//! time implementation for Redox, following http://pubs.opengroup.org/onlinepubs/7908799/xsh/time.h.html

use crate::{
    header::errno::EIO,
    platform::{self, types::*, Pal, Sys},
};

use self::constants::*;

pub mod constants;
mod strftime;

#[repr(C)]
#[derive(Default)]
pub struct timespec {
    pub tv_sec: time_t,
    pub tv_nsec: c_long,
}

#[cfg(target_os = "redox")]
impl<'a> From<&'a timespec> for syscall::TimeSpec {
    fn from(tp: &timespec) -> Self {
        Self {
            tv_sec: tp.tv_sec,
            tv_nsec: tp.tv_nsec as i32,
        }
    }
}

#[repr(C)]
pub struct tm {
    pub tm_sec: c_int,
    pub tm_min: c_int,
    pub tm_hour: c_int,
    pub tm_mday: c_int,
    pub tm_mon: c_int,
    pub tm_year: c_int,
    pub tm_wday: c_int,
    pub tm_yday: c_int,
    pub tm_isdst: c_int,
    pub tm_gmtoff: c_long,
    pub tm_zone: *const c_char,
}

unsafe impl Sync for tm {}

// The C Standard says that localtime and gmtime return the same pointer.
static mut TM: tm = tm {
    tm_sec: 0,
    tm_min: 0,
    tm_hour: 0,
    tm_mday: 0,
    tm_mon: 0,
    tm_year: 0,
    tm_wday: 0,
    tm_yday: 0,
    tm_isdst: 0,
    tm_gmtoff: 0,
    tm_zone: UTC,
};

// The C Standard says that ctime and asctime return the same pointer.
static mut ASCTIME: [c_char; 26] = [0; 26];

#[repr(C)]
pub struct itimerspec {
    pub it_interval: timespec,
    pub it_value: timespec,
}

pub struct sigevent;

#[no_mangle]
pub unsafe extern "C" fn asctime(timeptr: *const tm) -> *mut c_char {
    asctime_r(timeptr, &mut ASCTIME as *mut [i8; 26] as *mut i8)
}

#[no_mangle]
pub unsafe extern "C" fn asctime_r(tm: *const tm, buf: *mut c_char) -> *mut c_char {
    let tm = &*tm;
    let result = core::fmt::write(
        &mut platform::UnsafeStringWriter(buf as *mut u8),
        format_args!(
            "{:.3} {:.3}{:3} {:02}:{:02}:{:02} {}\n",
            DAY_NAMES[tm.tm_wday as usize],
            MON_NAMES[tm.tm_mon as usize],
            tm.tm_mday as usize,
            tm.tm_hour as usize,
            tm.tm_min as usize,
            tm.tm_sec as usize,
            (1900 + tm.tm_year)
        ),
    );
    match result {
        Ok(_) => buf,
        Err(_) => {
            platform::errno = EIO;
            core::ptr::null_mut()
        }
    }
}

#[no_mangle]
pub extern "C" fn clock() -> clock_t {
    let mut ts = core::mem::MaybeUninit::<timespec>::uninit();

    if clock_gettime(CLOCK_PROCESS_CPUTIME_ID, ts.as_mut_ptr()) != 0 {
        return -1;
    }
    let ts = unsafe { ts.assume_init() };

    if ts.tv_sec > time_t::max_value() / CLOCKS_PER_SEC
        || ts.tv_nsec / (1_000_000_000 / CLOCKS_PER_SEC)
            > time_t::max_value() - CLOCKS_PER_SEC * ts.tv_sec
    {
        return -1;
    }

    ts.tv_sec * CLOCKS_PER_SEC + ts.tv_nsec / (1_000_000_000 / CLOCKS_PER_SEC)
}

// #[no_mangle]
pub extern "C" fn clock_getres(clock_id: clockid_t, res: *mut timespec) -> c_int {
    unimplemented!();
}

