'use client'
import { useState, useEffect } from 'react'
import {
  Container,
  Box,
  Typography,
  Button,
  Card,
  CardContent,
  Paper,
  LinearProgress,
  Chip,
  CircularProgress,
  Alert,
  Switch,
  FormControlLabel,
  Divider
} from '@mui/material'
import {
  CheckCircle,
  Favorite,
  TrendingUp,
  Settings as SettingsIcon
} from '@mui/icons-material'
import { useRouter } from 'next/navigation'
import { useTranslations, useLocale } from 'next-intl'

interface UserSubscriptionData {
  tier: string
  status: string
  conversationLimit: number
  conversationCount: number
  limitResetDate: string | null
}

const STRIPE_PRICES = {
  monthly: process.env.NEXT_PUBLIC_STRIPE_PREMIUM_MONTHLY_PRICE_ID || '',
  yearly: process.env.NEXT_PUBLIC_STRIPE_PREMIUM_YEARLY_PRICE_ID || ''
}

export default function SubscriptionPage() {
  const router = useRouter()
  const locale = useLocale()
  const t = useTranslations('subscription')

  const [loading, setLoading] = useState(true)
  const [processing, setProcessing] = useState(false)
  const [error, setError] = useState('')
  const [userData, setUserData] = useState<UserSubscriptionData | null>(null)
  const [billingInterval, setBillingInterval] = useState<'month' | 'year'>('month')

  useEffect(() => {
    fetchUserData()
  }, [])

  const fetchUserData = async () => {
    try {
      const token = localStorage.getItem('authToken')
      if (!token) {
        router.push(`/${locale}/login`)
        return
      }

      const response = await fetch('/api/user/profile', {
        headers: {
          'Authorization': `Bearer ${token}`
        }
      })

      if (response.ok) {
        const data = await response.json()
        setUserData({
          tier: data.user.subscriptionTier || 'free',
          status: data.user.subscriptionStatus || 'active',
          conversationLimit: data.user.conversationLimit || 10,
          conversationCount: data.user.conversationCount || 0,
          limitResetDate: data.user.limitResetDate
        })
      } else {
        setError(t('errors.loadFailed'))
      }
    } catch (err) {
      console.error('Error fetching user data:', err)
      setError(t('errors.generic'))
    } finally {
      setLoading(false)
    }
  }

  const handleUpgrade = async () => {
    setProcessing(true)
    setError('')

    try {
      const token = localStorage.getItem('authToken')
      if (!token) {
        router.push(`/${locale}/login`)
        return
      }

      const priceId = billingInterval === 'month' ? STRIPE_PRICES.monthly : STRIPE_PRICES.yearly

      const response = await fetch('/api/subscriptions/checkout', {
        method: 'POST',
        headers: {
          'Authorization': `Bearer ${token}`,
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          priceId,
          interval: billingInterval,
          locale
        })
      })

      const data = await response.json()

      if (data.success && data.url) {
        window.location.href = data.url
      } else {
        setError(data.error || t('errors.checkoutFailed'))
      }
    } catch (err) {
      console.error('Error creating checkout:', err)
      setError(t('errors.generic'))
    } finally {
      setProcessing(false)
    }
  }

  const handleManageSubscription = async () => {
    setProcessing(true)
    setError('')

    try {
      const token = localStorage.getItem('authToken')
      if (!token) {
        router.push(`/${locale}/login`)
        return
      }

      const response = await fetch('/api/subscriptions/portal', {
        method: 'POST',
        headers: {
          'Authorization': `Bearer ${token}`,
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({ locale })
      })

      const data = await response.json()

      if (data.success && data.url) {
        window.location.href = data.url
      } else {
        setError(data.error || t('errors.portalFailed'))
      }
    } catch (err) {
      console.error('Error opening portal:', err)
      setError(t('errors.generic'))
    } finally {
      setProcessing(false)
    }
  }

