import React, { useState, useCallback } from 'react'
import { useQuery } from '@tanstack/react-query'
import { useNavigate, useLocation, Link } from 'react-router-dom'
import { billingAPI, authAPI } from '@/services/api'
import { useAuthStore } from '@/store/authStore'
import { Button, Card, Input } from '@/components/ui'
import { useToast } from '@/contexts/ToastContext'
import { useThemeStore } from '@/store/themeStore'
import { getPlanColor, formatDate } from '@/lib/utils'
import { CreditCard, User, ExternalLink, AlertTriangle, Moon, Sun } from 'lucide-react'

export const SettingsPage: React.FC = () => {
  const navigate = useNavigate()
  const location = useLocation()
  const { success: showToast, error: showError } = useToast()
  const { isDark, toggle: toggleTheme } = useThemeStore()

  const tab: 'profile' | 'billing' = location.pathname === '/settings/billing' ? 'billing' : 'profile'

  const handleTabChange = useCallback((newTab: 'profile' | 'billing') => {
    const newPath = newTab === 'billing' ? '/settings/billing' : '/settings'
    if (location.pathname !== newPath) {
      navigate(newPath, { replace: true })
    }
  }, [navigate, location.pathname])

  return (
      <div className="p-6 max-w-3xl mx-auto">
        <div className="flex items-center justify-between mb-6">
          <h1 className="text-2xl font-bold text-gray-900">Settings</h1>
          <button
            onClick={toggleTheme}
            className="flex items-center gap-2 px-3 py-2 rounded-lg border border-gray-200 hover:bg-gray-100 text-sm text-gray-600 transition-colors"
            aria-label="Toggle dark mode"
          >
            {isDark ? <Sun className="w-4 h-4" /> : <Moon className="w-4 h-4" />}
            {isDark ? 'Light mode' : 'Dark mode'}
          </button>
        </div>

        {/* Tabs */}
        <div className="flex gap-1 mb-6 bg-gray-100 p-1 rounded-xl w-fit">
          {[
            { id: 'profile' as const, label: 'Profile', icon: User },
            { id: 'billing' as const, label: 'Billing', icon: CreditCard },
          ].map(({ id, label, icon: Icon }) => (
              <button
                  key={id}
                  onClick={() => handleTabChange(id)}
                  className={`flex items-center gap-1.5 px-4 py-2 rounded-lg text-sm font-medium transition-colors ${
                      tab === id
                          ? 'bg-white shadow-sm text-gray-900'
                          : 'text-gray-500 hover:text-gray-700'
                  }`}
              >
                <Icon className="w-3.5 h-3.5" />
                {label}
              </button>
          ))}
        </div>

        {tab === 'profile' && <ProfileSettings onToast={showToast} onError={showError} />}
        {tab === 'billing' && <BillingSettings onToast={showToast} onError={showError} />}
      </div>
  )
}

const ProfileSettings: React.FC<{ onToast: (msg: string) => void; onError: (msg: string) => void }> = ({ onToast, onError }) => {
  const { user, setAuth, token, logout } = useAuthStore()
  const navigate = useNavigate()
  const [companyName, setCompanyName] = useState(user?.company_name || '')
  const [currentPassword, setCurrentPassword] = useState('')
  const [newPassword, setNewPassword] = useState('')
  const [saving, setSaving] = useState(false)
  const [showDeleteModal, setShowDeleteModal] = useState(false)
  const [deleteConfirm, setDeleteConfirm] = useState('')
  const [deleting, setDeleting] = useState(false)

  const handleSave = async () => {
    setSaving(true)
    try {
      const payload: { company_name?: string; current_password?: string; new_password?: string } = {}
      if (companyName !== user?.company_name) payload.company_name = companyName
      if (newPassword) {
        payload.current_password = currentPassword
        payload.new_password = newPassword
      }
      if (Object.keys(payload).length === 0) {
        onToast('No changes to save')
        return
      }
      const updated = await authAPI.updateProfile(payload)
      setAuth(updated, token || '')
      setCurrentPassword('')
      setNewPassword('')
      onToast('Profile updated successfully')
    } catch (err) {
      const e = err as { response?: { data?: { detail?: string } } }
      onError(e.response?.data?.detail || 'Failed to update profile')
    } finally {
      setSaving(false)
    }
  }

  const handleDeleteAccount = async () => {
    if (deleteConfirm !== 'DELETE') return
    setDeleting(true)
    try {
      await authAPI.deleteAccount()
      logout()
      navigate('/')
    } catch (err) {
      const e = err as { response?: { data?: { detail?: string } } }
      onError(e.response?.data?.detail || 'Failed to delete account')
      setDeleting(false)
    }
  }

  return (
      <div className="space-y-4">
        <Card className="p-6 space-y-4">
          <h2 className="font-semibold text-gray-900">Profile Information</h2>
          <Input label="Email" value={user?.email || ''} disabled hint="Email cannot be changed" />
          <Input
            label="Company Name"
            value={companyName}
            onChange={e => setCompanyName(e.target.value)}
            placeholder="Your company name"
          />
          <div>
            <label className="block text-sm font-medium text-gray-700 mb-1.5">Plan</label>
            <div className="flex items-center gap-2">
              <span className={`px-3 py-1 text-sm font-medium rounded-full capitalize ${getPlanColor(user?.plan || 'free')}`}>
                {user?.plan || 'free'}
              </span>
              <Link to="/pricing" className="text-sm text-primary-600 hover:underline">
                Manage plan
              </Link>
            </div>
          </div>
        </Card>

