            </CardDescription>
          </CardHeader>
          <CardContent>
            <form onSubmit={handleVerify} className="space-y-4">
              <div className="space-y-2">
                <Label htmlFor="email">Email Address</Label>
                <Input
                  id="email"
                  type="email"
                  placeholder={`yourname@${MAIL_DOMAIN}`}
                  value={email}
                  onChange={(e) => setEmail(e.target.value)}
                  required
                  autoComplete="email"
                />
              </div>

              <div className="space-y-2">
                <Label htmlFor="current-password">Current Password</Label>
                <div className="relative">
                  <Input
                    id="current-password"
                    type={showCurrentPassword ? 'text' : 'password'}
                    value={currentPassword}
                    onChange={(e) => setCurrentPassword(e.target.value)}
                    required
                    autoComplete="current-password"
                  />
                  <button
                    type="button"
                    className="absolute right-3 top-1/2 -translate-y-1/2 text-muted-foreground hover:text-foreground"
                    onClick={() => setShowCurrentPassword(!showCurrentPassword)}
                    tabIndex={-1}
                  >
                    {showCurrentPassword ? <EyeOff className="h-4 w-4" /> : <Eye className="h-4 w-4" />}
                  </button>
                </div>
              </div>

              {error && (
                <div className="flex items-center gap-2 text-sm text-destructive">
                  <AlertCircle className="h-4 w-4 shrink-0" />
                  <span>{error}</span>
                </div>
              )}

              <Button type="submit" className="w-full" disabled={loading}>
                {loading ? (
                  <>
                    <Loader2 className="mr-2 h-4 w-4 animate-spin" />
                    Verifying...
                  </>
                ) : (
                  'Continue'
                )}
              </Button>
            </form>
          </CardContent>
        </Card>
      )}

      {step === 'change' && (
        <Card>
          <CardHeader>
            <CardTitle>Set New Password</CardTitle>
            <CardDescription>
              Choose a new password for <strong>{email.toLowerCase().trim()}</strong>.
              Must be at least 8 characters with uppercase, lowercase, and a number.
            </CardDescription>
          </CardHeader>
          <CardContent>
            <form onSubmit={handleChangePassword} className="space-y-4">
              <div className="space-y-2">
                <Label htmlFor="new-password">New Password</Label>
                <div className="relative">
                  <Input
                    id="new-password"
                    type={showNewPassword ? 'text' : 'password'}
                    value={newPassword}
                    onChange={(e) => setNewPassword(e.target.value)}
                    required
                    autoComplete="new-password"
                    minLength={8}
                  />
                  <button
                    type="button"
                    className="absolute right-3 top-1/2 -translate-y-1/2 text-muted-foreground hover:text-foreground"
                    onClick={() => setShowNewPassword(!showNewPassword)}
                    tabIndex={-1}
                  >
                    {showNewPassword ? <EyeOff className="h-4 w-4" /> : <Eye className="h-4 w-4" />}
                  </button>
                </div>
              </div>

              <div className="space-y-2">
                <Label htmlFor="confirm-password">Confirm New Password</Label>
                <div className="relative">
                  <Input
                    id="confirm-password"
                    type={showConfirmPassword ? 'text' : 'password'}
                    value={confirmPassword}
                    onChange={(e) => setConfirmPassword(e.target.value)}
                    required
                    autoComplete="new-password"
                    minLength={8}
                  />
                  <button
                    type="button"
                    className="absolute right-3 top-1/2 -translate-y-1/2 text-muted-foreground hover:text-foreground"
                    onClick={() => setShowConfirmPassword(!showConfirmPassword)}
                    tabIndex={-1}
                  >
                    {showConfirmPassword ? <EyeOff className="h-4 w-4" /> : <Eye className="h-4 w-4" />}
                  </button>
                </div>
              </div>

              {error && (
                <div className="flex items-center gap-2 text-sm text-destructive">
                  <AlertCircle className="h-4 w-4 shrink-0" />
                  <span>{error}</span>
                </div>
              )}

              <div className="flex gap-3">
                <Button
                  type="button"
                  variant="outline"
                  onClick={() => {
                    setStep('verify')
                    setNewPassword('')
                    setConfirmPassword('')
                    setError('')
                  }}
                >
                  Back
                </Button>
                <Button type="submit" className="flex-1" disabled={loading}>
                  {loading ? (
                    <>
                      <Loader2 className="mr-2 h-4 w-4 animate-spin" />
                      Changing Password...
                    </>
                  ) : (
                    'Change Password'
                  )}
                </Button>
              </div>
            </form>
          </CardContent>
        </Card>
      )}

