<?php

namespace App\Http\Controllers;

use App\Models\PurchaseOrder;
use App\Models\Vendor;
use App\Models\Warehouse;
use Illuminate\Http\Request;
use Inertia\Inertia;
use Illuminate\Support\Facades\DB;

class PurchaseOrderController extends Controller
{
    public function index(Request $request)
    {
        $query = PurchaseOrder::with(['vendor', 'warehouse', 'user']);

        // Search
        if ($request->search) {
            $query->where(function($q) use ($request) {
                $q->where('code', 'like', "%{$request->search}%")
                  ->orWhereHas('vendor', function($vq) use ($request) {
                      $vq->where('name', 'like', "%{$request->search}%");
                  });
            });
        }

        // Filters
        if ($request->status && $request->status !== 'all') {
            $query->where('status', $request->status);
        }

        if ($request->warehouse_id && $request->warehouse_id !== 'all') {
            $query->where('warehouse_id', $request->warehouse_id);
        }

        // Sorting
        $sortField = $request->sort_field ?? 'id';
        $sortDirection = $request->sort_direction ?? 'desc';
        $allowedSortFields = ['id', 'code', 'status', 'total_amount', 'created_at', 'expected_delivery_date'];
        
        if (in_array($sortField, $allowedSortFields)) {
            $query->orderBy($sortField, $sortDirection);
        }

        $orders = $query->paginate(15)->withQueryString();

        return Inertia::render('PurchaseOrder/Index', [
            'orders' => $orders,
            'filters' => $request->only(['search', 'status', 'warehouse_id', 'sort_field', 'sort_direction']),
            'warehouses' => Warehouse::all(['id', 'name']),
        ]);
    }

    public function create()
    {
        $vendors = Vendor::with(['products.baseUnit', 'products.largeUnit', 'products.purchaseUnit'])->get()->map(function ($vendor) {
            return [
                'id' => (string) $vendor->id,
                'name' => $vendor->name,
                'commonProducts' => $vendor->products->map(function ($product) {
                    return [
                        'productId' => (string) $product->id,
                        'productName' => $product->name,
                        'base_unit_id' => $product->base_unit_id,
                        'base_unit_name' => $product->baseUnit?->name,
                        'large_unit_id' => $product->large_unit_id,
                        'large_unit_name' => $product->largeUnit?->name,
                        'purchase_unit_id' => $product->purchase_unit_id,
                        'conversion_rate' => (float) $product->conversion_rate,
                        'lastPrice' => (float) ($product->pivot->last_price ?? 0),
                    ];
                })
            ];
        });

        $warehouses = Warehouse::all()->map(function ($w) {
            return [
                'id' => (string) $w->id,
                'name' => $w->name,
            ];
        });

        return Inertia::render('PurchaseOrder/Create', [
            'suppliers' => $vendors,
            'warehouses' => $warehouses,
        ]);
    }

    public function store(Request $request)
    {
        $validated = $request->validate([
            'vendor_id' => 'required|exists:vendors,id',
            'warehouse_id' => 'required|exists:warehouses,id',
            'expected_delivery_date' => 'nullable|date',
            'remark' => 'nullable|string',
            'items' => 'required|array|min:1',
            'items.*.productId' => 'required|exists:products,id',
            'items.*.quantity' => 'required|numeric|min:0.01',
            'items.*.unitPrice' => 'required|numeric|min:0',
            'items.*.unitId' => 'nullable|exists:units,id', // 驗證單位ID
        ]);

        try {
            DB::beginTransaction();

            // 生成單號：YYYYMMDD001
            $today = now()->format('Ymd');
            $lastOrder = PurchaseOrder::where('code', 'like', $today . '%')
                ->lockForUpdate() // 鎖定以避免並發衝突
                ->orderBy('code', 'desc')
                ->first();

            if ($lastOrder) {
                // 取得最後 3 碼序號並加 1
                $lastSequence = intval(substr($lastOrder->code, -3));
                $sequence = str_pad($lastSequence + 1, 3, '0', STR_PAD_LEFT);
            } else {
                $sequence = '001';
            }
            $code = $today . $sequence;

            $totalAmount = 0;
            foreach ($validated['items'] as $item) {
                $totalAmount += $item['quantity'] * $item['unitPrice'];
            }

