<?php

/**
 * ProductManager
 *
 * Handles all CRUD and soft-delete operations for products and product categories.
 *
 * Method order:
 *   Master file basis  → get/save/delete for product categories and products
 *   Transaction basis  → (none — products are master data only)
 *   Report basis       → getRackOccupancy (cross-warehouse physical inventory view)
 *
 * Note: Write methods do NOT manage their own DB transactions.
 * Callers must wrap multi-step operations inside dbTransaction().
 *
 * Security: All SQL uses PDO prepared statements with bound parameters.
 * No user input is ever interpolated directly into a query string.
 */
class ProductManager {

    private PDO $pdo;
    private int $company_id;

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

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

    /**
     * Scan all td_stock_* warehouse tables for any active stock row
     * that references the given SKU.
     *
     * Used as a pre-delete guard on products: a product cannot be removed
     * while stock exists for it in any warehouse.
     * Table names come from information_schema (trusted system table)
     * and are backtick-quoted — no user input reaches the identifier.
     *
     * @param string $sku  The product SKU to search for.
     * @return string|null  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 standard audit log entry array for append-to-JSON log columns.
     *
     * Captures the acting user_id, current datetime, session login time,
     * and a short action label (e.g. 'delete', 'update').
     *
     * Usage:
     *   $log[] = $this->buildLogEntry('delete');
     *   $params[':log'] = json_encode($log);
     *
     * @param string $action  Short label describing the operation (e.g. 'delete').
     * @return array  Associative array ready to be appended to a log array.
     */
    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,
        ];
    }

    // ─────────────────────────────────────────────────────────────
    // MASTER FILE BASIS — Product Category
    // ─────────────────────────────────────────────────────────────

    /**
     * Return all product categories with their product count.
     *
     * Used to populate the category listing page and category dropdowns.
     * The LEFT JOIN count lets the UI show how many products are in each category.
     *
     * @return array  All md_product_category rows for this company,
     *                each augmented with a 'product_count' field.
     */
    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 product category row by its primary key.
     *
     * Used to pre-fill the edit form on the manage category page.
     *
     * @param int $id  The md_product_category.id to fetch.
     * @return array|false  Associative row, or false if not found.
     */
    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 a new product category or update an existing one.
     *
     * Pass $data['id'] = 0 to insert; pass $data['id'] > 0 to update.
     * The $logging array is appended to the row's JSON log column.
     *
     * Must be called inside dbTransaction() by the caller.
     *
     * @param array $data     Keys: id, category, slug, description, status.
     * @param array $logging  Audit entry to append to the log column.
     * @throws Exception  On validation failure (e.g. duplicate slug).
     */
    public function saveCategory(array $data, array $logging): void
    {
        $id   = (int)($data['id'] ?? 0);
        $slug = (string)($data['slug'] ?? '');

        $dupSth = $this->pdo->prepare(
            "SELECT id FROM md_product_category
             WHERE company_id = :cid AND slug = :slug" . ($id > 0 ? " AND id != :id" : "") . " LIMIT 1"
        );
        $dupParams = [':cid' => $this->company_id, ':slug' => $slug];
        if ($id > 0) $dupParams[':id'] = $id;
        $dupSth->execute($dupParams);
        if ($dupSth->fetchColumn()) throw new Exception("A category with this slug already exists.");

        $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);
        }
    }

    /**
     * Soft-delete a product category by negating its company_id.
     *
     * Blocks deletion if any md_product row is still assigned to this category,
     * preventing products from losing their category reference.
     *
     * Must be called inside dbTransaction() by the caller.
     *
     * @param int $category_id  The md_product_category.id to delete.
     * @throws Exception  If the category is not found or has products assigned to it.
     */
    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: negate company_id so row is hidden but recoverable
        $this->pdo->prepare(
            "UPDATE md_product_category
             SET company_id = company_id * -1,
                 `log`      = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $category_id,
            ':company_id' => $this->company_id,
        ]);
    }

    // ─────────────────────────────────────────────────────────────
    // MASTER FILE BASIS — Product
    // ─────────────────────────────────────────────────────────────

    /**
     * Return all products with their current aggregate warehouse balance.
     *
     * The balance is the sum of (total_in - total_out) across all warehouses
     * from the etl_stock_summary table. Products with no balance rows show 0.
     *
     * Used to populate the product listing page.
     *
     * @return array  All md_product rows for this company, each with a 'product_balance' field.
     */
    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 etl_stock_summary 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 its primary key.
     *
     * Used to pre-fill the edit form on the manage product page.
     *
     * @param int $id  The md_product.id to fetch.
     * @return array|false  Associative row, or false if not found.
     */
    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);
    }

    public function getProductImage(int $id): string
    {
        $sth = $this->pdo->prepare(
            "SELECT product_image FROM md_product
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $id]);
        return (string)($sth->fetchColumn() ?: '');
    }

