<?php

namespace App\Services\Admin;

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

class AdminNotificationService
{
    public function alertsPayload(): array
    {
        $admins = $this->fetchAdminNotificationUsers();
        $subjects = $this->notificationSubjectOptions();
        $assignedSubjects = [];
        $tableReady = $this->hasTable('admin_notification_subjects');

        if ($tableReady && !empty($admins)) {
            $adminIds = array_map('intval', array_column($admins, 'id'));

            $rows = DB::table('admin_notification_subjects')
                ->select('id', 'admin_id', 'subject')
                ->whereIn('admin_id', $adminIds)
                ->get();

            foreach ($rows as $row) {
                $adminId = (int) ($row->admin_id ?? 0);
                $subject = (string) ($row->subject ?? '');

                if ($adminId <= 0 || $subject === '') {
                    continue;
                }

                $assignedSubjects[$adminId] ??= [];
                $assignedSubjects[$adminId][$subject] = true;
            }
        }

        return [
            'admins' => $admins,
            'subjects' => $subjects,
            'assigned_subjects' => $assignedSubjects,
            'table_ready' => $tableReady,
        ];
    }

    /**
     * Input shape (API):
     * [
     *   'subjects' => [
     *      12 => ['finance' => true, 'attendance' => true],
     *      15 => ['general', 'events']
     *   ]
     * ]
     */
    public function saveSubjects(array $posted): array
    {
        if (!$this->hasTable('admin_notification_subjects')) {
            return [
                'ok' => false,
                'message' => 'Notification subject storage is missing. Run migrations first.',
                'updated' => 0,
            ];
        }

        $subjectsMap = $this->notificationSubjectOptions();
        $allowed = array_keys($subjectsMap);

        $admins = $this->fetchAdminNotificationUsers();
        $adminIds = array_map('intval', array_column($admins, 'id'));

        if (empty($adminIds)) {
            return [
                'ok' => true,
                'message' => 'No admins found to update.',
                'updated' => 0,
            ];
        }

        $existing = DB::table('admin_notification_subjects')
            ->select('id', 'admin_id', 'subject')
            ->whereIn('admin_id', $adminIds)
            ->get();

        $existingMap = [];
        foreach ($existing as $row) {
            $adminId = (int) ($row->admin_id ?? 0);
            $subject = (string) ($row->subject ?? '');
            if ($adminId <= 0 || $subject === '') {
                continue;
            }
            $existingMap[$adminId] ??= [];
            $existingMap[$adminId][$subject] = (int) ($row->id ?? 0);
        }

        $updates = 0;

        DB::transaction(function () use ($posted, $adminIds, $allowed, $existingMap, &$updates) {
            foreach ($adminIds as $adminId) {
                $subjectRaw = $posted[$adminId] ?? [];

                $selected = [];
                if (is_array($subjectRaw)) {
                    foreach ($subjectRaw as $key => $value) {
                        $candidate = is_string($key) ? $key : $value;
                        if (!is_string($candidate)) {
                            continue;
                        }
                        $candidate = trim($candidate);
                        if ($candidate !== '') {
                            $selected[] = $candidate;
                        }
                    }
                }

                $selected = array_values(array_unique(array_filter(
                    $selected,
                    fn ($value) => in_array($value, $allowed, true)
                )));

                $current = array_keys($existingMap[$adminId] ?? []);
                $toDelete = array_values(array_diff($current, $selected));
                $toInsert = array_values(array_diff($selected, $current));

                if (!empty($toDelete)) {
                    DB::table('admin_notification_subjects')
                        ->where('admin_id', $adminId)
                        ->whereIn('subject', $toDelete)
                        ->delete();

                    $updates += count($toDelete);
                }

                if (!empty($toInsert)) {
                    $batch = [];
                    foreach ($toInsert as $subject) {
                        $batch[] = [
                            'admin_id' => $adminId,
                            'subject' => $subject,
                        ];
                    }

                    DB::table('admin_notification_subjects')->insert($batch);
                    $updates += count($toInsert);
                }
            }
        });

        return [
            'ok' => true,
            'message' => $updates > 0 ? 'Notification subjects updated.' : 'No changes were made.',
            'updated' => $updates,
        ];
    }

    public function printRecipientsPayload(): array
    {
        $admins = $this->fetchAdminNotificationUsers();
        $tableReady = $this->hasTable('admin_notification_subjects');
        $assigned = [];

        if ($tableReady && !empty($admins)) {
            $adminIds = array_map('intval', array_column($admins, 'id'));