            // Simple tax calculation (e.g., 5%)
            $taxAmount = round($totalAmount * 0.05, 2);
            $grandTotal = $totalAmount + $taxAmount;

            // 確保有一個有效的使用者 ID
            $userId = auth()->id();
            if (!$userId) {
                $user = \App\Models\User::first();
                if (!$user) {
                    $user = \App\Models\User::create([
                        'name' => '系統管理員',
                        'email' => 'admin@example.com',
                        'password' => bcrypt('password'),
                    ]);
                }
                $userId = $user->id;
            }

            $order = PurchaseOrder::create([
                'code' => $code,
                'vendor_id' => $validated['vendor_id'],
                'warehouse_id' => $validated['warehouse_id'],
                'user_id' => $userId,
                'status' => 'draft',
                'expected_delivery_date' => $validated['expected_delivery_date'],
                'total_amount' => $totalAmount,
                'tax_amount' => $taxAmount,
                'grand_total' => $grandTotal,
                'remark' => $validated['remark'],
            ]);

            foreach ($validated['items'] as $item) {
                $order->items()->create([
                    'product_id' => $item['productId'],
                    'quantity' => $item['quantity'],
                    'unit_id' => $item['unitId'] ?? null, // 儲存單位ID
                    'unit_price' => $item['unitPrice'],
                    'subtotal' => $item['quantity'] * $item['unitPrice'],
                ]);
            }

            DB::commit();

            return redirect()->route('purchase-orders.index')->with('success', '採購單已成功建立');

        } catch (\Exception $e) {
            DB::rollBack();
            return back()->withErrors(['error' => '建立失敗：' . $e->getMessage()]);
        }
    }

    public function show($id)
    {
        $order = PurchaseOrder::with(['vendor', 'warehouse', 'user', 'items.product.baseUnit', 'items.product.largeUnit'])->findOrFail($id);
        
        $order->items->transform(function ($item) use ($order) {
            $product = $item->product;
            if ($product) {
                // 手動附加所有必要的屬性
                $item->productId = (string) $product->id;
                $item->productName = $product->name;
                $item->base_unit_id = $product->base_unit_id;
                $item->base_unit_name = $product->baseUnit?->name;
                $item->large_unit_id = $product->large_unit_id;
                $item->large_unit_name = $product->largeUnit?->name;
                $item->purchase_unit_id = $product->purchase_unit_id;
                
                $item->conversion_rate = (float) $product->conversion_rate;
                
                // Fetch last price
                $lastPrice = DB::table('product_vendor')
                    ->where('vendor_id', $order->vendor_id)
                    ->where('product_id', $product->id)
                    ->value('last_price');
                $item->previousPrice = (float) ($lastPrice ?? 0);

                // 設定當前選中的單位 ID (from saved item)
                $item->unitId = $item->unit_id; 

                // 決定 selectedUnit (用於 UI 顯示)
                if ($item->unitId && $item->large_unit_id && $item->unitId == $item->large_unit_id) {
                    $item->selectedUnit = 'large';
                } else {
                    $item->selectedUnit = 'base';
                }

                $item->unitPrice = (float) $item->unit_price;
            }
            return $item;
        });

        return Inertia::render('PurchaseOrder/Show', [
            'order' => $order
        ]);
    }

    public function edit($id)
    {
        $order = PurchaseOrder::with(['items.product'])->findOrFail($id);

        $vendors = Vendor::with(['products.baseUnit', 'products.largeUnit', 'products.purchaseUnit'])->get()->map(function ($vendor) {
            return [
                'id' => (string) $vendor->id,
                'name' => $vendor->name,
                'commonProducts' => $vendor->products->map(function ($product) {
                    return [
                        'productId' => (string) $product->id,
                        'productName' => $product->name,
                        'base_unit_id' => $product->base_unit_id,
                        'base_unit_name' => $product->baseUnit?->name,
                        'large_unit_id' => $product->large_unit_id,
                        'large_unit_name' => $product->largeUnit?->name,
                        'purchase_unit_id' => $product->purchase_unit_id,
                        'conversion_rate' => (float) $product->conversion_rate,
                        'lastPrice' => (float) ($product->pivot->last_price ?? 0),
                    ];
                })
            ];
        });

        $warehouses = Warehouse::all()->map(function ($w) {
            return [
                'id' => (string) $w->id,
                'name' => $w->name,
            ];
        });

