import { useEffect, useState, useCallback } from 'react';
import {
  Plus,
  Search,
  Pencil,
  Trash2,
  TrendingUp,
  TrendingDown,
  ChevronDown,
  ClipboardPaste,
} from 'lucide-react';

import api, { type Transaction, type Category } from '../api';
import TransactionModal from '../components/TransactionModal';
import PasteImportModal from '../components/PasteImportModal';
import ConfirmDialog from '../components/ConfirmDialog';
import BillingCycleSelector from '../components/BillingCycleSelector';

function formatAmount(amount: number, currency: string) {
  const abs = Math.abs(amount);
  if (currency === 'USD') {
    return `$${abs.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 })}`;
  }
  return `₡${abs.toLocaleString('es-CR', { minimumFractionDigits: 2, maximumFractionDigits: 2 })}`;
}

export default function Transactions() {
  const [transactions, setTransactions] = useState<Transaction[]>([]);
  const [categories, setCategories] = useState<Category[]>([]);
  const [search, setSearch] = useState('');
  const [categoryFilter, setCategoryFilter] = useState('');
  const [loading, setLoading] = useState(true);
  const [modalOpen, setModalOpen] = useState(false);
  const [importOpen, setImportOpen] = useState(false);
  const [editing, setEditing] = useState<Transaction | null>(null);
  const [deleteId, setDeleteId] = useState<number | null>(null);
  const [deleting, setDeleting] = useState(false);
  const [cycle, setCycle] = useState<{ year: number; month: number } | null>(null);

  const fetchTransactions = useCallback(async () => {
    setLoading(true);
    try {
      const params: Record<string, string> = { source: 'CREDIT_CARD', limit: '200' };
      if (search) params.search = search;
      if (categoryFilter) params.category_id = categoryFilter;
      if (cycle) {
        params.cycle_year = String(cycle.year);
        params.cycle_month = String(cycle.month);
      }
      const { data } = await api.get('/transactions/', { params });
      setTransactions(data);
    } finally {
      setLoading(false);
    }
  }, [search, categoryFilter, cycle]);

  useEffect(() => {
    api.get('/categories/').then((r) => setCategories(r.data));
  }, []);

  useEffect(() => {
    const timer = setTimeout(fetchTransactions, 300);
    return () => clearTimeout(timer);
  }, [fetchTransactions]);

  const handleDelete = async () => {
    if (deleteId === null) return;
    setDeleting(true);
    try {
      await api.delete(`/transactions/${deleteId}`);
      setDeleteId(null);
      fetchTransactions();
    } finally {
      setDeleting(false);
    }
  };

  const totalCRC = transactions
    .filter((tx) => tx.currency === 'CRC')
    .reduce((sum, tx) => sum + (tx.transaction_type === 'DEVOLUCION' ? -tx.amount : tx.amount), 0);
  const totalUSD = transactions
    .filter((tx) => tx.currency === 'USD')
    .reduce((sum, tx) => sum + (tx.transaction_type === 'DEVOLUCION' ? -tx.amount : tx.amount), 0);

  return (
    <div className="space-y-5">
      <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-4">
        <div>
          <h1 className="text-2xl font-bold">Credit Card Transactions</h1>
          <p className="text-sm text-text-muted mt-1">
            {transactions.length} transactions
            {totalCRC !== 0 && (
              <> &middot; <span className="font-mono text-text-primary">{formatAmount(totalCRC, 'CRC')}</span></>
            )}
            {totalUSD !== 0 && (
              <> &middot; <span className="font-mono text-text-primary">{formatAmount(totalUSD, 'USD')}</span></>
            )}
          </p>
        </div>
        <div className="flex gap-2">
          <button
            onClick={() => setImportOpen(true)}
            className="flex items-center gap-2 border border-border hover:bg-surface-hover text-text-secondary font-semibold px-4 py-2.5 rounded-lg text-sm transition-colors"
          >
            <ClipboardPaste className="w-4 h-4" />
            Import
          </button>
          <button
            onClick={() => {
              setEditing(null);
              setModalOpen(true);
            }}
            className="flex items-center gap-2 bg-[#606C38] hover:bg-[#7a8a4a] text-white dark:text-[#FEFAE0] font-semibold px-4 py-2.5 rounded-lg text-sm transition-colors"
          >
            <Plus className="w-4 h-4" />
            Add Transaction
          </button>
        </div>
      </div>

      {/* Billing cycle */}
      <BillingCycleSelector value={cycle} onChange={setCycle} />

      {/* Filters */}
      <div className="flex flex-col sm:flex-row gap-3">
        <div className="relative flex-1">
          <Search className="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-text-muted" />
          <input
            value={search}
            onChange={(e) => setSearch(e.target.value)}
            className="w-full bg-input-bg border border-border rounded-lg pl-10 pr-4 py-2.5 text-sm text-text-primary placeholder-text-faint focus:outline-none focus:border-[#606C38]/50 transition-colors"
            placeholder="Search merchants..."
          />
        </div>
        <div className="relative">
          <select
            value={categoryFilter}
            onChange={(e) => setCategoryFilter(e.target.value)}
            className="appearance-none bg-input-bg border border-border rounded-lg pl-4 pr-10 py-2.5 text-sm text-text-primary focus:outline-none focus:border-[#606C38]/50 transition-colors"
          >
            <option value="">All Categories</option>
            {categories.map((c) => (
              <option key={c.id} value={c.id}>
                {c.name}
              </option>
            ))}
          </select>
          <ChevronDown className="absolute right-3 top-1/2 -translate-y-1/2 w-4 h-4 text-text-muted pointer-events-none" />
        </div>
      </div>

