<?php

/**
 * PurchaseRequestManager
 *
 * All read/write operations for td_purchase_request and td_purchase_request_item.
 *
 * Status flow:  0=draft → 1=submitted → 2=approved → 5=converted
 *                          1/2/3       ← reopen     3=rejected
 *               0/1        → -1=cancelled
 *
 * Tax: tax_amount is stored per line at full precision (decimal 18,4).
 *      document.tax = ROUND(SUM(items.tax_amount), 2) — never passed from caller.
 *
 * Write methods do NOT manage their own DB transactions.
 * Callers must wrap multi-step operations inside dbTransaction().
 */
class PurchaseRequestManager
{
    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 generateNumber(): string
    {
        $prefix = 'PR-' . date('Ym') . '-';
        $sth = $this->pdo->prepare(
            "SELECT request_number FROM td_purchase_request
             WHERE company_id = :cid AND request_number LIKE :prefix
             ORDER BY request_number DESC LIMIT 1"
        );
        $sth->execute([':cid' => $this->company_id, ':prefix' => $prefix . '%']);
        $last = $sth->fetchColumn();
        $seq  = $last ? ((int)substr($last, -4) + 1) : 1;
        return $prefix . str_pad($seq, 4, '0', STR_PAD_LEFT);
    }

    /**
     * Derive document-level totals from line items.
     * tax = ROUND(SUM(items.tax_amount), 2) — never accepted from caller.
     */
    private function computeTotals(array $items, float $discount, float $shipping_fee): array
    {
        $subtotal = array_sum(array_map(fn($i) => (float)($i['total_price'] ?? 0), $items));
        $tax      = round(array_sum(array_map(fn($i) => (float)($i['tax_amount'] ?? 0), $items)), 2);
        $grand    = max(0, $subtotal - $discount + $tax + $shipping_fee);
        return [round($subtotal, 4), $tax, round($grand, 4)];
    }

    /** DELETE + INSERT all line items. converted_qty is always reset to 0 on save. */
    private function syncItems(int $request_id, array $items): void
    {
        $this->pdo->prepare(
            "DELETE FROM td_purchase_request_item
             WHERE request_id = :rid AND company_id = :cid"
        )->execute([':rid' => $request_id, ':cid' => $this->company_id]);

        $sth = $this->pdo->prepare(
            "INSERT INTO td_purchase_request_item
                (company_id, request_id, item_id, product_sku, product_name,
                 quantity, unit_price, total_price, tax_amount, tax_rate, converted_qty)
             VALUES
                (:company_id, :request_id, :item_id, :product_sku, :product_name,
                 :quantity, :unit_price, :total_price, :tax_amount, :tax_rate, 0)"
        );
        foreach ($items as $pos => $item) {
            $sth->execute([
                ':company_id'  => $this->company_id,
                ':request_id'  => $request_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),
            ]);
        }
    }

    // ─────────────────────────────────────────────────────────────
    // Read
    // ─────────────────────────────────────────────────────────────

    public function getList(): array
    {
        $sth = $this->pdo->prepare(
            "SELECT r.*, COALESCE(c.contact_name, '') AS contact_name,
                    (SELECT COUNT(*) FROM td_purchase_order p
                     WHERE p.company_id = r.company_id
                       AND p.source     = 'purchase_request'
                       AND p.source_id  = r.id
                       AND p.status    != -1) AS linked_po_count
             FROM td_purchase_request r
             LEFT JOIN md_contact c
               ON c.company_id = r.company_id AND c.id = r.contact_id
             WHERE r.company_id = :cid
             ORDER BY r.id DESC"
        );
        $sth->execute([':cid' => $this->company_id]);
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    }

    public function getById(int $id): array|false
    {
        $sth = $this->pdo->prepare(
            "SELECT r.*, COALESCE(c.contact_name, '') AS contact_name
             FROM td_purchase_request r
             LEFT JOIN md_contact c
               ON c.company_id = r.company_id AND c.id = r.contact_id
             WHERE r.company_id = :cid AND r.id = :id
             LIMIT 1"
        );
        $sth->execute([':cid' => $this->company_id, ':id' => $id]);
        $row = $sth->fetch(PDO::FETCH_ASSOC);
        if (!$row) return false;

