'use client';
import { useState, useEffect, useCallback } from 'react';
import { productsApi, inventoryApi, pricingApi } from '@/lib/api-client';
import type { ProductVariant, StockAvailability, VariantPrice } from '@/types';

interface ProductRow {
  productId: string;
  productName: string;
  variant: ProductVariant;
  stock: StockAvailability | null;
  price: VariantPrice | null;
  expirationDate: string | null;
  loading: boolean;
  editing: boolean;
  editValue: string;
  saving: boolean;
  msg: string;
  editingEan: boolean;
  editEanValue: string;
  savingEan: boolean;
}

type RowFilter = 'all' | 'in_stock' | 'low_stock' | 'out_of_stock' | 'expiring' | 'low_margin';

const FILTER_LABELS: Record<RowFilter, string> = {
  all: 'Todos',
  in_stock: 'En stock',
  low_stock: 'Stock bajo',
  out_of_stock: 'Sin stock',
  expiring: '⏳ Por caducar (<30 días)',
  low_margin: '📉 Margen <30%',
};

const VAT_MULTIPLIER: Record<string, number> = {
  general: 1.21,
  reduced: 1.1,
  'super-reduced': 1.04,
};

function StockBadge({ qty }: { qty: number }) {
  if (qty === 0) return <span className="px-2 py-0.5 rounded-full text-xs font-medium bg-red-100 text-red-700">Sin stock</span>;
  if (qty < 5) return <span className="px-2 py-0.5 rounded-full text-xs font-medium bg-amber-100 text-amber-700">Stock bajo ({qty})</span>;
  return <span className="px-2 py-0.5 rounded-full text-xs font-medium bg-green-100 text-green-700">En stock ({qty})</span>;
}

/** Días hasta la fecha de caducidad (negativo si ya caducó). */
function daysUntil(dateIso: string): number {
  const target = new Date(`${dateIso.slice(0, 10)}T00:00:00`);
  const today = new Date();
  today.setHours(0, 0, 0, 0);
  return Math.round((target.getTime() - today.getTime()) / 86_400_000);
}

/** Margen bruto % = (PVP − coste) / PVP × 100. Null si falta coste o precio. */
function marginPercent(price: VariantPrice | null): number | null {
  if (!price || price.costCents === null) return null;
  const grossCents = Math.round(price.netUnitAmountCents * (VAT_MULTIPLIER[price.vatRate] ?? 1.21));
  if (grossCents <= 0) return null;
  return Math.round(((grossCents - price.costCents) / grossCents) * 100);
}

function ExpirationCell({ dateIso }: { dateIso: string | null }) {
  if (!dateIso) return <span className="text-gray-300">—</span>;
  const days = daysUntil(dateIso);
  const label = new Date(`${dateIso.slice(0, 10)}T00:00:00`).toLocaleDateString('es-ES', {
    day: '2-digit', month: '2-digit', year: 'numeric',
  });
  if (days < 0) {
    return <span className="px-2 py-0.5 rounded-full text-xs font-medium bg-red-100 text-red-700">Caducado ({label})</span>;
  }
  if (days <= 30) {
    return (
      <span className="px-2 py-0.5 rounded-full text-xs font-medium bg-amber-100 text-amber-700" title={label}>
        Caduca en {days} día{days === 1 ? '' : 's'}
      </span>
    );
  }
  return <span className="text-xs text-gray-600">{label}</span>;
}

export default function InventoryPage() {
  const [rows, setRows] = useState<ProductRow[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState('');
  const [filter, setFilter] = useState<RowFilter>('all');
  const [search, setSearch] = useState('');
  const [debouncedSearch, setDebouncedSearch] = useState('');

  useEffect(() => {
    const t = setTimeout(() => setDebouncedSearch(search), 400);
    return () => clearTimeout(t);
  }, [search]);

  // Load products + single internal variant + stock + price (F-108/F-110)
  const load = useCallback(async () => {
    setLoading(true);
    setError('');
    try {
      const { items: products } = await productsApi.list({
        limit: 100,
        q: debouncedSearch || undefined,
      });

      const productRows: ProductRow[] = [];

      for (const product of products ?? []) {
        const { items: variants } = await productsApi.getVariants(product.id);
        const variant = variants?.[0];
        if (!variant) continue;
        productRows.push({
          productId: product.id,
          productName: product.name,
          variant,
          stock: null,
          price: null,
          expirationDate: product.expirationDate ?? null,
          loading: true,
          editing: false,
          editValue: '',
          saving: false,
          msg: '',
          editingEan: false,
          editEanValue: '',
          savingEan: false,
        });
      }

