<?php

namespace App\Services;

use App\Models\PlacementBatchModel;
use App\Models\PlacementLevelModel;
use App\Models\PlacementScoreModel;
use App\Models\StudentModel;

class PlacementGradingService
{
    protected $db;
    protected $studentModel;
    protected $placementLevelModel;
    protected $placementBatchModel;
    protected $placementScoreModel;
    protected string $schoolYear = '';

    public function __construct(
        \CodeIgniter\Database\BaseConnection $db,
        StudentModel $studentModel,
        PlacementLevelModel $placementLevelModel,
        PlacementBatchModel $placementBatchModel,
        PlacementScoreModel $placementScoreModel,
        string $schoolYear = ''
    ) {
        $this->db = $db;
        $this->studentModel = $studentModel;
        $this->placementLevelModel = $placementLevelModel;
        $this->placementBatchModel = $placementBatchModel;
        $this->placementScoreModel = $placementScoreModel;
        $this->schoolYear = $schoolYear;
    }

    public function setSchoolYear(string $schoolYear): void
    {
        $this->schoolYear = $schoolYear;
    }

public function updatePlacementLevel(array $params = [])
{
    $get = $params['get'] ?? [];
    $post = $params['post'] ?? [];

    $studentId = (int) (($post['student_id'] ?? null) ?? 0);
    $levelRaw = trim((string) (($post['placement_level'] ?? null) ?? ''));
    $schoolYear = (string) (($post['school_year'] ?? null) ?? $this->schoolYear);

    if ($studentId <= 0 || $schoolYear === '') {
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'error', 'message' => 'Missing student or school year.'];
    }

    $level = $levelRaw === '' ? null : (int) $levelRaw;
    if ($level !== null && !in_array($level, [1, 2, 3], true)) {
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'error', 'message' => 'Invalid placement level.'];
    }

    $existing = $this->placementLevelModel
        ->where('student_id', $studentId)
        ->first();

    if ($level === null) {
        if ($existing) {
            $this->placementLevelModel->delete($existing['id']);
        }
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'status', 'message' => 'Placement level cleared.'];
    }

    $payload = [
        'student_id' => $studentId,
        'level' => $level,
        'updated_by' => session()->get('user_id'),
    ];

    if ($existing) {
        $this->placementLevelModel->update($existing['id'], $payload);
    } else {
        $payload['created_by'] = session()->get('user_id');
        $this->placementLevelModel->insert($payload);
    }

    return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'status', 'message' => 'Placement level updated.'];
}

public function placementPage(array $params = [])
{
    $get = $params['get'] ?? [];
    $post = $params['post'] ?? [];

    $classSectionId = (int) (($get['class_section_id'] ?? null) ?? 0);
    $schoolYear = (string) (($get['school_year'] ?? null) ?? $this->schoolYear);
    $placementTest = (string) (($get['placement_test'] ?? null) ?? '');
    $openFlag = (string) (($get['open'] ?? null) ?? '');

    if ($classSectionId <= 0 || $schoolYear === '') {
        $showStudents = ($placementTest !== '' && $openFlag === '1');
        $students = $showStudents ? $this->fetchActiveStudentsWithSection($schoolYear) : [];
        $batches = $this->fetchPlacementBatches($schoolYear);
        $batchDetails = $this->fetchPlacementBatchDetails($batches, $schoolYear);
        return ['kind' => 'view', 'view' => 'grading/placement_index', 'data' => [
            'schoolYear' => $schoolYear,
            'students' => $students,
            'batches' => $batches,
            'batchDetails' => $batchDetails,
            'placementTest' => $placementTest,
            'showStudents' => $showStudents,
        ]];
    }

    $sectionName = $this->classSection->getClassSectionNameBySectionId($classSectionId) ?? '';
    $classId = $this->classSection->getClassId($classSectionId);

