<?php
require_once __DIR__ . '/DocumentNumberManager.php';
require_once __DIR__ . '/DocumentValidator.php';
require_once __DIR__ . '/WarehouseManager.php';
require_once __DIR__ . '/StockManager.php';
require_once __DIR__ . '/../classes_ac/PostingWindowGuard.php';

/**
 * PurchaseOrderManager
 *
 * Handles all read and write operations for td_purchase_order
 * and the downstream stock-in effects on td_stock_<warehouse_id> tables.
 *
 * Method order:
 *   Transaction basis  → getPoList, getPoById, generatePoNumber,
 *                        savePo, confirmPo, receivePo, cancelPo
 *
 * Key design decisions:
 *   - PO items are stored as a JSON array in td_purchase_order.items.
 *     Same pattern as td_order. No separate child table.
 *   - receivePo() calls StockManager::saveStockIn() for each received line
 *     with source='po' and source_id=po_id. This means received goods appear
 *     in the existing Stock In list automatically under source='po'.
 *   - stock_in_id is written back into the items JSON after each receive call,
 *     same pattern as stock_out_id in OrderManager::confirmOrder().
 *   - Partial receipt is supported: receivePo() can be called multiple times.
 *   - PO stored statuses: -2 (pending warehouse), -1 (cancelled), 0 (draft), 1 (confirmed).
 *     Receipt progress (pending/partial/received) is derived via deriveReceiptStatus(),
 *     same pattern as fulfillment_status on SO. Never stored in td_purchase_order.
 *   - cancelPo() is blocked if any linked stock-in rows have been approved (status=1),
 *     because those have already modified bin and balance.
 *   - 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.
 * Dynamic stock table names are derived only from md_warehouse.id.
 */
class PurchaseOrderManager {

    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
    // ─────────────────────────────────────────────────────────────

    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,
        ];
    }

    /**
     * Generate next sequential PO number in PO-YYYYMMDD-XXXX format.
     */
    private function generatePoNumber(array $data = []): string
    {
        return (new DocumentNumberManager($this->pdo, $this->company_id))
            ->resolveNumber($data, 'purchase_order', 'td_purchase_order', 'po_number');
    }

    /**
     * Derive receipt status from linked stock-in rows — never stored in DB.
     *
     * 0 = no stock-in rows linked yet
     * 1 = pending  (stock-in rows exist but none approved)
     * 2 = partial  (some approved, quantities not fully received)
     * 3 = received (all approved, all quantities received)
     */
    private function deriveReceiptStatus(array $po): int
    {
        if ((int)($po['status'] ?? 0) < 1) return 0;

        $po_id = (int)($po['id'] ?? 0);

        // Fetch items from normalized table
        $sth = $this->pdo->prepare(
            "SELECT item_id, quantity, received_qty, stock_in_id FROM td_purchase_order_item
             WHERE order_id = :po_id AND company_id = :company_id"
        );
        $sth->execute([':po_id' => $po_id, ':company_id' => $this->company_id]);
        $items = $sth->fetchAll(PDO::FETCH_ASSOC);

        $has_any_stock_in = false;
        foreach ($items as $item) {
            if ((int)($item['stock_in_id'] ?? 0) > 0) {
                $has_any_stock_in = true;
                break;
            }
        }
        if (!$has_any_stock_in) return 0;

        $tables = (new WarehouseManager($this->pdo, $this->company_id))->getStockTables();

        $total   = 0;
        $pending = 0;

        foreach ($tables as $table) {
            $sth = $this->pdo->prepare(
                "SELECT status FROM `{$table}`
                 WHERE company_id = :company_id
                   AND source     = 'po'
                   AND source_id  = :po_id
                   AND type       = 'in'
                   AND status    != -1"
            );
            $sth->execute([':company_id' => $this->company_id, ':po_id' => $po_id]);
            foreach ($sth->fetchAll(PDO::FETCH_COLUMN) as $s) {
                $total++;
                if ((int)$s === 0) $pending++;
            }
        }

        if ($total === 0) return 0;
        if ($pending > 0) return 1;

        $all_received = true;
        foreach ($items as $item) {
            if ((float)($item['received_qty'] ?? 0) < (float)($item['quantity'] ?? 0)) {
                $all_received = false;
                break;
            }
        }
        return $all_received ? 3 : 2;
    }

    private function stockTableNameFromWarehouseId(int $warehouse_id): string
    {
        if ($warehouse_id <= 0) {
            throw new Exception("Invalid warehouse id.");
        }

        $sth = $this->pdo->prepare(
            "SELECT id FROM md_warehouse
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $warehouse_id]);
        if (!$sth->fetchColumn()) {
            throw new Exception("Warehouse ID {$warehouse_id} not found.");
        }

        return 'td_stock_' . $warehouse_id;
    }

    private function syncPoItems(int $po_id, array $items): void
    {
        $this->pdo->prepare(
            "DELETE FROM td_purchase_order_item WHERE order_id = :po_id AND company_id = :company_id"
        )->execute([':po_id' => $po_id, ':company_id' => $this->company_id]);

