<?php

namespace App\Services;

use App\Controllers\View\EmailController;
use App\Models\AttendanceDayModel;
use App\Models\ClassSectionModel;
use App\Models\ConfigurationModel;
use App\Models\ExamDraftModel;
use App\Models\HomeworkModel;
use App\Models\ScoreCommentModel;
use App\Models\SemesterScoreModel;
use App\Models\StudentClassModel;
use App\Models\TeacherSubmissionNotificationHistoryModel;
use App\Models\UserModel;

class TeacherSubmissionReportService
{
    protected $db;
    protected $configModel;
    protected $studentClassModel;
    protected $classSectionModel;
    protected $userModel;
    protected string $schoolYear = '';
    protected string $semester = '';

    public function __construct(
        \CodeIgniter\Database\BaseConnection $db,
        ConfigurationModel $configModel,
        StudentClassModel $studentClassModel,
        ClassSectionModel $classSectionModel,
        UserModel $userModel
    ) {
        $this->db = $db;
        $this->configModel = $configModel;
        $this->studentClassModel = $studentClassModel;
        $this->classSectionModel = $classSectionModel;
        $this->userModel = $userModel;
    }

public function buildReport(string $semester, string $schoolYear, array $lowProgressSectionIds = []): array
{
    $this->schoolYear = $schoolYear;
    $this->semester = $semester;
    $semesterResolver = new SemesterRangeService($this->configModel);
    $semesterNorm = $semesterResolver->normalizeSemester($semester);
    $semesterFilter = $semesterNorm !== '' ? $semesterNorm : $semester;
    $semesterCandidates = $this->buildSemesterCandidates($semesterFilter);

    $scoreComments = new ScoreCommentModel();
    $semesterScores = new SemesterScoreModel();
    $attendanceDays = new AttendanceDayModel();
    $examDrafts = new ExamDraftModel();
    $homeworkModel = new HomeworkModel();
    $historyModel = new TeacherSubmissionNotificationHistoryModel();

    $assignmentQuery = $this->db->table('teacher_class tc')
        ->select([
            'tc.class_section_id',
            'cs.class_section_name',
            'tc.teacher_id',
            'u.firstname',
            'u.lastname',
            'tc.position',
        ])
        ->join('classSection cs', 'cs.class_section_id = tc.class_section_id', 'left')
        ->join('users u', 'u.id = tc.teacher_id', 'left')
        ->orderBy('cs.class_section_name', 'ASC');

    // teacher_class assignments are scoped by school year only.
    // The table has no semester column; semester filtering belongs on
    // semester-specific records such as scores, comments, attendance,
    // homework, and exam drafts.
    if ($schoolYear !== '') {
        $assignmentQuery->where('tc.school_year', $schoolYear);
    }

    $assignmentRows = $assignmentQuery->get()->getResultArray();

    $studentCounts = $this->studentClassModel->getStudentCountsBySection($schoolYear !== '' ? $schoolYear : null);
    $sectionRows = $this->classSectionModel
        ->select('class_section_id, class_section_name')
        ->orderBy('class_section_name', 'ASC')
        ->findAll();
    $sectionMap = [];
    foreach ($sectionRows as $sectionRow) {
        $sectionId = (int) ($sectionRow['class_section_id'] ?? 0);
        if ($sectionId <= 0) {
            continue;
        }
        if (empty($studentCounts[$sectionId])) {
            continue;
        }
        $sectionMap[$sectionId] = $sectionRow['class_section_name'] ?? "Section {$sectionId}";
    }
    $sectionIds = array_keys($sectionMap);

    [$progressExpectedWeeks, $progressSubmittedBySection] = $this->buildClassProgressStats($sectionIds);
    $examDraftCounts = [];
    $examDraftDeadline = $this->resolveTeacherDashboardExamDraftDeadline($semester, $schoolYear);
    $examDraftDeadlineConfig = trim((string) ($this->configModel->getConfig('exam_draft_deadline') ?? ''));
    $examDraftDeadlineFormatted = '';
    if ($examDraftDeadlineConfig !== '') {
        $parsedUi = $this->parseExamDraftDeadlineConfigValue();
        $examDraftDeadlineFormatted = $parsedUi !== null ? $parsedUi->format('M j, Y') : '';
    }
    $homeworkCounts = [];
    if (! empty($sectionIds)) {
        $draftBuilder = $examDrafts
            ->select('class_section_id')
            ->whereIn('class_section_id', $sectionIds);
        if ($schoolYear !== '') {
            $draftBuilder->where('school_year', $schoolYear);
        }
        if (!empty($semesterCandidates)) {
            $draftBuilder->whereIn('semester', $semesterCandidates);
        }
        if ($this->db->fieldExists('is_legacy', 'exam_drafts')) {
            $draftBuilder->where('is_legacy', 0);
        }
        $draftRows = $draftBuilder->findAll();
        foreach ($draftRows as $draft) {
            $sectionId = (int) ($draft['class_section_id'] ?? 0);
            if ($sectionId <= 0) {
                continue;
            }
            $examDraftCounts[$sectionId] = ($examDraftCounts[$sectionId] ?? 0) + 1;
        }