      setRows(productRows);

      for (const row of productRows) {
        inventoryApi.getAvailability(row.variant.id)
          .then((stock) => {
            setRows((prev) =>
              prev.map((r) =>
                r.variant.id === row.variant.id
                  ? { ...r, stock, loading: false, editValue: String(stock.availableQuantity) }
                  : r,
              ),
            );
          })
          .catch(() => {
            setRows((prev) =>
              prev.map((r) =>
                r.variant.id === row.variant.id ? { ...r, loading: false, editValue: '0' } : r,
              ),
            );
          });

        pricingApi.getVariantPrice(row.variant.id)
          .then((price) => {
            setRows((prev) =>
              prev.map((r) => (r.variant.id === row.variant.id ? { ...r, price } : r)),
            );
          })
          .catch(() => {
            // Sin precio: margen no disponible.
          });
      }
    } catch (e) {
      setError(e instanceof Error ? e.message : 'Error al cargar inventario');
    } finally {
      setLoading(false);
    }
  }, [debouncedSearch]);

  useEffect(() => { load(); }, [load]);

  // Save EAN inline
  const handleSaveEan = async (variantId: string, productId: string, newEan: string) => {
    setRows(prev => prev.map(r => r.variant.id === variantId ? { ...r, savingEan: true } : r));
    try {
      const updated = await productsApi.updateVariant(productId, variantId, { ean: newEan || null });
      setRows(prev => prev.map(r => r.variant.id === variantId ? { ...r, variant: { ...r.variant, ean: updated.ean }, editingEan: false, savingEan: false } : r));
    } catch {
      setRows(prev => prev.map(r => r.variant.id === variantId ? { ...r, savingEan: false } : r));
    }
  };

  // Save Stock inline (used by Stock cell on blur/Enter)
  const saveStockInline = async (variantId: string, value: string) => {
    const qty = parseInt(value, 10);
    if (isNaN(qty) || qty < 0) {
      setRows((prev) =>
        prev.map((r) =>
          r.variant.id === variantId
            ? { ...r, editing: false, editValue: String(r.stock?.availableQuantity ?? 0), msg: 'Error' }
            : r,
        ),
      );
      return;
    }
    setRows((prev) => prev.map((r) => (r.variant.id === variantId ? { ...r, saving: true } : r)));
    try {
      const result = await inventoryApi.setStock(variantId, qty);
      setRows((prev) =>
        prev.map((r) =>
          r.variant.id === variantId
            ? {
                ...r,
                stock: { available: result.available > 0, availableQuantity: result.available },
                editing: false,
                saving: false,
                editValue: String(result.available),
                msg: '✓ Guardado',
              }
            : r,
        ),
      );
      setTimeout(() => {
        setRows((prev) => prev.map((r) => (r.variant.id === variantId ? { ...r, msg: '' } : r)));
      }, 3000);
    } catch {
      setRows((prev) =>
        prev.map((r) =>
          r.variant.id === variantId
            ? {
                ...r,
                saving: false,
                editing: false,
                editValue: String(r.stock?.availableQuantity ?? 0),
                msg: 'Error',
              }
            : r,
        ),
      );
    }
  };

  // Filter + sort rows
  const filtered = (() => {
    let result = rows.filter((r) => {
      const qty = r.stock?.availableQuantity ?? 0;
      if (filter === 'in_stock') return qty >= 5;
      if (filter === 'low_stock') return qty > 0 && qty < 5;
      if (filter === 'out_of_stock') return qty === 0;
      if (filter === 'expiring') {
        return r.expirationDate !== null && daysUntil(r.expirationDate) <= 30;
      }
      if (filter === 'low_margin') {
        const margin = marginPercent(r.price);
        return margin !== null && margin < 30;
      }
      return true;
    });
    if (filter === 'expiring') {
      result = [...result].sort(
        (a, b) => daysUntil(a.expirationDate ?? '') - daysUntil(b.expirationDate ?? ''),
      );
    } else if (filter === 'low_margin') {
      result = [...result].sort(
        (a, b) => (marginPercent(a.price) ?? 0) - (marginPercent(b.price) ?? 0),
      );
    }
    return result;
  })();

  const inStockCount = rows.filter((r) => (r.stock?.availableQuantity ?? 0) >= 5).length;
  const lowStockCount = rows.filter((r) => {
    const q = r.stock?.availableQuantity ?? 0;
    return q > 0 && q < 5;
  }).length;
  const outOfStockCount = rows.filter((r) => (r.stock?.availableQuantity ?? 0) === 0).length;

  return (
    <div className="space-y-6">
      {/* Header */}
      <div className="flex items-center justify-between">
        <div>
          <h1 className="text-2xl font-bold text-gray-900">Inventario</h1>
          <p className="text-sm text-gray-500 mt-0.5">{rows.length} productos</p>
        </div>
      </div>