        $sth = $this->pdo->prepare(
            "INSERT INTO td_purchase_order_item
                (company_id, order_id, item_id, product_sku, product_name,
                 quantity, unit_price, total_price, tax_amount, tax_rate, received_qty, stock_in_id, invoiced_qty)
             VALUES
                (:company_id, :order_id, :item_id, :product_sku, :product_name,
                 :quantity, :unit_price, :total_price, :tax_amount, :tax_rate, :received_qty, :stock_in_id, 0)"
        );
        foreach ($items as $pos => $item) {
            $sth->execute([
                ':company_id'   => $this->company_id,
                ':order_id'     => $po_id,
                ':item_id'      => $pos + 1,
                ':product_sku'  => $item['product_sku']  ?? '',
                ':product_name' => $item['product_name'] ?? '',
                ':quantity'     => (float)($item['quantity']     ?? 0),
                ':unit_price'   => (float)($item['unit_price']   ?? 0),
                ':total_price'  => (float)($item['total_price']  ?? 0),
                ':tax_amount'   => (float)($item['tax_amount']   ?? 0),
                ':tax_rate'     => (float)($item['tax_rate']     ?? 0),
                ':received_qty' => (float)($item['received_qty'] ?? 0),
                ':stock_in_id'  => (int)($item['stock_in_id']   ?? 0),
            ]);
        }
    }

    // ─────────────────────────────────────────────────────────────
    // TRANSACTION BASIS — Read
    // ─────────────────────────────────────────────────────────────

    /**
     * Return all POs for the company, ordered by created_at DESC.
     * Joins md_contact for supplier name display.
     */
    public function getPoList(): array
    {
        $sth = $this->pdo->prepare(
            "SELECT p.*,
                    COALESCE(c.contact_name, '') AS contact_name,
                    (SELECT COUNT(*) FROM td_purchase_order_item i
                     WHERE i.company_id = p.company_id
                       AND i.order_id   = p.id) AS item_count
             FROM td_purchase_order p
             LEFT JOIN md_contact c
                 ON  c.company_id = p.company_id
                 AND c.id         = p.contact_id
             WHERE p.company_id = :company_id
             ORDER BY p.po_date DESC, p.id DESC"
        );
        $sth->execute([':company_id' => $this->company_id]);
        $rows = $sth->fetchAll(PDO::FETCH_ASSOC);
        foreach ($rows as &$row) {
            $row['receipt_status'] = $this->deriveReceiptStatus($row);
        }
        return $rows;
    }

    /**
     * Fetch a single PO by its primary key.
     * Returns the row with items decoded as a PHP array.
     */
    public function getPoById(int $id): array|false
    {
        $sth = $this->pdo->prepare(
            "SELECT p.*,
                    COALESCE(c.contact_name, '') AS contact_name
             FROM td_purchase_order p
             LEFT JOIN md_contact c
                 ON  c.company_id = p.company_id
                 AND c.id         = p.contact_id
             WHERE p.company_id = :company_id
               AND p.id         = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $id]);
        $row = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$row) return false;

        $sth2 = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order_item
             WHERE order_id = :order_id AND company_id = :company_id
             ORDER BY item_id"
        );
        $sth2->execute([':order_id' => $id, ':company_id' => $this->company_id]);
        $row['items'] = $sth2->fetchAll(PDO::FETCH_ASSOC);

        $row['receipt_status'] = $this->deriveReceiptStatus($row);
        return $row;
    }

    public function getReceivableItems(array $po): array
    {
        $receivable = [];
        foreach (($po['items'] ?? []) as $i => $item) {
            $ordered   = (float)($item['quantity']     ?? 0);
            $received  = (float)($item['received_qty'] ?? 0);
            $remaining = $ordered - $received;
            if ($remaining > 0) {
                $receivable[] = array_merge($item, [
                    'item_id'       => (int)($item['item_id'] ?? $i),
                    'ordered_qty'   => $ordered,
                    'received_qty'  => $received,
                    'remaining_qty' => $remaining,
                ]);
            }
        }

        return $receivable;
    }

    public function getReturnableItems(array $po): array
    {
        $returnable = [];
        foreach (($po['items'] ?? []) as $i => $item) {
            $received = (float)($item['received_qty'] ?? 0);
            if ($received > 0) {
                $ordered = (float)($item['quantity'] ?? 0);
                $returnable[] = array_merge($item, [
                    'item_id'        => (int)($item['item_id'] ?? $i),
                    'ordered_qty'    => $ordered,
                    'received_qty'   => $received,
                    'returnable_qty' => $received,
                    'warehouse_id'   => (int)($item['receive_wh']    ?? 0),
                    'zone'           => $item['receive_zone']         ?? '',
                    'aisle'          => $item['receive_aisle']        ?? '',
                    'bin'           => $item['receive_bin']         ?? '',
                ]);
            }
        }

