<?php
declare(strict_types=1);

namespace AttHc\Server;

final class Validate {
    /** Hard exit 422 with a message. */
    public static function fail(string $message): never {
        Http::error(422, 'invalid', $message);
        exit;
    }

    public static function requireString(array $body, string $key, int $maxLen = 1024): string {
        if (!isset($body[$key]) || !is_string($body[$key]) || $body[$key] === '') {
            self::fail("missing or empty string field: {$key}");
        }
        if (strlen($body[$key]) > $maxLen) self::fail("{$key} exceeds {$maxLen} chars");
        return $body[$key];
    }

    public static function optionalString(array $body, string $key, int $maxLen = 1024): ?string {
        if (!isset($body[$key])) return null;
        if (!is_string($body[$key])) self::fail("{$key} must be a string");
        if (strlen($body[$key]) > $maxLen) self::fail("{$key} exceeds {$maxLen} chars");
        return $body[$key];
    }

    public static function requireInt(array $body, string $key): int {
        if (!isset($body[$key]) || !is_int($body[$key])) {
            self::fail("missing or non-int field: {$key}");
        }
        return $body[$key];
    }

    public static function optionalInt(array $body, string $key): ?int {
        if (!isset($body[$key]) || $body[$key] === null) return null;
        if (!is_int($body[$key])) self::fail("{$key} must be an integer");
        return $body[$key];
    }

    /**
     * A calendar date as 'YYYY-MM-DD', or null.
     *
     * Absent, null, and '' all mean "no date" (the plugin sends '' when the tech
     * clears the field). Anything else must be a real date in exactly that
     * format — the round-trip comparison rejects both sloppy input ('2026-2-3')
     * and impossible dates ('2026-02-30', which createFromFormat would silently
     * roll forward to March 2nd).
     */
    public static function optionalDate(array $body, string $key): ?string {
        if (!isset($body[$key])) return null;
        if (!is_string($body[$key])) self::fail("{$key} must be a YYYY-MM-DD date string or null");

        $value = trim($body[$key]);
        if ($value === '') return null;

        $date = \DateTimeImmutable::createFromFormat('!Y-m-d', $value);
        if ($date === false || $date->format('Y-m-d') !== $value) {
            self::fail("{$key} must be a valid calendar date in YYYY-MM-DD format");
        }
        return $value;
    }

    public static function status(string $status): string {
        $valid = ['not_started', 'done', 'skipped', 'blocked', 'n_a'];
        if (!in_array($status, $valid, true)) self::fail('status must be one of ' . implode(', ', $valid));
        return $status;
    }
}