<?php

namespace App\Controllers\View;

use App\Controllers\BaseController;
use App\Models\PurchaseOrderModel;
use App\Models\PurchaseOrderItemModel;
use App\Models\SupplierModel;
use App\Models\SupplyModel;
use App\Models\SupplyTransactionModel;

class PurchaseOrderController extends BaseController
{
    protected $poModel;
    protected $itemModel;
    protected $supplierModel;
    protected $supplyModel;
    protected $txnModel;
    protected $db;

    public function __construct()
    {
        $this->poModel       = new PurchaseOrderModel();
        $this->itemModel     = new PurchaseOrderItemModel();
        $this->supplierModel = new SupplierModel();
        $this->supplyModel   = new SupplyModel();
        $this->txnModel      = new SupplyTransactionModel();
        $this->db            = \Config\Database::connect();
    }

    public function index()
    {
        $q = trim($this->request->getGet('q') ?? '');
        $builder = $this->poModel->select('purchase_orders.*, suppliers.name AS supplier_name')
            ->join('suppliers', 'suppliers.id = purchase_orders.supplier_id', 'left');

        if ($q !== '') {
            $builder->groupStart()
                ->like('po_number', $q)
                ->orLike('suppliers.name', $q)
                ->groupEnd();
        }

        $orders = $builder->orderBy('purchase_orders.created_at', 'DESC')->paginate(20);
        return view('inventory/po_index', [
            'orders' => $orders,
            'pager'  => $this->poModel->pager,
            'q'      => $q,
        ]);
    }

    public function create()
    {
        return view('inventory/po_form', [
            'title'     => 'Create Purchase Order',
            'action'    => site_url('inventory/po/store'),
            'suppliers' => $this->supplierModel->orderBy('name')->findAll(),
            'supplies'  => $this->supplyModel->orderBy('name')->findAll(),
        ]);
    }

    public function store()
    {
        $po = $this->request->getPost([
            'po_number','supplier_id','order_date','expected_date','notes'
        ]);
        $status = $this->request->getPost('status') ?? 'ordered';

        $supply_ids  = $this->request->getPost('item_supply_id') ?? [];
        $descs       = $this->request->getPost('item_description') ?? [];
        $qtys        = $this->request->getPost('item_quantity') ?? [];
        $unit_costs  = $this->request->getPost('item_unit_cost') ?? [];

        if (empty($supply_ids)) {
            return redirect()->back()->withInput()->with('error', 'Add at least one line item.');
        }

        // compute totals
        $subtotal = 0.0;
        $items = [];
        foreach ($supply_ids as $i => $sid) {
            $q  = (int)($qtys[$i] ?? 0);
            $uc = (float)($unit_costs[$i] ?? 0);
            if ($sid && ($q <= 0 || $uc < 0)) {
                return redirect()->back()->withInput()->with('error', 'Quantity must be greater than zero and unit cost cannot be negative.');
            }
            if ($sid && $q > 0) {
                $line = $q * $uc;
                $subtotal += $line;
                $items[] = [
                    'supply_id'   => (int)$sid,
                    'description' => trim($descs[$i] ?? ''),
                    'quantity'    => $q,
                    'unit_cost'   => $uc,
                    'received_qty'=> 0,
                ];
            }
        }
        if (!$items) {
            return redirect()->back()->withInput()->with('error', 'Valid line items required.');
        }
        $tax  = 0.00;
        $total = $subtotal + $tax;

        $this->db->transStart();

        $po['status'] = in_array($status, ['draft','ordered'], true) ? $status : 'ordered';
        $po['subtotal'] = $subtotal;
        $po['tax'] = $tax;
        $po['total'] = $total;

        if (!$this->poModel->save($po)) {
            $this->db->transRollback();
            return redirect()->back()->withInput()->with('error', implode("\n", $this->poModel->errors()));
        }
        $poId = $this->poModel->getInsertID();

        foreach ($items as $it) {
            $it['purchase_order_id'] = $poId;
            if (!$this->itemModel->insert($it)) {
                $this->db->transRollback();
                return redirect()->back()->withInput()->with('error', 'Failed to save line items.');
            }
        }

        $this->db->transComplete();
        if ($this->db->transStatus() === false) {
            return redirect()->back()->withInput()->with('error', 'Failed to save purchase order.');
        }

        return redirect()->to(site_url('inventory/po/show/'.$poId))->with('success', 'PO created.');
    }

    public function show($id)
    {
        $po = $this->poModel->select('purchase_orders.*, suppliers.name AS supplier_name')
              ->join('suppliers', 'suppliers.id = purchase_orders.supplier_id', 'left')
              ->find($id);
        if (!$po) return redirect()->to('inventory/po')->with('error', 'PO not found.');