        return $returnable;
    }

    public function getActivePurchaseInvoiceId(int $po_id): int
    {
        $sth = $this->pdo->prepare(
            "SELECT id FROM td_invoice
             WHERE company_id = :company_id
               AND source     = 'po'
               AND source_id  = :po_id
               AND doc_type   = 'purchase_invoice'
               AND status    != 4
             LIMIT 1"
        );
        $sth->execute([':company_id' => $this->company_id, ':po_id' => $po_id]);
        return (int)$sth->fetchColumn();
    }

    // ─────────────────────────────────────────────────────────────
    // TRANSACTION BASIS — Write
    // ─────────────────────────────────────────────────────────────

    /**
     * Insert a new PO or update metadata on an existing pending/draft PO.
     *
     * Insert (id=0): generates po_number. Accounting-sourced POs start
     * as pending warehouse (-2), direct WMS POs start as draft (0).
     * Update (id>0): only allowed while status=-2 (pending) or 0 (draft).
     *
     * @param array  $data     Keys: id, contact_id, po_date, expected_date,
     *                         warehouse_id, items (array), discount, tax,
     *                         shipping_fee, notes.
     * @param array  $logging  Audit entry.
     * @return int  New td_purchase_order.id on insert, 0 on update.
     */
    public function savePo(array $data, array $logging): int
    {
        $id    = (int)($data['id'] ?? 0);
        $items = DocumentValidator::normaliseLines($data['items'] ?? [], 'Purchase order');
        $data['items'] = $items;
        DocumentValidator::requireId($data['contact_id'] ?? 0, 'Supplier is required.');
        if ($id === 0 || array_key_exists('department_id', $data)) {
            $data['department_id'] = DocumentValidator::requireDepartment($this->pdo, $this->company_id, $data['department_id'] ?? 0);
        }

        $skus = array_filter(array_column($items, 'product_sku'));
        if (count($skus) !== count(array_unique($skus))) {
            throw new Exception("Duplicate products found — each product may only appear once per PO.");
        }

        $subtotal       = array_reduce($items, fn($carry, $item) =>
            $carry + (float)($item['total_price'] ?? 0), 0.0
        );
        $discount       = DocumentValidator::discount($data['discount'] ?? 0, $subtotal);
        $tax_adjustment = (float)($data['tax_adjustment'] ?? 0);
        if (abs($tax_adjustment) > 0.30) {
            throw new Exception("Tax adjustment cannot exceed ±0.30.");
        }
        $tax            = round(array_reduce($items, fn($carry, $item) =>
            $carry + (float)($item['tax_amount'] ?? 0), 0.0
        ), 2) + $tax_adjustment;
        $shipping_fee   = DocumentValidator::amount($data['shipping_fee'] ?? 0, 'Shipping fee');
        $grand_total    = $subtotal - $discount + $tax + $shipping_fee;

        if ($id > 0) {

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

            if (!$row) throw new Exception("Purchase order not found.");
            $cur_status = (int)$row['status'];
            if (!in_array($cur_status, [-2, 0], true)) {
                throw new Exception("Only pending or draft POs can be edited.");
            }
            $warehouse_id = (int)($data['warehouse_id'] ?? 0);
            $new_status = ($cur_status === -2 && $warehouse_id > 0) ? 0 : $cur_status;

            $log   = json_decode($row['log'] ?? '[]', true) ?: [];
            $log[] = $logging;

            $this->pdo->prepare(
                "UPDATE td_purchase_order SET
                    contact_id      = :contact_id,
                    department_id   = :department_id,
                    po_date         = :po_date,
                    expected_date   = :expected_date,
                    warehouse_id    = :warehouse_id,
                    subtotal        = :subtotal,
                    discount        = :discount,
                    tax             = :tax,
                    tax_adjustment  = :tax_adjustment,
                    shipping_fee    = :shipping_fee,
                    grand_total     = :grand_total,
                    notes           = :notes,
                    status          = :status,
                    `log`           = :log
                 WHERE id = :id AND company_id = :company_id"
            )->execute([
                ':contact_id'    => (int)($data['contact_id']    ?? 0),
                ':department_id' => (int)($data['department_id'] ?? 0),
                ':po_date'       => $data['po_date']             ?? date('Y-m-d'),
                ':expected_date' => $data['expected_date']      ?: null,
                ':warehouse_id'  => $warehouse_id,
                ':subtotal'        => $subtotal,
                ':discount'        => $discount,
                ':tax'             => $tax,
                ':tax_adjustment'  => $tax_adjustment,
                ':shipping_fee'    => $shipping_fee,
                ':grand_total'     => $grand_total,
                ':notes'           => $data['notes'] ?? '',
                ':status'          => $new_status,
                ':log'             => json_encode($log),
                ':id'              => $id,
                ':company_id'      => $this->company_id,
            ]);