      {/* Table */}
      <div className="bg-surface-card border border-border rounded-xl overflow-hidden">
        <div className="overflow-x-auto">
          <table className="w-full text-sm">
            <thead>
              <tr className="border-b border-border-subtle">
                <th className="text-left px-5 py-3 text-xs font-medium text-text-muted uppercase tracking-wider">
                  Date
                </th>
                <th className="text-left px-5 py-3 text-xs font-medium text-text-muted uppercase tracking-wider">
                  Merchant
                </th>
                <th className="text-left px-5 py-3 text-xs font-medium text-text-muted uppercase tracking-wider hidden md:table-cell">
                  Category
                </th>
                <th className="text-right px-5 py-3 text-xs font-medium text-text-muted uppercase tracking-wider">
                  Amount
                </th>
                <th className="text-right px-5 py-3 text-xs font-medium text-text-muted uppercase tracking-wider w-20">
                  Actions
                </th>
              </tr>
            </thead>
            <tbody className="divide-y divide-border-subtle">

                {transactions.map((tx) => (
                  <tr
                    key={tx.id}
                    className="hover:bg-surface-hover transition-colors group"
                  >
                    <td className="px-5 py-3 whitespace-nowrap">
                      <span className="font-mono text-text-secondary text-xs">
                        {new Date(tx.date).toLocaleDateString('en-US', {
                          month: 'short',
                          day: 'numeric',
                          year: 'numeric',
                        })}
                      </span>
                    </td>
                    <td className="px-5 py-3">
                      <div className="flex items-center gap-2">
                        <div
                          className={`w-6 h-6 rounded flex items-center justify-center flex-shrink-0 ${
                            tx.transaction_type === 'DEVOLUCION'
                              ? 'bg-[#606C38]/10 text-[#606C38] dark:text-[#7a8a4a]'
                              : 'bg-red-500/10 text-red-500 dark:text-red-400'
                          }`}
                        >
                          {tx.transaction_type === 'DEVOLUCION' ? (
                            <TrendingUp className="w-3 h-3" />
                          ) : (
                            <TrendingDown className="w-3 h-3" />
                          )}
                        </div>
                        <span className="truncate max-w-[200px] sm:max-w-none">{tx.merchant}</span>
                      </div>
                    </td>
                    <td className="px-5 py-3 hidden md:table-cell">
                      {tx.category ? (
                        <span className="text-xs bg-surface-hover text-text-secondary px-2 py-1 rounded">
                          {tx.category.name}
                        </span>
                      ) : (
                        <span className="text-xs text-text-faint">—</span>
                      )}
                    </td>
                    <td className="px-5 py-3 text-right whitespace-nowrap">
                      <span
                        className={`font-mono font-medium ${
                          tx.transaction_type === 'DEVOLUCION'
                            ? 'text-[#606C38] dark:text-[#7a8a4a]'
                            : ''
                        }`}
                      >
                        {tx.transaction_type === 'DEVOLUCION' ? '+' : '-'}
                        {formatAmount(tx.amount, tx.currency)}
                      </span>
                    </td>
                    <td className="px-5 py-3 text-right">
                      <div className="flex items-center justify-end gap-1 opacity-0 group-hover:opacity-100 transition-opacity">
                        <button
                          onClick={() => {
                            setEditing(tx);
                            setModalOpen(true);
                          }}
                          className="p-1.5 rounded hover:bg-surface-hover text-text-muted hover:text-text-primary transition-colors"
                        >
                          <Pencil className="w-3.5 h-3.5" />
                        </button>
                        <button
                          onClick={() => setDeleteId(tx.id)}
                          className="p-1.5 rounded hover:bg-red-500/10 text-text-muted hover:text-red-500 dark:hover:text-red-400 transition-colors"
                        >
                          <Trash2 className="w-3.5 h-3.5" />
                        </button>
                      </div>
                    </td>
                  </tr>
                ))}
            </tbody>
          </table>
        </div>

        {transactions.length === 0 && !loading && (
          <div className="px-5 py-16 text-center text-text-faint text-sm">
            No transactions found
          </div>
        )}
      </div>

      {modalOpen && (
        <TransactionModal
          transaction={editing}
          source="CREDIT_CARD"
          onClose={() => setModalOpen(false)}
          onSaved={fetchTransactions}
        />
      )}

      {importOpen && (
        <PasteImportModal
          onClose={() => setImportOpen(false)}
          onImported={fetchTransactions}
        />
      )}

      {deleteId !== null && (
        <ConfirmDialog
          title="Delete Transaction"
          message="This transaction will be permanently deleted. This action cannot be undone."
          onConfirm={handleDelete}
          onCancel={() => setDeleteId(null)}
          loading={deleting}
        />
      )}
    </div>
  );
}