            $rows = DB::table('admin_notification_subjects')
                ->select('admin_id')
                ->where('subject', 'print_requests')
                ->whereIn('admin_id', $adminIds)
                ->get();

            foreach ($rows as $row) {
                $adminId = (int) ($row->admin_id ?? 0);
                if ($adminId > 0) {
                    $assigned[$adminId] = true;
                }
            }
        }

        return [
            'admins' => $admins,
            'assigned' => $assigned,
            'table_ready' => $tableReady,
        ];
    }

    /**
     * Input shape (API):
     * ['notify' => [12 => true, 15 => true]]
     */
    public function savePrintRecipients(array $postedNotify): array
    {
        if (!$this->hasTable('admin_notification_subjects')) {
            return [
                'ok' => false,
                'message' => 'Notification subject storage is missing. Run migrations first.',
                'updated' => 0,
            ];
        }

        $admins = $this->fetchAdminNotificationUsers();
        $adminIds = array_map('intval', array_column($admins, 'id'));

        if (empty($adminIds)) {
            return [
                'ok' => true,
                'message' => 'No admins found to update.',
                'updated' => 0,
            ];
        }

        $selected = [];
        foreach ((array) $postedNotify as $key => $value) {
            $adminId = (int) $key;
            if ($adminId <= 0) continue;
            if (!in_array($adminId, $adminIds, true)) continue;
            $selected[] = $adminId;
        }
        $selected = array_values(array_unique($selected));

        $existingRows = DB::table('admin_notification_subjects')
            ->select('admin_id')
            ->where('subject', 'print_requests')
            ->whereIn('admin_id', $adminIds)
            ->get();

        $current = array_values(array_unique(array_map(
            fn ($row) => (int) ($row->admin_id ?? 0),
            $existingRows->all()
        )));

        $toDelete = array_values(array_diff($current, $selected));
        $toInsert = array_values(array_diff($selected, $current));

        DB::transaction(function () use ($toDelete, $toInsert) {
            if (!empty($toDelete)) {
                DB::table('admin_notification_subjects')
                    ->where('subject', 'print_requests')
                    ->whereIn('admin_id', $toDelete)
                    ->delete();
            }

            if (!empty($toInsert)) {
                $batch = [];
                foreach ($toInsert as $adminId) {
                    $batch[] = [
                        'admin_id' => $adminId,
                        'subject' => 'print_requests',
                    ];
                }
                DB::table('admin_notification_subjects')->insert($batch);
            }
        });

        $changes = count($toDelete) + count($toInsert);

        return [
            'ok' => true,
            'message' => $changes > 0 ? 'Print notification recipients updated.' : 'No changes were made.',
            'updated' => $changes,
            'selected_admin_ids' => $selected,
        ];
    }

    public function notificationSubjectOptions(): array
    {
        return [
            'academics' => 'Academics',
            'attendance' => 'Attendance',
            'events' => 'Events',
            'finance' => 'Finance',
            'general' => 'General',
            'print_requests' => 'Print Requests',
        ];
    }

    private function getAdminNotificationExcludedRoles(): array
    {
        return [
            'parent',
            'student',
            'guest',
            'teacher',
            'assistant teacher',
            'teacher assistant',
            'teacher_assistant',
            'assistant_teacher',
            'ta',
            'authorized_user',
        ];
    }

    public function fetchAdminNotificationUsers(): array
    {
        $excluded = array_map(
            fn ($value) => strtolower(trim((string) $value)),
            $this->getAdminNotificationExcludedRoles()
        );

        // Safer than raw NOT IN string: use bindings + lower(name)
        $rows = DB::table('users as u')
            ->select('u.id', 'u.firstname', 'u.lastname', 'u.email')
            ->join('user_roles as ur', 'ur.user_id', '=', 'u.id')
            ->join('roles as r', 'r.id', '=', 'ur.role_id')
            ->whereNull('ur.deleted_at')
            ->whereNotNull('r.name')
            ->whereNotIn(DB::raw('LOWER(r.name)'), $excluded)
            ->groupBy('u.id', 'u.firstname', 'u.lastname', 'u.email')
            ->orderBy('u.lastname')
            ->orderBy('u.firstname')
            ->get();

        return $rows->map(function ($row) {
            return [
                'id' => (int) $row->id,
                'firstname' => (string) ($row->firstname ?? ''),
                'lastname' => (string) ($row->lastname ?? ''),
                'email' => (string) ($row->email ?? ''),
                'full_name' => trim((string)($row->firstname ?? '') . ' ' . (string)($row->lastname ?? '')),
            ];
        })->all();
    }

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