            $this->syncPoItems($id, $items);
            return 0;

        } else {

            $log = [$logging];
            $source = trim((string)($data['source'] ?? ''));
            $source_id = (int)($data['source_id'] ?? 0);
            $init_status = $source !== '' ? -2 : 0;

            $this->pdo->prepare(
                "INSERT INTO td_purchase_order
                    (company_id, uuid, source_id, `source`, po_number, contact_id, department_id, po_date, expected_date,
                     warehouse_id, status, subtotal, discount, tax, tax_adjustment,
                     shipping_fee, grand_total, notes, `log`, created_at)
                 VALUES
                    (:company_id, :uuid, :source_id, :source, :po_number, :contact_id, :department_id, :po_date, :expected_date,
                     :warehouse_id, :status, :subtotal, :discount, :tax, :tax_adjustment,
                     :shipping_fee, :grand_total, :notes, :log, :created_at)"
            )->execute([
                ':company_id'    => $this->company_id,
                ':uuid'          => bin2hex(random_bytes(16)),
                ':source_id'     => $source_id,
                ':source'        => $source,
                ':po_number'     => $this->generatePoNumber($data),
                ':contact_id'    => (int)($data['contact_id']    ?? 0),
                ':department_id' => (int)($data['department_id'] ?? 0),
                ':po_date'       => $data['po_date']             ?? date('Y-m-d'),
                ':expected_date' => $data['expected_date']      ?: null,
                ':warehouse_id'  => (int)($data['warehouse_id'] ?? 0),
                ':status'          => $init_status,
                ':subtotal'        => $subtotal,
                ':discount'        => $discount,
                ':tax'             => $tax,
                ':tax_adjustment'  => $tax_adjustment,
                ':shipping_fee'    => $shipping_fee,
                ':grand_total'     => $grand_total,
                ':notes'           => $data['notes'] ?? '',
                ':log'             => json_encode($log),
                ':created_at'      => date('Y-m-d H:i:s'),
            ]);

            $new_id = (int)$this->pdo->lastInsertId();
            $this->syncPoItems($new_id, $items);
            return $new_id;
        }
    }

    /**
     * Confirm a draft PO — advance status 0 → 1.
     * No stock rows are created at this stage; receipt happens via receivePo().
     *
     * @throws Exception  If PO not found or not in draft.
     */
    public function confirmPo(int $po_id, array $logging): void
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $po_id]);
        $po = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$po) throw new Exception("Purchase order not found.");
        if ((int)$po['status'] !== 0) throw new Exception("Only draft POs can be confirmed.");

        $log   = json_decode($po['log'] ?? '[]', true) ?: [];
        $log[] = array_merge($logging, ['action' => 'confirm']);

        $this->pdo->prepare(
            "UPDATE td_purchase_order SET
                status = 1,
                `log`  = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $po_id,
            ':company_id' => $this->company_id,
        ]);
    }

    /**
     * Receive goods against a confirmed PO — creates draft stock-in rows.
     *
     * Flow per received line:
     *   1. Calls StockManager::saveStockIn() with source='po', source_id=po_id.
     *   2. Writes stock_in_id back into the PO item object (same as stock_out_id in orders).
     *   3. Increments received_qty on the item.
     *
     * After all lines:
     *   4. If all items are fully received → status = 3 (completed).
     *   5. If partially received → status = 2 (partial).
     *
     * Can be called multiple times for partial deliveries.
     * If auto_approve=true (from company settings), approveStock() is also called.
     *
     * @param int    $po_id          td_purchase_order.id
     * @param array  $receive_items  Each item: { item_id, product_sku, warehouse_id,
     *                               quantity, zone, aisle, bin, lot_number,
     *                               expiry_date, serial_number, contact_id }
     * @param string $uuid           UUID prefix for stock-in rows.
     * @param array  $logging        Audit entry.
     * @param bool   $auto_approve   Auto-approve stock-in rows immediately.
     */
    public function receivePo(
        int    $po_id,
        array  $receive_items,
        string $uuid,
        array  $logging,
        bool   $auto_approve = false
    ): void {
        $sth = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $po_id]);
        $po = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$po) throw new Exception("Purchase order not found.");

        $status = (int)$po['status'];
        if ($status === -1) throw new Exception("Cannot receive against a cancelled PO.");
        if ($status === 0)  throw new Exception("Confirm the PO before receiving goods.");
        if (!empty($po['closed_at'])) throw new Exception("This PO has been closed — no further receipts are allowed.");

