<?php

namespace App\Support;

use App\Models\Course;
use App\Models\CourseCheckinDay;
use Carbon\Carbon;
use Carbon\CarbonPeriod;

class CourseCheckinDaySync
{
    /**
     * @return list<array{id: int, course_id: int, teach_date: string}>
     */
    public static function listTeachDates(Course $course): array
    {
        if (! $course->teach_start_date || ! $course->teach_end_date) {
            return [];
        }

        $start = $course->teach_start_date->copy()->startOfDay();
        $end = $course->teach_end_date->copy()->startOfDay();
        if ($start->gt($end)) {
            return [];
        }

        $items = [];
        $seq = 0;
        foreach (CarbonPeriod::create($start, $end) as $day) {
            /** @var Carbon $day */
            $seq++;
            $items[] = [
                'id' => $seq,
                'course_id' => $course->id,
                'teach_date' => $day->toDateString(),
            ];
        }

        return $items;
    }

    public static function isTeachDate(Course $course, string $dateYmd): bool
    {
        foreach (self::listTeachDates($course) as $item) {
            if ($item['teach_date'] === $dateYmd) {
                return true;
            }
        }

        return false;
    }

    public static function syncForCourse(Course $course): void
    {
        if (! $course->teach_start_date || ! $course->teach_end_date) {
            CourseCheckinDay::query()->where('course_id', $course->id)->delete();

            return;
        }

        $start = $course->teach_start_date->copy()->startOfDay();
        $end = $course->teach_end_date->copy()->startOfDay();
        if ($start->gt($end)) {
            CourseCheckinDay::query()->where('course_id', $course->id)->delete();

            return;
        }

        $period = CarbonPeriod::create($start, $end);
        $keepDates = [];

        foreach ($period as $day) {
            /** @var Carbon $day */
            $dateStr = $day->toDateString();
            $keepDates[] = $dateStr;

            CourseCheckinDay::query()->updateOrCreate(
                [
                    'course_id' => $course->id,
                    'teach_date' => $dateStr,
                ],
                ['signin_code' => $course->id.'-'.$dateStr]
            );
        }

        CourseCheckinDay::query()
            ->where('course_id', $course->id)
            ->whereNotIn('teach_date', $keepDates)
            ->delete();
    }

    public static function courseSigninCode(Course $course): string
    {
        if ($course->code) {
            $base = preg_replace('/[^A-Za-z0-9_-]/', '', $course->code) ?: ('C'.$course->id);

            return strtoupper($base);
        }

        if ($course->code_prefix) {
            $base = preg_replace('/[^A-Za-z0-9_-]/', '', $course->code_prefix) ?: ('C'.$course->id);

            return strtoupper($base);
        }

        return 'COURSE-'.str_pad((string) $course->id, 3, '0', STR_PAD_LEFT);
    }

    public static function ensureCourseCode(Course $course): void
    {
        if ($course->code) {
            return;
        }

        $prefix = $course->code_prefix
            ? preg_replace('/[^A-Za-z0-9_-]/', '', $course->code_prefix)
            : '';
        $course->code = $prefix
            ? 'COURSE-'.strtoupper($prefix).'-'.str_pad((string) $course->id, 3, '0', STR_PAD_LEFT)
            : 'COURSE-'.str_pad((string) $course->id, 3, '0', STR_PAD_LEFT);
        $course->save();
    }
}