#[no_mangle]
pub extern "C" fn clock_gettime(clock_id: clockid_t, tp: *mut timespec) -> c_int {
    Sys::clock_gettime(clock_id, tp)
}

// #[no_mangle]
pub extern "C" fn clock_settime(clock_id: clockid_t, tp: *const timespec) -> c_int {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn ctime(clock: *const time_t) -> *mut c_char {
    asctime(localtime(clock))
}

#[no_mangle]
pub unsafe extern "C" fn ctime_r(clock: *const time_t, buf: *mut c_char) -> *mut c_char {
    let mut tm1: tm = core::mem::uninitialized();
    localtime_r(clock, &mut tm1);
    asctime_r(&mut tm1, buf)
}

#[no_mangle]
pub extern "C" fn difftime(time1: time_t, time0: time_t) -> c_double {
    (time1 - time0) as c_double
}

// #[no_mangle]
pub extern "C" fn getdate(string: *const c_char) -> tm {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn gmtime(timer: *const time_t) -> *mut tm {
    gmtime_r(timer, &mut TM)
}

const MONTH_DAYS: [[c_int; 12]; 2] = [
    // Non-leap years:
    [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31],
    // Leap years:
    [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31],
];

#[inline(always)]
fn leap_year(year: c_int) -> bool {
    year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)
}

#[no_mangle]
pub unsafe extern "C" fn gmtime_r(clock: *const time_t, t: *mut tm) -> *mut tm {
    let clock = *clock;

    let mut day = (clock / (60 * 60 * 24)) as c_int;
    if clock < 0 && clock % (60 * 60 * 24) != 0 {
        // -1 because for negative values round upwards
        // -0.3 == 0, but we want -1
        day -= 1;
    }

    (*t).tm_sec = (clock % 60) as c_int;
    (*t).tm_min = ((clock / 60) % 60) as c_int;
    (*t).tm_hour = ((clock / (60 * 60)) % 24) as c_int;

    while (*t).tm_sec < 0 {
        (*t).tm_sec += 60;
        (*t).tm_min -= 1;
    }
    while (*t).tm_min < 0 {
        (*t).tm_min += 60;
        (*t).tm_hour -= 1;
    }
    while (*t).tm_hour < 0 {
        (*t).tm_hour += 24;
    }

    // Jan 1th was a thursday, 4th of a zero-indexed week.
    (*t).tm_wday = (day + 4) % 7;
    if (*t).tm_wday < 0 {
        (*t).tm_wday += 7;
    }

    let mut year = 1970;
    if day < 0 {
        while day < 0 {
            let days_in_year = if leap_year(year) { 366 } else { 365 };

            day += days_in_year;
            year -= 1;
        }
        (*t).tm_year = year - 1900;
        (*t).tm_yday = day + 1;
    } else {
        loop {
            let days_in_year = if leap_year(year) { 366 } else { 365 };

            if day < days_in_year {
                break;
            }

            day -= days_in_year;
            year += 1;
        }
        (*t).tm_year = year - 1900;
        (*t).tm_yday = day;
    }

    let leap = if leap_year(year) { 1 } else { 0 };
    (*t).tm_mon = 0;
    loop {
        let days_in_month = MONTH_DAYS[leap][(*t).tm_mon as usize];

        if day < days_in_month {
            break;
        }

        day -= days_in_month;
        (*t).tm_mon += 1;
    }
    (*t).tm_mday = 1 + day as c_int;

    (*t).tm_isdst = 0;
    (*t).tm_gmtoff = 0;
    (*t).tm_zone = UTC;

    t
}

#[no_mangle]
pub unsafe extern "C" fn localtime(clock: *const time_t) -> *mut tm {
    localtime_r(clock, &mut TM)
}

#[no_mangle]
pub unsafe extern "C" fn localtime_r(clock: *const time_t, t: *mut tm) -> *mut tm {
    // TODO: Change tm_isdst, tm_gmtoff, tm_zone
    gmtime_r(clock, t)
}

