<?php

namespace App\Services;

use App\Models\SchoolClass;
use App\Models\ClassAttendance;
use App\Models\Student;
use Illuminate\Database\Eloquent\Collection;
use Illuminate\Support\Facades\DB;

class ClassService
{
    /**
     * Aulas da unidade ativa, com nome do pacote e contadores
     * (total de alunos do pacote e quantos foram marcados presentes).
     */
    public function getAllByUnit(int $unitId): Collection
    {
        return SchoolClass::with('packageUnit')
            ->withCount([
                'attendances as present_count' => fn ($q) => $q->where('in_class', true),
            ])
            ->where('unit_id', $unitId)
            ->orderBy('date_time_start')
            ->get()
            ->each(function (SchoolClass $class) {
                $class->students_count = $this->activeStudentsQuery($class->class_package_unit_id, $class->unit_id)->count();
            });
    }

    public function findByIdForUnit(int $id, int $unitId): SchoolClass
    {
        return SchoolClass::with('packageUnit')
            ->where('unit_id', $unitId)
            ->findOrFail($id);
    }

    public function create(array $data): SchoolClass
    {
        return SchoolClass::create($data)->load('packageUnit');
    }

    public function update(int $id, int $unitId, array $data): SchoolClass
    {
        $model = $this->findByIdForUnit($id, $unitId);

        $model->update($data);
        return $model->fresh('packageUnit');
    }

    public function delete(int $id, int $unitId): bool
    {
        $model = $this->findByIdForUnit($id, $unitId);

        return (bool) $model->delete();
    }

    /**
     * Lista os alunos com contrato ATIVO no pacote vinculado à aula,
     * já mesclando a presença registrada (se houver) para aquela aula.
     */
    public function getStudentsForClass(int $classId, int $unitId): array
    {
        $class = $this->findByIdForUnit($classId, $unitId);

        $students = $this->activeStudentsQuery($class->class_package_unit_id, $class->unit_id)
            ->orderBy('students.name')
            ->get();

        // Presenças já registradas nesta aula, indexadas por aluno
        $attendances = ClassAttendance::where('class_id', $classId)
            ->get()
            ->keyBy('student_id');

        // Total de aulas presenciadas por aluno (em qualquer aula)
        $attendedCounts = ClassAttendance::select('student_id', DB::raw('COUNT(*) as total'))
            ->whereIn('student_id', $students->pluck('id'))
            ->where('in_class', true)
            ->groupBy('student_id')
            ->pluck('total', 'student_id');

        return $students->map(function (Student $student) use ($attendances, $attendedCounts) {
            $attendance = $attendances->get($student->id);

            return [
                'student_id'    => $student->id,
                'name'          => $student->name,
                'photo_url'     => $student->photo_url,
                'classes_count' => (int) ($attendedCounts[$student->id] ?? 0),
                'in_class'      => (bool) ($attendance?->in_class ?? false),
                'justified'     => (bool) ($attendance?->justified ?? false),
                'notes'         => $attendance?->notes,
            ];
        })->all();
    }

    /**
     * Salva a presença da aula em lote (upsert por aluno).
     *
     * @param array<int, array{student_id:int, in_class:bool, justified?:bool, notes?:string|null}> $items
     */
    public function saveAttendance(int $classId, int $unitId, array $items): void
    {
        $class = $this->findByIdForUnit($classId, $unitId);
        $allowedStudentIds = $this->activeStudentsQuery($class->class_package_unit_id, $unitId)
            ->whereIn('students.id', collect($items)->pluck('student_id'))
            ->pluck('students.id');

        abort_unless($allowedStudentIds->count() === count($items), 422, 'A lista contém alunos que não pertencem a esta aula.');

        DB::transaction(function () use ($classId, $items) {
            foreach ($items as $item) {
                $inClass   = (bool) ($item['in_class'] ?? false);
                // Justificativa só vale para faltas; presença nunca fica justificada.
                $justified = $inClass ? false : (bool) ($item['justified'] ?? false);

                ClassAttendance::updateOrCreate(
                    [
                        'class_id'   => $classId,
                        'student_id' => $item['student_id'],
                    ],
                    [
                        'in_class'  => $inClass,
                        'justified' => $justified,
                        'notes'     => $justified ? ($item['notes'] ?? null) : null,
                    ],
                );
            }
        });
    }

    /**
     * Query base: alunos com contrato ativo no pacote informado (e na unidade).
     */
    private function activeStudentsQuery(?int $classPackageUnitId, int $unitId)
    {
        return Student::query()
            ->whereHas('contracts', function ($q) use ($classPackageUnitId, $unitId) {
                $q->where('status', 'active')
                    ->where('unit_id', $unitId);

                if ($classPackageUnitId) {
                    $q->where('class_package_unit_id', $classPackageUnitId);
                }
            });
    }
}