<?php

namespace App\Modules\Inventory\Services;

use App\Modules\Inventory\Models\Inventory;
use App\Modules\Inventory\Models\InventoryCountDoc;
use App\Modules\Inventory\Models\InventoryCountItem;
use App\Modules\Inventory\Models\Warehouse;
use App\Modules\Inventory\Models\Product;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;

class CountService
{
    /**
     * 建立新的盤點單並執行快照
     */
    public function createDoc(string $warehouseId, string $remarks = null, int $userId): InventoryCountDoc
    {
        return DB::transaction(function () use ($warehouseId, $remarks, $userId) {
            $doc = InventoryCountDoc::create([
                'warehouse_id' => $warehouseId,
                'status' => 'draft',
                'remarks' => $remarks,
                'created_by' => $userId,
            ]);

            return $doc;
        });
    }

    /**
     * 執行快照：鎖定當前庫存量
     */
    public function snapshot(InventoryCountDoc $doc): void
    {
        DB::transaction(function () use ($doc) {
            // 清除舊的 items (如果有)
            $doc->items()->delete();

            // 取得該倉庫所有庫存 (包含 quantity = 0 但未軟刪除的)
            // 這裡可以根據需求決定是否要過濾掉 0 庫存，通常盤點單會希望能看到所有 "帳上有紀錄" 的東西
            $inventories = Inventory::where('warehouse_id', $doc->warehouse_id)
                ->whereNull('deleted_at') 
                ->get();

            $items = [];
            foreach ($inventories as $inv) {
                $items[] = [
                    'count_doc_id' => $doc->id,
                    'product_id' => $inv->product_id,
                    'batch_number' => $inv->batch_number,
                    'system_qty' => $inv->quantity,
                    'counted_qty' => null, // 預設未盤點
                    'diff_qty' => 0,
                    'created_at' => now(),
                    'updated_at' => now(),
                ];
            }

            if (!empty($items)) {
                InventoryCountItem::insert($items);
            }

            $doc->update([
                'status' => 'counting',
                'snapshot_date' => now(),
            ]);
        });
    }

    /**
     * 完成盤點：過帳差異
     */
    public function complete(InventoryCountDoc $doc, int $userId): void
    {
        DB::transaction(function () use ($doc, $userId) {
            foreach ($doc->items as $item) {
                // 如果沒有輸入實盤數量，預設跳過或是視為 0? 
                // 安全起見：如果 counted_qty 是 null，表示沒盤到，跳過不處理 (或者依業務邏輯視為0)
                // 這裡假設前端會確保有送出資料，若 null 則不做異動
                if (is_null($item->counted_qty)) {
                    continue;
                }

                $diff = $item->counted_qty - $item->system_qty;

                // 如果無差異，更新 item 狀態即可 (diff_qty 已經是 computed field 或在儲存時計算)
                // 這裡 update 一下 diff_qty 以防萬一
                $item->update(['diff_qty' => $diff]);

                if (abs($diff) > 0.0001) {
                    // 找回原本的 Inventory
                    $inventory = Inventory::where('warehouse_id', $doc->warehouse_id)
                        ->where('product_id', $item->product_id)
                        ->where('batch_number', $item->batch_number)
                        ->first();

                    if (!$inventory) {
                        // 如果原本沒庫存紀錄 (例如是新增的盤點項目)，需要新建 Inventory
                        // 但目前 snapshot 邏輯只抓現有。若允許 "盤盈" (發現不在帳上的)，需要額外邏輯
                        // 暫時略過 "新增 Inventory" 的複雜邏輯，假設只能針對 existing batch 調整
                        continue; 
                    }

                    $oldQty = $inventory->quantity;
                    $newQty = $oldQty + $diff;

                    $inventory->quantity = $newQty;
                    $inventory->total_value = $inventory->unit_cost * $newQty;
                    $inventory->save();

                    // 寫入 Transaction
                    $inventory->transactions()->create([
                        'type' => '盤點調整',
                        'quantity' => $diff,
                        'unit_cost' => $inventory->unit_cost,
                        'balance_before' => $oldQty,
                        'balance_after' => $newQty,
                        'reason' => "盤點單 {$doc->doc_no} 過帳",
                        'actual_time' => now(),
                        'user_id' => $userId,
                    ]);
                }
            }

            $doc->update([
                'status' => 'completed',
                'completed_at' => now(),
                'completed_by' => $userId,
            ]);
        });
    }

    /**
     * 更新盤點數量
     */
    public function updateCount(InventoryCountDoc $doc, array $itemsData): void
    {
        DB::transaction(function () use ($doc, $itemsData) {
            foreach ($itemsData as $data) {
                $item = $doc->items()->find($data['id']);
                if ($item) {
                    $countedQty = $data['counted_qty'];
                    $diff = is_numeric($countedQty) ? ($countedQty - $item->system_qty) : 0;
                    
                    $item->update([
                        'counted_qty' => $countedQty,
                        'diff_qty' => $diff,
                        'notes' => $data['notes'] ?? $item->notes,
                    ]);
                }
            }
        });
    }
}