<?php

namespace App\Services\Interview;

use App\Models\Interview;
use Carbon\Carbon;
use Spatie\IcalendarGenerator\Components\Calendar;
use Spatie\IcalendarGenerator\Components\Event;
use Spatie\IcalendarGenerator\Enums\EventStatus;
use Spatie\IcalendarGenerator\Enums\ParticipationStatus;
use Spatie\IcalendarGenerator\Properties\TextProperty;

class InterviewCalendarService
{
    /**
     * Generate an RFC 5545 / RFC 5546 compliant iCalendar (.ics) string for an interview assessment.
     */
    public function generateIcs(Interview $interview): string
    {
        $calendar = Calendar::create($interview->event_title)
            ->appendProperty(TextProperty::create('METHOD', 'REQUEST'))
            ->event($this->generateEvent($interview));

        return $calendar->get();
    }

    /**
     * Build the Spatie Event component for the given interview.
     */
    public function generateEvent(Interview $interview): Event
    {
        $startsAt = $interview->scheduled_at
            ? Carbon::parse($interview->scheduled_at)->toDateTime()
            : now()->toDateTime();

        $endsAt = $interview->expires_at
            ? Carbon::parse($interview->expires_at)->toDateTime()
            : Carbon::parse($startsAt)->addHours(2)->toDateTime();

        $organizerEmail = config('mail.from.address') ?: 'no-reply@singlelogin.com';
        $organizerName = config('mail.from.name') ?: 'SingleLogin Assessment Portal';

        $event = Event::create($interview->event_title)
            ->uniqueIdentifier('sls-interview-'.$interview->submission_unique_id)
            ->status(EventStatus::Confirmed)
            ->startsAt($startsAt)
            ->endsAt($endsAt)
            ->organizer($organizerEmail, $organizerName)
            ->appendProperty(TextProperty::create('SEQUENCE', '0'))
            ->description($this->generateDescription($interview));

        // Candidate Attendee: RSVP / Response is required
        if (! empty($interview->candidate_email)) {
            $event->attendee(
                email: $interview->candidate_email,
                name: $interview->candidate_name,
                participationStatus: ParticipationStatus::NeedsAction,
                requiresResponse: true
            );
        }

        // Assigned Panelists / Interviewers
        $assignedUsers = $interview->assignedUsers();
        foreach ($assignedUsers as $interviewer) {
            if (! empty($interviewer->email)) {
                $event->attendee(
                    email: $interviewer->email,
                    name: $interviewer->name,
                    participationStatus: ParticipationStatus::Accepted,
                    requiresResponse: false
                );
            }
        }

        // 15-minute advance alert notification (RFC 5545 VALARM)
        $reminderMessage = sprintf(
            'Interview Reminder: %s (%s) with %s starts in 15 minutes.',
            $interview->job_title ?? 'Candidate Assessment',
            $interview->round ?? 'R1',
            $interview->candidate_name ?? 'Candidate'
        );

        $event->alertMinutesBefore(15, $reminderMessage);

        // Note: No organizer is specified on the event as per requirement

        return $event;
    }

    /**
     * Generate structured event description with credentials, proctoring guidelines, and portal links.
     */
    public function generateDescription(Interview $interview): string
    {
        $jobTitle = $interview->job_title ?: 'Assessment';
        $round = $interview->round ?: 'R1';
        $candidateName = $interview->candidate_name ?: 'Candidate';
        $loginUrl = route('interview.candidate.login');

        $assignedNames = $interview->assignedUsers()->pluck('name')->implode(', ');
        if (empty($assignedNames)) {
            $assignedNames = 'Hiring Panel';
        }

        $lines = [
            'Candidate Assessment Invitation',
            '----------------------------------------',
            "Candidate: {$candidateName}",
            "Position: {$jobTitle}",
            "Assessment Round: {$round}",
            'Coding Language: '.strtoupper($interview->language ?? 'Python'),
            'Access Duration: '.($interview->valid_hours ?? 2).' Hour(s)',
            '',
            'CANDIDATE ACCESS & CREDENTIALS',
            '----------------------------------------',
            "Portal URL: {$loginUrl}",
            "Identifier: {$interview->candidate_email}",
            "Temporary Password: {$interview->temp_password}",
            "Unique Session ID: {$interview->submission_unique_id}",
            '',
            'PANELISTS / REVIEWERS',
            '----------------------------------------',
            "Assigned Interviewers: {$assignedNames}",
        ];

        if (! empty($interview->description)) {
            $lines[] = '';
            $lines[] = 'ADDITIONAL INSTRUCTIONS';
            $lines[] = '----------------------------------------';
            $lines[] = $interview->description;
        }

        $lines[] = '';
        $lines[] = 'IMPORTANT NOTES';
        $lines[] = '----------------------------------------';
        $lines[] = '- Please join the assessment room 5 minutes prior to the scheduled start time.';
        $lines[] = '- Ensure your web camera and microphone are connected for live proctoring.';
        $lines[] = '- This session contains an automated 15-minute advance reminder alarm.';

        return implode("\n", $lines);
    }

    /**
     * Format a safe filename for the .ics attachment.
     */
    public function generateFilename(Interview $interview): string
    {
        $cleanTitle = preg_replace('/[^A-Za-z0-9_-]/', '_', $interview->event_title);

        return 'invitation_'.substr($cleanTitle, 0, 80).'.ics';
    }
}