        $homeworkBuilder = $homeworkModel
            ->select('class_section_id, homework_index')
            ->whereIn('class_section_id', $sectionIds);
        if ($schoolYear !== '') {
            $homeworkBuilder->where('school_year', $schoolYear);
        }
        if (!empty($semesterCandidates)) {
            $homeworkBuilder->whereIn('semester', $semesterCandidates);
        }
        $homeworkRows = $homeworkBuilder
            ->where('score IS NOT NULL', null, false)
            ->where('score !=', '')
            ->groupBy('class_section_id, homework_index')
            ->findAll();
        foreach ($homeworkRows as $row) {
            $sectionId = (int) ($row['class_section_id'] ?? 0);
            if ($sectionId <= 0) {
                continue;
            }
            $homeworkCounts[$sectionId] = ($homeworkCounts[$sectionId] ?? 0) + 1;
        }
    }

    if (empty($lowProgressSectionIds)) {
        $lowProgressSectionIds = $this->resolveLowProgressSectionIds($sectionIds);
    }

    $teachersBySection = [];
    foreach ($assignmentRows as $assignment) {
        $sectionId = (int)($assignment['class_section_id'] ?? 0);
        if ($sectionId <= 0) {
            continue;
        }

        $positionKey = strtolower(trim((string)($assignment['position'] ?? '')));
        $roleKey = $positionKey !== '' ? $positionKey : 'teacher';
        $positionLabel = match ($roleKey) {
            'ta' => 'TA',
            'main' => 'Main',
            default => $roleKey !== '' ? ucfirst($roleKey) : 'Teacher',
        };

        $teacherFullName = trim(($assignment['firstname'] ?? '') . ' ' . ($assignment['lastname'] ?? ''));
        $teacherId = (int)($assignment['teacher_id'] ?? 0);
        if ($teacherFullName === '' || $teacherId <= 0) {
            continue;
        }

        $entry = &$teachersBySection[$sectionId];
        if (!isset($entry)) {
            $entry = [
                'class_section' => $assignment['class_section_name'] ?? ($sectionMap[$sectionId] ?? "Section {$sectionId}"),
                'teachers' => [],
            ];
        }

        $entry['teachers'][] = [
            'id' => $teacherId,
            'label' => "{$positionLabel}: {$teacherFullName}",
            'role_key' => $roleKey,
        ];
        unset($entry);
    }

    $today = (new \DateTimeImmutable('now', new \DateTimeZone(date_default_timezone_get() ?: 'UTC')))->format('Y-m-d');

    $rows = [];
    $totalStatuses = 0;
    $missingItemCount = 0;
    $allTeacherIds = [];
    $allClassSectionIds = [];
    $examTerm = $this->resolveExamTermLabel($semester);
    $examScoreField = $examTerm === 'final' ? 'final_exam_score' : 'midterm_exam_score';

    foreach ($sectionMap as $classSectionId => $sectionName) {
        $classSectionId = (int)$classSectionId;
        if ($classSectionId <= 0) {
            continue;
        }

        $studentEntries = $this->db->table('student_class')
            ->select('student_id')
            ->where('class_section_id', $classSectionId)
            ->where('school_year', $schoolYear)
            ->get()
            ->getResultArray();
        if (empty($studentEntries)) {
            $studentEntries = $this->studentClassModel
                ->select('student_id')
                ->where('class_section_id', $classSectionId)
                ->where('school_year', $schoolYear)
                ->findAll();
        }
        $studentIds = array_filter(array_map(static fn($entry) => (int)($entry['student_id'] ?? 0), $studentEntries));
        $expected = count($studentIds);

        $midtermStudents = [];
        $participationStudents = [];
        if ($classSectionId > 0) {
            $scoreQuery = $semesterScores
                ->where('class_section_id', $classSectionId)
                ->where('school_year', $schoolYear);
            if (!empty($semesterCandidates)) {
                $scoreQuery->whereIn('semester', $semesterCandidates);
            }
            $scoreRecords = $scoreQuery->findAll();
            foreach ($scoreRecords as $score) {
                $sid = (int)($score['student_id'] ?? 0);
                if ($sid <= 0 || ($expected > 0 && !in_array($sid, $studentIds, true))) {
                    continue;
                }
                $midtermValue = trim((string)($score[$examScoreField] ?? ''));
                if ($midtermValue !== '') {
                    $midtermStudents[$sid] = true;
                }
                $participationValue = trim((string)($score['participation_score'] ?? ''));
                if ($participationValue !== '') {
                    $participationStudents[$sid] = true;
                }
            }
        }

