<?php

namespace App\Services\Events;

use App\Models\QrCode;
use App\Models\User;
use App\Services\Identity\IdentityClient;
use App\Services\Integrations\MailCalendarClient;
use Carbon\CarbonInterface;
use Illuminate\Support\Carbon;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Str;

class EventMailCalendarSyncService
{
    public function __construct(
        private readonly MailCalendarClient $mail,
        private readonly IdentityClient $identity,
    ) {}

    public function sync(QrCode $event, User $owner): QrCode
    {
        if ($event->type !== QrCode::TYPE_EVENT || ! $this->mail->isConfigured()) {
            return $event;
        }

        $mailbox = $this->resolveMailbox($owner);
        if ($mailbox === null) {
            return $event;
        }

        $entries = $this->entriesFor($event);
        $previous = (array) data_get($event->payload, 'calendar_sync.items', []);
        $synced = [];

        foreach ($entries as $entry) {
            $result = $this->mail->upsertEvent(array_merge($entry, [
                'mailbox_email' => $mailbox,
            ]));

            if ($result && isset($result['id'])) {
                $synced[$entry['external_ref']] = (int) $result['id'];
            }
        }

        foreach ($previous as $externalRef => $eventId) {
            if (! isset($synced[$externalRef]) && is_numeric($eventId)) {
                $this->mail->deleteEvent((int) $eventId, $mailbox, (string) $externalRef);
            }
        }

        if ($entries === [] && $previous !== []) {
            foreach ($previous as $externalRef => $eventId) {
                if (is_numeric($eventId)) {
                    $this->mail->deleteEvent((int) $eventId, $mailbox, (string) $externalRef);
                }
            }
        }

        $payload = (array) ($event->payload ?? []);
        $payload['calendar_sync'] = ['items' => $synced];
        $event->payload = $payload;
        $event->save();

        Log::info('Events mail calendar synced', [
            'event_id' => $event->id,
            'entries' => count($synced),
        ]);

        return $event->fresh();
    }

    /**
     * @return list<array<string, mixed>>
     */
    public function entriesFor(QrCode $event): array
    {
        $content = $event->content();
        $format = (string) ($content['format'] ?? 'in_person');
        $sessions = array_values(array_filter(
            (array) ($content['virtual_sessions'] ?? []),
            fn ($session) => is_array($session) && trim((string) ($session['title'] ?? '')) !== '',
        ));

        $entries = [];

        if (in_array($format, ['virtual', 'hybrid'], true) && $sessions !== []) {
            foreach ($sessions as $session) {
                $entry = $this->sessionEntry($event, $content, $session);
                if ($entry !== null) {
                    $entries[] = $entry;
                }
            }

            if ($entries === [] && filled($content['starts_at'] ?? null)) {
                $entries[] = $this->mainEventEntry($event, $content);
            } elseif ($format === 'hybrid' && filled($content['starts_at'] ?? null)) {
                $entries[] = $this->mainEventEntry($event, $content, ' (in person)');
            }

            return $entries;
        }

        if (filled($content['starts_at'] ?? null)) {
            $entries[] = $this->mainEventEntry($event, $content);
        }

        return $entries;
    }

    /**
     * @param  array<string, mixed>  $content
     * @param  array<string, mixed>  $session
     * @return array<string, mixed>|null
     */
    private function sessionEntry(QrCode $event, array $content, array $session): ?array
    {
        $sessionId = trim((string) ($session['id'] ?? ''));
        if ($sessionId === '') {
            $sessionId = 'vs-'.Str::lower(Str::random(12));
        }

        $starts = $this->parseDate($session['scheduled_at'] ?? $content['starts_at'] ?? null);
        if ($starts === null) {
            return null;
        }

        $duration = max(15, (int) ($session['duration_minutes'] ?? 60));
        $joinUrl = trim((string) ($session['join_url'] ?? ''));
        $description = trim((string) ($content['description'] ?? ''));

        return [
            'external_ref' => $this->sessionExternalRef($event->id, $sessionId),
            'title' => trim((string) ($session['title'] ?? $content['name'] ?? $event->label)),
            'body' => $description !== '' ? $description : null,
            'starts_at' => $starts->toIso8601String(),
            'ends_at' => $starts->copy()->addMinutes($duration)->toIso8601String(),
            'join_url' => $joinUrl !== '' ? $joinUrl : $event->publicUrl(),
        ];
    }

    /**
     * @param  array<string, mixed>  $content
     * @return array<string, mixed>
     */
    private function mainEventEntry(QrCode $event, array $content, string $titleSuffix = ''): array
    {
        $starts = $this->parseDate($content['starts_at'] ?? null) ?? now();
        $ends = $this->parseDate($content['ends_at'] ?? null) ?? $starts->copy()->addHours(2);
        $name = trim((string) ($content['name'] ?? $event->label));
        $location = trim((string) ($content['location'] ?? ''));
        $body = trim((string) ($content['description'] ?? ''));
        if ($location !== '') {
            $body = $body !== '' ? $body."\n\n".$location : $location;
        }

        return [
            'external_ref' => $this->eventExternalRef($event->id),
            'title' => $name.$titleSuffix,
            'body' => $body !== '' ? $body : null,
            'starts_at' => $starts->toIso8601String(),
            'ends_at' => $ends->toIso8601String(),
            'join_url' => $event->publicUrl(),
        ];
    }

    private function eventExternalRef(int $eventId): string
    {
        return 'events:'.$eventId;
    }

    private function sessionExternalRef(int $eventId, string $sessionId): string
    {
        return 'events:'.$eventId.':session:'.$sessionId;
    }

    private function parseDate(mixed $value): ?CarbonInterface
    {
        if ($value === null || $value === '') {
            return null;
        }

        try {
            return Carbon::parse($value);
        } catch (\Throwable) {
            return null;
        }
    }

    private function resolveMailbox(User $user): ?string
    {
        try {
            $status = $this->identity->mailboxLinkStatus($user->public_id);
            $linked = strtolower(trim((string) ($status['linked_mailbox'] ?? '')));
            if (filter_var($linked, FILTER_VALIDATE_EMAIL)) {
                return $linked;
            }
        } catch (\Throwable) {
            // Fall back to the account email.
        }

        $email = strtolower(trim((string) $user->email));

        return filter_var($email, FILTER_VALIDATE_EMAIL) ? $email : null;
    }
}