  const formatResetDate = (dateString: string | null) => {
    if (!dateString) return ''
    const date = new Date(dateString)
    return date.toLocaleDateString(locale, { year: 'numeric', month: 'long', day: 'numeric' })
  }

  const isPremium = userData?.tier === 'premium'
  const usagePercentage = userData ? (userData.conversationCount / userData.conversationLimit) * 100 : 0
  const remaining = userData ? Math.max(0, userData.conversationLimit - userData.conversationCount) : 0

  if (loading) {
    return (
      <Container maxWidth="lg" sx={{ py: 8, display: 'flex', justifyContent: 'center' }}>
        <CircularProgress />
      </Container>
    )
  }

  return (
    <Container maxWidth="lg" sx={{ py: 8 }}>
      {/* Header */}
      <Box sx={{ mb: 6, textAlign: 'center' }}>
        <Typography variant="h3" component="h1" gutterBottom>
          {t('title')}
        </Typography>
        <Typography variant="body1" color="text.secondary">
          {t('subtitle')}
        </Typography>
      </Box>

      {/* Error Alert */}
      {error && (
        <Alert severity="error" sx={{ mb: 4 }} onClose={() => setError('')}>
          {error}
        </Alert>
      )}

      {/* Current Plan & Usage */}
      {userData && (
        <Paper elevation={2} sx={{ p: 4, mb: 6 }}>
          <Box sx={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', mb: 3 }}>
            <Box>
              <Typography variant="h5" gutterBottom>
                {t('currentPlan')}
              </Typography>
              <Chip
                label={isPremium ? t('premium.name') : t('free.name')}
                color={isPremium ? 'primary' : 'default'}
                sx={{ fontWeight: 600 }}
              />
              {isPremium && (
                <Chip
                  label={t(`status.${userData.status}`)}
                  color={userData.status === 'active' ? 'success' : 'warning'}
                  size="small"
                  sx={{ ml: 1 }}
                />
              )}
            </Box>
            {isPremium && (
              <Button
                variant="outlined"
                startIcon={<SettingsIcon />}
                onClick={handleManageSubscription}
                disabled={processing}
              >
                {t('managePlan')}
              </Button>
            )}
          </Box>

          <Divider sx={{ my: 3 }} />

          {/* Usage Statistics */}
          <Box>
            <Typography variant="h6" gutterBottom>
              {t('usage.title')}
            </Typography>
            <Box sx={{ mb: 2 }}>
              <Box sx={{ display: 'flex', justifyContent: 'space-between', mb: 1 }}>
                <Typography variant="body2">
                  {t('usage.conversations')}
                </Typography>
                <Typography variant="body2" fontWeight="600">
                  {isPremium ? (
                    t('usage.unlimited')
                  ) : (
                    `${userData.conversationCount} ${t('usage.of')} ${userData.conversationLimit}`
                  )}
                </Typography>
              </Box>
              {!isPremium && (
                <>
                  <LinearProgress
                    variant="determinate"
                    value={Math.min(usagePercentage, 100)}
                    sx={{ height: 8, borderRadius: 1 }}
                  />
                  <Typography variant="caption" color="text.secondary" sx={{ mt: 1, display: 'block' }}>
                    {remaining} {t('usage.remaining')} • {t('usage.resetsOn')} {formatResetDate(userData.limitResetDate)}
                  </Typography>
                </>
              )}
            </Box>
          </Box>
        </Paper>
      )}

      {/* Billing Interval Toggle */}
      {!isPremium && (
        <Box sx={{ display: 'flex', justifyContent: 'center', mb: 4 }}>
          <FormControlLabel
            control={
              <Switch
                checked={billingInterval === 'year'}
                onChange={(e) => setBillingInterval(e.target.checked ? 'year' : 'month')}
              />
            }
            label={
              <Box sx={{ display: 'flex', alignItems: 'center', gap: 1 }}>
                <Typography>{t('billing.yearly')}</Typography>
                <Chip label={t('premium.savings')} size="small" color="success" />
              </Box>
            }
          />
        </Box>
      )}

