'use client';

import { useState, useEffect } from 'react';
import { db, Item } from '@/lib/db';
import { inventoryApi } from '@/lib/api';
import PageShell from '@/components/PageShell';
import { toast } from 'react-hot-toast';
import { 
  Package, 
  ChevronRight, 
  ChevronDown, 
  BarChart3, 
  Layers, 
  Plus, 
  Minus, 
  Trash2, 
  X,
  AlertTriangle,
  Tag,
  Edit2
} from 'lucide-react';
import { clsx, type ClassValue } from 'clsx';
import { twMerge } from 'tailwind-merge';

function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs));
}

export default function InventoryPage() {
  const [mounted, setMounted] = useState(false);
  const [inventory, setInventory] = useState<Item[]>([]);
  const [stats, setStats] = useState<any>(null);
  const [expandedCategory, setExpandedCategory] = useState<string | null>(null);
  const [searchQuery, setSearchQuery] = useState('');
  const [currentUser, setCurrentUser] = useState<any | null>(null);
  
  // Stock Adjustment State
  const [selectedItem, setSelectedItem] = useState<Item | null>(null);
  const [adjustQty, setAdjustQty] = useState<number>(1);
  const [adjustType, setAdjustType] = useState<'ADD' | 'REMOVE' | 'TRASH'>('ADD');
  const [trashReason, setTrashReason] = useState('Damaged');

  // Item Editing state
  const [isEditing, setIsEditing] = useState(false);
  const [editedItem, setEditedItem] = useState<Partial<Item>>({});
  const [categoriesList, setCategoriesList] = useState<any[]>([]);

  // Category Editing state
  const [editingCategory, setEditingCategory] = useState<any | null>(null);
  const [catEditedName, setCatEditedName] = useState('');
  const [catEditedDesc, setCatEditedDesc] = useState('');

  useEffect(() => {
    setMounted(true);
    const savedUser = localStorage.getItem('inventory_user');
    if (savedUser) {
      setCurrentUser(JSON.parse(savedUser));
    }
    
    loadData();
  }, []);

  const loadData = async () => {
    // Load local items
    const cached = await db.items.toArray();
    setInventory(cached);

    try {
      // Load backend stats
      const s = await inventoryApi.getStats();
      setStats(s);
      
      const cats = await inventoryApi.getCategories();
      setCategoriesList(cats);

      // Load fresh items
      const res = await inventoryApi.getItems();
      setInventory(res);
      // Sync local DB
      await db.items.clear();
      await db.items.bulkAdd(res);
    } catch (err) {
      console.error("Failed to load backend data", err);
    }
  };

  const handleAdjustStock = async () => {
    if (!selectedItem) return;
    const toastId = toast.loading("Processing...");
    
    try {
      const isOnline = navigator.onLine;
      const finalAdjustQty = adjustQty;
      const newQty = selectedItem.quantity + (adjustType === 'ADD' ? adjustQty : -adjustQty);

      // Local Update
      await db.items.update(selectedItem.id!, { quantity: newQty });
      setInventory(prev => prev.map(i => i.id === selectedItem.id ? { ...i, quantity: newQty } : i));
      
      if (isOnline) {
        const endpoint = adjustType === 'ADD' ? 'check-in' : (adjustType === 'TRASH' ? 'trash' : 'check-out');
        const payload: any = {
           barcode: selectedItem.barcode,
           quantity: finalAdjustQty,
           user_id: currentUser?.id || 1
        };
        if (adjustType === 'TRASH') payload.reason = trashReason;
        
        await inventoryApi.adjustStock(endpoint, payload);
        toast.success("Inventory updated & synced", { id: toastId });
      } else {
        await db.pendingOperations.add({
          type: adjustType === 'ADD' ? 'CHECK_IN' : (adjustType === 'TRASH' ? 'TRASH' : 'CHECK_OUT'),
          barcode: selectedItem.barcode,
          quantity: finalAdjustQty,
          timestamp: Date.now(),
          synced: 0,
          uuid: crypto.randomUUID()
        } as any);
        toast.success("Saved locally (Offline)", { id: toastId });
      }

