<?php

/**
 * ProductManager
 *
 * Encapsulates product and product category operations:
 * - Soft-delete with downstream validation
 *
 * Note: Methods that modify data do NOT manage their own DB transactions.
 * Callers are responsible for wrapping operations in dbTransaction() when atomicity is needed.
 */
class ProductManager {

    private $pdo;
    private $company_id;

    public function __construct($pdo, $company_id) {
        $this->pdo        = $pdo;
        $this->company_id = $company_id;
    }

    // ─────────────────────────────────────────────────────────────
    // Private helpers
    // ─────────────────────────────────────────────────────────────

    /**
     * Check if a SKU has any active stock across all td_stock_* tables.
     * Returns the first blocking table name found, or null if clear.
     */
    private function findActiveStock(string $sku): ?string {

        $sth = $this->pdo->prepare(
            "SELECT table_name FROM information_schema.tables
             WHERE table_schema = DATABASE()
               AND table_name LIKE 'td_stock_%'"
        );
        $sth->execute();
        $tables = $sth->fetchAll(PDO::FETCH_COLUMN);

        foreach ($tables as $table) {
            $sth = $this->pdo->prepare(
                "SELECT COUNT(*) FROM `$table`
                 WHERE company_id = :company_id
                   AND product_sku = :sku"
            );
            $sth->execute([
                ':company_id' => $this->company_id,
                ':sku'        => $sku,
            ]);
            if ($sth->fetchColumn() > 0) {
                return $table;
            }
        }

        return null;
    }

    /**
     * Build a log entry array for audit context.
     */
    private function buildLogEntry(string $action): array {
        return [
            'user_id' => $_SESSION['login_user_id'] ?? null,
            'dt'      => date('Y-m-d H:i:s'),
            'login'   => isset($_SESSION['otpTime'])
                         ? date('Y-m-d H:i:s', $_SESSION['otpTime'])
                         : null,
            'action'  => $action,
        ];
    }

    // ─────────────────────────────────────────────────────────────
    // Product category
    // ─────────────────────────────────────────────────────────────

    /**
     * Soft-delete a product category.
     *
     * Blocks if any md_product references this category.
     *
     * @throws Exception if category not found or has dependent products
     */
    public function deleteCategory(int $category_id): void {

        $sth = $this->pdo->prepare(
            "SELECT id, category, `log` FROM md_product_category
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([
            ':company_id' => $this->company_id,
            ':id'         => $category_id,
        ]);
        $row = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$row) {
            throw new Exception("Product category not found.");
        }

        // Block if any product references this category
        $sth = $this->pdo->prepare(
            "SELECT COUNT(*) FROM md_product
             WHERE company_id = :company_id
               AND category = :category_id"
        );
        $sth->execute([
            ':company_id'  => $this->company_id,
            ':category_id' => $category_id,
        ]);

        if ($sth->fetchColumn() > 0) {
            throw new Exception(
                "Cannot delete — category \"{$row['category']}\" " .
                "still has products assigned to it."
            );
        }

        // Append delete event to log
        $log   = json_decode($row['log'] ?? '[]', true) ?: [];
        $log[] = $this->buildLogEntry('delete');

        // Soft-delete
        $this->pdo->prepare(
            "UPDATE md_product_category
             SET company_id = company_id * -1,
                 `log`      = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $category_id,
            ':company_id' => $this->company_id,
        ]);
    }

    // ─────────────────────────────────────────────────────────────
    // Product
    // ─────────────────────────────────────────────────────────────

    /**
     * Soft-delete a product.
     *
     * Blocks if the product SKU has any active stock across any td_stock_* table.
     *
     * @throws Exception if product not found or has active stock
     */
    public function deleteProduct(int $product_id): void {

        $sth = $this->pdo->prepare(
            "SELECT id, product_name, sku, `log` FROM md_product
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([
            ':company_id' => $this->company_id,
            ':id'         => $product_id,
        ]);
        $row = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$row) {
            throw new Exception("Product not found.");
        }

        // Block if active stock exists for this SKU in any warehouse
        $blocking_table = $this->findActiveStock($row['sku']);
        if ($blocking_table !== null) {
            throw new Exception(
                "Cannot delete — \"{$row['product_name']}\" " .
                "still has active stock in the system."
            );
        }

        // Append delete event to log
        $log   = json_decode($row['log'] ?? '[]', true) ?: [];
        $log[] = $this->buildLogEntry('delete');

        // Soft-delete
        $this->pdo->prepare(
            "UPDATE md_product
             SET company_id = company_id * -1,
                 `log`      = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $product_id,
            ':company_id' => $this->company_id,
        ]);
    }
}