    $students = $this->studentModel->getStudentInfoByClassSectionId($classSectionId, null, $schoolYear);
    $studentIds = array_values(array_filter(array_map(
        static fn($row) => (int) ($row['student_id'] ?? 0),
        $students
    ), static fn($id) => $id > 0));

    $levels = [];
    if (!empty($studentIds)) {
        $rows = $this->placementLevelModel
            ->whereIn('student_id', $studentIds)
            ->findAll();
        foreach ($rows as $row) {
            $levels[(int) $row['student_id']] = $row['level'] ?? null;
        }
    }

    return ['kind' => 'view', 'view' => 'grading/placement', 'data' => [
        'classSectionId' => $classSectionId,
        'classSectionName' => $sectionName,
        'classId' => $classId,
        'schoolYear' => $schoolYear,
        'students' => $students,
        'levels' => $levels,
    ]];
}

public function updatePlacementLevels(array $params = [])
{
    $get = $params['get'] ?? [];
    $post = $params['post'] ?? [];

    $classSectionId = (int) (($post['class_section_id'] ?? null) ?? 0);
    $schoolYear = (string) (($post['school_year'] ?? null) ?? $this->schoolYear);
    $levels = ($post['placement_level'] ?? null) ?? [];

    if ($classSectionId <= 0 || $schoolYear === '') {
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'error', 'message' => 'Missing class section or school year.'];
    }

    $students = $this->studentModel->getStudentInfoByClassSectionId($classSectionId, null, $schoolYear);
    $validIds = array_values(array_filter(array_map(
        static fn($row) => (int) ($row['student_id'] ?? 0),
        $students
    ), static fn($id) => $id > 0));

    $validSet = array_flip($validIds);
    $existingRows = [];
    if (!empty($validIds)) {
        $rows = $this->placementLevelModel
            ->whereIn('student_id', $validIds)
            ->findAll();
        foreach ($rows as $row) {
            $existingRows[(int) $row['student_id']] = $row;
        }
    }

    $userId = session()->get('user_id');
    foreach ($levels as $studentIdRaw => $levelRaw) {
        $studentId = (int) $studentIdRaw;
        if (!isset($validSet[$studentId])) {
            continue;
        }
        $levelRaw = trim((string) $levelRaw);
        $level = $levelRaw === '' ? null : (int) $levelRaw;
        if ($level !== null && !in_array($level, [1, 2, 3], true)) {
            continue;
        }

        if ($level === null) {
            if (isset($existingRows[$studentId])) {
                $this->placementLevelModel->delete($existingRows[$studentId]['id']);
            }
            continue;
        }

        $payload = [
            'student_id' => $studentId,
            'level' => $level,
            'updated_by' => $userId,
        ];

        if (isset($existingRows[$studentId])) {
            $this->placementLevelModel->update($existingRows[$studentId]['id'], $payload);
        } else {
            $payload['created_by'] = $userId;
            $this->placementLevelModel->insert($payload);
        }
    }

    return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'status', 'message' => 'Placement levels updated.'];
}

public function updatePlacementLevelsAll(array $params = [])
{
    $get = $params['get'] ?? [];
    $post = $params['post'] ?? [];

    $schoolYear = (string) (($post['school_year'] ?? null) ?? $this->schoolYear);
    $placementTest = (string) (($post['placement_test'] ?? null) ?? '');
    $levels = ($post['placement_level'] ?? null) ?? [];

    if ($schoolYear === '' || $placementTest === '') {
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'error', 'message' => 'Missing placement test or school year.'];
    }

    $students = $this->fetchActiveStudentsWithSection($schoolYear);
    $validIds = array_values(array_filter(array_map(
        static fn($row) => (int) ($row['student_id'] ?? 0),
        $students
    ), static fn($id) => $id > 0));

    $validSet = array_flip($validIds);
    $userId = session()->get('user_id');