        $midtermCommentStudents = [];
        $ptapCommentStudents = [];
        if (!empty($studentIds)) {
            $commentQuery = $scoreComments
                ->select('student_id, score_type, comment')
                ->whereIn('student_id', $studentIds)
                ->where('school_year', $schoolYear)
                ->whereIn('score_type', [$examTerm, 'ptap']);
            if (!empty($semesterCandidates)) {
                $commentQuery->whereIn('semester', $semesterCandidates);
            }
            $comments = $commentQuery->findAll();
            foreach ($comments as $comment) {
                $sid = (int)($comment['student_id'] ?? 0);
                if ($sid <= 0) {
                    continue;
                }
                $text = trim((string)($comment['comment'] ?? ''));
                if ($text === '') {
                    continue;
                }
                $type = strtolower(trim((string)($comment['score_type'] ?? '')));
                if ($type === $examTerm) {
                    $midtermCommentStudents[$sid] = true;
                }
                if ($type === 'ptap') {
                    $ptapCommentStudents[$sid] = true;
                }
            }
        }

        $attendanceQuery = $attendanceDays
            ->where('class_section_id', $classSectionId)
            ->where('school_year', $schoolYear)
            ->where('date', $today);
        if (!empty($semesterCandidates)) {
            $attendanceQuery->whereIn('semester', $semesterCandidates);
        }
        $attendanceRow = $attendanceQuery->first();
        $attendanceSubmitted = $attendanceRow && in_array(strtolower((string)($attendanceRow['status'] ?? '')), ['submitted', 'published', 'finalized'], true);

        $section = $teachersBySection[$classSectionId] ?? ['teachers' => []];
        $teacherList = $section['teachers'] ?? [];
        if (!empty($teacherList)) {
            usort($teacherList, function ($a, $b) {
                return $this->teacherRolePriority($a['role_key'] ?? 'teacher') <=> $this->teacherRolePriority($b['role_key'] ?? 'teacher');
            });
            $teacherList = array_values($teacherList);
        }

        foreach ($teacherList as $teacherEntry) {
            if (!empty($teacherEntry['id'])) {
                $allTeacherIds[] = $teacherEntry['id'];
            }
        }
        $allClassSectionIds[] = $classSectionId;

        $midtermScoreStatus = $this->submissionStatus(count($midtermStudents), $expected);
        $midtermCommentStatus = $this->submissionStatus(count($midtermCommentStudents), $expected);
        $participationStatus = $this->submissionStatus(count($participationStudents), $expected);
        $ptapCommentStatus = $this->submissionStatus(count($ptapCommentStudents), $expected);
        $attendanceStatus = $this->attendanceStatus($attendanceSubmitted);
        $progressSubmitted = (int) ($progressSubmittedBySection[$classSectionId] ?? 0);
        $classProgressStatus = $this->progressStatus($progressSubmitted, $progressExpectedWeeks);
        $draftSubmitted = (int) ($examDraftCounts[$classSectionId] ?? 0);
        $examDraftStatus = $this->draftStatus($draftSubmitted, $examDraftDeadline);
        $homeworkSubmitted = (int) ($homeworkCounts[$classSectionId] ?? 0);
        $homeworkStatus = $this->homeworkStatus($homeworkSubmitted);
        $statusDetails = [
            'midterm_score_status' => $midtermScoreStatus,
            'midterm_comment_status' => $midtermCommentStatus,
            'participation_status' => $participationStatus,
            'ptap_comment_status' => $ptapCommentStatus,
            'class_progress_status' => $classProgressStatus,
            'exam_draft_status' => $examDraftStatus,
            'homework_status' => $homeworkStatus,
        ];
        $missingItemsForSection = $this->buildMissingItems($statusDetails, $semester);
        $missingItemCount += count($missingItemsForSection);
        $totalStatuses += count($statusDetails);

        $rows[] = [
            'class_section' => $sectionMap[$classSectionId] ?? ($section['class_section'] ?? "Section {$classSectionId}"),
            'class_section_id' => $classSectionId,
            'teachers' => $teacherList,
            'midterm_score_status' => $midtermScoreStatus,
            'midterm_comment_status' => $midtermCommentStatus,
            'participation_status' => $participationStatus,
            'ptap_comment_status' => $ptapCommentStatus,
            'attendance_status' => $attendanceStatus,
            'class_progress_status' => $classProgressStatus,
            'exam_draft_status' => $examDraftStatus,
            'homework_status' => $homeworkStatus,
            'missing_items' => $missingItemsForSection,
            'student_count' => $expected,
        ];
    }