        // Load PO items from normalized table
        $sth2 = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order_item
             WHERE order_id = :po_id AND company_id = :company_id
             ORDER BY item_id"
        );
        $sth2->execute([':po_id' => $po_id, ':company_id' => $this->company_id]);
        $po_items = $sth2->fetchAll(PDO::FETCH_ASSOC);

        $all_done = !empty($po_items) && array_reduce($po_items, fn($ok, $item) =>
            $ok && (float)($item['received_qty'] ?? 0) >= (float)($item['quantity'] ?? 0), true
        );
        if ($all_done) throw new Exception("This PO is already fully received.");

        if (empty($receive_items)) {
            throw new Exception("No items provided to receive.");
        }

        // Index PO items by item_id for quick lookup
        $po_items_by_id = [];
        foreach ($po_items as $i => $item) {
            $po_items_by_id[(int)($item['item_id'] ?? $i)] = $i;
        }

        $stock  = new StockManager($this->pdo, $this->company_id);
        $whMgmt = new WarehouseManager($this->pdo, $this->company_id);

        // Validate all warehouse IDs in one query before entering the item loop.
        $recvWarehouseIds = array_values(array_unique(array_filter(
            array_map(fn($recv) => (int)($recv['warehouse_id'] ?? $po['warehouse_id']), $receive_items),
            fn($id) => $id > 0
        )));
        if (!empty($recvWarehouseIds)) {
            $placeholders = implode(',', array_fill(0, count($recvWarehouseIds), '?'));
            $sth = $this->pdo->prepare(
                "SELECT id FROM md_warehouse WHERE company_id = ? AND id IN ($placeholders)"
            );
            $sth->execute([$this->company_id, ...$recvWarehouseIds]);
            $validWarehouseIds = array_flip($sth->fetchAll(PDO::FETCH_COLUMN));
        } else {
            $validWarehouseIds = [];
        }

        foreach ($receive_items as $j => $recv) {
            $item_id      = (int)($recv['item_id'] ?? -1);
            $product_sku  = $recv['product_sku'] ?? '';
            $warehouse_id = (int)($recv['warehouse_id'] ?? $po['warehouse_id']);
            $quantity     = (float)($recv['quantity'] ?? 0);

            // A blank line is a line the user chose not to receive — skip it.
            if ($quantity == 0) continue;

            // Anything positive has to survive the decimal(18,4) columns it is
            // about to be written to. Without this, 0.0000001 was accepted, was
            // stored as 0.0000, produced a stock movement of nothing, and still
            // advanced received_qty enough to leave the PO stuck on "Partial".
            $name     = $po_items[$po_items_by_id[$item_id] ?? -1]['product_name'] ?? $product_sku;
            $quantity = StockManager::normaliseQuantity($quantity, "Receiving quantity for \"{$name}\"");

            if (!$product_sku) throw new Exception("Item #{$j}: missing product_sku.");
            if (!$warehouse_id) throw new Exception("Item #{$j}: missing warehouse_id.");

            // Cap against PO quantity — prevent over-receiving
            if ($item_id >= 0 && isset($po_items_by_id[$item_id])) {
                $idx              = $po_items_by_id[$item_id];
                $already_received = (float)($po_items[$idx]['received_qty'] ?? 0);
                $max_receivable   = (float)($po_items[$idx]['quantity']     ?? 0) - $already_received;
                if ($quantity - $max_receivable > 0.000001) {
                    $name = $po_items[$idx]['product_name'] ?? $product_sku;
                    throw new Exception(
                        "Cannot receive {$quantity} for \"{$name}\": " .
                        "only {$max_receivable} unit(s) remaining on this PO."
                    );
                }
            }

            $item_uuid = $uuid . '_' . $j;
            $item_log  = array_merge($logging, ['action' => 'receive_item']);

            $bin  = $recv['bin']  ?? '';
            $zone  = $recv['zone']  ?? '';
            $aisle = $recv['aisle'] ?? '';

            // Expiry dates live on md_lot, keyed by lot number, so an expiry
            // entered without one is silently dropped and the received stock
            // shows no expiry at all. Say so instead of discarding it.
            if (trim((string)($recv['expiry_date'] ?? '')) !== ''
                && trim((string)($recv['lot_number'] ?? '')) === '') {
                throw new Exception(
                    "Enter a lot number for \"{$name}\" — an expiry date is recorded against its lot."
                );
            }

            // Simple location mode: zone and aisle must mirror the bin value
            // (same convention as manage_stock_in.php).
            // occupyBin() looks up md_bin WHERE zone=:zone AND aisle=:aisle AND bin=:bin,
            // so all three must match — a blank zone/aisle produces "Bin --b does not exist".
            if ($zone === '' && $bin !== '') $zone  = $bin;
            if ($aisle === '' && $bin !== '') $aisle = $bin;