      {/* Stats */}
      <div className="grid grid-cols-3 gap-4">
        {[
          { label: 'En stock', count: inStockCount, cls: 'bg-green-50 border-green-100 text-green-700' },
          { label: 'Stock bajo', count: lowStockCount, cls: 'bg-amber-50 border-amber-100 text-amber-700' },
          { label: 'Sin stock', count: outOfStockCount, cls: 'bg-red-50 border-red-100 text-red-700' },
        ].map(({ label, count, cls }) => (
          <div key={label} className={`p-4 rounded-xl border ${cls}`}>
            <p className="text-2xl font-bold">{count}</p>
            <p className="text-sm font-medium">{label}</p>
          </div>
        ))}
      </div>

      {/* Search + filters */}
      <div className="flex items-center gap-4 flex-wrap">
        <div className="relative flex-1 max-w-sm min-w-52">
          <input
            type="search"
            id="admin-inventory-search"
            name="q"
            placeholder="Buscar por EAN o nombre..."
            value={search}
            onChange={(e) => setSearch(e.target.value)}
            className="w-full pl-10 pr-4 py-2.5 border border-gray-300 rounded-xl text-sm focus:ring-2 focus:ring-[#2D6A4F] focus:border-transparent outline-none"
          />
          <svg className="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-gray-400" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
            <circle cx="11" cy="11" r="8" /><path d="M21 21l-4.35-4.35" />
          </svg>
        </div>

        <div className="flex gap-2 flex-wrap">
          {(Object.keys(FILTER_LABELS) as RowFilter[]).map((f) => (
            <button
              key={f}
              onClick={() => setFilter(f)}
              className={`px-3 py-1.5 rounded-lg text-xs font-medium transition-colors ${
                filter === f
                  ? 'bg-[#2D6A4F] text-white'
                  : 'bg-white border border-gray-300 text-gray-600 hover:bg-gray-50'
              }`}
            >
              {FILTER_LABELS[f]}
            </button>
          ))}
        </div>

        <button
          onClick={load}
          className="text-sm text-[#2D6A4F] hover:underline"
        >
          Recargar
        </button>
      </div>

