import { useEffect, useMemo, useState, useCallback } from 'react'
import QRCode from 'react-qr-code'
import type { AlbyInvoice } from '@/types/alby'
import { getAlbyService, isWebLNAvailable } from '@/lib/alby'
import { AlbyInstaller } from './AlbyInstaller'

interface PaymentModalProps {
  invoice: AlbyInvoice
  onClose: () => void
  onPaymentComplete: () => void
}

function useInvoiceTimer(expiresAt?: number) {
  const [timeRemaining, setTimeRemaining] = useState<number | null>(null)

  useEffect(() => {
    if (!expiresAt) {
      return
    }
    const updateTimeRemaining = () => {
      const now = Math.floor(Date.now() / 1000)
      const remaining = expiresAt - now
      setTimeRemaining(remaining > 0 ? remaining : 0)
    }
    updateTimeRemaining()
    const interval = setInterval(updateTimeRemaining, 1000)
    return () => clearInterval(interval)
  }, [expiresAt])

  return timeRemaining
}

function PaymentHeader({
  amount,
  timeRemaining,
  onClose,
}: {
  amount: number
  timeRemaining: number | null
  onClose: () => void
}) {
  const timeLabel = useMemo(() => {
    if (timeRemaining === null) {
      return null
    }
    if (timeRemaining <= 0) {
      return 'Expired'
    }
    const minutes = Math.floor(timeRemaining / 60)
    const secs = timeRemaining % 60
    return `${minutes}:${secs.toString().padStart(2, '0')}`
  }, [timeRemaining])

  return (
    <div className="flex justify-between items-center mb-4">
      <div>
        <h2 className="text-xl font-bold">Pay {amount} sats</h2>
        {timeLabel && (
          <p className={`text-sm ${timeRemaining !== null && timeRemaining <= 60 ? 'text-red-600 font-semibold' : 'text-gray-600'}`}>
            Time remaining: {timeLabel}
          </p>
        )}
      </div>
      <button onClick={onClose} className="text-gray-500 hover:text-gray-700 text-2xl">
        ×
      </button>
    </div>
  )
}

function InvoiceDisplay({ invoiceText, paymentUrl }: { invoiceText: string; paymentUrl: string }) {
  return (
    <div className="mb-4">
      <p className="text-sm text-gray-600 mb-2">Lightning Invoice:</p>
      <div className="bg-gray-100 p-3 rounded break-all text-sm font-mono mb-4">{invoiceText}</div>
      <div className="flex justify-center mb-4">
        <div className="bg-white p-4 rounded-lg border-2 border-gray-200">
          <QRCode
            value={paymentUrl}
            size={200}
            style={{ height: 'auto', maxWidth: '100%', width: '100%' }}
            viewBox="0 0 256 256"
          />
        </div>
      </div>
      <p className="text-xs text-gray-500 text-center mb-2">Scan with your Lightning wallet to pay</p>
    </div>
  )
}

function PaymentActions({
  copied,
  onCopy,
  onOpenWallet,
}: {
  copied: boolean
  onCopy: () => Promise<void>
  onOpenWallet: () => void
}) {
  return (
    <div className="flex gap-2">
      <button
        onClick={() => {
          void onCopy()
        }}
        className="flex-1 px-4 py-2 bg-gray-200 hover:bg-gray-300 rounded-lg font-medium transition-colors"
      >
        {copied ? 'Copied!' : 'Copy Invoice'}
      </button>
      <button
        onClick={onOpenWallet}
        className="flex-1 px-4 py-2 bg-orange-500 hover:bg-orange-600 text-white rounded-lg font-medium transition-colors"
      >
        Pay with Alby
      </button>
    </div>
  )
}

function ExpiredNotice({ show }: { show: boolean }) {
  if (!show) {
    return null
  }
  return (
    <div className="mt-4 p-3 bg-red-50 border border-red-200 rounded-lg">
      <p className="text-sm text-red-700 font-semibold mb-2">This invoice has expired</p>
      <p className="text-xs text-red-600">Please close this modal and try again to generate a new invoice.</p>
    </div>
  )
}

function usePaymentModalState(invoice: AlbyInvoice, onPaymentComplete: () => void) {
  const [copied, setCopied] = useState(false)
  const [errorMessage, setErrorMessage] = useState<string | null>(null)
  const paymentUrl = `lightning:${invoice.invoice}`
  const timeRemaining = useInvoiceTimer(invoice.expiresAt)

  const handleCopy = useCallback(async () => {
    try {
      await navigator.clipboard.writeText(invoice.invoice)
      setCopied(true)
      setTimeout(() => setCopied(false), 2000)
    } catch (e) {
      console.error('Failed to copy:', e)
      setErrorMessage('Failed to copy the invoice')
    }
  }, [invoice.invoice])

  const handleOpenWallet = useCallback(async () => {
    try {
      const alby = getAlbyService()
      if (!isWebLNAvailable()) {
        throw new Error('WebLN is not available. Please install Alby or another Lightning wallet extension.')
      }
      await alby.enable()
      await alby.sendPayment(invoice.invoice)
      onPaymentComplete()
    } catch (e) {
      const error = e instanceof Error ? e : new Error(String(e))
      if (error.message.includes('user rejected') || error.message.includes('cancelled')) {
        return
      }
      console.error('Payment failed:', error)
      setErrorMessage(error.message)
    }
  }, [invoice.invoice, onPaymentComplete])

  return { copied, errorMessage, paymentUrl, timeRemaining, handleCopy, handleOpenWallet }
}

export function PaymentModal({ invoice, onClose, onPaymentComplete }: PaymentModalProps) {
  const { copied, errorMessage, paymentUrl, timeRemaining, handleCopy, handleOpenWallet } =
    usePaymentModalState(invoice, onPaymentComplete)
  const handleOpenWalletSync = () => {
    void handleOpenWallet()
  }

  return (
    <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50">
      <div className="bg-white rounded-lg p-6 max-w-md w-full mx-4 max-h-[90vh] overflow-y-auto">
        <AlbyInstaller />
        <PaymentHeader amount={invoice.amount} timeRemaining={timeRemaining} onClose={onClose} />
        <InvoiceDisplay invoiceText={invoice.invoice} paymentUrl={paymentUrl} />
        <PaymentActions
          copied={copied}
          onCopy={handleCopy}
          onOpenWallet={handleOpenWalletSync}
        />
        <ExpiredNotice show={timeRemaining !== null && timeRemaining <= 0} />
        {errorMessage && (
          <p className="text-xs text-red-600 mt-3 text-center" role="alert">
            {errorMessage}
          </p>
        )}
        <p className="text-xs text-gray-500 mt-4 text-center">
          Payment will be automatically verified once completed
        </p>
      </div>
    </div>
  )
}