//! Wall-clock time: the CMOS real-time clock read once at boot and anchored to the
//! monotonic clock, so a query is a cheap arithmetic offset — no per-call CMOS poll,
//! no lock, no SMP hazard on the shared 0x70/0x71 ports.
//!
//! Wall-clock *seconds* are mechanism the kernel owns, exactly like the monotonic
//! clock ([[time-architecture]]): reading the hardware's value is not policy.
//! Calendars, timezones, and formatting layer on top in user space. It exists so the
//! filesystem can stamp real timestamps (mtime) — see docs/zig-self-hosting.md.

const architecture = @import("architecture");

var boot_unix_seconds: u64 = 0;
var boot_nanos: u64 = 0;

/// Read the RTC once and anchor it to the monotonic clock. Call at boot, after the
/// monotonic clock is calibrated.
pub fn init() void {
    boot_unix_seconds = architecture.readRtcUnixSeconds();
    boot_nanos = architecture.nanos();
}

/// The current wall-clock time in Unix epoch seconds (UTC): the boot RTC value plus
/// the monotonic time elapsed since. Zero until `init` runs.
pub fn nowSeconds() u64 {
    return boot_unix_seconds + (architecture.nanos() -% boot_nanos) / 1_000_000_000;
}

/// The wall-clock time of boot itself (the RTC anchor) — what klog_status hands
/// the logger service to name a per-boot log directory. Zero until `init` runs.
pub fn bootSeconds() u64 {
    return boot_unix_seconds;
}
