#pragma once

#include <Arduino.h>
#include <time.h>

// Returns true if the system clock has been set to a plausible time (year >= 2020).
inline bool hasValidTime() {
    time_t now = time(nullptr);
    struct tm t;
    gmtime_r(&now, &t);
    return (t.tm_year + 1900) >= 2020;
}

// Returns the current UTC time as an ISO 8601 string (e.g., "2026-08-04T17:30:00.000Z").
inline String isoNow() {
    time_t now = time(nullptr);
    struct tm t;
    gmtime_r(&now, &t);
    char buf[32];
    strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S.000Z", &t);
    return String(buf);
}

// Returns (now - 30 days) as an ISO 8601 UTC string.
inline String isoNowMinus30d() {
    time_t now = time(nullptr);
    now -= 30 * 24 * 3600;  // Subtract 30 days in seconds
    struct tm t;
    gmtime_r(&now, &t);
    char buf[32];
    strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S.000Z", &t);
    return String(buf);
}