    /**
     * Search products by SKU keyword — for live autocomplete on stock forms.
     *
     * Returns up to 50 matches. The keyword is safely bound as a LIKE parameter;
     * no wildcard escaping is needed here since '%' wrapping is the intended behaviour.
     *
     * @param string $keyword  Partial SKU to match.
     * @return array  Matching md_product rows.
     */
    public function searchProduct(string $keyword): array
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM md_product
            WHERE company_id = :company_id
            AND (sku LIKE :keyword OR barcode LIKE :keyword)
            AND status > 0
            LIMIT 50"
        );
        $sth->execute([
            ':company_id' => $this->company_id,
            ':keyword'    => '%' . $keyword . '%',
        ]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }

    /**
     * Insert a new product or update an existing one.
     *
     * Pass $data['id'] = 0 to insert; pass $data['id'] > 0 to update.
     * $product_image is the resolved filename/path from FileUploader — may be
     * the existing image when no new file was uploaded.
     * The $logging array is appended to the row's JSON log column.
     *
     * Must be called inside dbTransaction() by the caller.
     *
     * @param array  $data           Keys: id, product_name, sku, price, min_stock,
     *                               reorder_point, category, description, status.
     * @param array  $logging        Audit entry to append to the log column.
     * @param string $product_image  Stored filename for the product image.
     */
    public function saveProduct(array $data, array $logging, string $product_image): void
    {
        $id  = (int)($data['id'] ?? 0);
        $sku = (string)($data['sku'] ?? '');

        $dupSth = $this->pdo->prepare(
            "SELECT id FROM md_product
             WHERE company_id = :cid AND sku = :sku" . ($id > 0 ? " AND id != :id" : "") . " LIMIT 1"
        );
        $dupParams = [':cid' => $this->company_id, ':sku' => $sku];
        if ($id > 0) $dupParams[':id'] = $id;
        $dupSth->execute($dupParams);
        if ($dupSth->fetchColumn()) throw new Exception("A product with this SKU already exists.");

        $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'           => $data['sku'],
            ':barcode'       => trim($data['barcode'] ?? '') ?: null,
            ':uom'           => $data['uom'] ?? 'pcs',
            ':price'         => $data['price'],
            ':cost_price'    => (float)($data['cost_price'] ?? 0),
            ':min_stock'     => $data['min_stock'],
            ':reorder_point' => $data['reorder_point'],
            ':category'      => $data['category'],
            ':product_image' => $product_image,
            ':description'   => $data['description'],
            ':sales_account_code'    => trim((string)($data['sales_account_code'] ?? '')) ?: null,
            ':purchase_account_code' => trim((string)($data['purchase_account_code'] ?? '')) ?: null,
            ':status'        => (int)$data['status'],
            ':log'           => json_encode($table_log),
        ];

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

    /**
     * Update only the accounting account mapping fields for a product.
     *
     * This is used by Accounting so product master data can stay locked while
     * finance users maintain GL routing for SKU-based posting.
     */
    public function updateAccountMapping(int $id, ?string $sales_account_code, ?string $purchase_account_code, array $logging): void
    {
        $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]);
        $existing_log = $sth->fetchColumn();

        if ($existing_log === false) {
            throw new Exception('Product not found.');
        }

        $table_log   = json_decode($existing_log ?: '[]', true) ?: [];
        $table_log[] = $logging;

        $sth = $this->pdo->prepare(
            "UPDATE md_product SET
                sales_account_code    = :sales_account_code,
                purchase_account_code = :purchase_account_code,
                `log`                 = :log
            WHERE id = :id AND company_id = :company_id"
        );
        $sth->execute([
            ':company_id'            => $this->company_id,
            ':id'                    => $id,
            ':sales_account_code'    => $sales_account_code,
            ':purchase_account_code' => $purchase_account_code,
            ':log'                   => json_encode($table_log),
        ]);
    }

    /**
     * Soft-delete a product by negating its company_id.
     *
     * Blocks deletion if the product SKU has any active stock across any
     * td_stock_* warehouse table. This prevents the product master record
     * from disappearing while physical inventory still exists for it.
     *
     * Must be called inside dbTransaction() by the caller.
     *
     * @param int $product_id  The md_product.id to delete.
     * @throws Exception  If the product is 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: negate company_id so row is hidden but recoverable
        $this->pdo->prepare(
            "UPDATE md_product
             SET company_id = company_id * -1,
                 `log`      = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $product_id,
            ':company_id' => $this->company_id,
        ]);
    }

    // ─────────────────────────────────────────────────────────────
    // REPORT BASIS
    // ─────────────────────────────────────────────────────────────

    /**
     * Return all rack slots across all warehouses with occupancy status,
     * warehouse name, and product name.
     *
     * Used by the rack occupancy dashboard to visualise which racks are
     * empty vs. occupied, and which product is in each slot.
     * Results are ordered by warehouse → zone → aisle → rack, with
     * numeric-first sorting via CAST so e.g. "2" sorts before "10".
     *
     * Security fix: was previously using $this->companyId (undefined property),
     * corrected to $this->company_id.
     *
     * @return array  All md_rack rows joined to warehouse and product, with 'status' field.
     */
    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->company_id]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }
}