            // Resolve unit_price: prefer the receive-time override, fall back to PO item price
            $po_item_price = 0;
            if ($item_id >= 0 && isset($po_items_by_id[$item_id])) {
                $po_item_price = (float)($po_items[$po_items_by_id[$item_id]]['unit_price'] ?? 0);
            }
            $unit_price = (float)($recv['unit_price'] ?? $po_item_price);

            $stock_data = [
                'id'            => 0,
                'warehouse'     => $warehouse_id,
                'product_sku'   => $product_sku,
                'quantity'      => $quantity,
                'price'         => $unit_price,
                'zone'          => $zone,
                'aisle'         => $aisle,
                'bin'          => $bin,
                'lot_number'    => $recv['lot_number']    ?? '',
                'expiry_date'   => $recv['expiry_date']   ?? '',
                'serial_number' => $recv['serial_number'] ?? '',
                'contact_id'    => (int)($recv['contact_id'] ?? $po['contact_id'] ?? 0),
                'description'   => $po['po_number'],
                'source'        => 'po',
                'source_id'     => $po_id,
            ];

            $new_stock_in_id = $stock->saveStockIn($stock_data, $item_log, $item_uuid);

            if ($new_stock_in_id > 0) {
                // saveStockIn() does not write source/source_id — stamp them here.
                // This links the stock-in row back to this PO for cancellation guards
                // and makes it appear under the "PO" source tab on the Stock In list.
                if (!isset($validWarehouseIds[$warehouse_id])) {
                    throw new Exception("Warehouse ID {$warehouse_id} not found.");
                }
                $table = 'td_stock_' . $warehouse_id;
                $this->pdo->prepare(
                    "UPDATE `{$table}` SET source = 'po', source_id = :po_id
                     WHERE id = :id AND company_id = :company_id"
                )->execute([
                    ':po_id'      => $po_id,
                    ':id'         => $new_stock_in_id,
                    ':company_id' => $this->company_id,
                ]);

                // approveStock() handles balance updates. saveStockIn() has
                // already reserved the bin so draft receipts cannot be reused.
                if ($auto_approve) {
                    $stock->approveStock($new_stock_in_id, $warehouse_id, 'in', $whMgmt);
                }
            }

            // Write stock_in_id + received qty back into td_purchase_order_item
            if ($item_id >= 0 && isset($po_items_by_id[$item_id])) {
                $idx = $po_items_by_id[$item_id];
                $already_received = (float)($po_items[$idx]['received_qty'] ?? 0);
                $new_received_qty = $already_received + $quantity;

                $this->pdo->prepare(
                    "UPDATE td_purchase_order_item SET
                        stock_in_id  = :stock_in_id,
                        received_qty = :received_qty
                     WHERE order_id = :po_id AND item_id = :item_id AND company_id = :company_id"
                )->execute([
                    ':stock_in_id'  => $new_stock_in_id,
                    ':received_qty' => $new_received_qty,
                    ':po_id'        => $po_id,
                    ':item_id'      => $item_id,
                    ':company_id'   => $this->company_id,
                ]);
            }
        }

        $log   = json_decode($po['log'] ?? '[]', true) ?: [];
        $log[] = array_merge($logging, ['action' => 'receive']);

        $this->pdo->prepare(
            "UPDATE td_purchase_order SET `log` = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $po_id,
            ':company_id' => $this->company_id,
        ]);
    }

    /**
     * Close a confirmed PO — sets closed_at to prevent further receipts.
     *
     * Use when the supplier will send no more goods (short-shipped, agreement closed).
     * Does not affect receipt_status — partial receipt is preserved.
     * Blocked if PO is cancelled or not yet confirmed.
     *
     * @throws Exception
     */
    public function closePo(int $po_id, array $logging): void
    {
        $sth = $this->pdo->prepare(
            "SELECT status, closed_at, `log` FROM td_purchase_order
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $po_id]);
        $po = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$po) throw new Exception("Purchase order not found.");
        if ((int)$po['status'] === -1) throw new Exception("Cannot close a cancelled PO.");
        if ((int)$po['status'] === 0)  throw new Exception("Confirm the PO before closing it.");
        if (!empty($po['closed_at']))  throw new Exception("This PO is already closed.");

        $log   = json_decode($po['log'] ?? '[]', true) ?: [];
        $log[] = array_merge($logging, ['action' => 'close']);

        $this->pdo->prepare(
            "UPDATE td_purchase_order SET
                closed_at = NOW(),
                `log`     = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $po_id,
            ':company_id' => $this->company_id,
        ]);
    }