      setSelectedItem(null);
      setAdjustQty(1);
    } catch (error: any) {
       console.error("Adjustment failure:", error);
       toast.error("Error saving operation", { id: toastId });
    }
  };

  const handleUpdateItem = async () => {
    if (!selectedItem) return;
    try {
      const updated = { ...selectedItem, ...editedItem };
      if (updated.part_number) updated.part_number = updated.part_number.toUpperCase();

      await db.items.update(selectedItem.id!, updated);
      if (navigator.onLine) {
        await inventoryApi.updateItem(selectedItem.id!, updated);
      }
      
      toast.success("Item updated successfully");
      setIsEditing(false);
      setSelectedItem(updated as Item);
      await loadData();
    } catch (err) {
      console.error(err);
      toast.error("Failed to update item");
    }
  };

  const handleDeleteItem = async () => {
    if (!selectedItem || !selectedItem.id) return;
    if (!window.confirm(`Are you sure you want to delete "${selectedItem.name}"?`)) return;
    
    try {
      await db.items.delete(selectedItem.id);
      if (navigator.onLine) {
        await inventoryApi.deleteItem(selectedItem.id);
      }
      toast.success("Item deleted");
      setSelectedItem(null);
      await loadData();
    } catch (err) {
      console.error(err);
      toast.error("Failed to delete item");
    }
  };

  const handleUpdateCategory = async () => {
    if (!editingCategory) return;
    try {
      await inventoryApi.updateCategory(editingCategory.id, {
        name: catEditedName,
        description: catEditedDesc
      });
      toast.success("Category updated");
      setEditingCategory(null);
      await loadData();
    } catch (err) {
      toast.error("Update failed");
    }
  };

  // Group items by category
  const categories = Array.from(new Set(inventory.map(i => i.category)));
  const filteredCategories = categories.filter(c => 
    c.toLowerCase().includes(searchQuery.toLowerCase()) ||
    inventory.some(i => i.category === c && i.name.toLowerCase().includes(searchQuery.toLowerCase()))
  );

  if (!mounted) return null;

  return (
    <PageShell>
      <div className="p-3 md:p-8 max-w-4xl mx-auto space-y-6">
      
      <header className="max-w-4xl mx-auto w-full mb-8">
        <h1 className="text-2xl font-black flex items-center gap-3">
          <Package className="text-primary" size={28} />
          Inventory Catalog
        </h1>
        <p className="text-sm text-slate-500 mt-1">Detailed view of all stock items by category</p>
      </header>

      <div className="max-w-4xl mx-auto w-full space-y-8">
        {/* Stats Dashboard */}
        <section className="grid grid-cols-2 md:grid-cols-4 gap-3">
          <div className="bg-slate-900/50 border border-slate-800 p-4 rounded-3xl">
            <div className="w-8 h-8 rounded-xl bg-primary/10 text-primary flex items-center justify-center mb-3">
              <Layers size={18} />
            </div>
            <p className="text-[10px] font-black uppercase tracking-widest text-slate-500">Categories</p>
            <p className="text-2xl font-black mt-1">{stats?.total_categories || categories.length}</p>
          </div>
          <div className="bg-slate-900/50 border border-slate-800 p-4 rounded-3xl">
            <div className="w-8 h-8 rounded-xl bg-green-500/10 text-green-500 flex items-center justify-center mb-3">
              <Package size={18} />
            </div>
            <p className="text-[10px] font-black uppercase tracking-widest text-slate-500">Item Types</p>
            <p className="text-2xl font-black mt-1">{stats?.total_items || inventory.length}</p>
          </div>
        </section>

