import { useState, useEffect } from 'react';
import { useToast } from '../../components/ui/toast/ToastContainer';
import { getCreditTransactions, CreditTransaction as BillingTransaction } from '../../services/billing.api';
import { useBillingStore } from '../../store/billingStore';
import { Card } from '../../components/ui/card';
import Badge from '../../components/ui/badge/Badge';
import { CompactPagination } from '../ui/pagination';

// Credit costs per operation (copied from Billing usage page)
const CREDIT_COSTS: Record<string, { cost: number | string; description: string }> = {
  clustering: { cost: 10, description: 'Per clustering request' },
  idea_generation: { cost: 15, description: 'Per cluster → ideas request' },
  content_generation: { cost: '1 per 100 words', description: 'Per 100 words generated' },
  image_prompt_extraction: { cost: 2, description: 'Per content piece' },
  image_generation: { cost: 5, description: 'Per image generated' },
  linking: { cost: 8, description: 'Per content piece' },
  optimization: { cost: '1 per 200 words', description: 'Per 200 words optimized' },
  site_structure_generation: { cost: 50, description: 'Per site blueprint' },
  site_page_generation: { cost: 20, description: 'Per page generated' },
};

export default function BillingUsagePanel() {
  const toast = useToast();
  const [transactions, setTransactions] = useState<BillingTransaction[]>([]);
  const [loading, setLoading] = useState(true);
  const [page, setPage] = useState(1);
  const [pageSize, setPageSize] = useState(10);
  const { balance, usageLimits, loadBalance, loadUsageLimits } = useBillingStore();

  useEffect(() => {
    loadUsage();
    loadBalance();
    loadUsageLimits();
  }, [loadBalance, loadUsageLimits]);

  const loadUsage = async () => {
    try {
      setLoading(true);
      const txnData = await getCreditTransactions();
      setTransactions(txnData.results || []);
    } catch (error: any) {
      toast.error(`Failed to load credit usage: ${error.message}`);
    } finally {
      setLoading(false);
    }
  };

  const totalPages = Math.max(1, Math.ceil(transactions.length / pageSize));
  const paginated = transactions.slice((page - 1) * pageSize, page * pageSize);

  if (loading) {
    return (
      <div className="p-4">
        <div className="text-gray-500">Loading credit usage...</div>
      </div>
    );
  }

  return (
    <div className="space-y-6">
      {balance && (
        <div className="grid grid-cols-1 md:grid-cols-3 gap-4 mb-4">
          <Card className="p-6">
            <h3 className="text-sm font-medium text-gray-600 dark:text-gray-400 mb-2">Current Balance</h3>
            <div className="text-3xl font-bold text-gray-900 dark:text-white">
              {(balance?.credits ?? 0).toLocaleString()}
            </div>
            <p className="text-sm text-gray-500 dark:text-gray-400 mt-1">Available credits</p>
          </Card>

          <Card className="p-6">
            <h3 className="text-sm font-medium text-gray-600 dark:text-gray-400 mb-2">Monthly Allocation</h3>
            <div className="text-3xl font-bold text-gray-900 dark:text-white">
              {(balance?.plan_credits_per_month ?? 0).toLocaleString()}
            </div>
            <p className="text-sm text-gray-500 dark:text-gray-400 mt-1">
              {(balance as any)?.subscription_plan || 'No plan'}
            </p>
          </Card>

          <Card className="p-6">
            <h3 className="text-sm font-medium text-gray-600 dark:text-gray-400 mb-2">Status</h3>
            <div className="mt-2">
              <Badge variant="light" className="text-lg">
                {(balance as any)?.subscription_status || 'No subscription'}
              </Badge>
            </div>
          </Card>
        </div>
      )}

      {usageLimits && (
        <Card className="p-6">
          <h2 className="text-lg font-semibold text-gray-800 dark:text-white mb-4">Plan Limits</h2>
          <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
            <div className="p-4 rounded-lg border border-gray-200 dark:border-gray-700">
              <div className="text-sm text-gray-600 dark:text-gray-400">Monthly Credits</div>
              <div className="text-2xl font-bold text-gray-900 dark:text-white">
                {usageLimits.plan_credits_per_month?.toLocaleString?.() || 0}
              </div>
              <div className="text-sm text-gray-500 dark:text-gray-400">
                {usageLimits.credits_used_this_month?.toLocaleString?.() || 0} used
              </div>
            </div>
            <div className="p-4 rounded-lg border border-gray-200 dark:border-gray-700">
              <div className="text-sm text-gray-600 dark:text-gray-400">Remaining</div>
              <div className="text-2xl font-bold text-gray-900 dark:text-white">
                {usageLimits.credits_remaining?.toLocaleString?.() || 0}
              </div>
              {usageLimits.approaching_limit && (
                <div className="text-sm text-amber-600 dark:text-amber-400 mt-1">Approaching limit</div>
              )}
            </div>
            <div className="p-4 rounded-lg border border-gray-200 dark:border-gray-700">
              <div className="text-sm text-gray-600 dark:text-gray-400">Usage %</div>
              <div className="text-2xl font-bold text-gray-900 dark:text-white">
                {usageLimits.percentage_used?.toFixed?.(0) || 0}%
              </div>
            </div>
          </div>
        </Card>
      )}