        $items = $this->itemModel->select('purchase_order_items.*, supplies.name AS supply_name, supplies.unit as supply_unit')
                ->join('supplies', 'supplies.id = purchase_order_items.supply_id', 'left')
                ->where('purchase_order_id', $id)->findAll();

        return view('inventory/po_show', [
            'po' => $po,
            'items' => $items,
        ]);
    }

    /**
     * Receive items (partial or full)
     * POST body: received[item_id] = qty_to_receive
     */
    public function receive($id)
    {
        $received = $this->request->getPost('received') ?? []; // [itemId => qty]
        if (!$received) {
            return redirect()->to('inventory/po/show/'.$id)->with('error', 'No items to receive.');
        }
        $idempotencyKey = trim((string)($this->request->getPost('idempotency_key') ?? ''));
        if ($idempotencyKey === '') {
            $idempotencyKey = bin2hex(random_bytes(16));
        }
        $fingerprint = $this->buildReceiptFingerprint((int)$id, $received);

        $issuedBy = (string) (session('user.email') ?? session('user.username') ?? 'system');

        $this->db->transBegin();
        try {
            $existingOperation = $this->db->query(
                'SELECT * FROM inventory_receipt_operations WHERE idempotency_key = ? FOR UPDATE',
                [$idempotencyKey]
            )->getRowArray();
            if ($existingOperation) {
                if ((int)$existingOperation['purchase_order_id'] !== (int)$id || (string)$existingOperation['request_fingerprint_hash'] !== $fingerprint) {
                    $this->db->transCommit();
                    return redirect()->to('inventory/po/show/'.$id)->with('error', 'Receipt idempotency key conflicts with a different request.');
                }
                $this->db->transCommit();
                return redirect()->to('inventory/po/show/'.$id)->with('success', 'Receipt already recorded.');
            }

            $po = $this->db->query('SELECT * FROM purchase_orders WHERE id = ? FOR UPDATE', [(int) $id])->getRowArray();
            if (!$po || in_array($po['status'], ['canceled','received'], true)) {
                throw new \RuntimeException('PO not receivable.');
            }

            $items = $this->db->query(
                'SELECT * FROM purchase_order_items WHERE purchase_order_id = ? FOR UPDATE',
                [(int) $id]
            )->getResultArray();
            if ($items === []) {
                throw new \RuntimeException('PO has no receivable lines.');
            }

            $operationInserted = $this->db->table('inventory_receipt_operations')->insert([
                'idempotency_key' => $idempotencyKey,
                'purchase_order_id' => (int)$id,
                'request_fingerprint_hash' => $fingerprint,
                'status' => 'processing',
                'actor_id' => (int)(session()->get('user_id') ?? 0) ?: null,
                'created_at' => utc_now(),
                'updated_at' => utc_now(),
            ]);
            $operationId = (int)$this->db->insertID();
            if (!$operationInserted) {
                $operationId = 0;
            }
            if ($operationId <= 0) {
                throw new \RuntimeException('Failed to create receipt operation.');
            }

            $itemsById = [];
            foreach ($items as $item) {
                $ordered = (int) ($item['quantity'] ?? 0);
                $alreadyReceived = (int) ($item['received_qty'] ?? 0);
                if ($ordered <= 0 || $alreadyReceived < 0 || $alreadyReceived > $ordered) {
                    throw new \RuntimeException('PO contains invalid received quantities.');
                }
                $itemsById[(int) $item['id']] = $item;
            }

            foreach ($received as $itemId => $qty) {
                $itemId = (int) $itemId;
                $qty = (int)$qty;
                if ($qty <= 0) {
                    continue;
                }
                if (!isset($itemsById[$itemId])) {
                    throw new \RuntimeException('Submitted item does not belong to this PO.');
                }

                $item = $itemsById[$itemId];
                $remaining = (int)$item['quantity'] - (int)$item['received_qty'];
                if ($qty > $remaining) {
                    throw new \RuntimeException('Received quantity exceeds ordered quantity.');
                }

                $supply = $this->db->query('SELECT * FROM supplies WHERE id = ? FOR UPDATE', [(int) $item['supply_id']])->getRowArray();
                if (!$supply) {
                    throw new \RuntimeException('Supply not found for PO line.');
                }

                if (!$this->db->table('supplies')
                    ->where('id', (int) $supply['id'])
                    ->set('qty_on_hand', 'qty_on_hand + ' . $qty, false)
                    ->update()) {
                    throw new \RuntimeException('Failed to update supply quantity.');
                }