        {/* Search */}
        <div className="relative">
          <input 
            type="text"
            placeholder="Search categories or items..."
            value={searchQuery}
            onChange={(e) => setSearchQuery(e.target.value)}
            className="w-full bg-slate-900 border border-slate-800 rounded-2xl py-4 pl-12 pr-4 text-sm focus:border-primary outline-none transition-all"
          />
          <div className="absolute left-4 top-1/2 -translate-y-1/2 text-slate-600">
            🔍
          </div>
        </div>

        {/* Categorized List (Accordion) */}
        <section className="space-y-3">
          {filteredCategories.map(cat => (
            <div key={cat} className="bg-slate-900/40 border border-slate-800/50 rounded-3xl overflow-hidden active:scale-[0.995] transition-all">
              <div 
                className="w-full p-5 flex items-center justify-between hover:bg-slate-900/60 transition-colors cursor-pointer"
                onClick={() => setExpandedCategory(expandedCategory === cat ? null : cat)}
              >
                <div className="flex items-center gap-3">
                  <div className="w-10 h-10 rounded-2xl bg-slate-800 flex items-center justify-center text-slate-400 group-hover:text-primary transition-colors">
                    <Tag size={20} />
                  </div>
                  <div className="text-left">
                    <h3 className="font-bold text-lg">{cat}</h3>
                    <p className="text-[10px] font-black text-slate-500 uppercase tracking-widest">
                       {inventory.filter(i => i.category === cat).length} Item types in stock
                    </p>
                  </div>
                </div>
                <div className="flex items-center gap-3">
                  {expandedCategory === cat ? <ChevronDown size={20} className="text-primary" /> : <ChevronRight size={20} className="text-slate-600" />}
                  <button 
                    onClick={(e) => {
                      e.stopPropagation();
                      const categoryObj = categoriesList.find(c => c.name === cat);
                      if (categoryObj) {
                        setEditingCategory(categoryObj);
                        setCatEditedName(categoryObj.name);
                        setCatEditedDesc(categoryObj.description || '');
                      }
                    }}
                    className="p-2 hover:bg-slate-800 rounded-full text-slate-500 hover:text-primary transition-colors relative z-10"
                  >
                    <Edit2 size={16} />
                  </button>
                </div>
              </div>
              
              {expandedCategory === cat && (
                <div className="p-4 pt-0 space-y-2 animate-in slide-in-from-top-4 duration-300">
                  <div className="h-px bg-slate-800/50 mb-4 mx-2" />
                  {inventory
                    .filter(i => i.category === cat)
                    .filter(i => i.name.toLowerCase().includes(searchQuery.toLowerCase()))
                    .map(item => (
                      <div 
                        key={item.id}
                        onClick={() => setSelectedItem(item)}
                        className="bg-slate-950/40 border border-slate-800/50 p-4 rounded-2xl flex items-center justify-between hover:border-primary/40 cursor-pointer transition-all active:scale-[0.98]"
                      >
                        <div className="flex-1 min-w-0 pr-4">
                          <h4 className="font-bold text-slate-200 truncate">{item.name}</h4>
                          <p className="text-[10px] text-slate-500 truncate mt-0.5">{item.specs}</p>
                        </div>
                        <div className="text-right shrink-0">
                          <span className={cn(
                            "text-lg font-black",
                            item.quantity <= item.min_quantity ? "text-amber-500" : "text-primary"
                          )}>
                            {item.quantity}
                          </span>
                          <p className="text-[8px] text-slate-600 uppercase tracking-widest font-black">Stock</p>
                        </div>
                      </div>
                    ))}
                </div>
              )}
            </div>
          ))}

          {filteredCategories.length === 0 && (
            <div className="py-20 text-center text-slate-600">
               <Package size={48} className="mx-auto mb-4 opacity-10" />
               <p className="font-medium">No results found</p>
            </div>
          )}
        </section>
      </div>

