<?php

namespace App\Http\Controllers\Admin;

use App\Http\Controllers\Controller;
use App\Jobs\GenerateCertificateJob;
use App\Models\Certificate;
use App\Models\Program;
use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;
use Illuminate\View\View;

class CertificateController extends Controller
{
    public function index(Program $program): View
    {
        $certificates = $program->certificates()
            ->with('participant')
            ->latest()
            ->paginate(50);

        $stats = [
            'total'     => $program->certificates()->count(),
            'generated' => $program->certificates()->whereIn('status', ['generated', 'emailed', 'downloaded'])->count(),
            'pending'   => $program->certificates()->where('status', 'pending')->count(),
            'failed'    => $program->certificates()->where('status', 'failed')->count(),
            'emailed'   => $program->certificates()->where('status', 'emailed')->count(),
        ];

        return view('admin.programs.certificates.index', compact('program', 'certificates', 'stats'));
    }

    public function generateAll(Request $request, Program $program): RedirectResponse
    {
        $template = $program->certificateTemplate;
        if (! $template) {
            return back()->with('error', 'Template sijil belum ditetapkan untuk program ini.');
        }

        // Find all attended participants without certificates
        $existingIds = $program->certificates()->pluck('participant_id')->toArray();

        $attended = $program->attendances()
            ->whereNotIn('participant_id', $existingIds)
            ->get();

        if ($attended->isEmpty() && $program->certificates()->count() === 0) {
            return back()->with('error', 'Tiada peserta yang hadir untuk dijana sijil.');
        }

        $sequence = $program->certificates()->count();
        $created  = 0;

        foreach ($attended as $attendance) {
            $sequence++;
            $cert = Certificate::firstOrCreate(
                ['program_id' => $program->id, 'participant_id' => $attendance->participant_id],
                [
                    'certificate_template_id' => $template->id,
                    'certificate_no'          => $this->buildCertNo($program, $sequence),
                    'status'                  => 'pending',
                ]
            );

            if ($cert->wasRecentlyCreated || $cert->status === 'failed') {
                $cert->update(['certificate_template_id' => $template->id, 'status' => 'pending']);
                GenerateCertificateJob::dispatch($cert);
                $created++;
            }
        }

        // Re-queue failed certificates
        $failed = $program->certificates()->where('status', 'failed')->get();
        foreach ($failed as $cert) {
            $cert->update(['status' => 'pending', 'error_message' => null]);
            GenerateCertificateJob::dispatch($cert);
            $created++;
        }

        return back()->with('success', "Penjanaan sijil telah diantri untuk {$created} peserta.");
    }

    public function emailAll(Program $program): RedirectResponse
    {
        $toEmail = $program->certificates()
            ->whereIn('status', ['generated'])
            ->whereNull('emailed_at')
            ->count();

        if ($toEmail === 0) {
            return back()->with('error', 'Tiada sijil yang sedia untuk dihantar emel.');
        }

        // Dispatch email blast job — implemented in Fasa 8
        \App\Jobs\SendCertificateEmailJob::dispatchBatch($program);

        return back()->with('success', "Penghantaran emel sijil dijadualkan untuk {$toEmail} peserta.");
    }

    private function buildCertNo(Program $program, int $seq): string
    {
        $year   = now()->format('Y');
        $prefix = strtoupper(substr(preg_replace('/[^A-Za-z]/', '', $program->title), 0, 4));
        return sprintf('%s/%s/%04d', $prefix ?: 'ECT', $year, $seq);
    }
}