    $batchId = $this->placementBatchModel->insert([
        'placement_test' => $placementTest,
        'school_year' => $schoolYear,
        'created_by' => $userId,
        'updated_by' => $userId,
    ]);

    if (!$batchId) {
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'error', 'message' => 'Unable to create placement batch.'];
    }

    $savedCount = 0;
    foreach ($levels as $studentIdRaw => $levelRaw) {
        $studentId = (int) $studentIdRaw;
        if (!isset($validSet[$studentId])) {
            continue;
        }
        $levelRaw = trim((string) $levelRaw);
        if ($levelRaw === '') {
            continue;
        }
        $level = (int) $levelRaw;
        if ($level < 0 || $level > 100) {
            continue;
        }

        $this->placementScoreModel->insert([
            'batch_id' => (int) $batchId,
            'student_id' => $studentId,
            'score' => $level,
            'created_by' => $userId,
            'updated_by' => $userId,
        ]);
        $savedCount++;
    }

    if ($savedCount === 0) {
        $this->placementBatchModel->delete((int) $batchId);
        return ['kind' => 'flash', 'redirect' => 'back', 'type' => 'error', 'message' => 'No scores entered. Batch not saved.'];
    }

    return ['kind' => 'flash', 'redirect' => base_url('grading/placement'), 'type' => 'status', 'message' => 'Placement batch saved.'];
}

public function editPlacementBatch(int $batchId, array $params = [])
{
    $get = $params['get'] ?? [];
    $post = $params['post'] ?? [];

    $batch = $this->placementBatchModel->find($batchId);
    if (!$batch) {
        return ['kind' => 'flash', 'redirect' => base_url('grading/placement'), 'type' => 'error', 'message' => 'Placement batch not found.'];
    }

    $schoolYear = (string) ($batch['school_year'] ?? $this->schoolYear);
    $students = $this->fetchActiveStudentsWithSection($schoolYear);
    $scores = $this->fetchPlacementScoresForBatch($batchId);

    return ['kind' => 'view', 'view' => 'grading/placement_batch', 'data' => [
        'batch' => $batch,
        'students' => $students,
        'scores' => $scores,
    ]];
}

public function updatePlacementBatch(int $batchId, array $params = [])
{
    $get = $params['get'] ?? [];
    $post = $params['post'] ?? [];

    $batch = $this->placementBatchModel->find($batchId);
    if (!$batch) {
        return ['kind' => 'flash', 'redirect' => base_url('grading/placement'), 'type' => 'error', 'message' => 'Placement batch not found.'];
    }

    $schoolYear = (string) ($batch['school_year'] ?? $this->schoolYear);
    $levels = ($post['placement_level'] ?? null) ?? [];

    $students = $this->fetchActiveStudentsWithSection($schoolYear);
    $validIds = array_values(array_filter(array_map(
        static fn($row) => (int) ($row['student_id'] ?? 0),
        $students
    ), static fn($id) => $id > 0));

    $validSet = array_flip($validIds);
    $existing = $this->fetchPlacementScoresForBatch($batchId);

    $userId = session()->get('user_id');
    foreach ($levels as $studentIdRaw => $scoreRaw) {
        $studentId = (int) $studentIdRaw;
        if (!isset($validSet[$studentId])) {
            continue;
        }
        $scoreRaw = trim((string) $scoreRaw);
        if ($scoreRaw === '') {
            if (isset($existing[$studentId])) {
                $this->placementScoreModel->delete($existing[$studentId]['id']);
            }
            continue;
        }
        $score = (int) $scoreRaw;
        if ($score < 0 || $score > 100) {
            continue;
        }

        if (isset($existing[$studentId])) {
            $this->placementScoreModel->update($existing[$studentId]['id'], [
                'score' => $score,
                'updated_by' => $userId,
            ]);
        } else {
            $this->placementScoreModel->insert([
                'batch_id' => $batchId,
                'student_id' => $studentId,
                'score' => $score,
                'created_by' => $userId,
                'updated_by' => $userId,
            ]);
        }
    }