      <Card className="p-6">
        <h2 className="text-lg font-semibold text-gray-800 dark:text-white mb-4">Credit Costs per Operation</h2>
        <p className="text-sm text-gray-600 dark:text-gray-400 mb-4">Understanding how credits are consumed for each operation type</p>
        <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4">
          {Object.entries(CREDIT_COSTS).map(([operation, info]) => (
            <div key={operation} className="flex items-start justify-between p-3 bg-gray-50 dark:bg-gray-800 rounded-lg">
              <div className="flex-1">
                <div className="font-medium text-gray-900 dark:text-white capitalize">
                  {operation.replace(/_/g, ' ')}
                </div>
                <div className="text-sm text-gray-600 dark:text-gray-400 mt-1">
                  {info.description}
                </div>
              </div>
              <div className="ml-4 text-right">
                <Badge variant="light" color="primary" className="font-semibold">
                  {typeof info.cost === 'number' ? `${info.cost} credits` : info.cost}
                </Badge>
              </div>
            </div>
          ))}
        </div>
      </Card>

      <div>
        <h2 className="text-lg font-semibold text-gray-800 dark:text-white mb-4">Credit Activity</h2>
        <Card className="p-6">
          <div className="overflow-x-auto">
            <table className="w-full">
              <thead>
                <tr className="border-b border-gray-200 dark:border-gray-700">
                  <th className="text-left py-3 px-4 text-sm font-medium text-gray-700 dark:text-gray-300">Date</th>
                  <th className="text-left py-3 px-4 text-sm font-medium text-gray-700 dark:text-gray-300">Type</th>
                  <th className="text-left py-3 px-4 text-sm font-medium text-gray-700 dark:text-gray-300">Amount</th>
                  <th className="text-left py-3 px-4 text-sm font-medium text-gray-700 dark:text-gray-300">Description</th>
                  <th className="text-left py-3 px-4 text-sm font-medium text-gray-700 dark:text-gray-300">Reference</th>
                </tr>
              </thead>
              <tbody>
                {paginated.map((txn) => (
                  <tr key={txn.id} className="border-b border-gray-100 dark:border-gray-800">
                    <td className="py-3 px-4 text-sm text-gray-900 dark:text-white">{new Date(txn.created_at).toLocaleString()}</td>
                    <td className="py-3 px-4">
                      <Badge variant="light" color={txn.amount >= 0 ? 'success' : 'error'}>{txn.transaction_type}</Badge>
                    </td>
                    <td className={`py-3 px-4 text-sm font-medium ${txn.amount >= 0 ? 'text-green-600 dark:text-green-400' : 'text-red-600 dark:text-red-400'}`}>
                      {txn.amount >= 0 ? '+' : ''}{txn.amount}
                    </td>
                    <td className="py-3 px-4 text-sm text-gray-600 dark:text-gray-400">{txn.description}</td>
                    <td className="py-3 px-4 text-sm text-gray-500 dark:text-gray-500">{txn.reference_id || '-'}</td>
                  </tr>
                ))}
                {transactions.length === 0 && (
                  <tr>
                    <td colSpan={5} className="py-8 text-center text-gray-500 dark:text-gray-400">No transactions yet</td>
                  </tr>
                )}
              </tbody>
            </table>
          </div>
          {transactions.length > 0 && (
            <div className="mt-4 flex justify-between items-center">
              <div className="text-sm text-gray-500 dark:text-gray-400">
                Showing {(page - 1) * pageSize + 1}-{Math.min(page * pageSize, transactions.length)} of {transactions.length}
              </div>
              <CompactPagination
                currentPage={page}
                totalPages={totalPages}
                pageSize={pageSize}
                onPageChange={(p) => setPage(p)}
                onPageSizeChange={(size) => {
                  setPageSize(size);
                  setPage(1);
                }}
              />
            </div>
          )}
        </Card>
      </div>
    </div>
  );
}