    $historyMap = [];
    $teacherIds = array_values(array_unique($allTeacherIds));
    $classSectionIds = array_values(array_unique($allClassSectionIds));
    if (!empty($teacherIds) && !empty($classSectionIds)) {
        $historyRecords = $historyModel
            ->select('teacher_submission_notification_history.*, u.firstname, u.lastname')
            ->join('users u', 'u.id = teacher_submission_notification_history.admin_id', 'left')
            ->where('notification_category', 'teacher_submissions')
            ->whereIn('teacher_submission_notification_history.teacher_id', $teacherIds)
            ->whereIn('teacher_submission_notification_history.class_section_id', $classSectionIds)
            ->orderBy('sent_at', 'DESC')
            ->findAll();

        foreach ($historyRecords as $record) {
            $sectionId = (int)($record['class_section_id'] ?? 0);
            $teacherId = (int)($record['teacher_id'] ?? 0);
            if ($sectionId <= 0 || $teacherId <= 0) {
                continue;
            }
            $sentAt = $record['sent_at'] ?? null;
            $sentAtText = $sentAt ? local_datetime($sentAt, 'M j, Y g:i A') : '';
            $adminName = trim(($record['firstname'] ?? '') . ' ' . ($record['lastname'] ?? ''));
            if ($adminName === '') {
                $adminName = 'Administrator';
            }
            $historyMap[$sectionId][$teacherId][] = [
                'sent_at_text' => $sentAtText,
                'admin_name' => $adminName,
                'status' => strtolower((string)($record['status'] ?? 'sent')),
            ];
        }

        foreach ($historyMap as &$teachersHistory) {
            foreach ($teachersHistory as &$entries) {
                $entries = array_slice($entries, 0, 3);
            }
            unset($entries);
        }
        unset($teachersHistory);
    }

    $summary = [
        'total_items' => $totalStatuses,
        'missing_items' => $missingItemCount,
        'submitted_items' => max(0, $totalStatuses - $missingItemCount),
        'submission_percentage' => $totalStatuses > 0
            ? (int)round((($totalStatuses - $missingItemCount) / $totalStatuses) * 100)
            : 100,
    ];

    return [
        'rows' => $rows,
        'semester' => $semester,
        'schoolYear' => $schoolYear,
        'notificationHistory' => $historyMap,
        'summary' => $summary,
        'lowProgressSectionIds' => $lowProgressSectionIds,
        'examDraftDeadlineConfig' => $examDraftDeadlineConfig,
        'examDraftDeadlineFormatted' => $examDraftDeadlineFormatted,
    ];
}

public function sendNotifications(array $post, string $semester, int $adminId): array
{
    $notify = $post['notify'] ?? null;
    if (!is_array($notify)) {
        return ['redirect' => 'back', 'type' => 'info', 'message' => 'Select at least one teacher to notify.'];
    }
    $semester = (string)(getSemester() ?? $this->semester ?? '');
    $missingItemsPayload = $post['missing_items'] ?? [];
    $homeworkNotifyAll = (bool) ($post['homework_notify_all'] ?? false);
    $examTerm = $this->resolveExamTermLabel($semester);
    $examScoreLabel = $examTerm === 'final' ? 'final scores' : 'midterm scores';
    $examCommentLabel = $examTerm === 'final' ? 'final comments' : 'midterm comments';
    $forcedItems = [];
    if (!empty($post['notify_midterm_score'])) {
        $forcedItems[] = $examScoreLabel;
    }
    if (!empty($post['notify_midterm_comment'])) {
        $forcedItems[] = $examCommentLabel;
    }
    if (!empty($post['notify_participation'])) {
        $forcedItems[] = 'participation';
    }
    if (!empty($post['notify_ptap_comment'])) {
        $forcedItems[] = 'PTAP comments';
    }
    if (!empty($post['notify_class_progress'])) {
        $forcedItems[] = 'class progress';
    }
    if (!empty($post['notify_exam_draft'])) {
        $forcedItems[] = 'exam draft';
    }

    $targets = [];
    foreach ($notify as $sectionIdRaw => $teachers) {
        $sectionId = (int)$sectionIdRaw;
        if ($sectionId <= 0 || !is_array($teachers)) {
            continue;
        }
        foreach ($teachers as $teacherIdRaw => $value) {
            $teacherId = (int)$teacherIdRaw;
            if ($teacherId <= 0 || $value === null || $value === '') {
                continue;
            }
            $key = "{$sectionId}_{$teacherId}";
            $targets[$key] = [
                'class_section_id' => $sectionId,
                'teacher_id' => $teacherId,
            ];
        }
    }

    if (empty($targets)) {
        return ['redirect' => 'back', 'type' => 'info', 'message' => 'Select at least one teacher to notify.'];
    }

    $targets = array_values($targets);
    $teacherIds = array_values(array_unique(array_column($targets, 'teacher_id')));
    $classSectionIds = array_values(array_unique(array_column($targets, 'class_section_id')));

    $classSections = $this->classSectionModel
        ->select('class_section_id, class_section_name')
        ->whereIn('class_section_id', $classSectionIds)
        ->findAll();
    $classSectionMap = [];
    foreach ($classSections as $section) {
        $classSectionMap[(int)($section['class_section_id'] ?? 0)] = $section['class_section_name'] ?? '';
    }