    $this->placementBatchModel->update($batchId, [
        'updated_by' => $userId,
    ]);

    return ['kind' => 'flash', 'redirect' => base_url('grading/placement'), 'type' => 'status', 'message' => 'Placement batch updated.'];
}

public function fetchActiveStudentsWithSection(string $schoolYear): array
{
    return $this->db->table('students s')
        ->select('s.id AS student_id, s.school_id, s.firstname, s.lastname, s.is_active, sc.class_section_id, cs.class_section_name, c.class_name, e.enrollment_status, e.is_withdrawn')
        ->join('student_class sc', 'sc.student_id = s.id AND sc.school_year = ' . $this->db->escape($schoolYear), 'left')
        ->join('enrollments e', 'e.student_id = s.id AND e.school_year = ' . $this->db->escape($schoolYear), 'left')
        ->join('`classSection` cs', 'cs.class_section_id = sc.class_section_id', 'left')
        ->join('classes c', 'c.id = cs.class_id', 'left')
        ->groupStart()
            ->where('s.is_active', 1)
            ->orWhere("LOWER(TRIM(e.enrollment_status)) IN ('denied','withdrawn','waitlist')", null, false)
            ->orWhere('e.is_withdrawn', 1)
        ->groupEnd()
        ->orderBy('s.lastname', 'ASC')
        ->orderBy('s.firstname', 'ASC')
        ->get()
        ->getResultArray();
}

public function fetchPlacementBatches(string $schoolYear): array
{
    return $this->placementBatchModel
        ->where('school_year', $schoolYear)
        ->orderBy('created_at', 'DESC')
        ->findAll();
}

public function fetchPlacementBatchDetails(array $batches, string $schoolYear): array
{
    if (empty($batches)) {
        return [];
    }

    $batchIds = array_values(array_filter(array_map(
        static fn($row) => (int) ($row['id'] ?? 0),
        $batches
    ), static fn($id) => $id > 0));

    if (empty($batchIds)) {
        return [];
    }

    $rows = $this->db->table('placement_scores ps')
        ->select('ps.batch_id, ps.student_id, ps.score, s.school_id, s.firstname, s.lastname, s.is_active, e.enrollment_status, e.is_withdrawn, cs.class_section_name, c.class_name')
        ->join('students s', 's.id = ps.student_id', 'inner')
        ->join('student_class sc', 'sc.student_id = s.id AND sc.school_year = ' . $this->db->escape($schoolYear), 'left')
        ->join('enrollments e', 'e.student_id = s.id AND e.school_year = ' . $this->db->escape($schoolYear), 'left')
        ->join('`classSection` cs', 'cs.class_section_id = sc.class_section_id', 'left')
        ->join('classes c', 'c.id = cs.class_id', 'left')
        ->whereIn('ps.batch_id', $batchIds)
        ->groupStart()
            ->where('s.is_active', 1)
            ->orWhere("LOWER(TRIM(e.enrollment_status)) IN ('denied','withdrawn','waitlist')", null, false)
            ->orWhere('e.is_withdrawn', 1)
        ->groupEnd()
        ->orderBy('ps.batch_id', 'ASC')
        ->orderBy('s.lastname', 'ASC')
        ->orderBy('s.firstname', 'ASC')
        ->get()
        ->getResultArray();

    $details = [];
    foreach ($rows as $row) {
        $bid = (int) ($row['batch_id'] ?? 0);
        if ($bid <= 0) continue;
        $details[$bid][] = $row;
    }

    return $details;
}

public function fetchPlacementScoresForBatch(int $batchId): array
{
    $rows = $this->placementScoreModel
        ->where('batch_id', $batchId)
        ->findAll();
    $scores = [];
    foreach ($rows as $row) {
        $scores[(int) $row['student_id']] = $row;
    }
    return $scores;
}
}