      {step === 'success' && (
        <div className="space-y-6">
          <Card>
            <CardContent className="pt-6">
              <div className="flex flex-col items-center text-center space-y-3">
                <CheckCircle2 className="h-12 w-12 text-green-600" />
                <h2 className="text-xl font-semibold">Password Changed Successfully</h2>
                <p className="text-muted-foreground">
                  Your password for <strong>{email.toLowerCase().trim()}</strong> has been updated.
                  Use your new password to sign in to your email.
                </p>
              </div>
            </CardContent>
          </Card>

          <Card>
            <CardHeader>
              <CardTitle className="flex items-center gap-2">
                <Lock className="h-5 w-5" />
                Mail Client Setup
              </CardTitle>
              <CardDescription>
                Use these settings to add your email account to any mail app.
              </CardDescription>
            </CardHeader>
            <CardContent className="space-y-6">
              <div className="grid gap-4 sm:grid-cols-2">
                <div className="rounded-lg border p-4 space-y-3">
                  <h3 className="font-semibold text-sm uppercase tracking-wide text-muted-foreground">
                    Incoming Mail (IMAP)
                  </h3>
                  <dl className="space-y-2 text-sm">
                    <div>
                      <dt className="text-muted-foreground">Server</dt>
                      <dd className="font-mono font-medium">{MAIL_SERVER}</dd>
                    </div>
                    <div>
                      <dt className="text-muted-foreground">Port</dt>
                      <dd className="font-mono font-medium">993</dd>
                    </div>
                    <div>
                      <dt className="text-muted-foreground">Security</dt>
                      <dd className="font-mono font-medium">SSL/TLS</dd>
                    </div>
                    <div>
                      <dt className="text-muted-foreground">Username</dt>
                      <dd className="font-mono font-medium text-xs break-all">{email.toLowerCase().trim()}</dd>
                    </div>
                  </dl>
                </div>

                <div className="rounded-lg border p-4 space-y-3">
                  <h3 className="font-semibold text-sm uppercase tracking-wide text-muted-foreground">
                    Outgoing Mail (SMTP)
                  </h3>
                  <dl className="space-y-2 text-sm">
                    <div>
                      <dt className="text-muted-foreground">Server</dt>
                      <dd className="font-mono font-medium">{MAIL_SERVER}</dd>
                    </div>
                    <div>
                      <dt className="text-muted-foreground">Port</dt>
                      <dd className="font-mono font-medium">587</dd>
                    </div>
                    <div>
                      <dt className="text-muted-foreground">Security</dt>
                      <dd className="font-mono font-medium">STARTTLS</dd>
                    </div>
                    <div>
                      <dt className="text-muted-foreground">Username</dt>
                      <dd className="font-mono font-medium text-xs break-all">{email.toLowerCase().trim()}</dd>
                    </div>
                  </dl>
                </div>
              </div>

              <div className="rounded-lg bg-muted/50 p-4 space-y-3">
                <h3 className="font-semibold text-sm flex items-center gap-2">
                  <Smartphone className="h-4 w-4" />
                  Mobile Apps
                </h3>
                <ul className="text-sm space-y-1 text-muted-foreground">
                  <li><strong>iPhone/iPad:</strong> Settings &gt; Mail &gt; Accounts &gt; Add Account &gt; Other</li>
                  <li><strong>Gmail App:</strong> Settings &gt; Add Account &gt; Other</li>
                  <li><strong>Outlook App:</strong> Settings &gt; Add Email Account</li>
                </ul>
              </div>

              <div className="rounded-lg bg-muted/50 p-4 space-y-3">
                <h3 className="font-semibold text-sm flex items-center gap-2">
                  <Monitor className="h-4 w-4" />
                  Desktop Apps
                </h3>
                <ul className="text-sm space-y-1 text-muted-foreground">
                  <li><strong>Apple Mail:</strong> Mail &gt; Add Account &gt; Other Mail Account</li>
                  <li><strong>Outlook:</strong> File &gt; Add Account</li>
                  <li><strong>Thunderbird:</strong> Account Settings &gt; Account Actions &gt; Add Mail Account</li>
                </ul>
              </div>
            </CardContent>
          </Card>
        </div>
      )}
    </div>
  )
}