<?php

namespace App\Services\Frontend;

use App\Models\AttendanceDay;
use App\Models\AttendanceRecord;
use App\Models\Calendar;
use App\Models\ClassSection;
use App\Models\ScoreComment;
use App\Models\SemesterScore;
use App\Models\TeacherClass;
use DateTimeImmutable;
use DateTimeZone;
use Illuminate\Support\Facades\DB;

class LandingPageTeacherSummaryService
{
    public function __construct(private LandingPageContextService $context) {}

    public function summary(int $teacherId, ?int $requestedClassSectionId = null): array
    {
        $context = $this->context->context();
        $schoolYear = (string) ($context['school_year'] ?? '');
        $semester = (string) ($context['semester'] ?? '');

        $assignments = TeacherClass::getClassAssignmentsByUserId($teacherId, $schoolYear, $semester);
        $availableIds = array_values(array_filter(array_unique(array_map(
            static fn (array $row) => (int) ($row['class_section_id'] ?? 0),
            $assignments
        ))));

        $activeId = null;
        if ($requestedClassSectionId && in_array($requestedClassSectionId, $availableIds, true)) {
            $activeId = $requestedClassSectionId;
        } elseif (! empty($availableIds)) {
            $activeId = $availableIds[0];
        }

        $activeName = null;
        foreach ($assignments as $row) {
            if ((int) ($row['class_section_id'] ?? 0) === (int) $activeId) {
                $activeName = $row['class_section_name'] ?? null;
                break;
            }
        }

        $normalizedSemester = ucfirst(strtolower(trim((string) $semester)));
        if (! in_array($normalizedSemester, ['Fall', 'Spring'], true)) {
            $normalizedSemester = 'Fall';
        }

        $classSectionIds = $availableIds;
        $dashboardSummary = $this->buildTeacherDashboardSummary($classSectionIds, $normalizedSemester, $schoolYear);

        return [
            'class_section_id' => $activeId,
            'active_class_name' => $activeName,
            'classes' => $assignments,
            'jobCount' => count($assignments),
            'scoreSummary' => $dashboardSummary['scoreSummary'],
            'commentSummary' => $dashboardSummary['commentSummary'],
            'attendanceSummary' => $dashboardSummary['attendanceSummary'],
            'deadlineEvents' => $dashboardSummary['deadlineEvents'],
            'participationSummary' => $dashboardSummary['participationSummary'],
            'attendanceStatus' => $dashboardSummary['attendanceStatus'],
            'dashboardNotifications' => $dashboardSummary['notifications'],
            'school_year' => $schoolYear,
            'semester' => $semester,
        ];
    }

    private function buildTeacherDashboardSummary(array $classSectionIds, string $semester, string $schoolYear): array
    {
        $scoreField = $semester === 'Spring' ? 'final_exam_score' : 'midterm_exam_score';
        $scoreLabel = $semester === 'Spring' ? 'Final Exam' : 'Midterm';

        $summary = [
            'scoreSummary' => [
                'completionPct' => 0,
                'missing' => 0,
                'expected' => 0,
                'filled' => 0,
                'fieldLabel' => $scoreLabel,
            ],
            'commentSummary' => [
                'total' => 0,
                'pendingReview' => 0,
                'reviewed' => 0,
                'byType' => [],
            ],
            'attendanceSummary' => [
                'recorded' => 0,
                'students' => 0,
                'completionPct' => 0,
                'avgAbsences' => 0,
            ],
            'participationSummary' => [
                'filled' => 0,
                'missing' => 0,
                'completionPct' => 0,
                'expected' => 0,
            ],
            'deadlineEvents' => [],
            'notifications' => [],
            'attendanceStatus' => [
                'date' => '',
                'missingSections' => [],
                'missingNames' => [],
                'submitted' => true,
            ],
        ];

        $uniqueStudentIds = [];
        if (! empty($classSectionIds)) {
            $studentRows = DB::table('student_class as sc')
                ->select('sc.student_id', 'sc.class_section_id')
                ->join('students as s', 's.id', '=', 'sc.student_id')
                ->whereIn('sc.class_section_id', $classSectionIds)
                ->where('s.is_active', 1)
                ->where('sc.school_year', $schoolYear)
                ->get();

            foreach ($studentRows as $row) {
                $studentId = (int) ($row->student_id ?? 0);
                if ($studentId > 0) {
                    $uniqueStudentIds[] = $studentId;
                }
            }
        }