        $sth2 = $this->pdo->prepare(
            "SELECT *, (quantity - converted_qty) AS remaining_qty
             FROM td_purchase_request_item
             WHERE request_id = :rid AND company_id = :cid
             ORDER BY item_id"
        );
        $sth2->execute([':rid' => $id, ':cid' => $this->company_id]);
        $row['items']           = $sth2->fetchAll(PDO::FETCH_ASSOC);
        $row['total_remaining'] = array_sum(array_column($row['items'], 'remaining_qty'));

        $sth3 = $this->pdo->prepare(
            "SELECT id, po_number, status, grand_total, created_at
             FROM td_purchase_order
             WHERE company_id = :cid
               AND source     = 'purchase_request'
               AND source_id  = :rid
               AND status    != -1
             ORDER BY id"
        );
        $sth3->execute([':cid' => $this->company_id, ':rid' => $id]);
        $row['linked_pos'] = $sth3->fetchAll(PDO::FETCH_ASSOC);

        return $row;
    }

    // ─────────────────────────────────────────────────────────────
    // Write
    // ─────────────────────────────────────────────────────────────

    /**
     * Create (id=0) or update an existing draft purchase request.
     *
     * @param array $data  Keys: id, contact_id, department_id, request_date,
     *                           required_date, items (array), discount,
     *                           shipping_fee, notes.
     *                           Each item must include tax_amount.
     * @return int  The purchase request id (new or existing).
     */
    public function save(array $data, array $logging): int
    {
        $id           = (int)($data['id'] ?? 0);
        $items        = $data['items'] ?? [];
        $discount     = (float)($data['discount']     ?? 0);
        $shipping_fee = (float)($data['shipping_fee'] ?? 0);

        if (empty($items)) throw new Exception('At least one item is required.');

        [$subtotal, $tax, $grand] = $this->computeTotals($items, $discount, $shipping_fee);

        if ($id === 0) {
            $number = $this->generateNumber();
            $log    = [array_merge($logging, ['action' => 'create_purchase_request'])];

            $this->pdo->prepare(
                "INSERT INTO td_purchase_request
                    (company_id, uuid, request_number, contact_id, department_id,
                     request_date, required_date, status,
                     subtotal, discount, tax, shipping_fee, grand_total,
                     notes, `log`, created_at)
                 VALUES
                    (:cid, :uuid, :num, :contact_id, :department_id,
                     :request_date, :required_date, 0,
                     :sub, :disc, :tax, :ship, :grand,
                     :notes, :log, NOW())"
            )->execute([
                ':cid'           => $this->company_id,
                ':uuid'          => bin2hex(random_bytes(16)),
                ':num'           => $number,
                ':contact_id'    => (int)($data['contact_id']    ?? 0),
                ':department_id' => (int)($data['department_id'] ?? 0),
                ':request_date'  => $data['request_date']  ?: null,
                ':required_date' => $data['required_date'] ?: null,
                ':sub'           => $subtotal,
                ':disc'          => $discount,
                ':tax'           => $tax,
                ':ship'          => $shipping_fee,
                ':grand'         => $grand,
                ':notes'         => $data['notes'] ?? '',
                ':log'           => json_encode($log),
            ]);

            $id = (int)$this->pdo->lastInsertId();
            $this->syncItems($id, $items);
            return $id;
        }

        // Update — only allowed on draft (status = 0)
        $sth = $this->pdo->prepare(
            "SELECT status, `log` FROM td_purchase_request
             WHERE company_id = :cid AND id = :id LIMIT 1"
        );
        $sth->execute([':cid' => $this->company_id, ':id' => $id]);
        $row = $sth->fetch(PDO::FETCH_ASSOC);
        if (!$row) throw new Exception('Purchase request not found.');
        if ((int)$row['status'] !== 0) throw new Exception('Only draft purchase requests can be edited.');