                $movementId = $this->txnModel->insert([
                    'supply_id' => (int) $supply['id'],
                    'type'      => 'in',
                    'quantity'  => $qty,
                    'ref'       => 'PO ' . $po['po_number'],
                    'issued_to' => 'Inventory',
                    'issued_by' => $issuedBy,
                    'notes'     => 'Received against PO',
                ]);
                if (!$movementId) {
                    throw new \RuntimeException('Failed to record inventory transaction.');
                }
                if (!$this->db->table('inventory_receipt_lines')->insert([
                    'operation_id' => $operationId,
                    'purchase_order_item_id' => $itemId,
                    'quantity' => $qty,
                    'movement_id' => (int)$movementId,
                    'reversed_quantity' => 0,
                    'created_at' => utc_now(),
                ])) {
                    throw new \RuntimeException('Failed to record receipt line.');
                }

                if (!$this->itemModel->update($itemId, [
                    'received_qty' => (int)$item['received_qty'] + $qty
                ])) {
                    throw new \RuntimeException('Failed to update PO line quantity.');
                }

                $itemsById[$itemId]['received_qty'] = (int)$item['received_qty'] + $qty;
            }

            $completed = true;
            foreach ($itemsById as $item) {
                if ((int) $item['received_qty'] < (int) $item['quantity']) {
                    $completed = false;
                    break;
                }
            }

            if (!$this->poModel->update($id, ['status' => $completed ? 'received' : 'ordered'])) {
                throw new \RuntimeException('Failed to update PO status.');
            }
            $this->db->table('inventory_receipt_operations')
                ->where('id', $operationId)
                ->update(['status' => 'completed', 'updated_at' => utc_now()]);

            if (!$this->db->transStatus()) {
                throw new \RuntimeException('PO receive transaction failed.');
            }

            $this->db->transCommit();
        } catch (\Throwable $e) {
            $this->db->transRollback();
            log_message('error', 'Failed to receive PO #{po}: {msg}', ['po' => $id, 'msg' => $e->getMessage()]);
            return redirect()->to('inventory/po/show/'.$id)->with('error', 'Failed to receive items.');
        }

        return redirect()->to('inventory/po/show/'.$id)->with('success', $completed ? 'PO fully received.' : 'PO partially received.');
    }

    public function reverseReceipt(int $operationId)
    {
        $reason = trim((string)($this->request->getPost('reason') ?? ''));
        if ($reason === '') {
            return redirect()->back()->with('error', 'Receipt reversal reason is required.');
        }

        $issuedBy = (string) (session('user.email') ?? session('user.username') ?? 'system');
        $poId = 0;

        $this->db->transBegin();
        try {
            $operation = $this->db->query(
                'SELECT * FROM inventory_receipt_operations WHERE id = ? FOR UPDATE',
                [$operationId]
            )->getRowArray();
            if (!$operation || (string)($operation['status'] ?? '') !== 'completed') {
                throw new \RuntimeException('Receipt operation is not reversible.');
            }

            $poId = (int)$operation['purchase_order_id'];
            $po = $this->db->query('SELECT * FROM purchase_orders WHERE id = ? FOR UPDATE', [$poId])->getRowArray();
            if (!$po) {
                throw new \RuntimeException('Purchase order not found.');
            }

            $lines = $this->db->query(
                'SELECT rl.*, poi.supply_id, poi.received_qty, poi.quantity AS ordered_quantity
                   FROM inventory_receipt_lines rl
                   JOIN purchase_order_items poi ON poi.id = rl.purchase_order_item_id
                  WHERE rl.operation_id = ?
                  FOR UPDATE',
                [$operationId]
            )->getResultArray();
            if ($lines === []) {
                throw new \RuntimeException('Receipt operation has no lines.');
            }

            $reversedAny = false;
            foreach ($lines as $line) {
                $remaining = (int)$line['quantity'] - (int)$line['reversed_quantity'];
                if ($remaining <= 0) {
                    continue;
                }