        $uniqueStudentIds = array_values(array_unique($uniqueStudentIds));
        $totalStudents = count($uniqueStudentIds);
        $summary['attendanceSummary']['students'] = $totalStudents;

        $scoreRows = [];
        if (! empty($classSectionIds)) {
            $scoreRows = SemesterScore::query()
                ->select(['student_id', 'class_section_id', 'midterm_exam_score', 'final_exam_score', 'participation_score'])
                ->whereIn('class_section_id', $classSectionIds)
                ->where('semester', $semester)
                ->where('school_year', $schoolYear)
                ->get()
                ->toArray();
        }

        $scoreTypesConfig = [
            'participation' => ['label' => 'Participation', 'field' => 'participation_score'],
        ];
        if ($semester === 'Fall') {
            $scoreTypesConfig = array_merge([
                'midterm' => ['label' => 'Midterm', 'field' => 'midterm_exam_score'],
            ], $scoreTypesConfig);
        }
        if ($semester === 'Spring') {
            $scoreTypesConfig = array_merge([
                'final' => ['label' => 'Final exam', 'field' => 'final_exam_score'],
            ], $scoreTypesConfig);
        }

        $filledCounts = array_fill_keys(array_keys($scoreTypesConfig), 0);
        foreach ($scoreRows as $row) {
            foreach ($scoreTypesConfig as $key => $cfg) {
                $value = trim((string) ($row[$cfg['field']] ?? ''));
                if ($value !== '') {
                    $filledCounts[$key]++;
                }
            }
        }

        $expectedScoreCount = $totalStudents > 0 ? $totalStudents : count($scoreRows);
        $scoreDetails = [];
        foreach ($scoreTypesConfig as $key => $cfg) {
            $filled = $filledCounts[$key] ?? 0;
            $missing = max(0, $expectedScoreCount - $filled);
            $completionPct = $expectedScoreCount > 0 ? (int) round(min(100, ($filled / $expectedScoreCount) * 100)) : 0;
            $scoreDetails[$key] = [
                'label' => $cfg['label'],
                'field' => $cfg['field'],
                'filled' => $filled,
                'missing' => $missing,
                'expected' => $expectedScoreCount,
                'completionPct' => $completionPct,
            ];
        }

        $scoreTypeByField = [];
        if ($semester === 'Fall') {
            $scoreTypeByField['midterm_exam_score'] = 'midterm';
        }
        if ($semester === 'Spring') {
            $scoreTypeByField['final_exam_score'] = 'final';
        }
        $activeScoreType = $scoreTypeByField[$scoreField] ?? array_key_first($scoreDetails);
        $activeScoreDetails = $scoreDetails[$activeScoreType] ?? array_values($scoreDetails)[0];

        $summary['scoreSummary'] = [
            'completionPct' => $activeScoreDetails['completionPct'],
            'missing' => $activeScoreDetails['missing'],
            'expected' => $activeScoreDetails['expected'],
            'filled' => $activeScoreDetails['filled'],
            'fieldLabel' => $scoreLabel,
            'types' => $scoreDetails,
        ];

        $participationMetrics = $scoreDetails['participation'];
        $summary['participationSummary'] = [
            'filled' => $participationMetrics['filled'],
            'missing' => $participationMetrics['missing'],
            'completionPct' => $participationMetrics['completionPct'],
            'expected' => $participationMetrics['expected'],
        ];

        $commentRows = [];
        if (! empty($uniqueStudentIds)) {
            $commentRows = ScoreComment::query()
                ->select(['student_id', 'score_type', 'comment', 'comment_review'])
                ->whereIn('student_id', $uniqueStudentIds)
                ->where('semester', $semester)
                ->where('school_year', $schoolYear)
                ->get()
                ->toArray();
        }

        $expectedCommentTypes = array_values(array_filter([
            'ptap',
            $semester === 'Fall' ? 'midterm' : null,
            $semester === 'Spring' ? 'final' : null,
        ]));

