import React, { useState, useEffect, useMemo } from 'react';
import {
  CheckCircle2, Loader2, Link2, Search, Plus,
} from 'lucide-react';
import { cn } from '@/lib/utils';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import {
  Dialog, DialogContent, DialogDescription, DialogFooter,
  DialogHeader, DialogTitle,
} from '@/components/ui/dialog';

export function transactionDate(tx) {
  return tx?.posted_date || String(tx?.transacted_at || '').slice(0, 10) || '—';
}

export function transactionTitle(tx) {
  return tx?.payee || tx?.description || tx?.memo || 'Transaction';
}

export function formatTransactionAmount(amount, currency = 'USD') {
  const value = Math.abs(Number(amount || 0)) / 100;
  const sign = Number(amount || 0) < 0 ? '-' : '+';
  return `${sign}${new Intl.NumberFormat(undefined, {
    style: 'currency',
    currency: currency || 'USD',
  }).format(value)}`;
}

export function MatchBillDialog({ open, onOpenChange, transaction, bills, onConfirm, loading, onCreateBill }) {
  const [query, setQuery] = useState('');
  const [selectedBillId, setSelectedBillId] = useState('');

  useEffect(() => {
    if (open) {
      setQuery('');
      setSelectedBillId(transaction?.matched_bill_id ? String(transaction.matched_bill_id) : '');
    }
  }, [open, transaction?.id, transaction?.matched_bill_id]);

  const filteredBills = useMemo(() => {
    const q = query.trim().toLowerCase();
    if (!q) return bills.slice(0, 40);
    return bills
      .filter(bill => String(bill.name || '').toLowerCase().includes(q))
      .slice(0, 40);
  }, [bills, query]);

  const selectedBill = bills.find(bill => String(bill.id) === String(selectedBillId));

  return (
    <Dialog open={open} onOpenChange={onOpenChange}>
      <DialogContent className="sm:max-w-2xl">
        <DialogHeader>
          <DialogTitle>Match Transaction</DialogTitle>
          <DialogDescription>
            Choose the bill this transaction paid. Nothing changes until you confirm.
          </DialogDescription>
        </DialogHeader>

        {transaction && (
          <div className="rounded-lg border border-border/60 bg-muted/25 p-3">
            <div className="flex flex-wrap items-center justify-between gap-2">
              <div className="min-w-0">
                <p className="truncate text-sm font-medium">{transactionTitle(transaction)}</p>
                <p className="mt-0.5 text-xs text-muted-foreground">
                  {transactionDate(transaction)} · {transaction.source_label || transaction.source_type_label || 'Transaction'}
                </p>
              </div>
              <p className={cn(
                'text-sm font-semibold tabular-nums',
                Number(transaction.amount) < 0 ? 'text-destructive' : 'text-emerald-600',
              )}>
                {formatTransactionAmount(transaction.amount, transaction.currency)}
              </p>
            </div>
            {transaction.description && transaction.description !== transactionTitle(transaction) && (
              <p className="mt-2 text-xs text-muted-foreground">{transaction.description}</p>
            )}
          </div>
        )}

        <div className="space-y-3">
          <label className="space-y-1.5">
            <span className="text-xs font-medium text-muted-foreground">Find bill</span>
            <div className="relative">
              <Search className="pointer-events-none absolute left-2.5 top-2.5 h-4 w-4 text-muted-foreground" />
              <Input
                value={query}
                onChange={e => setQuery(e.target.value)}
                placeholder="Search bills"
                className="pl-8"
              />
            </div>
          </label>

          <div className="max-h-72 overflow-y-auto rounded-lg border border-border/60">
            {filteredBills.length === 0 ? (
              <div className="flex flex-col items-center gap-3 px-4 py-8 text-center">
                <p className="text-sm text-muted-foreground">No bills found.</p>
                {onCreateBill && (() => {
                  const af = transaction?.advisory_filter;
                  const label = query.trim()
                    ? `Create "${query.trim()}" as a new bill`
                    : 'Create a new bill';
                  if (af?.confidence === 'high') {
                    return (
                      <span className="text-xs text-muted-foreground">
                        Probably not a bill ·{' '}
                        <button
                          type="button"
                          className="underline hover:text-foreground transition-colors"
                          onClick={() => { onOpenChange(false); onCreateBill(transaction, query.trim() || undefined); }}
                        >
                          {label}
                        </button>
                      </span>
                    );
                  }
                  return (
                    <button
                      type="button"
                      onClick={() => { onOpenChange(false); onCreateBill(transaction, query.trim() || undefined); }}
                      className={cn(
                        'flex items-center gap-1.5 text-xs hover:underline',
                        af?.confidence === 'medium' ? 'text-muted-foreground' : 'text-primary',
                      )}
                    >
                      <Plus className="h-3.5 w-3.5" />
                      {label}
                    </button>
                  );
                })()}
              </div>
            ) : (
              <div className="divide-y divide-border/40">
                {filteredBills.map(bill => (
                  <button
                    key={bill.id}
                    type="button"
                    onClick={() => setSelectedBillId(String(bill.id))}
                    className={cn(
                      'flex w-full items-center justify-between gap-3 px-4 py-3 text-left transition-colors hover:bg-muted/30',
                      String(selectedBillId) === String(bill.id) && 'bg-primary/5',
                    )}
                  >
                    <div className="min-w-0">
                      <p className="truncate text-sm font-medium">{bill.name}</p>
                      <p className="mt-0.5 text-xs text-muted-foreground">
                        Due day {bill.due_day ?? '—'} · expected ${Number(bill.expected_amount || 0).toFixed(2)}
                      </p>
                    </div>
                    {String(selectedBillId) === String(bill.id) && (
                      <CheckCircle2 className="h-4 w-4 shrink-0 text-primary" />
                    )}
                  </button>
                ))}
              </div>
            )}
          </div>
        </div>

        <DialogFooter className="gap-2">
          {onCreateBill && (() => {
            const af = transaction?.advisory_filter;
            if (af?.confidence === 'high') {
              return (
                <span className="mr-auto flex items-center gap-2 text-xs text-muted-foreground">
                  Probably not a bill
                  <button
                    type="button"
                    className="underline hover:text-foreground transition-colors"
                    onClick={() => { onOpenChange(false); onCreateBill(transaction); }}
                  >
                    create anyway
                  </button>
                </span>
              );
            }
            return (
              <Button
                type="button"
                variant="ghost"
                className={cn(
                  'mr-auto text-xs',
                  af?.confidence === 'medium'
                    ? 'text-muted-foreground/60 hover:text-muted-foreground'
                    : 'text-muted-foreground hover:text-foreground',
                )}
                onClick={() => { onOpenChange(false); onCreateBill(transaction); }}
              >
                <Plus className="h-3.5 w-3.5 mr-1.5" />
                Create Bill
              </Button>
            );
          })()}
          <Button type="button" variant="outline" onClick={() => onOpenChange(false)}>
            Cancel
          </Button>
          <Button
            type="button"
            disabled={!selectedBill || loading}
            onClick={() => selectedBill && onConfirm(selectedBill.id)}
          >
            {loading ? <><Loader2 className="h-3.5 w-3.5 mr-1.5 animate-spin" />Matching…</> : <><Link2 className="h-3.5 w-3.5 mr-1.5" />Confirm Match</>}
          </Button>
        </DialogFooter>
      </DialogContent>
    </Dialog>
  );
}