use crate::api::clock::DATE_TIME_ZONE;
use crate::api::fs::{FileIO, IO};
use crate::sys;
use crate::sys::cmos::CMOS;

use time::{Duration, OffsetDateTime};

const DAYS_BEFORE_MONTH: [u64; 13] = [
    0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
];

#[derive(Debug, Clone)]
pub struct Uptime;

impl Uptime {
    pub fn new() -> Self {
        Self {}
    }

    pub fn size() -> usize {
        core::mem::size_of::<f64>()
    }
}

impl FileIO for Uptime {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, ()> {
        let time = uptime().to_be_bytes();
        let n = time.len();
        if buf.len() >= n {
            buf[0..n].clone_from_slice(&time);
            Ok(n)
        } else {
            Err(())
        }
    }

    fn write(&mut self, _buf: &[u8]) -> Result<usize, ()> {
        unimplemented!();
    }

    fn close(&mut self) {}

    fn poll(&mut self, event: IO) -> bool {
        match event {
            IO::Read => true,
            IO::Write => false,
        }
    }
}

// NOTE: This clock is monotonic
pub fn uptime() -> f64 {
    sys::time::time_between_ticks() * sys::time::ticks() as f64
}

#[derive(Debug, Clone)]
pub struct Realtime;

impl Realtime {
    pub fn new() -> Self {
        Self {}
    }

    pub fn size() -> usize {
        core::mem::size_of::<f64>()
    }
}

impl FileIO for Realtime {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, ()> {
        let time = realtime().to_be_bytes();
        let n = time.len();
        if buf.len() >= n {
            buf[0..n].clone_from_slice(&time);
            Ok(n)
        } else {
            Err(())
        }
    }

    fn write(&mut self, _buf: &[u8]) -> Result<usize, ()> {
        unimplemented!();
    }

    fn close(&mut self) {}

    fn poll(&mut self, event: IO) -> bool {
        match event {
            IO::Read => true,
            IO::Write => false,
        }
    }
}

// NOTE: This clock is not monotonic
pub fn realtime() -> f64 {
    let rtc = CMOS::new().rtc(); // Assuming GMT

    let ts = 86400 * days_before_year(rtc.year as u64)
           + 86400 * days_before_month(rtc.year as u64, rtc.month as u64)
           + 86400 * (rtc.day - 1) as u64
           + 3600 * rtc.hour as u64
           + 60 * rtc.minute as u64
           + rtc.second as u64;

    let fract = sys::time::time_between_ticks()
              * (sys::time::ticks() - sys::time::last_rtc_update()) as f64;

    (ts as f64) + fract
}

fn days_before_year(year: u64) -> u64 {
    (1970..year).fold(0, |days, y|
        days + if is_leap_year(y) { 366 } else { 365 }
    )
}

fn days_before_month(year: u64, month: u64) -> u64 {
    let leap_day = is_leap_year(year) && month > 2;
    DAYS_BEFORE_MONTH[(month as usize) - 1] + (leap_day as u64)
}

fn is_leap_year(year: u64) -> bool {
    if year % 4 != 0 {
        false
    } else if year % 100 != 0 {
        true
    } else if year % 400 != 0 {
        false
    } else {
        true
    }
}

pub fn init() {
    let s = realtime();
    let ns = Duration::nanoseconds(
        libm::floor(1e9 * (s - libm::floor(s))) as i64
    );
    let dt = OffsetDateTime::from_unix_timestamp(s as i64) + ns;
    let rtc = dt.format(DATE_TIME_ZONE);
    log!("RTC {}", rtc);
}

#[test_case]
fn test_uptime() {
    assert!(uptime() > 0.0);
}

#[test_case]
fn test_realtime() {
    assert!(realtime() > 1234567890.0);
}