        $commentStats = [];
        $commentsByStudent = [];
        foreach ($commentRows as $row) {
            $sid = (int) ($row['student_id'] ?? 0);
            $type = strtolower(trim((string) ($row['score_type'] ?? '')));
            if ($type === '') {
                $type = 'general';
            }
            if (! isset($commentStats[$type])) {
                $commentStats[$type] = ['pending' => 0, 'reviewed' => 0];
            }

            $commentText = trim((string) ($row['comment'] ?? ''));
            $reviewValue = trim((string) ($row['comment_review'] ?? ''));

            if ($sid > 0 && $commentText !== '') {
                $commentsByStudent[$sid][$type] = $commentText;
            }

            if ($commentText === '') {
                continue;
            }

            if ($reviewValue === '') {
                $commentStats[$type]['pending']++;
            } else {
                $commentStats[$type]['reviewed']++;
            }
        }

        foreach ($expectedCommentTypes as $type) {
            if (! isset($commentStats[$type])) {
                $commentStats[$type] = ['pending' => 0, 'reviewed' => 0];
            }
        }

        $missingComments = 0;
        $missingDetail = [];
        foreach ($uniqueStudentIds as $sid) {
            foreach ($expectedCommentTypes as $type) {
                $text = $commentsByStudent[$sid][$type] ?? '';
                if ($text === '') {
                    $missingDetail[$type] = ($missingDetail[$type] ?? 0) + 1;
                    $missingComments++;
                }
            }
        }

        $commentTypes = [];
        foreach ($expectedCommentTypes as $type) {
            $stats = $commentStats[$type];
            $filled = $stats['pending'] + $stats['reviewed'];
            $completionPct = $totalStudents > 0 ? (int) round(min(100, ($filled / $totalStudents) * 100)) : 0;

            $commentTypes[$type] = [
                'label' => ucfirst($type).' comments',
                'pending' => $stats['pending'],
                'reviewed' => $stats['reviewed'],
                'filled' => $filled,
                'missing' => $missingDetail[$type] ?? 0,
                'expected' => $totalStudents,
                'completionPct' => $completionPct,
            ];
        }

        $totalPending = array_sum(array_column($commentTypes, 'pending'));
        $totalReviewed = array_sum(array_column($commentTypes, 'reviewed'));
        $totalFilled = array_sum(array_column($commentTypes, 'filled'));
        $totalExpected = array_sum(array_column($commentTypes, 'expected'));
        $commentCompletionPct = $totalExpected > 0 ? (int) round(min(100, ($totalFilled / $totalExpected) * 100)) : 0;

        $summary['commentSummary'] = [
            'total' => $totalFilled,
            'pendingReview' => $totalPending,
            'reviewed' => $totalReviewed,
            'missing' => $missingComments,
            'missingDetail' => $missingDetail,
            'completionPct' => $commentCompletionPct,
            'types' => $commentTypes,
        ];

        $attendanceRows = [];
        if (! empty($classSectionIds)) {
            $attendanceRows = AttendanceRecord::query()
                ->select(['student_id', 'class_section_id', 'total_absence'])
                ->whereIn('class_section_id', $classSectionIds)
                ->where('semester', $semester)
                ->where('school_year', $schoolYear)
                ->get()
                ->toArray();
        }

        $attendanceSet = [];
        $totalAbsences = 0;
        foreach ($attendanceRows as $record) {
            $studentId = (int) ($record['student_id'] ?? 0);
            $sectionId = (int) ($record['class_section_id'] ?? 0);
            if ($studentId <= 0 || $sectionId <= 0) {
                continue;
            }
            $key = "{$sectionId}:{$studentId}";
            $attendanceSet[$key] = true;
            $totalAbsences += (int) ($record['total_absence'] ?? 0);
        }

        $attendanceRecorded = count($attendanceSet);
        $attendancePct = $totalStudents > 0 ? (int) round(min(100, ($attendanceRecorded / $totalStudents) * 100)) : 0;
        $avgAbsence = $attendanceRecorded > 0 ? round($totalAbsences / $attendanceRecorded, 1) : 0;

