<?php

namespace App\Modules\Inventory\Imports;

use App\Modules\Inventory\Models\InventoryTransferItem;
use App\Modules\Inventory\Models\InventoryTransferOrder;
use App\Modules\Inventory\Models\Product;
use Illuminate\Support\Collection;
use Maatwebsite\Excel\Concerns\ToCollection;
use Maatwebsite\Excel\Concerns\WithHeadingRow;
use Maatwebsite\Excel\Concerns\WithMultipleSheets;
use Exception;

class InventoryTransferItemImport implements ToCollection, WithMultipleSheets
{
    protected $transferOrder;

    public function __construct(InventoryTransferOrder $transferOrder)
    {
        $this->transferOrder = $transferOrder;
    }

    public function collection(Collection $rows)
    {
        if ($rows->isEmpty()) {
            throw new Exception("檔案中沒有資料。");
        }

        // 移除標題列並解析索引
        $headerRow = $rows->shift();
        $headers = $headerRow->toArray();
        
        // 建立標題對應索引 (支援中文與英文)
        $colMap = [
            'product_code' => -1,
            'batch_number' => -1,
            'quantity' => -1,
            'position' => -1,
            'notes' => -1,
        ];

        foreach ($headers as $index => $label) {
            $label = trim((string)$label);
            if (in_array($label, ['商品代碼', 'product_code', 'shang_pin_dai_ma'])) $colMap['product_code'] = $index;
            if (in_array($label, ['批號', 'batch_number', 'pi_hao'])) $colMap['batch_number'] = $index;
            if (in_array($label, ['數量', 'quantity', 'shu_liang'])) $colMap['quantity'] = $index;
            if (in_array($label, ['貨道/儲位', '貨道', 'position', 'slot', 'huo_dao'])) $colMap['position'] = $index;
            if (in_array($label, ['備註', 'notes', 'bei_zhu'])) $colMap['notes'] = $index;
        }

        // 檢查必要欄位是否有找到
        if ($colMap['product_code'] === -1 || $colMap['quantity'] === -1) {
            $foundHeaders = implode(', ', array_filter($headers));
            throw new Exception("找不到必要的欄位「商品代碼」或「數量」。讀取到的標題為：{$foundHeaders}。請確認使用的是正確的範本。");
        }

        // 預先載入商品 (優化效能)
        $productCodes = $rows->map(fn($row) => trim((string)($row[$colMap['product_code']] ?? '')))->filter()->unique()->toArray();
        $products = Product::whereIn('code', $productCodes)->get()->keyBy('code');

        $newItems = [];
        $errors = [];

        foreach ($rows as $index => $row) {
            $productCode = trim((string)($row[$colMap['product_code']] ?? ''));
            $quantity = $row[$colMap['quantity']] ?? null;
            $batchNumber = $colMap['batch_number'] !== -1 ? trim((string)($row[$colMap['batch_number']] ?? '')) : '';
            $position = $colMap['position'] !== -1 ? trim((string)($row[$colMap['position']] ?? '')) : null;
            $notes = $colMap['notes'] !== -1 ? ($row[$colMap['notes']] ?? null) : null;

            // 跳過全空行
            if (empty($productCode) && ($quantity === null || $quantity === '')) {
                continue;
            }

            $lineNum = $index + 2; // 因為 shift 過，且 Excel 從 1 開始

            if (empty($productCode)) {
                $errors[] = "第 {$lineNum} 行：商品代碼不能為空";
                continue;
            }

            $product = $products->get($productCode);
            if (!$product) {
                $errors[] = "第 {$lineNum} 行：找不到商品代碼 '{$productCode}'";
                continue;
            }

            if (!is_numeric($quantity) || (float)$quantity <= 0) {
                $errors[] = "第 {$lineNum} 行：數量必須為大於 0 的數字 (目前值: " . ($quantity ?? '空') . ")";
                continue;
            }

            if (empty($batchNumber)) {
                $batchNumber = 'NO-BATCH';
            }

            $newItems[] = [
                'transfer_order_id' => $this->transferOrder->id,
                'product_id' => $product->id,
                'batch_number' => $batchNumber,
                'quantity' => (float)$quantity,
                'position' => $position,
                'notes' => $notes,
                'created_at' => now(),
                'updated_at' => now(),
            ];
        }

        if (count($errors) > 0) {
            throw new Exception(implode("\n", $errors));
        }

        if (count($newItems) === 0) {
            throw new Exception("檔案中沒有可匯入的有效資料。");
        }

        InventoryTransferItem::insert($newItems);
        $this->transferOrder->touch();
    }

    /**
     * 指定只匯入第一個分頁 (明細匯入)
     */
    public function sheets(): array
    {
        return [
            0 => $this,
        ];
    }
}