// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License..

use crate::cmp;
use crate::ffi::CStr;
use crate::io;
use crate::mem;
use crate::num::NonZeroUsize;
use crate::ptr;
use crate::sys::os;
use crate::time::Duration;

use sgx_trts::enclave;
use sgx_types::{sgx_ocalloc, sgx_ocfree, sgx_status_t};

pub struct Thread {
    id: libc::pthread_t,
}
// Some platforms may have pthread_t as a pointer in which case we still want
// a thread to be Send/Sync
unsafe impl Send for Thread {}
unsafe impl Sync for Thread {}

impl Thread {
    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
    pub unsafe fn new(p: Box<dyn FnOnce()>) -> io::Result<Thread> {
        let p = Box::into_raw(box p);
        let mut native: libc::pthread_t = mem::zeroed();
        let attr: libc::pthread_attr_t = mem::zeroed();
        let ret = libc::pthread_create(&mut native, &attr, thread_start, p as *mut _);

        return if ret != 0 {
            // The thread failed to start and as a result p was not consumed. Therefore, it is
            // safe to reconstruct the box so that it gets deallocated.
            drop(Box::from_raw(p));
            if ret == libc::EAGAIN {
                Err(io::Error::from_sgx_error(sgx_status_t::SGX_ERROR_OUT_OF_TCS))
            } else {
                Err(io::Error::from_raw_os_error(ret))
            }
        } else {
            Ok(Thread { id: native })
        };

        extern "C" fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
            unsafe {
                // Finally, let's run some code.
                Box::from_raw(main as *mut Box<dyn FnOnce()>)();
            }
            ptr::null_mut()
        }
    }

    pub fn yield_now() {
        let ret = unsafe { libc::sched_yield() };
        debug_assert_eq!(ret, 0);
    }

    pub fn set_name(name: &CStr) {
        const PR_SET_NAME: libc::c_int = 15;
        // pthread wrapper only appeared in glibc 2.12, so we use syscall
        // directly.
        let name = name.to_bytes_with_nul();
        unsafe {
            let ptr = sgx_ocalloc(name.len());
            if !ptr.is_null() {
                ptr::copy_nonoverlapping(name.as_ptr() as *const u8, ptr as *mut u8, name.len());
                libc::prctl(PR_SET_NAME, ptr as libc::c_ulong, 0, 0, 0);
                sgx_ocfree();
            }
        }
    }

    pub fn sleep(dur: Duration) {
        let mut secs = dur.as_secs();
        let mut nsecs = dur.subsec_nanos() as _;

        // If we're awoken with a signal then the return value will be -1 and
        // nanosleep will fill in `ts` with the remaining time.
        unsafe {
            while secs > 0 || nsecs > 0 {
                let mut ts = libc::timespec {
                    tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
                    tv_nsec: nsecs,
                };
                secs -= ts.tv_sec as u64;
                let ts_ptr = &mut ts as *mut _;
                if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
                    assert_eq!(os::errno(), libc::EINTR);
                    secs += ts.tv_sec as u64;
                    nsecs = ts.tv_nsec;
                } else {
                    nsecs = 0;
                }
            }
        }
    }

    pub fn join(self) {
        unsafe {
            let ret = libc::pthread_join(self.id, ptr::null_mut());
            mem::forget(self);
            assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
        }
    }

    pub fn id(&self) -> libc::pthread_t {
        self.id
    }

    pub fn into_id(self) -> libc::pthread_t {
        let id = self.id;
        mem::forget(self);
        id
    }
}

impl Drop for Thread {
    fn drop(&mut self) {
        //let ret = unsafe { libc::pthread_detach(self.id) };
        //debug_assert_eq!(ret, 0);
    }
}

pub fn available_parallelism() -> io::Result<NonZeroUsize> {
    let cpus = enclave::rsgx_get_cpu_core_num();
    NonZeroUsize::new(cpus as usize).ok_or_else(|| io::const_io_error!(
        io::ErrorKind::NotFound,
        "The number of hardware threads is not known for the target platform",
    ))
}

mod libc {
    pub use sgx_libc::ocall::{sched_yield, nanosleep, prctl};
    pub use sgx_libc::*;
    
}