<?php

namespace App\Services\Admin;

use Carbon\Carbon;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Mail;
use Throwable;

class TeacherSubmissionService
{
    public function __construct(
        private AdminContextService $context
    ) {}

    public function report(): array
    {
        $cfg = $this->context->currentConfig();
        $semester = (string) ($cfg['semester'] ?? '');
        $schoolYear = (string) ($cfg['school_year'] ?? '');

        $assignmentRows = DB::table('teacher_class as tc')
            ->select([
                'tc.class_section_id',
                'cs.class_section_name',
                'tc.teacher_id',
                'u.firstname',
                'u.lastname',
                'tc.position',
            ])
            ->leftJoin('classSection as cs', 'cs.class_section_id', '=', 'tc.class_section_id')
            ->leftJoin('users as u', 'u.id', '=', 'tc.teacher_id')
            ->where('tc.school_year', $schoolYear)
            ->where('tc.semester', $semester)
            ->orderBy('cs.class_section_name')
            ->get();

        $teachersBySection = [];
        foreach ($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',
            };

            $teacherFullName = trim(
                (string)($assignment->firstname ?? '') . ' ' . (string)($assignment->lastname ?? '')
            );
            $teacherId = (int) ($assignment->teacher_id ?? 0);

            if ($teacherId <= 0 || $teacherFullName === '') {
                continue;
            }

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

            $teachersBySection[$sectionId]['teachers'][] = [
                'id' => $teacherId,
                'label' => "{$positionLabel}: {$teacherFullName}",
                'role_key' => $roleKey,
            ];
        }

        $today = Carbon::now()->format('Y-m-d');

        $rows = [];
        $totalStatuses = 0;
        $missingItemCount = 0;
        $allTeacherIds = [];
        $allClassSectionIds = [];

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

            $studentIds = DB::table('student_class')
                ->where('class_section_id', $classSectionId)
                ->where('semester', $semester)
                ->where('school_year', $schoolYear)
                ->pluck('student_id')
                ->map(fn ($id) => (int) $id)
                ->filter(fn ($id) => $id > 0)
                ->values()
                ->all();

            $expected = count($studentIds);

            // semester_scores
            $midtermStudents = [];
            $participationStudents = [];

            $scoreRecords = DB::table('semester_scores')
                ->select('student_id', 'midterm_exam_score', 'participation_score')
                ->where('class_section_id', $classSectionId)
                ->where('semester', $semester)
                ->where('school_year', $schoolYear)
                ->get();

            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->midterm_exam_score ?? ''));
                if ($midtermValue !== '') {
                    $midtermStudents[$sid] = true;
                }

                $participationValue = trim((string) ($score->participation_score ?? ''));
                if ($participationValue !== '') {
                    $participationStudents[$sid] = true;
                }
            }

            // score_comments
            $midtermCommentStudents = [];
            $ptapCommentStudents = [];

            if (!empty($studentIds)) {
                $comments = DB::table('score_comments')
                    ->select('student_id', 'score_type', 'comment')
                    ->whereIn('student_id', $studentIds)
                    ->where('semester', $semester)
                    ->where('school_year', $schoolYear)
                    ->whereIn('score_type', ['midterm', 'ptap'])
                    ->get();

                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 === 'midterm') {
                        $midtermCommentStudents[$sid] = true;
                    }
                    if ($type === 'ptap') {
                        $ptapCommentStudents[$sid] = true;
                    }
                }
            }

            // attendance_days (today)
            $attendanceRow = DB::table('attendance_days')
                ->where('class_section_id', $classSectionId)
                ->where('semester', $semester)
                ->where('school_year', $schoolYear)
                ->where('date', $today)
                ->first();

            $attendanceSubmitted = $attendanceRow
                && in_array(
                    strtolower((string) ($attendanceRow->status ?? '')),
                    ['submitted', 'published', 'finalized'],
                    true
                );

            $teacherList = $section['teachers'] ?? [];
            if (!empty($teacherList)) {
                usort($teacherList, function (array $a, array $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[] = (int) $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);

            // CI original intentionally only counted score/comment statuses in summary (not attendance)
            $statusDetails = [
                'midterm_score_status' => $midtermScoreStatus,
                'midterm_comment_status' => $midtermCommentStatus,
                'participation_status' => $participationStatus,
                'ptap_comment_status' => $ptapCommentStatus,
            ];

