<?php

namespace App\Services\ClassSections;

use App\Models\ClassSection;
use Illuminate\Contracts\Pagination\LengthAwarePaginator;

class ClassSectionQueryService
{
    public function list(array $filters, int $page = 1, int $perPage = 20): LengthAwarePaginator
    {
        $query = ClassSection::query()
            ->leftJoin('classes', 'classSection.class_id', '=', 'classes.id')
            ->select('classSection.*', 'classes.class_name');

        if (!empty($filters['search'])) {
            $term = '%' . strtolower((string) $filters['search']) . '%';
            $query->where(function ($q) use ($term) {
                $q->whereRaw('LOWER(classSection.class_section_name) LIKE ?', [$term])
                    ->orWhereRaw('LOWER(classes.class_name) LIKE ?', [$term]);
            });
        }

        if (!empty($filters['class_id'])) {
            $query->where('classSection.class_id', (int) $filters['class_id']);
        }

        if (!empty($filters['school_year'])) {
            $query->where('classSection.school_year', (string) $filters['school_year']);
        }

        if (!empty($filters['semester'])) {
            $query->where('classSection.semester', (string) $filters['semester']);
        }

        if (!empty($filters['with_students'])) {
            $query->whereExists(function ($sub) use ($filters) {
                $sub->selectRaw('1')
                    ->from('student_class as sc')
                    ->join('students as s', 's.id', '=', 'sc.student_id')
                    ->whereColumn('sc.class_section_id', 'classSection.class_section_id')
                    ->where('s.is_active', 1);

                if (!empty($filters['school_year'])) {
                    $sub->where('sc.school_year', (string) $filters['school_year']);
                }
            });
        }

        $sortBy = (string) ($filters['sort_by'] ?? 'class_section_name');
        $sortDir = strtolower((string) ($filters['sort_dir'] ?? 'asc')) === 'desc' ? 'desc' : 'asc';

        $allowedSorts = [
            'class_section_name' => 'classSection.class_section_name',
            'class_section_id' => 'classSection.class_section_id',
            'class_id' => 'classSection.class_id',
            'school_year' => 'classSection.school_year',
            'semester' => 'classSection.semester',
            'class_name' => 'classes.class_name',
        ];

        $sortColumn = $allowedSorts[$sortBy] ?? $allowedSorts['class_section_name'];
        $query->orderBy($sortColumn, $sortDir);

        return $query->paginate($perPage, ['*'], 'page', $page);
    }

    public function find(int $id): ?ClassSection
    {
        return ClassSection::query()
            ->leftJoin('classes', 'classSection.class_id', '=', 'classes.id')
            ->select('classSection.*', 'classes.class_name')
            ->where('classSection.id', $id)
            ->first();
    }
}