      {/* Stock Adjustment / Edit Item Overlay */}
      {selectedItem && (
        <div className="fixed inset-0 z-50 flex items-end sm:items-center justify-center p-4 bg-slate-950/80 backdrop-blur-sm animate-in fade-in duration-200">
          <div className="w-full max-w-lg bg-slate-900 border border-slate-800 rounded-[2.5rem] shadow-2xl p-6 overflow-hidden animate-in slide-in-from-bottom-10 duration-300">
              <div className="flex justify-between items-center mb-6">
                <h3 className="text-xl font-black tracking-tight">
                  {isEditing ? "Edit Item" : selectedItem.name}
                </h3>
                <div className="flex gap-2">
                  {!isEditing && (
                    <button 
                      onClick={() => {
                        setEditedItem(selectedItem);
                        setIsEditing(true);
                      }} 
                      className="p-2 hover:bg-slate-800 rounded-full text-slate-400"
                    >
                      <Edit2 size={20} />
                    </button>
                  )}
                  {isEditing && (
                    <button 
                      onClick={handleDeleteItem} 
                      className="p-2 hover:bg-red-500/20 rounded-full text-red-500"
                    >
                      <Trash2 size={20} />
                    </button>
                  )}
                  <button 
                    onClick={() => {
                      setSelectedItem(null);
                      setIsEditing(false);
                      setAdjustQty(1);
                    }} 
                    className="p-2 hover:bg-slate-800 rounded-full"
                  >
                    <X size={20} />
                  </button>
                </div>
              </div>

              {isEditing ? (
                <div className="space-y-4 mb-8">
                  <div>
                    <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Name</label>
                    <input 
                      type="text" 
                      value={editedItem.name || ''} 
                      onChange={e => setEditedItem({...editedItem, name: e.target.value})}
                      className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-100 placeholder:text-slate-700"
                    />
                  </div>
                  <div>
                    <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Part Number</label>
                    <input 
                      type="text" 
                      value={editedItem.part_number || ''} 
                      onChange={e => setEditedItem({...editedItem, part_number: e.target.value})}
                      className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm font-mono outline-none text-slate-100 placeholder:text-slate-700 uppercase"
                    />
                  </div>
                  <div className="grid grid-cols-2 gap-4">
                    <div>
                      <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Category</label>
                      <select 
                        value={editedItem.category || ''} 
                        onChange={e => setEditedItem({...editedItem, category: e.target.value})}
                        className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-100"
                      >
                        <option value="">Select Category</option>
                        {categoriesList.map(c => (
                          <option key={c.id} value={c.name}>{c.name}</option>
                        ))}
                      </select>
                    </div>
                    <div>
                      <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Item Type</label>
                      <input 
                        type="text" 
                        value={editedItem.type || ''} 
                        onChange={e => setEditedItem({...editedItem, type: e.target.value})}
                        className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-100"
                      />
                    </div>
                  </div>
                  <div>
                    <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Specs / Comments</label>
                    <input 
                      type="text" 
                      value={editedItem.specs || ''} 
                      onChange={e => setEditedItem({...editedItem, specs: e.target.value})}
                      className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-100"
                    />
                  </div>
                </div>
              ) : (
                <>
                  <div className="flex p-1 bg-slate-950 rounded-2xl mb-8">
                    {[
                      { id: 'ADD', label: 'Buy More', icon: Plus, color: 'text-primary' },
                      { id: 'REMOVE', label: 'Subtract', icon: Minus, color: 'text-amber-500' },
                      { id: 'TRASH', label: 'Discard', icon: Trash2, color: 'text-red-500' }
                    ].map((t) => (
                      <button
                        key={t.id}
                        onClick={() => setAdjustType(t.id as any)}
                        className={cn(
                          "flex-1 flex flex-col items-center py-3 rounded-xl transition-all",
                          adjustType === t.id ? "bg-slate-800 shadow-lg" : "text-slate-500"
                        )}
                      >
                        <t.icon size={20} className={adjustType === t.id ? t.color : ""} />
                        <span className="text-[10px] font-black uppercase tracking-widest mt-1">{t.label}</span>
                      </button>
                    ))}
                  </div>

