<?php

namespace App\Http\Controllers\Api;

use App\Models\Calendar;
use App\Models\Configuration;
use App\Models\Homework;
use Illuminate\Support\Facades\DB;
use Symfony\Component\HttpFoundation\Response;

class HomeworkTrackingController extends BaseApiController
{
    protected Calendar $calendar;
    protected Homework $homework;
    protected Configuration $config;
    protected string $schoolYear;
    protected string $semester;

    public function __construct()
    {
        parent::__construct();
        $this->calendar = model(Calendar::class);
        $this->homework = model(Homework::class);
        $this->config = model(Configuration::class);
        $this->schoolYear = (string) ($this->config->getConfig('school_year') ?? '');
        $this->semester = (string) ($this->config->getConfig('semester') ?? '');
    }

    /**
     * Get homework tracking data with Sunday-based schedule
     */
    public function index()
    {
        try {
            // Get date range from request or use defaults
            $startDate = $this->request->getGet('start_date') ?? '2025-09-21';
            $endDate = $this->request->getGet('end_date') ?? '2026-01-18';

            // Parse dates
            try {
                $start = new \DateTime($startDate);
            } catch (\Throwable $e) {
                $start = new \DateTime('today');
            }

            try {
                $end = new \DateTime($endDate);
            } catch (\Throwable $e) {
                $end = new \DateTime('today');
            }

            // Move start to the first Sunday on/after start
            if ((int)$start->format('w') !== 0) {
                $start = (clone $start)->modify('next sunday');
            }

            // Collect all Sundays within range
            $sundays = [];
            $d = clone $start;
            while ($d <= $end) {
                $sundays[] = $d->format('Y-m-d');
                $d->modify('+7 days');
            }

            // Map "no school" events by date (Y-m-d) using explicit DB flag
            $events = $this->calendar->getEventsBySchoolYear($this->schoolYear) ?? [];
            $eventDays = [];

            foreach ($events as $ev) {
                $ymd = substr((string)($ev['date'] ?? $ev['start_date'] ?? ''), 0, 10);
                $no = (int)($ev['no_school'] ?? 0);
                if ($ymd && $no === 1) {
                    $eventDays[$ymd] = true; // yellow highlight for no-school day
                }
            }

            // Map Sundays to ordinal homework_index, skipping event Sundays
            $dateToIndex = [];
            $idx = 0;
            foreach ($sundays as $ymd) {
                if (!isset($eventDays[$ymd])) {
                    $idx++;
                    $dateToIndex[$ymd] = $idx;
                } else {
                    $dateToIndex[$ymd] = null; // event day (no homework expected)
                }
            }

            // Aggregate homework presence + first entered date per class_section_id + homework_index
            $rows = DB::table('homework')
                ->select('class_section_id', 'homework_index', DB::raw('MIN(created_at) AS first_created'), DB::raw('COUNT(*) AS cnt'))
                ->where('school_year', $this->schoolYear)
                ->where('semester', $this->semester)
                ->groupBy('class_section_id', 'homework_index')
                ->get()
                ->toArray();

            $hasHomework = [];
            $hwEnteredAt = [];

            foreach ($rows as $r) {
                $csid = (int)($r->class_section_id ?? 0);
                $hi = (int)($r->homework_index ?? 0);
                $cnt = (int)($r->cnt ?? 0);

                if ($csid > 0 && $hi > 0 && $cnt > 0) {
                    $hasHomework[$csid][$hi] = true;
                    $dateStr = substr((string)($r->first_created ?? ''), 0, 10);
                    $hwEnteredAt[$csid][$hi] = $dateStr ?: null;
                }
            }

            // Build date-based presence mapped to the nearest prior non-NoSchool Sunday
            $rowsByDate = DB::table('homework')
                ->select(DB::raw('class_section_id, DATE(created_at) AS hw_date, MIN(created_at) AS first_created, COUNT(*) AS cnt'))
                ->where('school_year', $this->schoolYear)
                ->where('semester', $this->semester)
                ->groupBy(DB::raw('class_section_id, DATE(created_at)'))
                ->orderBy('hw_date', 'ASC')
                ->get()
                ->toArray();

            $hasHomeworkByDate = [];
            $hwEnteredAtByDate = [];

            foreach ($rowsByDate as $r) {
                $csid = (int)($r->class_section_id ?? 0);
                $d = substr((string)($r->hw_date ?? ''), 0, 10);
                $cnt = (int)($r->cnt ?? 0);
                $firstCreated = substr((string)($r->first_created ?? ''), 0, 10);

                if ($csid <= 0 || !$d || $cnt <= 0) {
                    continue;
                }