    /**
     * Cancel a PO.
     *
     * Blocked if any linked stock-in rows have already been approved (status=1)
     * because those have modified bin occupancy and balance.
     *
     * For draft stock-in rows (status=0), they are soft-deleted (status=-1).
     *
     * @throws Exception
     */
    public function cancelPo(int $po_id, array $logging): void
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order
             WHERE company_id = :company_id AND id = :id"
        );
        $sth->execute([':company_id' => $this->company_id, ':id' => $po_id]);
        $po = $sth->fetch(PDO::FETCH_ASSOC);

        if (!$po) throw new Exception("Purchase order not found.");

        $status = (int)$po['status'];
        if ($status === -1) throw new Exception("PO is already cancelled.");

        // Guard: block if any approved stock-in rows exist for this PO
        $whMgmt = new WarehouseManager($this->pdo, $this->company_id);
        $tables = $whMgmt->getStockTables();

        foreach ($tables as $table) {
            $sth  = $this->pdo->prepare(
                "SELECT COUNT(*) FROM `{$table}`
                 WHERE company_id = :company_id
                   AND source     = 'po'
                   AND source_id  = :po_id
                   AND status     = 1"
            );
            $sth->execute([':company_id' => $this->company_id, ':po_id' => $po_id]);
            if ((int)$sth->fetchColumn() > 0) {
                throw new Exception(
                    "Cannot cancel — stock from this PO has already been approved and received. " .
                    "Please adjust stock manually if needed."
                );
            }
        }

        // Soft-delete draft stock-in rows and release their bin reservations.
        foreach ($tables as $table) {
            if (!preg_match('/^td_stock_(\d+)$/', $table, $m)) {
                continue;
            }
            $warehouse_id = (int)$m[1];

            $sth = $this->pdo->prepare(
                "SELECT id, zone, aisle, bin
                 FROM `{$table}`
                 WHERE company_id = :company_id
                   AND source     = 'po'
                   AND source_id  = :po_id
                   AND status     = 0"
            );
            $sth->execute([':company_id' => $this->company_id, ':po_id' => $po_id]);
            $draft_rows = $sth->fetchAll(PDO::FETCH_ASSOC);

            foreach ($draft_rows as $row) {
                $this->pdo->prepare(
                    "UPDATE `{$table}` SET status = -1
                     WHERE id = :id AND company_id = :company_id"
                )->execute([
                    ':id'         => (int)$row['id'],
                    ':company_id' => $this->company_id,
                ]);

                $whMgmt->releaseBin(
                    $warehouse_id,
                    $row['zone'],
                    $row['aisle'],
                    $row['bin']
                );
            }
        }

        $log   = json_decode($po['log'] ?? '[]', true) ?: [];
        $log[] = array_merge($logging, ['action' => 'cancel']);

        $this->pdo->prepare(
            "UPDATE td_purchase_order SET
                status = -1,
                `log`  = :log
             WHERE id = :id AND company_id = :company_id"
        )->execute([
            ':log'        => json_encode($log),
            ':id'         => $po_id,
            ':company_id' => $this->company_id,
        ]);

        // Release converted_qty on the originating purchase request items
        $source    = (string)($po['source']    ?? '');
        $source_id = (int)($po['source_id']   ?? 0);
        if ($source === 'purchase_request' && $source_id > 0) {
            $sth2 = $this->pdo->prepare(
                "SELECT item_id, quantity FROM td_purchase_order_item
                 WHERE order_id = :po_id AND company_id = :company_id
                 ORDER BY item_id"
            );
            $sth2->execute([':po_id' => $po_id, ':company_id' => $this->company_id]);
            $po_items = $sth2->fetchAll(PDO::FETCH_ASSOC);
            $dec = $this->pdo->prepare(
                "UPDATE td_purchase_request_item
                 SET converted_qty = GREATEST(0, converted_qty - :qty)
                 WHERE request_id = :rid AND item_id = :item_id AND company_id = :cid"
            );
            foreach ($po_items as $item) {
                $dec->execute([
                    ':qty'     => (float)($item['quantity'] ?? 0),
                    ':rid'     => $source_id,
                    ':item_id' => (int)($item['item_id'] ?? 0),
                    ':cid'     => $this->company_id,
                ]);
            }
            // Revert PR from fully-converted (status=5) back to Approved (status=2)
            $this->pdo->prepare(
                "UPDATE td_purchase_request SET status = 2
                 WHERE id = :id AND company_id = :cid AND status = 5"
            )->execute([':id' => $source_id, ':cid' => $this->company_id]);
        }
    }

    /**
     * Soft-delete a purchase order by negating company_id on the header, items, and all
     * linked draft stock-in rows. Blocked if any purchase invoice, supplier return, or
     * approved (received) stock-in rows exist.
     */
    public function softDelete(int $po_id): void
    {
        $sth = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order WHERE company_id = :cid AND id = :id"
        );
        $sth->execute([':cid' => $this->company_id, ':id' => $po_id]);
        $po = $sth->fetch(PDO::FETCH_ASSOC);
        if (!$po) throw new Exception('Purchase order not found.');

        global $pdo1;
        if (isset($pdo1) && $pdo1 instanceof PDO) {
            $guard = new PostingWindowGuard($pdo1, $this->company_id);
            $guard->assertOpenDate($po['po_date'] ?: date('Y-m-d'), 'Purchase order deletion');
        }