            $missingItemsForSection = $this->buildMissingItems($statusDetails);
            $missingItemCount += count($missingItemsForSection);
            $totalStatuses += count($statusDetails);

            $rows[] = [
                'class_section' => $section['class_section'] ?? "Section {$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,
                'missing_items' => $missingItemsForSection,
                'student_count' => $expected,
            ];
        }

        $historyMap = [];
        $teacherIds = array_values(array_unique($allTeacherIds));
        $classSectionIds = array_values(array_unique($allClassSectionIds));

        if (!empty($teacherIds) && !empty($classSectionIds) && $this->hasTable('teacher_submission_notification_history')) {
            $historyRecords = DB::table('teacher_submission_notification_history as h')
                ->select([
                    'h.*',
                    'u.firstname',
                    'u.lastname',
                ])
                ->leftJoin('users as u', 'u.id', '=', 'h.admin_id')
                ->where('h.notification_category', 'teacher_submissions')
                ->whereIn('h.teacher_id', $teacherIds)
                ->whereIn('h.class_section_id', $classSectionIds)
                ->orderByDesc('h.sent_at')
                ->get();

            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 = $sentAt ? Carbon::parse($sentAt)->format('M j, Y g:i A') : '';

                $adminName = trim((string)($record->firstname ?? '') . ' ' . (string)($record->lastname ?? ''));
                if ($adminName === '') {
                    $adminName = 'Administrator';
                }

                $historyMap[$sectionId][$teacherId][] = [
                    'sent_at_text' => $sentAtText,
                    'admin_name' => $adminName,
                    'status' => strtolower((string) ($record->status ?? 'sent')),
                ];
            }

            // keep latest 3 per section/teacher, same as CI
            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 [
            'semester' => $semester,
            'school_year' => $schoolYear,
            'rows' => $rows,
            'notification_history' => $historyMap,
            'summary' => $summary,
        ];
    }

    /**
     * API payload format expected:
     * [
     *   'notify' => [sectionId => [teacherId => 1, ...], ...],
     *   'missing_items' => [sectionId => [teacherId => base64(json(items))]]
     * ]
     */
    public function sendNotifications(int $adminId, array $payload): array
    {
        $notify = $payload['notify'] ?? null;
        if (!is_array($notify)) {
            return [
                'message' => 'Select at least one teacher to notify.',
                'sent' => 0,
                'failed' => 0,
                'results' => [],
            ];
        }

        $missingItemsPayload = is_array($payload['missing_items'] ?? null) ? $payload['missing_items'] : [];

        $targets = [];
        foreach ($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;
                }

                $targets["{$sectionId}_{$teacherId}"] = [
                    'class_section_id' => $sectionId,
                    'teacher_id' => $teacherId,
                ];
            }
        }

        if (empty($targets)) {
            return [
                'message' => 'Select at least one teacher to notify.',
                'sent' => 0,
                'failed' => 0,
                'results' => [],
            ];
        }

        $targets = array_values($targets);

        $teacherIds = array_values(array_unique(array_map(
            fn ($t) => (int) $t['teacher_id'],
            $targets
        )));
        $classSectionIds = array_values(array_unique(array_map(
            fn ($t) => (int) $t['class_section_id'],
            $targets
        )));

        $classSectionMap = DB::table('classSection')
            ->select('class_section_id', 'class_section_name')
            ->whereIn('class_section_id', $classSectionIds)
            ->get()
            ->mapWithKeys(fn ($row) => [(int)$row->class_section_id => (string)($row->class_section_name ?? '')])
            ->all();

        $teacherLookup = DB::table('users')
            ->select('id', 'firstname', 'lastname', 'email')
            ->whereIn('id', $teacherIds)
            ->get()
            ->keyBy(fn ($row) => (int) $row->id);

        $adminUser = DB::table('users')->select('id', 'firstname', 'lastname')->where('id', $adminId)->first();
        $adminName = $adminUser
            ? trim((string)($adminUser->firstname ?? '') . ' ' . (string)($adminUser->lastname ?? ''))
            : '';
        if ($adminName === '') {
            $adminName = 'Administrator';
        }

        $cfg = $this->context->currentConfig();
        $scoreUrl = rtrim((string) config('app.url'), '/') . '/';

        $sentCount = 0;
        $failCount = 0;
        $results = [];

        foreach ($targets as $target) {
            $classSectionId = (int) $target['class_section_id'];
            $teacherId = (int) $target['teacher_id'];