    $teachers = $this->userModel
        ->select('id, firstname, lastname, email')
        ->whereIn('id', $teacherIds)
        ->findAll();
    $teacherLookup = [];
    foreach ($teachers as $teacher) {
        $teacherLookup[(int)$teacher['id']] = $teacher;
    }

    $mailer = new EmailController();
    if ($adminId <= 0) {
        return ['redirect' => 'login', 'type' => 'error', 'message' => ''];
    }
    $adminUser = $this->userModel->find($adminId);
    $adminName = trim(($adminUser['firstname'] ?? '') . ' ' . ($adminUser['lastname'] ?? '')) ?: 'Administrator';

    $historyModel = new TeacherSubmissionNotificationHistoryModel();
    $scoreUrl = site_url('/');
    $progressUrl = site_url('teacher/progress/history');
    $examDraftUrl = site_url('teacher/exam-drafts');
    $homeworkUrl = site_url('teacher/addHomework');
    $examDraftDeadlineEmailHtml = $this->buildExamDraftDeadlineEmailHtml();
    $sentCount = 0;
    $failCount = 0;

    foreach ($targets as $target) {
        $classSectionId = (int)$target['class_section_id'];
        $teacherId = (int)$target['teacher_id'];
        $teacher = $teacherLookup[$teacherId] ?? null;
        $sectionName = $classSectionMap[$classSectionId] ?? "Section {$classSectionId}";
        $teacherName = $teacher ? trim(($teacher['firstname'] ?? '') . ' ' . ($teacher['lastname'] ?? '')) : '';
        if ($teacherName === '') {
            $teacherName = 'Teacher';
        }
        $subject = "Reminder: Complete submissions for {$sectionName}";
        $missingPayload = $missingItemsPayload[$classSectionId][$teacherId] ?? '';
        $missingItems = $this->parseMissingItemsPayload((string)$missingPayload);
        $selectedItems = $forcedItems;
        if ($homeworkNotifyAll && !in_array('homework', $selectedItems, true)) {
            $selectedItems[] = 'homework';
        }
        if (!empty($selectedItems)) {
            $missingItems = array_values(array_unique($selectedItems));
        }
        if (!empty($missingItems)) {
            $missingText = htmlspecialchars(
                $this->formatMissingItemsText($missingItems),
                ENT_QUOTES,
                'UTF-8'
            );
            $missingNote = "<p>Outstanding items: {$missingText}.</p>";
        } else {
            $missingNote = "<p>Our records show no outstanding submissions for this section, but please verify if anything still needs attention.</p>";
        }

        $subject = "Reminder: Complete submissions for {$sectionName}";
        $progressNote = '';
        if (in_array('class progress', $missingItems, true)) {
            $progressNote = "<p>Class progress submissions can be updated at <a href=\"{$progressUrl}\">Teacher Progress History</a>.</p>";
        }
        $examDraftNote = '';
        if (in_array('exam draft', $missingItems, true)) {
            $semesterLabel = strtolower(trim((string) $semester));
            if ($semesterLabel === 'fall') {
                $draftLabel = 'midterm exam draft';
            } elseif ($semesterLabel === 'spring') {
                $draftLabel = 'final exam draft';
            } else {
                $draftLabel = 'exam draft';
            }
            $examDraftNote = "<p>" . ucfirst($draftLabel) . " submissions can be updated at <a href=\"{$examDraftUrl}\">Teacher Exam Drafts</a>.</p>"
                . $examDraftDeadlineEmailHtml;
        }
        $homeworkNote = '';
        if (in_array('homework', $missingItems, true)) {
            $homeworkNote = "<p>Homework scores can be submitted at <a href=\"{$homeworkUrl}\">Teacher Homework</a>.</p>";
        }
        $hasScoreItems = (bool) array_intersect($missingItems, [
            'midterm scores',
            'midterm comments',
            'final scores',
            'final comments',
            'participation',
            'PTAP comments',
            'homework',
        ]);
        $nonScoreOnly = ! empty($missingItems) && ! $hasScoreItems;
        $body = "<p>Dear {$teacherName},</p>"
            . "<p>Administration is gently reminding you to wrap up any remaining "
            . ($nonScoreOnly ? "submissions for {$sectionName}." : "score submissions, comments, and related items for {$sectionName}.")
            . "</p>"
            . $missingNote
            . $progressNote
            . $examDraftNote
            . $homeworkNote
            . ($nonScoreOnly ? '' : "<p>Visit <a href=\"{$scoreUrl}\">Teacher Score Submission</a> to address any remaining items.</p>")
            . "<p>Thank you,<br>Al Rahma Administration</p>";

        $email = $teacher['email'] ?? '';
        $status = 'failed';
        if (!empty($email) && filter_var($email, FILTER_VALIDATE_EMAIL)) {
            $ok = $mailer->sendEmail($email, $subject, $body, 'notifications');
            $status = $ok ? 'sent' : 'failed';
        }

        if ($status === 'sent') {
            $sentCount++;
        } else {
            $failCount++;
        }

