<?php

namespace App\Services\Whatsapp;

use App\Models\Configuration;
use App\Models\StudentClass;

class WhatsappContextService
{
    /** @var array<string,bool> */
    private array $rosterPresenceCache = [];

    public function schoolYear(?string $override = null): string
    {
        foreach ([
            $override,
            request()->query('school_year'),
            request()->header('X-School-Year'),
            Configuration::getConfig('school_year'),
        ] as $candidate) {
            $value = trim((string) ($candidate ?? ''));
            if ($value !== '') {
                return $value;
            }
        }

        return '';
    }

    public function semester(?string $override = null): string
    {
        foreach ([
            $override,
            request()->query('semester'),
            request()->header('X-Semester'),
            request()->header('X-Selected-Semester'),
            Configuration::getConfig('semester'),
        ] as $candidate) {
            $value = trim((string) ($candidate ?? ''));
            if ($value !== '') {
                return $value;
            }
        }

        return '';
    }

    /**
     * School-year aliases like 2025-2026, 2025/2026, 2025-26, 2025.
     *
     * @return array{0: array<int,string>, 1: string, 2: int}
     */
    public function schoolYearAliases(string $schoolYear): array
    {
        $trim = trim($schoolYear);
        $normalized = str_replace(["\u{2013}", "\u{2014}", '/'], '-', $trim);

        if (preg_match('/\b(20\d{2})\b/', $normalized, $m)) {
            $start = (int) $m[1];
        } else {
            $start = (int) date('Y');
        }

        $end = $start + 1;
        $canonical = $start.'-'.$end;

        $aliases = [
            $canonical,
            $start.'/'.$end,
            sprintf('%d-%02d', $start, $end % 100),
            (string) $start,
        ];

        return [array_values(array_unique($aliases)), $canonical, $start];
    }

    /**
     * Semester aliases for filtering.
     *
     * @return array<int,string>
     */
    public function semesterAliases(string $semester): array
    {
        $s = strtolower(trim($semester));
        if ($s === 'fall') {
            return ['fall', 'sem1', 'semester 1', '1', 'f'];
        }
        if ($s === 'spring') {
            return ['spring', 'sem2', 'semester 2', '2', 's'];
        }
        if ($s === 'summer') {
            return ['summer', 'sem3', '3'];
        }

        return $s === '' ? [] : [$s];
    }

    public function hasRosterForYear(string $schoolYear): bool
    {
        $year = trim($schoolYear);
        if ($year === '') {
            return false;
        }

        if (array_key_exists($year, $this->rosterPresenceCache)) {
            return $this->rosterPresenceCache[$year];
        }

        $exists = StudentClass::query()
            ->where('school_year', $year)
            ->exists();

        $this->rosterPresenceCache[$year] = $exists;

        return $exists;
    }
}