<?php

declare(strict_types=1);

namespace App\Services\Academy;

use App\Models\AcademyCourse;
use App\Models\AcademyCourseLesson;
use App\Models\AcademyLesson;
use Illuminate\Support\Collection;

final class AcademyCourseNavigationService
{
    /**
     * @return Collection<int, AcademyCourseLesson>
     */
    public function orderedCourseLessons(AcademyCourse $course): Collection
    {
        return $course->courseLessons()
            ->with(['section', 'lesson.category'])
            ->get()
            ->filter(fn (AcademyCourseLesson $courseLesson): bool => $courseLesson->lesson instanceof AcademyLesson
                && (bool) $courseLesson->lesson->active
                && $courseLesson->lesson->published_at !== null
                && $courseLesson->lesson->published_at->lte(now()))
            ->sort(fn (AcademyCourseLesson $left, AcademyCourseLesson $right): int => $this->courseLessonSortKey($left) <=> $this->courseLessonSortKey($right))
            ->values();
    }

    /**
     * @return array<int, int>
     */
    private function courseLessonSortKey(AcademyCourseLesson $courseLesson): array
    {
        $section = $courseLesson->section;

        return [
            $courseLesson->section_id === null ? 0 : 1,
            (int) ($section?->order_num ?? 0),
            (int) ($section?->id ?? 0),
            (int) ($courseLesson->order_num ?? 0),
            (int) $courseLesson->id,
        ];
    }

    public function firstPublishedLesson(AcademyCourse $course): ?AcademyCourseLesson
    {
        return $this->orderedCourseLessons($course)->first();
    }

    public function findCourseLesson(AcademyCourse $course, AcademyLesson $lesson): ?AcademyCourseLesson
    {
        return $this->orderedCourseLessons($course)
            ->first(fn (AcademyCourseLesson $courseLesson): bool => $courseLesson->lesson?->is($lesson) ?? false);
    }

    public function nextLesson(AcademyCourse $course, AcademyLesson $lesson): ?AcademyCourseLesson
    {
        $ordered = $this->orderedCourseLessons($course);
        $index = $ordered->search(fn (AcademyCourseLesson $courseLesson): bool => $courseLesson->lesson?->is($lesson) ?? false);

        return is_int($index) ? $ordered->get($index + 1) : null;
    }

    public function previousLesson(AcademyCourse $course, AcademyLesson $lesson): ?AcademyCourseLesson
    {
        $ordered = $this->orderedCourseLessons($course);
        $index = $ordered->search(fn (AcademyCourseLesson $courseLesson): bool => $courseLesson->lesson?->is($lesson) ?? false);

        return is_int($index) && $index > 0 ? $ordered->get($index - 1) : null;
    }
}