        <Card className="p-6 space-y-4">
          <h2 className="font-semibold text-gray-900">Change Password</h2>
          <Input
            label="Current Password"
            type="password"
            value={currentPassword}
            onChange={e => setCurrentPassword(e.target.value)}
            placeholder="Enter current password"
          />
          <Input
            label="New Password"
            type="password"
            value={newPassword}
            onChange={e => setNewPassword(e.target.value)}
            placeholder="Min 8 characters"
            hint="Leave blank to keep current password"
          />
        </Card>

        <Button onClick={handleSave} loading={saving}>
          Save Changes
        </Button>

        {/* Danger Zone */}
        <Card className="p-6 border-red-200 bg-red-50/30">
          <h2 className="font-semibold text-red-800 mb-2 flex items-center gap-1.5">
            <AlertTriangle className="w-4 h-4" />
            Danger Zone
          </h2>
          <p className="text-sm text-red-700 mb-4">
            Permanently delete your account, all chatbots, documents, and data. This cannot be undone.
          </p>
          <Button variant="outline" className="border-red-300 text-red-700 hover:bg-red-50" onClick={() => setShowDeleteModal(true)}>
            Delete Account
          </Button>
        </Card>

        {/* Delete Account Modal */}
        {showDeleteModal && (
          <div className="fixed inset-0 bg-black/50 flex items-center justify-center z-50 p-4">
            <div className="bg-white rounded-2xl p-6 w-full max-w-md shadow-xl">
              <h3 className="text-lg font-bold text-gray-900 mb-2">Delete Account</h3>
              <p className="text-sm text-gray-500 mb-4">
                This will permanently delete your account and all associated data including chatbots, documents, conversations, and leads.
                <strong className="text-red-600"> This action cannot be undone.</strong>
              </p>
              <p className="text-sm text-gray-700 mb-2">Type <strong>DELETE</strong> to confirm:</p>
              <Input
                value={deleteConfirm}
                onChange={e => setDeleteConfirm(e.target.value)}
                placeholder="DELETE"
              />
              <div className="flex gap-3 mt-4">
                <Button variant="outline" className="flex-1" onClick={() => { setShowDeleteModal(false); setDeleteConfirm('') }}>
                  Cancel
                </Button>
                <Button
                  className="flex-1 bg-red-600 hover:bg-red-700"
                  disabled={deleteConfirm !== 'DELETE'}
                  loading={deleting}
                  onClick={handleDeleteAccount}
                >
                  Delete Account
                </Button>
              </div>
            </div>
          </div>
        )}
      </div>
  )
}

const BillingSettings: React.FC<{ onToast: (msg: string) => void; onError: (msg: string) => void }> = ({ onError }) => {
  const navigate = useNavigate()
  const [loading, setLoading] = useState(false)

  const { data: subscription } = useQuery({
    queryKey: ['subscription'],
    queryFn: billingAPI.getSubscription,
  })

  const handlePortal = async () => {
    setLoading(true)
    try {
      const { url } = await billingAPI.createPortal(window.location.href)
      window.location.href = url
    } catch (err) {
      const e = err as { response?: { data?: { detail?: string } } }
      onError(e.response?.data?.detail || 'Failed to open billing portal')
    } finally {
      setLoading(false)
    }
  }

  const plan = subscription?.plan || 'free'
  const isPaid = plan !== 'free'

  const planFeatures: Record<string, { published: string; conversations: string; codeExport: string }> = {
    free:       { published: '1',       conversations: '100/month',    codeExport: '❌ Agency+ only' },
    starter:    { published: '1',       conversations: '1,500/month',  codeExport: '❌ Agency+ only' },
    business:   { published: '3',       conversations: '5,000/month',  codeExport: '❌ Agency+ only' },
    agency:     { published: 'Unlimited', conversations: '20,000/month', codeExport: '✅ Included' },
    enterprise: { published: 'Unlimited', conversations: 'Unlimited',  codeExport: '✅ Included' },
  }
  const features = planFeatures[plan] || planFeatures.free

  return (
      <div className="space-y-4">
        <Card className="p-6">
          <h2 className="font-semibold text-gray-900 mb-4">Current Plan</h2>
          <div className="flex items-center justify-between mb-4">
            <div>
              <span className={`px-3 py-1 text-sm font-semibold rounded-full capitalize ${getPlanColor(plan)}`}>
                {plan}
              </span>
              <p className="text-xs text-gray-500 mt-1">
                Status:{' '}
                <span className={subscription?.status === 'active' ? 'text-green-600' : 'text-red-600'}>
                  {subscription?.status || 'active'}
                </span>
              </p>
            </div>
            {isPaid && subscription?.current_period_end && (
                <div className="text-right">
                  <p className="text-xs text-gray-500">Renews on</p>
                  <p className="text-sm font-medium">{formatDate(subscription.current_period_end)}</p>
                </div>
            )}
          </div>

          <div className="flex gap-3">
            {!isPaid ? (
                <Button onClick={() => navigate('/pricing')} className="flex-1">
                  Upgrade Plan
                </Button>
            ) : (
                <Button variant="outline" onClick={handlePortal} loading={loading} className="flex-1">
                  <ExternalLink className="w-3.5 h-3.5" />
                  Manage Billing
                </Button>
            )}
          </div>
        </Card>

        {/* Plan features */}
        <Card className="p-6">
          <h3 className="font-semibold text-gray-900 mb-4">Plan Features</h3>
          <div className="space-y-3">
            {[
              { label: 'Chatbots published', value: features.published },
              { label: 'Conversations/month', value: features.conversations },
              { label: 'Code export', value: features.codeExport },
            ].map(({ label, value }) => (
                <div key={label} className="flex justify-between py-2 border-b border-gray-100 last:border-0">
                  <span className="text-sm text-gray-600">{label}</span>
                  <span className="text-sm font-medium text-gray-900">{value}</span>
                </div>
            ))}
          </div>
        </Card>
      </div>
  )
}