use super::utils::{copy_cstr_into_wasm, write_to_buf};
use libc::{c_char, c_int, localtime, localtime_r, time as libc_time, time_t, timespec, tm};
use std::mem;
use std::time::SystemTime;

use time;

use crate::webassembly::Instance;

#[cfg(not(target_os = "windows"))]
use libc::{CLOCK_MONOTONIC, CLOCK_MONOTONIC_COARSE, CLOCK_REALTIME};

// some assumptions about the constants when targeting windows
#[cfg(target_os = "windows")]
const CLOCK_REALTIME: libc::c_int = 0;
#[cfg(target_os = "windows")]
const CLOCK_MONOTONIC: libc::c_int = 1;
#[cfg(target_os = "windows")]
const CLOCK_MONOTONIC_COARSE: libc::c_int = 6;

/// emscripten: _gettimeofday
pub extern "C" fn _gettimeofday(tp: c_int, tz: c_int, instance: &mut Instance) -> c_int {
    debug!("emscripten::_gettimeofday {} {}", tp, tz);
    #[repr(C)]
    struct GuestTimeVal {
        tv_sec: i32,
        tv_usec: i32,
    }

    assert!(
        tz == 0,
        "the timezone argument of `_gettimeofday` must be null"
    );
    unsafe {
        let now = SystemTime::now();
        let since_epoch = now.duration_since(SystemTime::UNIX_EPOCH).unwrap();
        let timeval_struct_ptr = instance.memory_offset_addr(0, tp as _) as *mut GuestTimeVal;

        (*timeval_struct_ptr).tv_sec = since_epoch.as_secs() as _;
        (*timeval_struct_ptr).tv_usec = since_epoch.subsec_nanos() as _;
    }
    0
}

/// emscripten: _clock_gettime
pub extern "C" fn _clock_gettime(clk_id: c_int, tp: c_int, instance: &mut Instance) -> c_int {
    debug!("emscripten::_clock_gettime {} {}", clk_id, tp);
    #[repr(C)]
    struct GuestTimeSpec {
        tv_sec: i32,
        tv_nsec: i32,
    }

    let timespec = match clk_id {
        CLOCK_REALTIME => time::get_time(),
        CLOCK_MONOTONIC | CLOCK_MONOTONIC_COARSE => {
            let precise_ns = time::precise_time_ns();
            time::Timespec::new(
                (precise_ns / 1000000000) as i64,
                (precise_ns % 1000000000) as i32,
            )
        }
        _ => panic!("Clock with id \"{}\" is not supported.", clk_id),
    };

    unsafe {
        let timespec_struct_ptr = instance.memory_offset_addr(0, tp as _) as *mut GuestTimeSpec;
        (*timespec_struct_ptr).tv_sec = timespec.sec as _;
        (*timespec_struct_ptr).tv_nsec = timespec.nsec as _;
    }
    0
}

/// emscripten: ___clock_gettime
pub extern "C" fn ___clock_gettime(clk_id: c_int, tp: c_int, instance: &mut Instance) -> c_int {
    debug!("emscripten::___clock_gettime {} {}", clk_id, tp);
    _clock_gettime(clk_id, tp, instance)
}

/// emscripten: _clock
pub extern "C" fn _clock() -> c_int {
    debug!("emscripten::_clock");
    0 // TODO: unimplemented
}

/// emscripten: _difftime
pub extern "C" fn _difftime(t0: u32, t1: u32) -> c_int {
    debug!("emscripten::_difftime");
    (t0 - t1) as _
}

#[repr(C)]
struct guest_tm {
    pub tm_sec: c_int,    // 0
    pub tm_min: c_int,    // 4
    pub tm_hour: c_int,   // 8
    pub tm_mday: c_int,   // 12
    pub tm_mon: c_int,    // 16
    pub tm_year: c_int,   // 20
    pub tm_wday: c_int,   // 24
    pub tm_yday: c_int,   // 28
    pub tm_isdst: c_int,  // 32
    pub tm_gmtoff: c_int, // 36
    pub tm_zone: c_int,   // 40
}

/// emscripten: _tvset
pub extern "C" fn _tvset() {
    debug!("emscripten::_tvset UNIMPLEMENTED");
}

/// formats time as a C string
unsafe extern "C" fn fmt_time(time: u32, instance: &Instance) -> *const c_char {
    let date = &*(instance.memory_offset_addr(0, time as _) as *mut guest_tm);

    let days = vec!["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];
    let months = vec![
        "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
    ];
    let year = 1900 + date.tm_year;

    let time_str = format!(
        // NOTE: TODO: Hack! The 14 accompanying chars are needed for some reason
        "{} {} {:2} {:02}:{:02}:{:02} {:4}\n\0\0\0\0\0\0\0\0\0\0\0\0\0",
        days[date.tm_wday as usize],
        months[date.tm_mon as usize],
        date.tm_mday,
        date.tm_hour,
        date.tm_min,
        date.tm_sec,
        year
    );

    time_str[0..26].as_ptr() as _
}

/// emscripten: _asctime
pub extern "C" fn _asctime(time: u32, instance: &mut Instance) -> u32 {
    debug!("emscripten::_asctime {}", time);

    unsafe {
        let time_str_ptr = fmt_time(time, instance);
        copy_cstr_into_wasm(instance, time_str_ptr)

        // let c_str = instance.memory_offset_addr(0, res as _) as *mut i8;
        // use std::ffi::CStr;
        // debug!("#### cstr = {:?}", CStr::from_ptr(c_str));
    }
}