            $teacher = $teacherLookup->get($teacherId);
            $sectionName = $classSectionMap[$classSectionId] ?? "Section {$classSectionId}";

            $teacherName = $teacher
                ? trim((string)($teacher->firstname ?? '') . ' ' . (string)($teacher->lastname ?? ''))
                : '';
            if ($teacherName === '') {
                $teacherName = 'Teacher';
            }

            $subject = "Reminder: Complete submissions for {$sectionName}";

            $missingPayload = $missingItemsPayload[$classSectionId][$teacherId] ?? '';
            $missingItems = $this->parseMissingItemsPayload((string) $missingPayload);

            if (!empty($missingItems)) {
                $missingText = e($this->formatMissingItemsText($missingItems));
                $missingNote = "<p>Outstanding items: {$missingText}.</p>";
            } else {
                $missingNote = "<p>Our records show no outstanding submissions for this section, but please verify if anything still needs attention.</p>";
            }

            $body = "<p>Dear {$teacherName},</p>"
                . "<p>Administration is gently reminding you to wrap up any remaining score submissions and/or comments for {$sectionName}.</p>"
                . $missingNote
                . "<p>Visit <a href=\"{$scoreUrl}\">Teacher Score Submission</a> to address any remaining items.</p>"
                . "<p>Thank you,<br>Al Rahma Administration</p>";

            $email = (string) ($teacher->email ?? '');
            $status = 'failed';
            $error = null;

            if ($email !== '' && filter_var($email, FILTER_VALIDATE_EMAIL)) {
                try {
                    Mail::html($body, function ($message) use ($email, $subject) {
                        $message->to($email)->subject($subject);
                    });
                    $status = 'sent';
                } catch (Throwable $e) {
                    $status = 'failed';
                    $error = $e->getMessage();
                }
            } else {
                $error = 'Missing or invalid email';
            }

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

            if ($this->hasTable('teacher_submission_notification_history')) {
                DB::table('teacher_submission_notification_history')->insert([
                    'teacher_id' => $teacherId,
                    'class_section_id' => $classSectionId,
                    'admin_id' => $adminId,
                    'notification_category' => 'teacher_submissions',
                    'message' => $this->truncateNotificationMessage($body),
                    'status' => $status,
                    'school_year' => $cfg['school_year'] ?? null,
                    'semester' => $cfg['semester'] ?? null,
                    'sent_at' => Carbon::now('UTC'),
                ]);
            }

            $results[] = [
                'teacher_id' => $teacherId,
                'class_section_id' => $classSectionId,
                'teacher_name' => $teacherName,
                'section_name' => $sectionName,
                'email' => $email,
                'status' => $status,
                'missing_items' => $missingItems,
                'error' => $error,
            ];
        }

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

        return [
            'message' => !empty($parts) ? implode(' and ', $parts) : 'No notifications were sent.',
            'sent' => $sentCount,
            'failed' => $failCount,
            'results' => $results,
        ];
    }

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

    private function buildMissingItems(array $statusMap): array
    {
        $labels = [
            'midterm_score_status' => 'midterm scores',
            'midterm_comment_status' => 'midterm comments',
            'participation_status' => 'participation',
            'ptap_comment_status' => 'PTAP comments',
            'attendance_status' => 'attendance',
        ];

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

        return array_values($items);
    }

    private function formatMissingItemsText(array $items): string
    {
        $items = array_values(array_unique(array_filter(array_map(
            fn ($v) => trim((string)$v),
            $items
        ))));

        $count = count($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 $roleKey): int
    {
        return match (strtolower($roleKey)) {
            'main' => 1,
            'ta' => 2,
            default => 3,
        };
    }

    private function truncateNotificationMessage(string $html, int $limit = 1000): string
    {
        $text = trim(strip_tags($html));
        if ($text === '') {
            return '';
        }

        return mb_strlen($text) <= $limit
            ? $text
            : mb_substr($text, 0, $limit) . '…';
    }

    private function parseMissingItemsPayload(string $payload): array
    {
        if ($payload === '') {
            return [];
        }

        $decodedRaw = base64_decode($payload, true);
        if ($decodedRaw === false) {
            return [];
        }

        $decoded = json_decode($decodedRaw, true);
        if (!is_array($decoded)) {
            return [];
        }

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

        return array_values(array_unique($items));
    }

    private function hasTable(string $table): bool
    {
        try {
            return DB::getSchemaBuilder()->hasTable($table);
        } catch (Throwable) {
            return false;
        }
    }
}