                // Find the index of the last Sunday on or before $d
                $baseIndex = -1;
                for ($i = count($sundays) - 1; $i >= 0; $i--) {
                    if ($sundays[$i] <= $d) {
                        $baseIndex = $i;
                        break;
                    }
                }

                if ($baseIndex < 0) {
                    continue;
                }

                // Map this homework day to only the nearest prior non–No School Sunday
                $j = $baseIndex;
                while ($j >= 0 && !empty($eventDays[$sundays[$j]])) {
                    $j--;
                }

                if ($j < 0) {
                    continue;
                }

                $sd = $sundays[$j];

                // Mark homework on that Sunday for this class_section (single mapping)
                $hasHomeworkByDate[$csid][$sd] = true;

                if (empty($hwEnteredAtByDate[$csid][$sd])) {
                    $hwEnteredAtByDate[$csid][$sd] = $firstCreated ?: $d;
                } else {
                    // Keep the earliest date for display
                    $existing = (string)$hwEnteredAtByDate[$csid][$sd];
                    $candidate = $firstCreated ?: $d;
                    if ($candidate && (!$existing || $candidate < $existing)) {
                        $hwEnteredAtByDate[$csid][$sd] = $candidate;
                    }
                }
            }

            // Fetch teachers and TAs per section for this term
            $teacherRows = DB::table('teacher_class as tc')
                ->select('tc.class_section_id', 'tc.position', 'cs.class_section_name', 'cs.class_id', 'u.firstname', 'u.lastname')
                ->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', $this->schoolYear)
                ->where('tc.semester', $this->semester)
                ->whereNotNull('tc.class_section_id')
                ->whereIn('tc.position', ['main', 'ta'])
                ->orderBy('cs.class_id', 'ASC')
                ->orderBy('cs.class_section_name', 'ASC')
                ->orderByRaw("FIELD(tc.position, 'main','ta')")
                ->orderBy('u.firstname', 'ASC')
                ->get()
                ->toArray();

            $bySection = [];

            foreach ($teacherRows as $r) {
                $sid = (int)($r->class_section_id ?? 0);
                if ($sid <= 0) continue;

                if (!isset($bySection[$sid])) {
                    $bySection[$sid] = [
                        'class_section_id' => $sid,
                        'class_id' => (int)($r->class_id ?? 0),
                        'class_section_name' => (string)($r->class_section_name ?? ''),
                        'teachers' => [],
                        'tas' => [],
                    ];
                }

                $name = trim(($r->firstname ?? '') . ' ' . ($r->lastname ?? ''));
                $pos = strtolower((string)($r->position ?? ''));

                if ($name !== '') {
                    if ($pos === 'main') {
                        $bySection[$sid]['teachers'][] = $name;
                    } elseif ($pos === 'ta') {
                        $bySection[$sid]['tas'][] = $name;
                    }
                }
            }

            $teachers = array_values($bySection);

            // Sort by grade order: KG(13) → Grade 1..11 → Youth(12) → others
            usort($teachers, function ($a, $b) {
                $ai = (int)($a['class_id'] ?? 0);
                $bi = (int)($b['class_id'] ?? 0);

                $ord = function ($cid) {
                    if ($cid === 13) return 0;      // KG first
                    if ($cid >= 1 && $cid <= 11) return $cid; // Grades 1..11
                    if ($cid === 12) return 99;     // Youth last of known
                    return 200 + $cid;              // any others after
                };

                $cmp = $ord($ai) <=> $ord($bi);
                if ($cmp !== 0) return $cmp;

                return strnatcasecmp($a['class_section_name'] ?? '', $b['class_section_name'] ?? '');
            });

            // Simple server-side pagination for rows (8 lines per page)
            $perPage = 8;
            $totalRows = count($teachers);
            $totalPages = max(1, (int)ceil($totalRows / $perPage));
            $page = (int) ($this->request->getGet('page') ?? 1);

            if ($page < 1) $page = 1;
            if ($page > $totalPages) $page = $totalPages;

            $offset = ($page - 1) * $perPage;
            $teachersPage = array_slice($teachers, $offset, $perPage);

            return $this->success([
                'semester' => $this->semester,
                'school_year' => $this->schoolYear,
                'sundays' => $sundays,
                'event_days' => $eventDays,
                'date_to_index' => $dateToIndex,
                'teachers' => $teachersPage,
                'has_homework' => $hasHomework,
                'hw_entered_at' => $hwEnteredAt,
                'has_homework_by_date' => $hasHomeworkByDate,
                'hw_entered_at_by_date' => $hwEnteredAtByDate,
                'pagination' => [
                    'page' => $page,
                    'total_pages' => $totalPages,
                    'per_page' => $perPage,
                    'total_rows' => $totalRows,
                ],
            ], 'Homework tracking retrieved successfully');
        } catch (\Throwable $e) {
            log_message('error', 'Homework tracking error: ' . $e->getMessage());
            return $this->respondError('Failed to retrieve homework tracking: ' . $e->getMessage(), Response::HTTP_INTERNAL_SERVER_ERROR);
        }
    }
}