      {/* Plan Comparison */}
      <Box sx={{ display: 'flex', gap: 4, flexWrap: 'wrap', justifyContent: 'center' }}>
        {/* Free Plan */}
        <Card sx={{ flex: { xs: '1 1 100%', md: '1 1 400px' }, maxWidth: 450 }}>
          <CardContent sx={{ p: 4 }}>
            <Typography variant="h5" gutterBottom fontWeight="600">
              {t('free.name')}
            </Typography>
            <Box sx={{ my: 3 }}>
              <Typography variant="h3" component="div" fontWeight="700">
                {t('free.price')}
              </Typography>
              <Typography variant="body2" color="text.secondary">
                {t('free.period')}
              </Typography>
            </Box>
            <Typography variant="body2" color="text.secondary" sx={{ mb: 3 }}>
              {t('free.description')}
            </Typography>
            <Box sx={{ mb: 3 }}>
              {[
                t('free.features.conversations'),
                t('free.features.bible'),
                t('free.features.prayer'),
                t('free.features.bookmarks')
              ].map((feature, index) => (
                <Box key={index} sx={{ display: 'flex', gap: 1, mb: 1.5 }}>
                  <CheckCircle color="success" fontSize="small" />
                  <Typography variant="body2">{feature}</Typography>
                </Box>
              ))}
            </Box>
            <Button
              variant="outlined"
              fullWidth
              disabled
              sx={{ py: 1.5 }}
            >
              {t('free.cta')}
            </Button>
          </CardContent>
        </Card>

        {/* Premium Plan */}
        <Card
          sx={{
            flex: { xs: '1 1 100%', md: '1 1 400px' },
            maxWidth: 450,
            border: 2,
            borderColor: 'primary.main',
            position: 'relative'
          }}
        >
          {!isPremium && (
            <Chip
              label="Recommended"
              color="primary"
              size="small"
              sx={{
                position: 'absolute',
                top: 16,
                right: 16,
                fontWeight: 600
              }}
            />
          )}
          <CardContent sx={{ p: 4 }}>
            <Typography variant="h5" gutterBottom fontWeight="600">
              {t('premium.name')}
            </Typography>
            <Box sx={{ my: 3 }}>
              <Typography variant="h3" component="div" fontWeight="700">
                {billingInterval === 'month' ? t('premium.priceMonthly') : t('premium.priceYearly')}
              </Typography>
              <Typography variant="body2" color="text.secondary">
                {billingInterval === 'month' ? t('premium.periodMonthly') : t('premium.periodYearly')}
              </Typography>
            </Box>
            <Typography variant="body2" color="text.secondary" sx={{ mb: 3 }}>
              {t('premium.description')}
            </Typography>
            <Box sx={{ mb: 3 }}>
              {[
                t('premium.features.conversations'),
                t('premium.features.bible'),
                t('premium.features.prayer'),
                t('premium.features.bookmarks'),
                t('premium.features.support'),
                t('premium.features.early')
              ].map((feature, index) => (
                <Box key={index} sx={{ display: 'flex', gap: 1, mb: 1.5 }}>
                  <CheckCircle color="primary" fontSize="small" />
                  <Typography variant="body2">{feature}</Typography>
                </Box>
              ))}
            </Box>
            <Button
              variant="contained"
              fullWidth
              size="large"
              startIcon={isPremium ? <TrendingUp /> : <Favorite />}
              onClick={isPremium ? handleManageSubscription : handleUpgrade}
              disabled={processing}
              sx={{ py: 1.5 }}
            >
              {processing ? t('premium.ctaProcessing') : isPremium ? t('managePlan') : t('premium.cta')}
            </Button>
          </CardContent>
        </Card>
      </Box>
    </Container>
  )
}