        $historyModel->insert([
            'teacher_id' => $teacherId,
            'class_section_id' => $classSectionId,
            'admin_id' => $adminId,
            'notification_category' => 'teacher_submissions',
            'message' => $this->truncateNotificationMessage($body),
            'status' => $status,
            'school_year' => $this->schoolYear,
            'semester' => $this->semester,
            'sent_at' => utc_now(),
        ]);
    }

    $statusParts = [];
    if ($sentCount > 0) {
        $statusParts[] = $sentCount . ' reminder' . ($sentCount === 1 ? '' : 's') . ' sent';
    }
    if ($failCount > 0) {
        $statusParts[] = $failCount . ' reminder' . ($failCount === 1 ? '' : 's') . ' failed';
    }

    $message = !empty($statusParts) ? implode(' and ', $statusParts) : 'No notifications were sent.';
    $flashType = $failCount === 0 ? 'success' : 'warning';

    return ['redirect' => 'back', 'type' => $flashType, 'message' => $message];
}

private function resolveLowProgressSectionIds(array $sectionIds): array
{
    [$expectedWeeks, $submittedBySection] = $this->buildClassProgressStats($sectionIds);
    if ($expectedWeeks <= 0) {
        return [];
    }

    $lowProgressSectionIds = [];
    foreach ($sectionIds as $sectionId) {
        $submitted = (int) ($submittedBySection[$sectionId] ?? 0);
        $percent = ($submitted / $expectedWeeks) * 100;
        if ($percent < 50) {
            $lowProgressSectionIds[] = $sectionId;
        }
    }

    return $lowProgressSectionIds;
}

private function buildClassProgressStats(array $sectionIds): array
{
    $sectionIds = array_values(array_unique(array_filter(array_map('intval', $sectionIds))));
    if (empty($sectionIds)) {
        return [0, []];
    }

    $semesterResolver = new SemesterRangeService($this->configModel);
    $schoolYear = (string) ($this->schoolYear ?? '');
    $semester = (string)(getSemester() ?? '');
    $schoolYearForRange = $schoolYear !== '' ? $schoolYear : (string) ($this->schoolYear ?? '');
    [$rangeStart, $rangeEnd] = $semesterResolver->getSchoolYearRange($schoolYearForRange);
    $semesterNorm = $semesterResolver->normalizeSemester($semester);
    if ($semesterNorm !== '' && $schoolYearForRange !== '') {
        $semRange = $semesterResolver->getSemesterRange($schoolYearForRange, $semesterNorm);
        if ($semRange) {
            [$rangeStart, $rangeEnd] = $semRange;
        }
    }

    $dateList = [];
    try {
        $start = new \DateTimeImmutable($rangeStart);
        $end = new \DateTimeImmutable($rangeEnd);
        $cursor = $start;
        $w = (int) $cursor->format('w');
        if ($w !== 0) {
            $cursor = $cursor->modify('next sunday');
        }
        while ($cursor <= $end) {
            $dateList[] = $cursor->format('Y-m-d');
            $cursor = $cursor->modify('+7 days');
        }
    } catch (\Throwable $e) {
        $dateList = [];
    }

    $noSchoolDays = [];
    $events = [];
    try {
        $calendarModel = new \App\Models\CalendarModel();
        $events = $calendarModel->getEvents();
    } catch (\Throwable $e) {
        $events = [];
    }
    foreach ($events as $event) {
        $d = substr((string) ($event['date'] ?? ''), 0, 10);
        if ($d === '' || empty($event['no_school'])) {
            continue;
        }
        if ($d < $rangeStart || $d > $rangeEnd) {
            continue;
        }
        $eventYear = trim((string) ($event['school_year'] ?? ''));
        if ($schoolYearForRange !== '' && $eventYear !== '' && $eventYear !== $schoolYearForRange) {
            continue;
        }
        $noSchoolDays[$d] = true;
    }

    $anchorSundayYmd = '';
    try {
        $tzName = (string) (config('School')->attendance['timezone'] ?? user_timezone());
        $tzObj = new \DateTimeZone($tzName ?: 'UTC');
    } catch (\Throwable $e) {
        try {
            $tzObj = new \DateTimeZone(user_timezone() ?: 'UTC');
        } catch (\Throwable $e2) {
            $tzObj = new \DateTimeZone('UTC');
        }
    }
    try {
        $nowDate = new \DateTime('now', $tzObj);
    } catch (\Throwable $e) {
        $nowDate = new \DateTime('now');
    }
    $weekday = (int) $nowDate->format('w');
    $anchorSundayYmd = $weekday === 0
        ? $nowDate->format('Y-m-d')
        : $nowDate->modify('next sunday')->format('Y-m-d');