        $summary['attendanceSummary'] = [
            'recorded' => $attendanceRecorded,
            'students' => $totalStudents,
            'completionPct' => $attendancePct,
            'avgAbsences' => $avgAbsence,
        ];

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

        $attendanceStatus = $this->buildAttendanceSubmissionStatus($classSectionIds, $semester, $schoolYear, $today);
        $summary['attendanceStatus'] = $attendanceStatus;

        $summary['deadlineEvents'] = Calendar::query()
            ->where('notify_teacher', 1)
            ->where('school_year', $schoolYear)
            ->where('semester', $semester)
            ->where('date', '>=', $today)
            ->orderBy('date', 'ASC')
            ->limit(5)
            ->get()
            ->toArray();

        if ($attendanceStatus['submitted'] === false && ! empty($classSectionIds)) {
            $summary['attendanceSummary']['completionPct'] = 0;
            $summary['attendanceSummary']['recorded'] = 0;
        }

        $summary['notifications'] = $this->buildDashboardNotifications($summary);

        return $summary;
    }

    private function buildDashboardNotifications(array $summary): array
    {
        $notifications = [];
        $buildScoreLink = static function (?string $focus): string {
            $base = '/teacher/scores';

            return $focus ? $base.'?focus='.urlencode($focus) : $base;
        };
        $determineFocus = static function (array $event): string {
            $eventTypeText = strtolower(trim((string) ($event['event_type'] ?? '')));
            if ($eventTypeText !== '' && str_contains($eventTypeText, 'draft')) {
                return 'comments';
            }
            $text = strtolower(trim(($event['title'] ?? '').' '.($event['description'] ?? '')));
            if ($text === '') {
                return 'scores';
            }
            if (str_contains($text, 'comment') || str_contains($text, 'ptap')) {
                return 'comments';
            }

            return 'scores';
        };
        $calendarLink = '/teacher/calendar';
        $attendanceLink = '/teacher/showupdate_attendance';
        $timezone = new DateTimeZone(date_default_timezone_get() ?: 'UTC');
        $todayDate = (new DateTimeImmutable('now', $timezone))->setTime(0, 0);

        $calendarNotificationConfig = [
            '1st Semester Scores' => 14,
            '2nd Semester Scores' => 14,
            'Final' => 14,
            'Final Exam Draft' => 42,
            'Midterm' => 14,
            'Midterm Exam Draft' => 42,
        ];

        $activeDeadline = false;
        foreach ($summary['deadlineEvents'] ?? [] as $event) {
            $eventTypeRaw = trim((string) ($event['event_type'] ?? ''));
            if ($eventTypeRaw === '') {
                continue;
            }
            $matchedType = null;
            $thresholdDays = null;
            foreach ($calendarNotificationConfig as $type => $days) {
                if (strcasecmp($eventTypeRaw, $type) === 0) {
                    $matchedType = $type;
                    $thresholdDays = $days;
                    break;
                }
            }
            if ($matchedType === null || $thresholdDays === null) {
                continue;
            }
            $rawDate = $event['date'] ?? '';
            if ($rawDate === '') {
                continue;
            }
            try {
                $eventDateTime = new DateTimeImmutable($rawDate, $timezone);
            } catch (\Exception $e) {
                continue;
            }
            $eventDateTime = $eventDateTime->setTime(0, 0);
            $daysUntil = (int) $todayDate->diff($eventDateTime)->format('%r%a');

            if ($daysUntil <= 0) {
                $activeDeadline = true;
                $eventFocus = $determineFocus($event);
                $notifications[] = [
                    'type' => 'danger',
                    'message' => sprintf(
                        'Deadline today: %s is due. Submit the remaining entries before the day ends.',
                        $matchedType
                    ),
                    'link' => $buildScoreLink($eventFocus),
                    'linkText' => 'Submit now',
                ];

                continue;
            }

            if ($daysUntil > $thresholdDays) {
                continue;
            }

            $relativeText = $daysUntil === 1 ? ' (tomorrow)' : " (in {$daysUntil} days)";
            $notifications[] = [
                'type' => 'warning',
                'message' => sprintf(
                    '%s is due on %s%s. Review it on the calendar so you don’t miss it.',
                    $matchedType,
                    $eventDateTime->format('M j, Y'),
                    $relativeText
                ),
                'link' => $calendarLink,
                'linkText' => 'View deadline',
            ];
        }

