<?php

namespace App\Services;

use App\Models\Product;
use App\Models\Dealer;
use App\Models\Stock;
use App\Models\StockLog;
use Carbon\Carbon;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;

class StockReportService
{
    /**
     * Get stock report data for all products and dealers on a specific date
     */
    public function getStockReportData($targetDate = null)
    {
        $targetDate = $targetDate ? Carbon::parse($targetDate) : now();
        
        // Get all dealers
        $dealers = Dealer::orderBy('name')->get();
        
        // Get all active products
        $products = Product::where('active', true)
            ->with(['category'])
            ->orderBy('name')
            ->get();

        $data = [];
        
        foreach ($products as $product) {
            $row = [
                'product_id' => $product->id,
                'product_code' => $product->code,
                'product_name' => $product->name,
                'category_name' => $product->category ? $product->category->name : '-',
                'unit' => $product->unit ?? '-',
                'total_stock' => 0
            ];

            // Calculate stock for each dealer on the target date
            foreach ($dealers as $dealer) {
                $stockOnDate = $this->getStockOnDate($product->id, $dealer->id, $targetDate);
                $row["dealer_{$dealer->id}"] = $stockOnDate;
                $row['total_stock'] += $stockOnDate;
            }

            $data[] = $row;
        }

        return [
            'data' => $data,
            'dealers' => $dealers
        ];
    }

    /**
     * Get stock quantity for a specific product and dealer on a given date
     */
    public function getStockOnDate($productId, $dealerId, $targetDate)
    {
        // Get the latest stock log entry before or on the target date
        $latestStockLog = StockLog::whereHas('stock', function($query) use ($productId, $dealerId) {
                $query->where('product_id', $productId)
                      ->where('dealer_id', $dealerId);
            })
            ->where('created_at', '<=', $targetDate->endOfDay())
            ->orderBy('created_at', 'desc')
            ->first();

        if ($latestStockLog) {
            // Return the new_quantity from the latest log entry
            return $latestStockLog->new_quantity;
        }

        // If no stock log found, check if there's a current stock record
        $currentStock = Stock::where('product_id', $productId)
            ->where('dealer_id', $dealerId)
            ->first();

        if ($currentStock) {
            // Check if the stock was created before or on the target date
            if ($currentStock->created_at <= $targetDate) {
                return $currentStock->quantity;
            }
        }

        // No stock data available for this date
        return 0;
    }

    /**
     * Get optimized stock data using a single query approach
     */
    public function getOptimizedStockReportData($targetDate = null)
    {
        $targetDate = $targetDate ? Carbon::parse($targetDate) : now();
        
        // Get all dealers
        $dealers = Dealer::orderBy('name')->get();
        
        // Get all active products with their stock data
        $products = Product::where('active', true)
            ->with(['category', 'stocks.dealer'])
            ->orderBy('name')
            ->get();

        $data = [];
        
        foreach ($products as $product) {
            $row = [
                'product_id' => $product->id,
                'product_code' => $product->code,
                'product_name' => $product->name,
                'category_name' => $product->category ? $product->category->name : '-',
                'unit' => $product->unit ?? '-',
                'total_stock' => 0
            ];

            // Calculate stock for each dealer on the target date
            foreach ($dealers as $dealer) {
                $stockOnDate = $this->getOptimizedStockOnDate($product->id, $dealer->id, $targetDate);
                $row["dealer_{$dealer->id}"] = $stockOnDate;
                $row['total_stock'] += $stockOnDate;
            }

            $data[] = $row;
        }

        return [
            'data' => $data,
            'dealers' => $dealers
        ];
    }

    /**
     * Optimized method to get stock on date using subquery
     */
    private function getOptimizedStockOnDate($productId, $dealerId, $targetDate)
    {
        try {
            // Use a subquery to get the latest stock log entry efficiently
            $latestStockLog = DB::table('stock_logs')
                ->join('stocks', 'stock_logs.stock_id', '=', 'stocks.id')
                ->where('stocks.product_id', $productId)
                ->where('stocks.dealer_id', $dealerId)
                ->where('stock_logs.created_at', '<=', $targetDate->endOfDay())
                ->orderBy('stock_logs.created_at', 'desc')
                ->select('stock_logs.new_quantity')
                ->first();

            if ($latestStockLog) {
                return $latestStockLog->new_quantity;
            }

            // If no stock log found, check current stock
            $currentStock = Stock::where('product_id', $productId)
                ->where('dealer_id', $dealerId)
                ->first();

            if ($currentStock && $currentStock->created_at <= $targetDate) {
                return $currentStock->quantity;
            }

            return 0;
        } catch (\Exception $e) {
            // Log error and return 0
            Log::error('Error getting stock on date: ' . $e->getMessage(), [
                'product_id' => $productId,
                'dealer_id' => $dealerId,
                'target_date' => $targetDate
            ]);
            return 0;
        }
    }
}