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

        $this->pdo->prepare(
            "UPDATE td_purchase_request SET
                contact_id    = :contact_id,
                department_id = :department_id,
                request_date  = :request_date,
                required_date = :required_date,
                subtotal      = :sub,
                discount      = :disc,
                tax           = :tax,
                shipping_fee  = :ship,
                grand_total   = :grand,
                notes         = :notes,
                `log`         = :log
             WHERE company_id = :cid AND id = :id"
        )->execute([
            ':contact_id'    => (int)($data['contact_id']    ?? 0),
            ':department_id' => (int)($data['department_id'] ?? 0),
            ':request_date'  => $data['request_date']  ?: null,
            ':required_date' => $data['required_date'] ?: null,
            ':sub'           => $subtotal,
            ':disc'          => $discount,
            ':tax'           => $tax,
            ':ship'          => $shipping_fee,
            ':grand'         => $grand,
            ':notes'         => $data['notes'] ?? '',
            ':log'           => json_encode($log),
            ':cid'           => $this->company_id,
            ':id'            => $id,
        ]);

        $this->syncItems($id, $items);
        return $id;
    }

    /**
     * Transition purchase request status.
     * Valid actions: submit, approve, reject, reopen, cancel.
     */
    public function updateStatus(int $id, string $action, array $logging): void
    {
        $transitions = [
            'submit'  => ['from' => [0],          'to' => 1,  'label' => 'Submitted'],
            'approve' => ['from' => [1],           'to' => 2,  'label' => 'Approved'],
            'reject'  => ['from' => [1],           'to' => 3,  'label' => 'Rejected'],
            'reopen'  => ['from' => [1, 2, 3],     'to' => 0,  'label' => 'Draft'],
            'cancel'  => ['from' => [0, 1],        'to' => -1, 'label' => 'Cancelled'],
        ];

        if (!isset($transitions[$action])) throw new Exception('Invalid action.');

        $sth = $this->pdo->prepare(
            "SELECT status, `log` FROM td_purchase_request
             WHERE company_id = :cid AND id = :id LIMIT 1"
        );
        $sth->execute([':cid' => $this->company_id, ':id' => $id]);
        $row = $sth->fetch(PDO::FETCH_ASSOC);
        if (!$row) throw new Exception('Purchase request not found.');

        $t = $transitions[$action];
        if (!in_array((int)$row['status'], $t['from'], true)) {
            throw new Exception('Transition not allowed from current status.');
        }

        if ($action === 'reopen') {
            $sth2 = $this->pdo->prepare(
                "SELECT COUNT(*) FROM td_purchase_request_item
                 WHERE request_id = :rid AND company_id = :cid AND converted_qty > 0"
            );
            $sth2->execute([':rid' => $id, ':cid' => $this->company_id]);
            if ((int)$sth2->fetchColumn() > 0) {
                throw new Exception('Cannot reopen — one or more items have already been converted to a purchase order.');
            }
        }

        $log   = json_decode($row['log'] ?: '[]', true);
        $log[] = array_merge($logging, ['action' => 'purchase_request_' . $action]);

        $this->pdo->prepare(
            "UPDATE td_purchase_request SET status = :status, `log` = :log
             WHERE company_id = :cid AND id = :id"
        )->execute([
            ':status' => $t['to'],
            ':log'    => json_encode($log),
            ':cid'    => $this->company_id,
            ':id'     => $id,
        ]);
    }

    /**
     * Increment converted_qty per item after a successful PO conversion.
     * Automatically sets PR status = 5 when all items are fully converted.
     *
     * @param array $validated  Each entry: ['item_id' => int, 'quantity' => float]
     */
    public function incrementConvertedQty(int $request_id, array $validated): void
    {
        $upd = $this->pdo->prepare(
            "UPDATE td_purchase_request_item
             SET converted_qty = converted_qty + :qty
             WHERE request_id = :rid AND item_id = :item_id AND company_id = :cid"
        );
        foreach ($validated as $v) {
            $upd->execute([
                ':qty'     => $v['quantity'],
                ':rid'     => $request_id,
                ':item_id' => $v['item_id'],
                ':cid'     => $this->company_id,
            ]);
        }

        $sth = $this->pdo->prepare(
            "SELECT COUNT(*) FROM td_purchase_request_item
             WHERE request_id = :rid AND company_id = :cid
               AND converted_qty < quantity - 0.000001"
        );
        $sth->execute([':rid' => $request_id, ':cid' => $this->company_id]);
        if ((int)$sth->fetchColumn() === 0) {
            $this->pdo->prepare(
                "UPDATE td_purchase_request SET status = 5
                 WHERE id = :id AND company_id = :cid"
            )->execute([':id' => $request_id, ':cid' => $this->company_id]);
        }
    }
}