        if (! $activeDeadline) {
            $scoreLabel = $summary['scoreSummary']['fieldLabel'] ?? 'Score';
            if (! empty($summary['scoreSummary']['missing'] ?? 0)) {
                $notifications[] = [
                    'type' => 'warning',
                    'message' => sprintf(
                        'You have %s %s entries missing on the scores page. Please finish submitting them.',
                        (int) $summary['scoreSummary']['missing'],
                        $scoreLabel
                    ),
                    'link' => $buildScoreLink('scores'),
                    'linkText' => 'Score sheet',
                ];
            }

            foreach (['midterm', 'final', 'ptap'] as $type) {
                $count = (int) ($summary['commentSummary']['missingDetail'][$type] ?? 0);
                if ($count <= 0) {
                    continue;
                }
                $notifications[] = [
                    'type' => 'warning',
                    'message' => sprintf(
                        '%s comment missing for %s student(s). Leave comments on the scores page.',
                        ucfirst($type),
                        $count
                    ),
                    'link' => $buildScoreLink('comments'),
                    'linkText' => ucfirst($type).' comments',
                ];
            }

            if (! empty($summary['participationSummary']['missing'] ?? 0)) {
                $notifications[] = [
                    'type' => 'warning',
                    'message' => sprintf(
                        'Participation entries are still missing for %s student(s). Please add them from the scores page.',
                        (int) $summary['participationSummary']['missing']
                    ),
                    'link' => $buildScoreLink('scores'),
                    'linkText' => 'Participation',
                ];
            }
        }

        if (! empty($summary['attendanceStatus']['missingSections'] ?? [])) {
            $missingNames = $summary['attendanceStatus']['missingNames'] ?? [];
            $label = '';
            if (! empty($missingNames)) {
                $label = ' ('.implode(', ', array_slice($missingNames, 0, 3)).(count($missingNames) > 3 ? '…' : '').')';
            }
            $notifications[] = [
                'type' => 'danger',
                'message' => "Today's attendance is still unsubmitted for {$summary['attendanceStatus']['date']}{$label}. Please submit it now.",
                'link' => $attendanceLink,
                'linkText' => 'Record attendance',
            ];
        }

        return $notifications;
    }

    private function buildAttendanceSubmissionStatus(array $classSectionIds, string $semester, string $schoolYear, string $date): array
    {
        if (empty($classSectionIds)) {
            return [
                'date' => $date,
                'missingSections' => [],
                'missingNames' => [],
                'submitted' => true,
            ];
        }

        $rows = AttendanceDay::query()
            ->select(['class_section_id', 'status'])
            ->whereIn('class_section_id', $classSectionIds)
            ->where('date', $date)
            ->where('semester', $semester)
            ->where('school_year', $schoolYear)
            ->get()
            ->toArray();

        $statusMap = [];
        foreach ($rows as $row) {
            $csId = (int) ($row['class_section_id'] ?? 0);
            if ($csId <= 0) {
                continue;
            }
            $statusMap[$csId] = strtolower(trim((string) ($row['status'] ?? '')));
        }

        $missingSections = [];
        foreach ($classSectionIds as $classSectionId) {
            $status = $statusMap[$classSectionId] ?? '';
            if (! in_array($status, ['submitted', 'published', 'finalized'], true)) {
                $missingSections[] = $classSectionId;
            }
        }

        $missingNames = [];
        if (! empty($missingSections)) {
            $sectionRows = ClassSection::query()
                ->select(['class_section_id', 'class_section_name'])
                ->whereIn('class_section_id', $missingSections)
                ->get()
                ->toArray();
            foreach ($sectionRows as $row) {
                $name = trim((string) ($row['class_section_name'] ?? ''));
                if ($name === '') {
                    $name = (string) ($row['class_section_id'] ?? '');
                }
                $missingNames[] = $name;
            }
        }

        return [
            'date' => $date,
            'missingSections' => $missingSections,
            'missingNames' => $missingNames,
            'submitted' => empty($missingSections),
        ];
    }
}