/// emscripten: _asctime_r
pub extern "C" fn _asctime_r(time: u32, buf: u32, instance: &mut Instance) -> u32 {
    debug!("emscripten::_asctime_r {}, {}", time, buf);

    unsafe {
        // NOTE: asctime_r is specced to behave in an undefined manner if the algorithm would attempt
        //      to write out more than 26 bytes (including the null terminator).
        //      See http://pubs.opengroup.org/onlinepubs/9699919799/functions/asctime.html
        //      Our undefined behavior is to truncate the write to at most 26 bytes, including null terminator.
        let time_str_ptr = fmt_time(time, instance);
        write_to_buf(time_str_ptr, buf, 26, instance)

        // let c_str = instance.memory_offset_addr(0, res as _) as *mut i8;
        // use std::ffi::CStr;
        // debug!("#### cstr = {:?}", CStr::from_ptr(c_str));
    }
}

/// emscripten: _localtime
pub extern "C" fn _localtime(time_p: u32, instance: &mut Instance) -> c_int {
    debug!("emscripten::_localtime {}", time_p);
    // NOTE: emscripten seems to want tzset() called in this function
    //      https://stackoverflow.com/questions/19170721/real-time-awareness-of-timezone-change-in-localtime-vs-localtime-r

    let timespec = unsafe {
        let time_p_addr = instance.memory_offset_addr(0, time_p as _) as *mut i64;
        let seconds = *time_p_addr.clone();
        time::Timespec::new(seconds, 0)
    };
    let result_tm = time::at(timespec);

    unsafe {
        let tm_struct_offset = (instance.emscripten_data.as_ref().unwrap().malloc)(
            mem::size_of::<guest_tm>() as _,
            instance,
        );
        let tm_struct_ptr = instance.memory_offset_addr(0, tm_struct_offset as _) as *mut guest_tm;
        // debug!(
        //     ">>>>>>> time = {}, {}, {}, {}, {}, {}, {}, {}",
        //     result_tm.tm_sec, result_tm.tm_min, result_tm.tm_hour, result_tm.tm_mday,
        //     result_tm.tm_mon, result_tm.tm_year, result_tm.tm_wday, result_tm.tm_yday,
        // );
        (*tm_struct_ptr).tm_sec = result_tm.tm_sec;
        (*tm_struct_ptr).tm_min = result_tm.tm_min;
        (*tm_struct_ptr).tm_hour = result_tm.tm_hour;
        (*tm_struct_ptr).tm_mday = result_tm.tm_mday;
        (*tm_struct_ptr).tm_mon = result_tm.tm_mon;
        (*tm_struct_ptr).tm_year = result_tm.tm_year;
        (*tm_struct_ptr).tm_wday = result_tm.tm_wday;
        (*tm_struct_ptr).tm_yday = result_tm.tm_yday;
        (*tm_struct_ptr).tm_isdst = result_tm.tm_isdst;
        (*tm_struct_ptr).tm_gmtoff = 0;
        (*tm_struct_ptr).tm_zone = 0;

        tm_struct_offset as _
    }
}
/// emscripten: _localtime_r
pub extern "C" fn _localtime_r(time_p: u32, result: u32, instance: &mut Instance) -> c_int {
    debug!("emscripten::_localtime_r {}", time_p);

    // NOTE: emscripten seems to want tzset() called in this function
    //      https://stackoverflow.com/questions/19170721/real-time-awareness-of-timezone-change-in-localtime-vs-localtime-r

    unsafe {
        let seconds = instance.memory_offset_addr(0, time_p as _) as *const i64;
        let timespec = time::Timespec::new(*seconds, 0);
        let result_tm = time::at(timespec);

        // debug!(
        //     ">>>>>>> time = {}, {}, {}, {}, {}, {}, {}, {}",
        //     result_tm.tm_sec, result_tm.tm_min, result_tm.tm_hour, result_tm.tm_mday,
        //     result_tm.tm_mon, result_tm.tm_year, result_tm.tm_wday, result_tm.tm_yday,
        // );

        let result_addr = instance.memory_offset_addr(0, result as _) as *mut guest_tm;

        (*result_addr).tm_sec = result_tm.tm_sec;
        (*result_addr).tm_min = result_tm.tm_min;
        (*result_addr).tm_hour = result_tm.tm_hour;
        (*result_addr).tm_mday = result_tm.tm_mday;
        (*result_addr).tm_mon = result_tm.tm_mon;
        (*result_addr).tm_year = result_tm.tm_year;
        (*result_addr).tm_wday = result_tm.tm_wday;
        (*result_addr).tm_yday = result_tm.tm_yday;
        (*result_addr).tm_isdst = result_tm.tm_isdst;
        (*result_addr).tm_gmtoff = 0;
        (*result_addr).tm_zone = 0;

        result as _
    }
}

/// emscripten: _time
pub extern "C" fn _time(time_p: u32, instance: &mut Instance) -> time_t {
    debug!("emscripten::_time {}", time_p);

    unsafe {
        let time_p_addr = instance.memory_offset_addr(0, time_p as _) as *mut i64;
        libc_time(time_p_addr)
    }
}

/// emscripten: _strftime
pub extern "C" fn _strftime(
    s_ptr: c_int,
    maxsize: u32,
    format_ptr: c_int,
    tm_ptr: c_int,
    _instance: &mut Instance,
) -> time_t {
    debug!(
        "emscripten::_strftime {} {} {} {}",
        s_ptr, maxsize, format_ptr, tm_ptr
    );
    0
}