        $sth2 = $this->pdo->prepare(
            "SELECT COUNT(*) FROM td_invoice
             WHERE company_id = :cid AND source = 'po' AND source_id = :id AND doc_type = 'purchase_invoice'"
        );
        $sth2->execute([':cid' => $this->company_id, ':id' => $po_id]);
        if ((int)$sth2->fetchColumn() > 0) {
            throw new Exception('Cannot delete — this PO has linked purchase invoices. Delete the invoices first.');
        }

        $sth3 = $this->pdo->prepare(
            "SELECT COUNT(*) FROM td_supplier_return
             WHERE company_id = :cid AND po_id = :id AND status != -1"
        );
        $sth3->execute([':cid' => $this->company_id, ':id' => $po_id]);
        if ((int)$sth3->fetchColumn() > 0) {
            throw new Exception('Cannot delete — this PO has linked supplier returns. Delete or cancel the returns first.');
        }

        $whMgmt = new WarehouseManager($this->pdo, $this->company_id);
        $tables = $whMgmt->getStockTables();

        foreach ($tables as $table) {
            $sth5 = $this->pdo->prepare(
                "SELECT COUNT(*) FROM `{$table}`
                 WHERE company_id = :cid AND source = 'po' AND source_id = :id AND status = 1"
            );
            $sth5->execute([':cid' => $this->company_id, ':id' => $po_id]);
            if ((int)$sth5->fetchColumn() > 0) {
                throw new Exception('Cannot delete — received stock from this PO must be reversed via ICS first.');
            }
        }

        // Release bins from draft stock-in rows and negate them
        foreach ($tables as $table) {
            if (!preg_match('/^td_stock_(\d+)$/', (string)$table, $matches)) continue;
            $warehouse_id = (int)$matches[1];

            $row_sth = $this->pdo->prepare(
                "SELECT id, zone, aisle, bin FROM `{$table}`
                 WHERE company_id = :cid AND source = 'po' AND source_id = :id AND status = 0"
            );
            $row_sth->execute([':cid' => $this->company_id, ':id' => $po_id]);
            $draft_rows = $row_sth->fetchAll(PDO::FETCH_ASSOC);

            foreach ($draft_rows as $row) {
                $whMgmt->releaseBin($warehouse_id, $row['zone'], $row['aisle'], $row['bin']);
            }

            $this->pdo->prepare(
                "UPDATE `{$table}` SET company_id = company_id * -1
                 WHERE company_id = :cid AND source = 'po' AND source_id = :id"
            )->execute([':cid' => $this->company_id, ':id' => $po_id]);
        }

        // Release converted_qty on source purchase request
        $source    = (string)($po['source']    ?? '');
        $source_id = (int)($po['source_id']   ?? 0);
        if ($source === 'purchase_request' && $source_id > 0) {
            $sth6 = $this->pdo->prepare(
                "SELECT item_id, quantity FROM td_purchase_order_item
                 WHERE order_id = :id AND company_id = :cid ORDER BY item_id"
            );
            $sth6->execute([':id' => $po_id, ':cid' => $this->company_id]);
            $po_items = $sth6->fetchAll(PDO::FETCH_ASSOC);
            $dec = $this->pdo->prepare(
                "UPDATE td_purchase_request_item
                 SET converted_qty = GREATEST(0, converted_qty - :qty)
                 WHERE request_id = :rid AND item_id = :item_id AND company_id = :cid"
            );
            foreach ($po_items as $item) {
                $dec->execute([
                    ':qty'     => (float)($item['quantity'] ?? 0),
                    ':rid'     => $source_id,
                    ':item_id' => (int)($item['item_id'] ?? 0),
                    ':cid'     => $this->company_id,
                ]);
            }
            $this->pdo->prepare(
                "UPDATE td_purchase_request SET status = 2
                 WHERE id = :id AND company_id = :cid AND status = 5"
            )->execute([':id' => $source_id, ':cid' => $this->company_id]);
        }

        $this->pdo->prepare(
            "UPDATE td_purchase_order_item SET company_id = company_id * -1
             WHERE order_id = :id AND company_id = :cid"
        )->execute([':id' => $po_id, ':cid' => $this->company_id]);

        $this->pdo->prepare(
            "UPDATE td_purchase_order SET company_id = company_id * -1
             WHERE id = :id AND company_id = :cid"
        )->execute([':id' => $po_id, ':cid' => $this->company_id]);
    }
}