<?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,
        ]);
    }


    // ─────────────────────────────────────────────────────────────
    // Product queries
    // ─────────────────────────────────────────────────────────────

    /**
     * Full product list with current warehouse balance.
     */
    public function getProductList(): array
    {
        $sth = $this->pdo->prepare(
            "SELECT a.*, IFNULL(SUM(b.total_in - b.total_out), 0) AS product_balance
            FROM md_product a
            LEFT JOIN warehouse_balance b
                ON a.company_id = b.company_id
                AND a.sku        = b.product_sku
            WHERE a.company_id = :company_id
            GROUP BY a.id"
        );
        $sth->execute([':company_id' => $this->company_id]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }

    /**
     * Fetch a single product row by ID.
     */
    public function getProductById(int $id): array|false
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM md_product
            WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $id]);
        return $sth->fetch(PDO::FETCH_ASSOC);
    }

    /**
     * Search products by SKU keyword — for autocomplete.
     */
    public function searchProduct(string $keyword): array
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM md_product
            WHERE company_id = :company_id
            AND sku LIKE :keyword
            LIMIT 50"
        );
        $sth->execute([
            ':company_id' => $this->company_id,
            ':keyword'    => '%' . $keyword . '%',
        ]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }

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

    /**
     * Full category list with product count per category.
     */
    public function getCategoryList(): array
    {
        $sth = $this->pdo->prepare(
            "SELECT a.*, COUNT(b.id) AS product_count
            FROM md_product_category a
            LEFT JOIN md_product b
                ON a.company_id = b.company_id
                AND a.id         = b.category
            WHERE a.company_id = :company_id
            GROUP BY a.id"
        );
        $sth->execute([':company_id' => $this->company_id]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }

    /**
     * Fetch a single category row by ID.
     */
    public function getCategoryById(int $id): array|false
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM md_product_category
            WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $id]);
        return $sth->fetch(PDO::FETCH_ASSOC);
    }

    /**
     * Insert or update a product category.
     * Pass $data['id'] > 0 for update, 0 for insert.
     * Must be called inside dbTransaction() by the caller.
     *
     * @throws Exception on validation failure
     */
    public function saveCategory(array $data, array $logging): void
    {
        $id = (int)($data['id'] ?? 0);

        $sth = $this->pdo->prepare(
            "SELECT `log` FROM md_product_category
            WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $id]);
        $table_log   = json_decode($sth->fetchColumn() ?: '[]', true) ?: [];
        $table_log[] = $logging;

        $params = [
            ':company_id'  => $this->company_id,
            ':category'    => $data['category'],
            ':slug'        => $data['slug'],
            ':description' => $data['description'],
            ':status'      => (int)$data['status'],
            ':log'         => json_encode($table_log),
        ];

        if ($id > 0) {
            $params[':id'] = $id;
            $this->pdo->prepare(
                "UPDATE md_product_category SET
                    `category`    = :category,
                    `slug`        = :slug,
                    `description` = :description,
                    `status`      = :status,
                    `log`         = :log
                WHERE id = :id AND company_id = :company_id"
            )->execute($params);
        } else {
            $this->pdo->prepare(
                "INSERT INTO md_product_category
                    (company_id, category, slug, `description`, `status`, `log`)
                VALUES
                    (:company_id, :category, :slug, :description, :status, :log)"
            )->execute($params);
        }
    }


    // ─────────────────────────────────────────────────────────────
    // Product write
    // ─────────────────────────────────────────────────────────────

    /**
     * Insert or update a product.
     * Pass $data['id'] > 0 for update, 0 for insert.
     * Must be called inside dbTransaction() by the caller.
     */
    public function saveProduct(array $data, array $logging, string $product_image): void
    {
        $id = (int)($data['id'] ?? 0);

        $sth = $this->pdo->prepare(
            "SELECT `log` FROM md_product
            WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $id]);
        $table_log   = json_decode($sth->fetchColumn() ?: '[]', true) ?: [];
        $table_log[] = $logging;

        $params = [
            ':company_id'    => $this->company_id,
            ':product_name'  => $data['product_name'],
            ':sku'           => $data['sku'],
            ':price'         => $data['price'],
            ':min_stock'     => $data['min_stock'],
            ':reorder_point' => $data['reorder_point'],
            ':category'      => $data['category'],
            ':product_image' => $product_image,
            ':description'   => $data['description'],
            ':status'        => (int)$data['status'],
            ':log'           => json_encode($table_log),
        ];

        if ($id > 0) {
            $params[':id'] = $id;
            $this->pdo->prepare(
                "UPDATE md_product SET
                    product_name   = :product_name,
                    sku            = :sku,
                    price          = :price,
                    min_stock      = :min_stock,
                    reorder_point  = :reorder_point,
                    category       = :category,
                    product_image  = :product_image,
                    `description`  = :description,
                    `status`       = :status,
                    `log`          = :log
                WHERE id = :id AND company_id = :company_id"
            )->execute($params);
        } else {
            $this->pdo->prepare(
                "INSERT INTO md_product
                    (company_id, product_name, sku, price, min_stock, reorder_point,
                    category, product_image, `description`, `status`, `log`)
                VALUES
                    (:company_id, :product_name, :sku, :price, :min_stock, :reorder_point,
                    :category, :product_image, :description, :status, :log)"
            )->execute($params);
        }
    }


    /**
     * Full rack list with warehouse name, product info and occupancy status.
     */
    public function getRackOccupancy(): array
    {
        $sth = $this->pdo->prepare(
            "SELECT
                r.id,
                r.zone,
                r.aisle,
                r.rack,
                r.product_sku,
                r.td_stock_id,
                mw.warehouse_name,
                mw.id AS warehouse_id,
                p.product_name,
                CASE WHEN r.product_sku IS NOT NULL THEN 'occupied' ELSE 'empty' END AS status
            FROM md_rack r
            INNER JOIN md_warehouse mw
                ON  mw.company_id = r.company_id
                AND mw.id         = r.warehouse
            LEFT JOIN md_product p
                ON  p.company_id = r.company_id
                AND p.sku        = r.product_sku
            WHERE r.company_id = :company_id
            ORDER BY mw.warehouse_name, r.zone,
                    CAST(r.aisle AS UNSIGNED), r.aisle,
                    CAST(r.rack AS UNSIGNED),  r.rack"
        );
        $sth->execute([':company_id' => $this->companyId]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }
}