      {/* Table */}
      <div className="bg-white border border-gray-200 rounded-xl overflow-hidden">
        {loading ? (
          <div className="p-12 flex items-center justify-center gap-3 text-gray-400">
            <div className="h-5 w-5 border-2 border-gray-300 border-t-[#2D6A4F] rounded-full animate-spin" />
            <span className="text-sm">Cargando inventario...</span>
          </div>
        ) : error ? (
          <div className="text-center">
            <p className="text-red-600 text-sm mb-3">{error}</p>
            <button onClick={load} className="text-sm text-[#2D6A4F] hover:underline">Reintentar</button>
          </div>
        ) : filtered.length === 0 ? (
          <div className="p-12 text-center">
            <p className="text-4xl mb-3">📦</p>
            <p className="text-gray-500 text-sm">No hay productos para este filtro</p>
          </div>
        ) : (
          <div className="overflow-x-auto">
            <table className="w-full text-sm">
              <thead>
                <tr className="bg-gray-50 border-b border-gray-200 text-left">
                  <th className="px-4 py-3 font-semibold text-gray-600 text-xs uppercase tracking-wide">Producto</th>
                  <th className="px-4 py-3 font-semibold text-gray-600 text-xs uppercase tracking-wide">EAN</th>
                  <th className="px-4 py-3 font-semibold text-gray-600 text-xs uppercase tracking-wide">Caducidad</th>
                  <th className="px-4 py-3 font-semibold text-gray-600 text-xs uppercase tracking-wide">Margen</th>
                  <th className="px-4 py-3 font-semibold text-gray-600 text-xs uppercase tracking-wide">Stock</th>
                  <th className="px-4 py-3 font-semibold text-gray-600 text-xs uppercase tracking-wide">Estado</th>
                </tr>
              </thead>
              <tbody className="divide-y divide-gray-50">
                {filtered.map((row) => {
                  const margin = marginPercent(row.price);
                  return (
                    <tr key={row.variant.id} className="hover:bg-gray-50/50 transition-colors">
                      <td className="px-4 py-3">
                        <p className="text-sm font-medium text-gray-900">{row.productName}</p>
                      </td>
                      <td className="px-4 py-3">
                        {row.editingEan ? (
                          <input
                            autoFocus
                            value={row.editEanValue}
                            onChange={e => setRows(prev => prev.map(r => r.variant.id === row.variant.id ? { ...r, editEanValue: e.target.value } : r))}
                            onBlur={() => handleSaveEan(row.variant.id, row.productId, row.editEanValue)}
                            onKeyDown={e => { if (e.key === 'Enter') handleSaveEan(row.variant.id, row.productId, row.editEanValue); if (e.key === 'Escape') setRows(prev => prev.map(r => r.variant.id === row.variant.id ? { ...r, editingEan: false } : r)); }}
                            disabled={row.savingEan}
                            placeholder="—"
                            className="w-full px-2 py-1 border border-[#2D6A4F] rounded text-xs focus:ring-1 focus:ring-[#2D6A4F] outline-none disabled:opacity-50"
                          />
                        ) : (
                          <button
                            onClick={() => setRows(prev => prev.map(r => r.variant.id === row.variant.id ? { ...r, editingEan: true, editEanValue: row.variant.ean ?? '' } : r))}
                            title="Clic para editar EAN"
                            className="font-mono text-xs text-gray-400 hover:text-[#2D6A4F] cursor-text text-left w-full truncate block disabled:opacity-50"
                          >
                            {row.variant.ean ?? '—'}
                          </button>
                        )}
                      </td>
                      <td className="px-4 py-3">
                        <ExpirationCell dateIso={row.expirationDate} />
                      </td>
                      <td className="px-4 py-3">
                        {margin === null ? (
                          <span className="text-gray-300">—</span>
                        ) : (
                          <span className={`text-xs font-bold ${margin >= 30 ? 'text-green-600' : margin >= 10 ? 'text-amber-600' : 'text-red-600'}`}>
                            {margin}%
                          </span>
                        )}
                      </td>
                      <td className="px-4 py-3">
                        {row.loading ? (
                          <span className="text-gray-300">—</span>
                        ) : row.editing ? (
                          <div className="flex items-center gap-2">
                            <input
                              autoFocus
                              type="number"
                              min={0}
                              value={row.editValue}
                              onChange={(e) =>
                                setRows((prev) =>
                                  prev.map((r) =>
                                    r.variant.id === row.variant.id
                                      ? { ...r, editValue: e.target.value }
                                      : r,
                                  ),
                                )
                              }
                              onBlur={() => saveStockInline(row.variant.id, row.editValue)}
                              onKeyDown={(e) => {
                                if (e.key === 'Enter') saveStockInline(row.variant.id, row.editValue);
                                if (e.key === 'Escape')
                                  setRows((prev) =>
                                    prev.map((r) =>
                                      r.variant.id === row.variant.id
                                        ? {
                                            ...r,
                                            editing: false,
                                            editValue: String(r.stock?.availableQuantity ?? 0),
                                          }
                                        : r,
                                    ),
                                  );
                              }}
                              disabled={row.saving}
                              className="w-20 px-2 py-1 border border-gray-300 rounded-lg text-sm focus:ring-1 focus:ring-[#2D6A4F] outline-none"
                            />
                            {row.msg && (
                              <span className={`text-xs ${row.msg === '✓' || row.msg === '✓ Guardado' ? 'text-green-600' : 'text-red-600'}`}>
                                {row.msg}
                              </span>
                            )}
                          </div>
                        ) : (
                          <button
                            onClick={() =>
                              setRows((prev) =>
                                prev.map((r) =>
                                  r.variant.id === row.variant.id
                                    ? { ...r, editing: true, editValue: String(r.stock?.availableQuantity ?? 0) }
                                    : r,
                                ),
                              )
                            }
                            title="Clic para editar stock"
                            className="font-medium text-gray-900 hover:text-[#2D6A4F] cursor-text disabled:opacity-50"
                          >
                            {row.stock?.availableQuantity ?? '—'}
                          </button>
                        )}
                      </td>
                      <td className="px-4 py-3">
                        <StockBadge qty={row.stock?.availableQuantity ?? 0} />
                      </td>
                    </tr>
                  );
                })}
              </tbody>
            </table>
          </div>
        )}
      </div>
    </div>
  );
}