                  <div className="flex flex-col items-center gap-6 mb-8">
                    <div className="flex items-center gap-8">
                      <button 
                        onClick={() => setAdjustQty(Math.max(1, adjustQty - 1))}
                        className="w-12 h-12 rounded-full border border-slate-800 flex items-center justify-center hover:bg-slate-800 transition-colors"
                      >
                        <Minus size={24} />
                      </button>
                      <span className="text-5xl font-black tabular-nums">{adjustQty}</span>
                      <button 
                        onClick={() => setAdjustQty(adjustQty + 1)}
                        className="w-12 h-12 rounded-full border border-slate-800 flex items-center justify-center hover:bg-slate-800 transition-colors"
                      >
                        <Plus size={24} />
                      </button>
                    </div>
                    
                    {adjustType === 'TRASH' && (
                      <div className="w-full bg-red-500/5 border border-red-500/20 p-4 rounded-2xl">
                         <select 
                          value={trashReason} 
                          onChange={(e) => setTrashReason(e.target.value)}
                          className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-300"
                        >
                          <option>Damaged</option>
                          <option>Expired</option>
                          <option>Lost</option>
                          <option>Technical Failure</option>
                        </select>
                      </div>
                    )}
                  </div>
                </>
              )}

              <button 
                onClick={isEditing ? handleUpdateItem : handleAdjustStock}
                className={cn(
                  "w-full py-5 rounded-[1.8rem] font-black text-lg transition-all active:scale-[0.98] shadow-xl",
                  isEditing ? "bg-white text-slate-950 shadow-white/10" : (
                    adjustType === 'ADD' ? "bg-primary text-white shadow-primary/20" : 
                    adjustType === 'REMOVE' ? "bg-amber-600 text-white shadow-amber-600/20" : 
                    "bg-red-600 text-white shadow-red-600/20"
                  )
                )}
              >
                {isEditing ? "Save Changes" : (
                  adjustType === 'ADD' ? `Add ${adjustQty} to Stock` : 
                  adjustType === 'REMOVE' ? `Subtract ${adjustQty} from Stock` : 
                  `Discard ${adjustQty} items`
                )}
              </button>
          </div>
        </div>
      )}

      {/* Category Edit Overlay */}
      {editingCategory && (
        <div className="fixed inset-0 z-50 flex items-center justify-center p-4 bg-slate-950/90 backdrop-blur-xl animate-in fade-in duration-300">
          <div className="bg-slate-900 border border-slate-800 rounded-3xl p-8 max-w-sm w-full shadow-2xl space-y-6 animate-in zoom-in-95 duration-200">
            <div className="flex justify-between items-center">
               <h2 className="text-xl font-black uppercase tracking-tight">Edit Category</h2>
               <button onClick={() => setEditingCategory(null)} className="p-2 hover:bg-slate-800 rounded-full transition-colors text-slate-400">
                 <X size={20} />
               </button>
            </div>
            
            <div className="space-y-4">
              <div>
                <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Name</label>
                <input 
                  type="text" 
                  value={catEditedName}
                  onChange={e => setCatEditedName(e.target.value)}
                  className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-100"
                />
              </div>
              <div>
                <label className="text-[10px] font-black uppercase tracking-widest text-slate-500 ml-1">Description</label>
                <textarea 
                  value={catEditedDesc}
                  onChange={e => setCatEditedDesc(e.target.value)}
                  className="w-full bg-slate-950 border border-slate-800 rounded-xl py-3 px-4 text-sm outline-none text-slate-100 h-24 resize-none"
                />
              </div>
            </div>

            <button 
              onClick={handleUpdateCategory}
              className="w-full bg-primary text-white font-black uppercase tracking-widest py-4 rounded-2xl shadow-xl shadow-primary/20 hover:scale-[1.02] active:scale-95 transition-all"
            >
              Update Category
            </button>
          </div>
        </div>
      )}

      </div>
    </PageShell>
  );
}
