// uptime — one-shot uptime monitor for /bin/uptime.
//
// Prints the seconds-since-boot, humanised, as a single key/value row, then
// exits — the focused sibling of sysinfo's broader summary, the same way
// cpuinfo focuses temperature + clock. The value comes from the architectural
// counter (sys_uptime), board-independent, so it reads the same under QEMU and
// on hardware.
//
// Print-and-exit, so it needs neither the alt-screen buffer nor readKey. Same
// coreutil recipe as cpuinfo / sysinfo (flibc _start shim, flibc_mem, single
// R+X PT_LOAD, stack buffers only). Kept out of the CI FSH_SCRIPT like sysinfo:
// the reading is non-deterministic and does not belong in the baseline-
// checkpoint trace. Source is Flash — flashc transpiles it to Zig at build
// time via addFlashSource.

use flibc
use console_ui

link "flibc_start"
link "flibc_mem"

fn sink(bytes []u8) void {
    _ = flibc.sys.write_fd(1, bytes.ptr, bytes.len)
}

export fn main(_ usize, _ argv) noreturn {
    console_ui.banner(sink, "FlashOS uptime")

    var buf [32]u8 = undefined
    console_ui.screen.kv(sink, "uptime", uptimeStr(&buf))

    flibc.exit()
}

// Seconds since boot, humanised: "<h>h <m>m <s>s", collapsing to "<s>s"
// under a minute. uptime() is monotonic across reads.
fn uptimeStr(buf []mut u8) []u8 {
    secs := flibc.sys.uptime()
    h := secs / 3600
    m := (secs % 3600) / 60
    s := secs % 60
    var i usize = 0
    if h > 0 {
        i += u64dec(buf[i..], h)
        buf[i] = 'h'
        i += 1
        buf[i] = ' '
        i += 1
    }
    if h > 0 || m > 0 {
        i += u64dec(buf[i..], m)
        buf[i] = 'm'
        i += 1
        buf[i] = ' '
        i += 1
    }
    i += u64dec(buf[i..], s)
    buf[i] = 's'
    i += 1
    return buf[0..i]
}

// Write `v` as decimal ASCII into `out` (>= 20 bytes for the u64 max),
// returning the byte count.
fn u64dec(out []mut u8, v u64) usize {
    if v == 0 {
        out[0] = '0'
        return 1
    }
    var tmp [20]u8 = undefined
    var n usize = 0
    var x u64 = v
    while x != 0 {
        tmp[n] = '0' + #as(u8, #intCast(x % 10))
        n += 1
        x /= 10
    }
    var i usize = 0
    while i < n {
        out[i] = tmp[n - 1 - i]
        i += 1
    }
    return n
}