                $supply = $this->db->query('SELECT * FROM supplies WHERE id = ? FOR UPDATE', [(int)$line['supply_id']])->getRowArray();
                if (!$supply) {
                    throw new \RuntimeException('Supply not found for receipt line.');
                }
                if ((int)($supply['qty_on_hand'] ?? 0) < $remaining) {
                    throw new \RuntimeException('Insufficient inventory for receipt reversal.');
                }
                if ((int)$line['received_qty'] < $remaining) {
                    throw new \RuntimeException('PO line received quantity cannot cover reversal.');
                }

                if (!$this->db->table('supplies')
                    ->where('id', (int)$supply['id'])
                    ->set('qty_on_hand', 'qty_on_hand - ' . $remaining, false)
                    ->update()) {
                    throw new \RuntimeException('Failed to update supply quantity.');
                }

                $movementId = $this->txnModel->insert([
                    'supply_id' => (int)$supply['id'],
                    'type'      => 'out',
                    'quantity'  => $remaining,
                    'ref'       => 'PO ' . ($po['po_number'] ?? $poId),
                    'issued_to' => 'Inventory',
                    'issued_by' => $issuedBy,
                    'notes'     => 'Reversal of receipt operation #' . $operationId . ': ' . $reason,
                ]);
                if (!$movementId) {
                    throw new \RuntimeException('Failed to record inventory reversal transaction.');
                }

                if (!$this->db->table('purchase_order_items')
                    ->where('id', (int)$line['purchase_order_item_id'])
                    ->set('received_qty', 'received_qty - ' . $remaining, false)
                    ->update()) {
                    throw new \RuntimeException('Failed to update PO line received quantity.');
                }

                if (!$this->db->table('inventory_receipt_lines')
                    ->where('id', (int)$line['id'])
                    ->update([
                        'reversed_quantity' => (int)$line['reversed_quantity'] + $remaining,
                        'reversal_movement_id' => (int)$movementId,
                    ])) {
                    throw new \RuntimeException('Failed to mark receipt line reversed.');
                }

                $reversedAny = true;
            }

            if (!$reversedAny) {
                throw new \RuntimeException('Receipt operation is already fully reversed.');
            }

            $items = $this->db->query(
                'SELECT quantity, received_qty FROM purchase_order_items WHERE purchase_order_id = ? FOR UPDATE',
                [$poId]
            )->getResultArray();
            $allReceived = $items !== [];
            foreach ($items as $item) {
                $allReceived = $allReceived && (int)($item['received_qty'] ?? 0) >= (int)($item['quantity'] ?? 0);
            }

            if (!$this->poModel->update($poId, ['status' => $allReceived ? 'received' : 'ordered'])) {
                throw new \RuntimeException('Failed to update PO status.');
            }

            $this->db->table('inventory_receipt_operations')
                ->where('id', $operationId)
                ->update(['status' => 'reversed', 'updated_at' => utc_now()]);

            if (!$this->db->transStatus()) {
                throw new \RuntimeException('Receipt reversal transaction failed.');
            }

            $this->db->transCommit();
        } catch (\Throwable $e) {
            $this->db->transRollback();
            log_message('error', 'Failed to reverse receipt operation #{operation}: {msg}', [
                'operation' => $operationId,
                'msg' => $e->getMessage(),
            ]);
            return redirect()->to($poId > 0 ? 'inventory/po/show/' . $poId : 'inventory/po')->with('error', 'Failed to reverse receipt.');
        }

        return redirect()->to('inventory/po/show/' . $poId)->with('success', 'Receipt reversed.');
    }

    public function cancel($id)
    {
        $po = $this->poModel->find($id);
        if (!$po || $po['status'] === 'received') {
            return redirect()->to('inventory/po/show/'.$id)->with('error', 'Cannot cancel this PO.');
        }
        $received = $this->itemModel
            ->where('purchase_order_id', (int) $id)
            ->where('received_qty >', 0)
            ->countAllResults();
        if ($received > 0) {
            return redirect()->to('inventory/po/show/'.$id)->with('error', 'Cannot cancel a partially received PO without inventory reversal.');
        }
        if (!$this->poModel->update($id, ['status' => 'canceled'])) {
            return redirect()->to('inventory/po/show/'.$id)->with('error', 'Failed to cancel PO.');
        }
        return redirect()->to('inventory/po/show/'.$id)->with('success', 'PO canceled.');
    }

    private function buildReceiptFingerprint(int $purchaseOrderId, array $received): string
    {
        $normalized = [];
        foreach ($received as $itemId => $qty) {
            $qty = (int)$qty;
            if ($qty > 0) {
                $normalized[(int)$itemId] = $qty;
            }
        }
        ksort($normalized);

        return hash('sha256', json_encode([
            'operation_type' => 'inventory_receipt',
            'purchase_order_id' => $purchaseOrderId,
            'received' => $normalized,
        ], JSON_UNESCAPED_SLASHES));
    }
}