    $activeDatesSet = [];
    if (! empty($dateList) && $anchorSundayYmd !== '') {
        foreach ($dateList as $d) {
            if ($d <= $anchorSundayYmd && empty($noSchoolDays[$d])) {
                $activeDatesSet[$d] = true;
            }
        }
    }
    $expectedWeeks = count($activeDatesSet);
    if ($expectedWeeks === 0) {
        return [0, []];
    }

    $builder = $this->db->table('class_progress_reports')
        ->select('class_section_id, week_start')
        ->whereIn('class_section_id', $sectionIds);
    if (! empty($activeDatesSet)) {
        $builder->whereIn('week_start', array_keys($activeDatesSet));
    }
    $rows = $builder->get()->getResultArray();

    $submittedBySection = [];
    foreach ($rows as $row) {
        $sectionId = (int) ($row['class_section_id'] ?? 0);
        $weekStart = (string) ($row['week_start'] ?? '');
        if ($sectionId === 0 || $weekStart === '' || empty($activeDatesSet[$weekStart])) {
            continue;
        }
        $submittedBySection[$sectionId][$weekStart] = true;
    }

    $counts = [];
    foreach ($sectionIds as $sectionId) {
        $counts[$sectionId] = isset($submittedBySection[$sectionId])
            ? count($submittedBySection[$sectionId])
            : 0;
    }

    return [$expectedWeeks, $counts];
}

private function submissionStatus(int $filled, int $expected): array
{
    if ($expected <= 0) {
        return [
            'label' => 'No students',
            'badge' => 'bg-secondary',
            'detail' => '',
            'completed' => true,
        ];
    }
    $completed = $filled >= $expected;
    return [
        'label' => $completed ? 'Submitted' : 'Missing',
        'badge' => $completed ? 'bg-success' : 'bg-danger',
        'detail' => "{$filled}/{$expected}",
        'completed' => $completed,
    ];
}

private function progressStatus(int $submitted, int $expected): array
{
    if ($expected <= 0) {
        return [
            'label' => 'N/A',
            'badge' => 'bg-secondary',
            'detail' => '',
            'completed' => true,
        ];
    }
    $completed = $submitted >= $expected;
    return [
        'label' => $completed ? 'Submitted' : 'Missing',
        'badge' => $completed ? 'bg-success' : 'bg-danger',
        'detail' => "{$submitted}/{$expected}",
        'completed' => $completed,
    ];
}

private function homeworkStatus(int $submitted): array
{
    $completed = $submitted > 0;
    return [
        'label' => $completed ? 'Submitted' : 'Missing',
        'badge' => $completed ? 'bg-success' : 'bg-danger',
        'detail' => $completed ? (string) $submitted : '0',
        'completed' => $completed,
    ];
}

private function draftStatus(int $submitted, ?\DateTimeImmutable $deadline): array
{
    if ($deadline !== null) {
        $today = new \DateTimeImmutable('today');
        if ($today < $deadline) {
            return [
                'label' => 'Pending',
                'badge' => 'bg-secondary',
                'detail' => 'Not due',
                'completed' => true,
            ];
        }
    }
    $completed = $submitted > 0;
    return [
        'label' => $completed ? 'Submitted' : 'Missing',
        'badge' => $completed ? 'bg-success' : 'bg-danger',
        'detail' => $completed ? (string) $submitted : '0',
        'completed' => $completed,
    ];
}

/**
 * Exam draft due date for the teacher submissions dashboard: prefers the configuration key
 * `exam_draft_deadline` (same as automated reminders); otherwise fall/spring exam deadlines.
 */
private function resolveTeacherDashboardExamDraftDeadline(string $semester, string $schoolYear): ?\DateTimeImmutable
{
    $fromExamDraftKey = $this->parseExamDraftDeadlineConfigValue();
    if ($fromExamDraftKey !== null) {
        return $fromExamDraftKey;
    }

    return $this->resolveExamDraftDeadline($semester, $schoolYear);
}

/**
 * Parses the `exam_draft_deadline` configuration value using the application timezone (midnight that calendar day).
 */
private function parseExamDraftDeadlineConfigValue(): ?\DateTimeImmutable
{
    $raw = trim((string) ($this->configModel->getConfig('exam_draft_deadline') ?? ''));
    if ($raw === '') {
        return null;
    }
    $tz = new \DateTimeZone(config('App')->appTimezone ?? 'UTC');
    try {
        $deadline = new \DateTimeImmutable($raw, $tz);
    } catch (\Throwable $e) {
        return null;
    }

    return $deadline->setTime(0, 0, 0);
}

/**
 * HTML snippet for reminder emails when exam draft is included (deadline from exam_draft_deadline config).
 */
private function buildExamDraftDeadlineEmailHtml(): string
{
    $raw = trim((string) ($this->configModel->getConfig('exam_draft_deadline') ?? ''));
    if ($raw === '') {
        return '';
    }
    $parsed = $this->parseExamDraftDeadlineConfigValue();
    $display = $parsed !== null
        ? htmlspecialchars($parsed->format('l, F j, Y'), ENT_QUOTES, 'UTF-8')
        : htmlspecialchars($raw, ENT_QUOTES, 'UTF-8');
    $rawEsc = htmlspecialchars($raw, ENT_QUOTES, 'UTF-8');

