<?php

namespace App\Ingest;

use App\Scheduling\DueResolver;
use Carbon\CarbonImmutable;
use InvalidArgumentException;

final class DueAtParser
{
    private const DATE = '/^(\d{4})-(\d{2})-(\d{2})$/';
    private const LOCAL_DATETIME = '/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(?::(\d{2}))?$/';
    private const FIXED_DATETIME = '/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(?::(\d{2}))?(Z|[+-]\d{2}:\d{2})$/';

    public static function parse(string $raw): ParsedDue
    {
        if (preg_match(self::DATE, $raw, $m)) {
            self::assertDate((int) $m[1], (int) $m[2], (int) $m[3], $raw);

            return ParsedDue::local($raw, DueResolver::WHOLE_DAY);
        }

        if (preg_match(self::LOCAL_DATETIME, $raw, $m)) {
            self::assertDate((int) $m[1], (int) $m[2], (int) $m[3], $raw);
            self::assertTime((int) $m[4], (int) $m[5], (int) ($m[6] ?? 0), $raw);

            return ParsedDue::local(
                sprintf('%s-%s-%s', $m[1], $m[2], $m[3]),
                sprintf('%s:%s:%02d', $m[4], $m[5], (int) ($m[6] ?? 0)),
            );
        }

        if (preg_match(self::FIXED_DATETIME, $raw, $m)) {
            self::assertDate((int) $m[1], (int) $m[2], (int) $m[3], $raw);
            self::assertTime((int) $m[4], (int) $m[5], (int) ($m[6] ?? 0), $raw);

            try {
                return ParsedDue::fixed(CarbonImmutable::parse($raw));
            } catch (\Throwable $e) {
                throw new InvalidArgumentException("due_at: невалидная дата-время «{$raw}»", 0, $e);
            }
        }

        throw new InvalidArgumentException("due_at: ожидается YYYY-MM-DD, YYYY-MM-DDTHH:MM или дата-время со смещением, получено «{$raw}»");
    }

    private static function assertDate(int $y, int $m, int $d, string $raw): void
    {
        if (! checkdate($m, $d, $y)) {
            throw new InvalidArgumentException("due_at: несуществующая дата «{$raw}»");
        }
    }

    private static function assertTime(int $h, int $i, int $s, string $raw): void
    {
        if ($h > 23 || $i > 59 || $s > 59) {
            throw new InvalidArgumentException("due_at: невалидное время «{$raw}»");
        }
    }
}