//! Counts its runs in its own data folder: the `storage` capability, which
//! it can do without (then it remembers nothing).

#![no_std]
#![forbid(unsafe_code)]
#![no_main]

extern crate libkos;

use libkos::fs::Storage;
use libkos::println;
use types::address::VirtualAddress;

const DATA_BUF_VA: VirtualAddress = VirtualAddress::from_raw(0x0180_0000);
const COUNT: &[u8] = b"count";

/// The number in the file, 0 if there is none yet.
fn read_count(fs: &mut Storage) -> u64 {
    let Ok(h) = fs.open(COUNT) else { return 0 };
    let mut buf = [0u8; 20];
    let n = fs.read(h, &mut buf).unwrap_or(0);
    let _ = fs.close(h);
    core::str::from_utf8(&buf[..n]).ok().and_then(|s| s.trim().parse().ok()).unwrap_or(0)
}

fn write_count(fs: &mut Storage, count: u64) -> bool {
    let mut digits = [0u8; 20];
    let mut n = 0;
    let mut v = count;
    loop {
        digits[n] = b'0' + (v % 10) as u8;
        n += 1;
        v /= 10;
        if v == 0 {
            break;
        }
    }
    digits[..n].reverse();
    let _ = fs.delete(COUNT);
    let Ok(h) = fs.create(COUNT) else { return false };
    let ok = fs.write(h, &digits[..n]) == Ok(n);
    let _ = fs.close(h);
    ok
}

fn main() {
    let Some(mut fs) = libkos::start::data().and_then(|d| Storage::attach(d, DATA_BUF_VA).ok()) else {
        println!("counter: not allowed to keep anything, so this is run 1 as far as it knows");
        return;
    };
    let count = read_count(&mut fs) + 1;
    if write_count(&mut fs, count) {
        println!("counter: run {} (kept in its own data folder)", count);
    } else {
        println!("counter: run {}, but it could not save that", count);
    }
}

libkos::entry!(main);