// Simple prediction: next 7 days demand
$predicted_7days = round($avg_daily * 7, 0);

// Confidence based on consistency
$confidence = min($trend['total_sales'] > 5 ? 0.9 : 0.6, 0.95);

// Generate recommendation
$recommendation = $this->generateRecommendation(
$product_id,
$predicted_7days,
$product['stock'],
$product['min_stock'],
$avg_daily
);

return [
'product_id' => $product_id,
'predicted_demand_7days' => $predicted_7days,
'predicted_monthly_demand' => round($avg_daily * 30, 0),
'confidence_level' => $confidence,
'current_stock' => $product['stock'],
'min_stock' => $product['min_stock'],
'recommendation' => $recommendation,
'analysis_date' => date('Y-m-d H:i:s')
];
}

/**
* Generate rekomendasi stok berdasarkan prediksi
*/
private function generateRecommendation($product_id, $predicted_demand, $current_stock, $min_stock, $avg_daily)
{
$safety_stock = round($avg_daily * 3, 0);
$optimal_stock = $predicted_demand + $safety_stock;

if ($current_stock < $min_stock) { return [ 'action'=> 'URGENT_RESTOCK',
    'message' => "Stok kritis! Pesan segera min {$optimal_stock} unit",
    'suggested_quantity' => $optimal_stock,
    'priority' => 'HIGH'
    ];
    } elseif ($current_stock <= $predicted_demand) { return [ 'action'=> 'RESTOCK_SOON',
        'message' => "Stok akan habis dalam 7 hari. Pesan {$optimal_stock} unit",
        'suggested_quantity' => $optimal_stock,
        'priority' => 'MEDIUM'
        ];
        } elseif ($current_stock > $predicted_demand * 2) {
        return [
        'action' => 'REDUCE_STOCK',
        'message' => "Stok berlebih. Pertimbangkan promosi atau review harga",
        'suggested_quantity' => $optimal_stock,
        'priority' => 'LOW'
        ];
        } else {
        return [
        'action' => 'OPTIMAL',
        'message' => "Stok dalam kondisi optimal",
        'suggested_quantity' => $optimal_stock,
        'priority' => 'INFO'
        ];
        }
        }

        /**
        * Auto-categorize produk menggunakan keyword analysis
        */
        public function autoCategorizProduct($name, $description)
        {
        $categories = [
        'Elektronik' => ['laptop', 'komputer', 'monitor', 'keyboard', 'mouse', 'cpu', 'gpu', 'ram', 'ssd', 'hardisk'],
        'Peralatan Kantor' => ['meja', 'kursi', 'lemari', 'rak', 'meja kerja', 'filing', 'kabinet'],
        'Perlengkapan Tulis' => ['pena', 'pensil', 'kertas', 'buku', 'notepad', 'sticky note', 'marker'],
        'Furniture' => ['sofa', 'meja makan', 'tempat tidur', 'almari', 'rak buku', 'rak dinding'],
        'Peralatan Rumah Tangga' => ['pot', 'panci', 'wajan', 'piring', 'gelas', 'sendok', 'garpu'],
        'Fashion' => ['baju', 'celana', 'jaket', 'topi', 'sepatu', 'kemeja', 'dress'],
        'Kesehatan' => ['vitamin', 'obat', 'serum', 'masker', 'hand sanitizer', 'thermometer']
        ];

        $text = strtolower($name . ' ' . $description);
        $scores = [];

        foreach ($categories as $category => $keywords) {
        $score = 0;
        foreach ($keywords as $keyword) {
        if (strpos($text, $keyword) !== false) {
        $score += 2;
        }
        }
        $scores[$category] = $score;
        }

        $best_category = array_key_first($scores);
        $best_score = max($scores);

        return [
        'category' => $best_score > 0 ? $best_category : 'Umum',
        'confidence' => min($best_score / 4, 1),
        'all_scores' => $scores
        ];
        }

        /**
        * Deteksi anomali dalam stok
        */
        public function detectAnomalies()
        {
        $query = "SELECT p.id, p.name, p.stock, p.min_stock,
        (SELECT COUNT(*) FROM stock_movements WHERE product_id = p.id AND type = 'out' AND created_at >= DATE_SUB(NOW(),
        INTERVAL 7 DAY)) as recent_outs
        FROM products p";

        $result = $this->conn->query($query);
        $anomalies = [];

        while ($row = $result->fetch_assoc()) {
        // Deteksi: stok habis tapi tidak ada aktivitas
        if ($row['stock'] == 0 && $row['recent_outs'] == 0) {
        $anomalies[] = [
        'type' => 'DEAD_STOCK',
        'product_id' => $row['id'],
        'product_name' => $row['name'],
        'message' => 'Barang tidak bergerak selama 7 hari'
        ];
        }

        // Deteksi: stok negatif (error)
        if ($row['stock'] < 0) { $anomalies[]=[ 'type'=> 'NEGATIVE_STOCK',
            'product_id' => $row['id'],
            'product_name' => $row['name'],
            'message' => 'Stok negatif, kemungkinan ada kesalahan input'
            ];
            }
            }

            return $anomalies;
            }

            /**
            * Generate AI insights summary
            */
            public function generateInsights()
            {
            $query = "SELECT p.id, p.name, p.stock,
            (SELECT COUNT(*) FROM transactions WHERE product_id = p.id AND transaction_type = 'sale' AND created_at >=
            DATE_SUB(NOW(), INTERVAL 30 DAY)) as monthly_sales
            FROM products p
            ORDER BY monthly_sales DESC
            LIMIT 10";

            $result = $this->conn->query($query);

            $insights = [];
            $top_products = [];
            $slow_moving = [];

            while ($row = $result->fetch_assoc()) {
            if ($row['monthly_sales'] > 20) {
            $top_products[] = [
            'name' => $row['name'],
            'sales' => $row['monthly_sales']
            ];
            } elseif ($row['monthly_sales'] < 3 && $row['stock']> 5) {
                $slow_moving[] = [
                'name' => $row['name'],
                'sales' => $row['monthly_sales'],
                'stock' => $row['stock']
                ];
                }
                }

                return [
                'top_products' => $top_products,
                'slow_moving_products' => $slow_moving,
                'total_insights' => count($top_products) + count($slow_moving),
                'generated_at' => date('Y-m-d H:i:s')
                ];
                }
                }