exchange/app/Http/Controllers/InvoiceController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Illuminate\Routing\ResponseFactory;
use Illuminate\Support\MessageBag;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Validator;
use Carbon\Carbon;
use Illuminate\Database\Eloquent\Model;
use App\Booking;

class InvoiceController extends Controller
{
    public function show($id)
    {

    }

    public function create(Request $request, $id)
    {
        $user = $request->user();

        // validate $id

        $validatedData = $request->validate([
            'address' => 'required',
            'buyer_company' => 'required',
            'contact_no' => 'required',
            'marking' => 'required',
            'lines.*.order' => 'required|numeric',
            'lines.*.stock_code' => 'required',
            'lines.*.description' => 'required',
            'lines.*.quantity' => 'required|numeric',
            'lines.*.unit_price_rm' => 'required|numeric',
            'lines.*.unit_price_rmb' => '',
            'lines.*.total' => 'required|numeric',
        ]);
        
        // booking_id belongs to user
        $booking = Booking::where('id', $id)->first();
        if (!$booking) {
            return response()->json(['message' => 'Unable to find booking'], 403);
        }

        // user_id in booking does not match
        if ($booking->user_id !== $user->id) {
            return response()->json([
                'message' => 'Booking does not belongs to you'
            ], 403);
        }

        // Amount match with total
        $subtotalArray = array_map(
            function ($line) { return $line['total']; },
            $validatedData['lines']
        );
        $total = array_reduce($subtotalArray, function ($v1, $v2) {
            return $v1 + $v2;
        });

        if ($total !== $booking->amount) {
            return response()->json([
                'message' => 'Booking amount expected is '.$booking->amount.'. Your Invoice amount is $total.'
            ], 400);
        }

        // Change Status to submitted

        // Write to database if does not exist
        $exist = DB::table('invoices')->where('booking_id', '=', $id)->first();
        if ($exist) {
            return response()
                    ->json(['message' => 'Invoice exist. Cannot create duplicate invoice. Try edit.'], 400);
        }

        // Generate PO Number - po20200810-001(PO Format)
        $dt = Carbon::now();
        $po_number = 'po'.$dt->year.$dt->month.$dt->day.'-'.$id;

        // Insert Invoice into database
        $invoice = DB::table('invoices')->insertGetId([
            'amount' => $total,
            'booking_id' => $id,
            'buyer_company' => $validatedData['buyer_company'],
            'address' => $validatedData['address'],
            'contact_no' => $validatedData['contact_no'],
            'po_number' => $po_number
        ]);

        if (!$invoice) {
            return response()
                    ->json(['message' => 'Unable to Save Data'], 500)
        }

        // Insert invoice_id into lines
        foreach( $validatedData['lines'] as $key => $line) {
            $validatedData['lines'][$key]['invoice_id'] = $invoice;
        }
        unset($line);

        $lines = DB::table('invoice_details')->insert($validatedData['lines']);

        if($lines) {
            return response(201);
        } else {
            return response(500);
        }
    }

    public function edit(Request $request, $id)
    {

    }

    public function updateStatus(Request $request, $id)
    {

    }

    public function getPO($id)
    {

    }

    public function getDO($id)
    {

    }

    public function getSupplierDO($id)
    {

    }
}