<?php

namespace App\Services\Qr;

use App\Models\Household;
use App\Models\PartnerStore;
use App\Models\QrCode;
use App\Models\QrCodeBatch;
use App\Models\ServiceArea;
use App\Models\User;
use App\States\QrCode\Active;
use App\States\QrCode\Unassigned;
use App\Tenancy\Tenancy;
use Illuminate\Support\Carbon;
use Illuminate\Support\Facades\DB;

class BatchGenerator
{
    public function __construct(private readonly QrSerialGenerator $serials) {}

    /**
     * Generate a new batch with $quantity codes in the unassigned state.
     */
    public function generate(
        int $quantity,
        string $purpose,
        ?ServiceArea $targetArea = null,
        ?int $targetStoreId = null,
        ?User $createdBy = null,
        ?\DateTimeInterface $expiresAt = null,
        ?string $notes = null,
        ?int $householdId = null,
    ): QrCodeBatch {
        $now = Carbon::now();
        $areaCode = $targetArea?->code ?? 'PH';
        $batchSeq = $this->nextBatchSeq($now);
        $batchNumber = sprintf('B%s%04d', $now->format('ymd'), $batchSeq);

        return DB::transaction(function () use (
            $batchNumber, $quantity, $purpose, $targetArea, $targetStoreId,
            $createdBy, $expiresAt, $notes, $now, $areaCode, $batchSeq, $householdId,
        ) {
            $tenantId = null;
            if ($householdId) {
                $tenantId = Household::find($householdId)?->tenant_id;
            } elseif ($targetArea) {
                $tenantId = $targetArea->tenant_id;
            } elseif ($targetStoreId) {
                $tenantId = PartnerStore::find($targetStoreId)?->tenant_id;
            }

            if (empty($tenantId)) {
                $tenantId = Tenancy::current()?->id;
            }

            $batch = QrCodeBatch::create([
                'tenant_id' => $tenantId,
                'batch_number' => $batchNumber,
                'quantity' => $quantity,
                'purpose' => $purpose,
                'target_area_id' => $targetArea?->id,
                'target_store_id' => $targetStoreId,
                'household_id' => $householdId,
                'created_by_admin_id' => $createdBy?->id,
                'expires_at' => $expiresAt,
                'notes' => $notes,
            ]);

            $rows = [];
            $tsNow = $now->toDateTimeString();
            // Bulk insert bypasses model events, so we have to set tenant_id
            // explicitly. Inherit from the just-created batch (which goes
            // through the HasTenant trait) so any cross-tenant subtleties
            // bubble up early.
            $tenantId = $batch->tenant_id ?? Tenancy::current()?->id;
            for ($i = 1; $i <= $quantity; $i++) {
                $serial = $this->serials->build($areaCode, $now, $batchSeq, $i);
                $rows[] = [
                    'tenant_id' => $tenantId,
                    'serial' => $serial,
                    'barcode_value' => $serial,
                    'batch_id' => $batch->id,
                    'status' => $householdId ? Active::$name : Unassigned::$name,
                    'assigned_to_household_id' => $householdId,
                    'allocated_at' => $householdId ? $tsNow : null,
                    'activated_at' => $householdId ? $tsNow : null,
                    'expires_at' => $expiresAt,
                    'created_at' => $tsNow,
                    'updated_at' => $tsNow,
                ];

                // Bulk insert in chunks to keep memory bounded for big batches.
                if (count($rows) >= 1000) {
                    QrCode::insert($rows);
                    $rows = [];
                }
            }

            if (! empty($rows)) {
                QrCode::insert($rows);
            }

            return $batch->fresh();
        });
    }

    private function nextBatchSeq(Carbon $when): int
    {
        // Per-month batch sequence to match the 'ym' format in QR serials
        $startOfMonth = $when->copy()->startOfMonth();
        $endOfMonth = $when->copy()->endOfMonth();

        return QrCodeBatch::withTrashed()->whereBetween('created_at', [$startOfMonth, $endOfMonth])->count() + 1;
    }
}