    return '<p><strong>Exam draft submission deadline</strong> (<code>exam_draft_deadline</code>): '
        . "<strong>{$display}</strong>"
        . ($parsed !== null && $rawEsc !== $display ? " <span style=\"color:#555;\">(configured value: {$rawEsc})</span>" : '')
        . '.</p>';
}

private function resolveExamDraftDeadline(string $semester, string $schoolYear): ?\DateTimeImmutable
{
    $semesterKey = strtolower(trim($semester));
    if ($semesterKey === 'fall') {
        $deadlineValue = (string)($this->configModel->getConfig('fall_exam_deadline') ?? '');
    } elseif ($semesterKey === 'spring') {
        $deadlineValue = (string)($this->configModel->getConfig('spring_exam_deadline') ?? '');
    } else {
        return null;
    }
    $deadlineValue = trim($deadlineValue);
    if ($deadlineValue === '') {
        return null;
    }
    try {
        $deadline = new \DateTimeImmutable($deadlineValue);
    } catch (\Throwable $e) {
        return null;
    }
    if ($schoolYear !== '' && preg_match('/^\d{4}-\d{4}$/', $schoolYear)) {
        $deadlineYear = $deadline->format('Y');
        if ($deadlineYear === '1970') {
            return null;
        }
    }
    return $deadline->setTime(0, 0, 0);
}

private function resolveExamTermLabel(string $semester): string
{
    $semesterKey = strtolower(trim($semester));
    if ($semesterKey === '') {
        return 'midterm';
    }
    if (str_contains($semesterKey, 'spring')) {
        return 'final';
    }
    if (str_contains($semesterKey, 'fall')) {
        return 'midterm';
    }
    return 'midterm';
}

private function buildSemesterCandidates(string $semester): array
{
    $semester = trim((string) $semester);
    if ($semester === '') {
        return [];
    }
    $candidates = [
        $semester,
        strtolower($semester),
        strtoupper($semester),
        ucfirst(strtolower($semester)),
    ];
    $candidates = array_values(array_unique(array_filter($candidates, static fn ($v) => $v !== '')));
    return $candidates;
}

private function attendanceStatus(bool $submitted): array
{
    return [
        'label' => $submitted ? 'Submitted' : 'Missing',
        'badge' => $submitted ? 'bg-success' : 'bg-danger',
        'completed' => $submitted,
    ];
}

private function buildMissingItems(array $statusMap, string $semester): array
{
    $examTerm = $this->resolveExamTermLabel($semester);
    $examScoreLabel = $examTerm === 'final' ? 'final scores' : 'midterm scores';
    $examCommentLabel = $examTerm === 'final' ? 'final comments' : 'midterm comments';
    $labels = [
        'midterm_score_status' => $examScoreLabel,
        'midterm_comment_status' => $examCommentLabel,
        'participation_status' => 'participation',
        'ptap_comment_status' => 'PTAP comments',
        'attendance_status' => 'attendance',
        'class_progress_status' => 'class progress',
        'exam_draft_status' => 'exam draft',
        'homework_status' => 'homework',
    ];

    $items = [];
    foreach ($statusMap as $key => $status) {
        $completed = $status['completed'] ?? true;
        if (!$completed && isset($labels[$key])) {
            $items[] = $labels[$key];
        }
    }

    return array_values($items);
}

private function formatMissingItemsText(array $items): string
{
    $items = array_values(array_filter(array_map('trim', $items), static fn($v) => $v !== ''));
    $count = count($items);
    if ($count === 0) {
        return '';
    }
    if ($count === 1) {
        return $items[0];
    }
    if ($count === 2) {
        return $items[0] . ' and ' . $items[1];
    }
    $last = array_pop($items);
    return implode(', ', $items) . ' and ' . $last;
}

private function teacherRolePriority(string $roleKey): int
{
    switch (strtolower($roleKey)) {
        case 'main':
            return 1;
        case 'ta':
            return 2;
        default:
            return 3;
    }
}

private function truncateNotificationMessage(string $html, int $limit = 1000): string
{
    $text = trim(strip_tags($html));
    if ($text === '') {
        return '';
    }
    if (mb_strlen($text) <= $limit) {
        return $text;
    }
    return mb_substr($text, 0, $limit) . '…';
}

private function parseMissingItemsPayload(string $payload): array
{
    if ($payload === '') {
        return [];
    }
    $decoded = @json_decode(base64_decode($payload, true) ?: '', true);
    if (!is_array($decoded)) {
        return [];
    }

    $items = [];
    foreach ($decoded as $item) {
        $item = trim((string)$item);
        if ($item === '') {
            continue;
        }
        $items[] = $item;
    }

    return array_values(array_unique($items));
}
}