        // Transform items for frontend form
        // Transform items for frontend form
        $vendorId = $order->vendor_id;
        $order->items->transform(function ($item) use ($vendorId) {
            $product = $item->product;
            if ($product) {
                // 手動附加所有必要的屬性
                $item->productId = (string) $product->id;
                $item->productName = $product->name;
                $item->base_unit_id = $product->base_unit_id;
                $item->base_unit_name = $product->baseUnit?->name;
                $item->large_unit_id = $product->large_unit_id;
                $item->large_unit_name = $product->largeUnit?->name;
                
                $item->conversion_rate = (float) $product->conversion_rate;
                
                // Fetch last price
                $lastPrice = DB::table('product_vendor')
                    ->where('vendor_id', $vendorId)
                    ->where('product_id', $product->id)
                    ->value('last_price');
                $item->previousPrice = (float) ($lastPrice ?? 0);
                
                // 設定當前選中的單位 ID
                $item->unitId = $item->unit_id; // 資料庫中的 unit_id

                // 決定 selectedUnit (用於 UI 狀態)
                if ($item->unitId && $item->large_unit_id && $item->unitId == $item->large_unit_id) {
                    $item->selectedUnit = 'large';
                } else {
                    $item->selectedUnit = 'base';
                }

                $item->unitPrice = (float) $item->unit_price;
            }
            return $item;
        });

        return Inertia::render('PurchaseOrder/Create', [
            'order' => $order,
            'suppliers' => $vendors,
            'warehouses' => $warehouses,
        ]);
    }

    public function update(Request $request, $id)
    {
        $order = PurchaseOrder::findOrFail($id);

        $validated = $request->validate([
            'vendor_id' => 'required|exists:vendors,id',
            'warehouse_id' => 'required|exists:warehouses,id',
            'expected_delivery_date' => 'nullable|date',
            'remark' => 'nullable|string',
            'status' => 'required|string|in:draft,pending,processing,shipping,confirming,completed,cancelled',
            'items' => 'required|array|min:1',
            'items.*.productId' => 'required|exists:products,id',
            'items.*.quantity' => 'required|numeric|min:0.01',
            'items.*.unitPrice' => 'required|numeric|min:0',
            'items.*.unitId' => 'nullable|exists:units,id', // 驗證單位ID
        ]);

        try {
            DB::beginTransaction();

            $totalAmount = 0;
            foreach ($validated['items'] as $item) {
                $totalAmount += $item['quantity'] * $item['unitPrice'];
            }

            // Simple tax calculation (e.g., 5%)
            $taxAmount = round($totalAmount * 0.05, 2);
            $grandTotal = $totalAmount + $taxAmount;

            $order->update([
                'vendor_id' => $validated['vendor_id'],
                'warehouse_id' => $validated['warehouse_id'],
                'expected_delivery_date' => $validated['expected_delivery_date'],
                'total_amount' => $totalAmount,
                'tax_amount' => $taxAmount,
                'grand_total' => $grandTotal,
                'remark' => $validated['remark'],
                'status' => $validated['status'],
            ]);

            // Sync items
            $order->items()->delete();
            foreach ($validated['items'] as $item) {
                $order->items()->create([
                    'product_id' => $item['productId'],
                    'quantity' => $item['quantity'],
                    'unit_id' => $item['unitId'] ?? null, // 儲存單位ID
                    'unit_price' => $item['unitPrice'],
                    'subtotal' => $item['quantity'] * $item['unitPrice'],
                ]);
            }

            DB::commit();

            return redirect()->route('purchase-orders.index')->with('success', '採購單已更新');

        } catch (\Exception $e) {
            DB::rollBack();
            return back()->withErrors(['error' => '更新失敗：' . $e->getMessage()]);
        }
    }

    public function destroy($id)
    {
        try {
            DB::beginTransaction();
            
            $order = PurchaseOrder::findOrFail($id);
            
            // Delete associated items first (due to FK constraints if not cascade)
            $order->items()->delete();
            $order->delete();
            
            DB::commit();
            
            return redirect()->route('purchase-orders.index')->with('success', '採購單已刪除');
        } catch (\Exception $e) {
            DB::rollBack();
            return back()->withErrors(['error' => '刪除失敗：' . $e->getMessage()]);
        }
    }
}