#[no_mangle]
pub unsafe extern "C" fn mktime(t: *mut tm) -> time_t {
    let mut year = (*t).tm_year + 1900;
    let mut month = (*t).tm_mon;
    let mut day = (*t).tm_mday as i64 - 1;

    let leap = if leap_year(year) { 1 } else { 0 };

    if year < 1970 {
        day = MONTH_DAYS[if leap_year(year) { 1 } else { 0 }][(*t).tm_mon as usize] as i64 - day;

        while year < 1969 {
            year += 1;
            day += if leap_year(year) { 366 } else { 365 };
        }

        while month < 11 {
            month += 1;
            day += MONTH_DAYS[leap][month as usize] as i64;
        }

        -(day * (60 * 60 * 24)
            - (((*t).tm_hour as i64) * (60 * 60) + ((*t).tm_min as i64) * 60 + (*t).tm_sec as i64))
    } else {
        while year > 1970 {
            year -= 1;
            day += if leap_year(year) { 366 } else { 365 };
        }

        while month > 0 {
            month -= 1;
            day += MONTH_DAYS[leap][month as usize] as i64;
        }

        (day * (60 * 60 * 24)
            + ((*t).tm_hour as i64) * (60 * 60)
            + ((*t).tm_min as i64) * 60
            + (*t).tm_sec as i64)
    }
}

#[no_mangle]
pub extern "C" fn nanosleep(rqtp: *const timespec, rmtp: *mut timespec) -> c_int {
    Sys::nanosleep(rqtp, rmtp)
}

#[no_mangle]
pub unsafe extern "C" fn strftime(
    s: *mut c_char,
    maxsize: size_t,
    format: *const c_char,
    timeptr: *const tm,
) -> size_t {
    let ret = strftime::strftime(
        &mut platform::StringWriter(s as *mut u8, maxsize),
        format,
        timeptr,
    );
    if ret < maxsize {
        ret
    } else {
        0
    }
}

// #[no_mangle]
pub extern "C" fn strptime(buf: *const c_char, format: *const c_char, tm: *mut tm) -> *mut c_char {
    unimplemented!();
}

#[no_mangle]
pub unsafe extern "C" fn time(tloc: *mut time_t) -> time_t {
    let mut ts = timespec::default();
    Sys::clock_gettime(CLOCK_REALTIME, &mut ts);
    if !tloc.is_null() {
        *tloc = ts.tv_sec
    };
    ts.tv_sec
}

#[no_mangle]
pub unsafe extern "C" fn timelocal(tm: *mut tm) -> time_t {
    //TODO: timezone
    timegm(tm)
}

#[no_mangle]
pub unsafe extern "C" fn timegm(tm: *mut tm) -> time_t {
    let mut y = (*tm).tm_year as time_t + 1900;
    let mut m = (*tm).tm_mon as time_t + 1;
    if m <= 2 {
        y -= 1;
        m += 12;
    }
    let d = (*tm).tm_mday as time_t;
    let h = (*tm).tm_hour as time_t;
    let mi = (*tm).tm_min as time_t;
    let s = (*tm).tm_sec as time_t;
    (365 * y + y / 4 - y / 100 + y / 400 + 3 * (m + 1) / 5 + 30 * m + d - 719561) * 86400
        + 3600 * h
        + 60 * mi
        + s
}

// #[no_mangle]
pub extern "C" fn timer_create(
    clock_id: clockid_t,
    evp: *mut sigevent,
    timerid: *mut timer_t,
) -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn timer_delete(timerid: timer_t) -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn tzset() {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn timer_settime(
    timerid: timer_t,
    flags: c_int,
    value: *const itimerspec,
    ovalue: *mut itimerspec,
) -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn timer_gettime(timerid: timer_t, value: *mut itimerspec) -> c_int {
    unimplemented!();
}

// #[no_mangle]
pub extern "C" fn timer_getoverrun(timerid: timer_t) -> c_int {
    unimplemented!();
}

/*
#[no_mangle]
pub extern "C" fn func(args) -> c_int {
    unimplemented!();
}
*/