//! `pthread.h` implementation.
//!
//! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/pthread.h.html>.

use alloc::collections::LinkedList;
use core::{cell::Cell, ptr::NonNull};

use crate::{
    error::Errno,
    header::{sched::*, time::timespec},
    platform::{
        Pal, Sys,
        types::{
            c_int, c_uchar, c_uint, c_void, clockid_t, pthread_attr_t, pthread_barrier_t,
            pthread_barrierattr_t, pthread_cond_t, pthread_condattr_t, pthread_key_t,
            pthread_mutex_t, pthread_mutexattr_t, pthread_once_t, pthread_rwlock_t,
            pthread_rwlockattr_t, pthread_spinlock_t, pthread_t, size_t,
        },
    },
    pthread,
};

pub fn e(result: Result<(), Errno>) -> i32 {
    match result {
        Ok(()) => 0,
        Err(Errno(error)) => error,
    }
}

#[derive(Clone, Copy)]
pub(crate) struct RlctAttr {
    pub detachstate: c_uchar,
    pub inheritsched: c_uchar,
    pub schedpolicy: c_uchar,
    pub scope: c_uchar,
    pub guardsize: size_t,
    pub stacksize: size_t,
    pub stack: size_t,
    pub param: sched_param,
    #[cfg(target_pointer_width = "32")]
    _pad: [u8; 12],
}

pub const _POSIX_THREADS: c_int = 1;

pub const PTHREAD_BARRIER_SERIAL_THREAD: c_int = -1;

pub const PTHREAD_CANCEL_ASYNCHRONOUS: c_int = 0;
pub const PTHREAD_CANCEL_ENABLE: c_int = 1;
pub const PTHREAD_CANCEL_DEFERRED: c_int = 2;
pub const PTHREAD_CANCEL_DISABLE: c_int = 3;
pub const PTHREAD_CANCELED: *mut c_void = (!0_usize) as *mut c_void;

pub const PTHREAD_CREATE_DETACHED: c_int = 0;
pub const PTHREAD_CREATE_JOINABLE: c_int = 1;

pub const PTHREAD_EXPLICIT_SCHED: c_int = 0;
pub const PTHREAD_INHERIT_SCHED: c_int = 1;

pub const PTHREAD_MUTEX_DEFAULT: c_int = 0;
pub const PTHREAD_MUTEX_ERRORCHECK: c_int = 1;
pub const PTHREAD_MUTEX_NORMAL: c_int = 2;
pub const PTHREAD_MUTEX_RECURSIVE: c_int = 3;

pub const PTHREAD_MUTEX_ROBUST: c_int = 0;
pub const PTHREAD_MUTEX_STALLED: c_int = 1;

pub const PTHREAD_PRIO_INHERIT: c_int = 0;

pub const PTHREAD_PRIO_NONE: c_int = 0;

pub const PTHREAD_PRIO_PROTECT: c_int = 0;

pub const PTHREAD_PROCESS_SHARED: c_int = 0;
pub const PTHREAD_PROCESS_PRIVATE: c_int = 1;

pub const PTHREAD_SCOPE_PROCESS: c_int = 0;
pub const PTHREAD_SCOPE_SYSTEM: c_int = 1;

pub mod attr;
pub use self::attr::*;

pub mod barrier;
pub use self::barrier::*;

pub mod cond;
pub use self::cond::*;

#[thread_local]
pub static mut fork_hooks: [LinkedList<extern "C" fn()>; 3] = [const { LinkedList::new() }; 3];

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_cancel.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_cancel(thread: pthread_t) -> c_int {
    match unsafe { pthread::cancel(&*thread.cast()) } {
        Ok(()) => 0,
        Err(Errno(error)) => error,
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_create.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_create(
    pthread: *mut pthread_t,
    attr: *const pthread_attr_t,
    start_routine: extern "C" fn(arg: *mut c_void) -> *mut c_void,
    arg: *mut c_void,
) -> c_int {
    let attr = unsafe { attr.cast::<RlctAttr>().as_ref() };

    match unsafe { pthread::create(attr, start_routine, arg) } {
        Ok(ptr) => {
            unsafe { core::ptr::write(pthread, ptr) };
            0
        }
        Err(Errno(code)) => code,
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_detach.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_detach(pthread: pthread_t) -> c_int {
    match unsafe { pthread::detach(&*pthread.cast()) } {
        Ok(()) => 0,
        Err(Errno(errno)) => errno,
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_equal.html>.
#[unsafe(no_mangle)]
pub extern "C" fn pthread_equal(pthread1: pthread_t, pthread2: pthread_t) -> c_int {
    core::ptr::eq(pthread1, pthread2).into()
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_atfork.html>.
#[unsafe(no_mangle)]
pub extern "C" fn pthread_atfork(
    prepare: Option<extern "C" fn()>,
    parent: Option<extern "C" fn()>,
    child: Option<extern "C" fn()>,
) -> c_int {
    if let Some(prepare) = prepare {
        unsafe {
            fork_hooks[0].push_back(prepare);
        }
    }
    if let Some(parent) = parent {
        unsafe {
            fork_hooks[1].push_back(parent);
        }
    }
    if let Some(child) = child {
        unsafe {
            fork_hooks[2].push_back(child);
        }
    }
    0
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_exit.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_exit(retval: *mut c_void) -> ! {
    unsafe { pthread::exit_current_thread(pthread::Retval(retval)) }
}

// Not in latest POSIX, mark as depreciated?
/// See <https://pubs.opengroup.org/onlinepubs/009696799/functions/pthread_getconcurrency.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_getconcurrency() -> c_int {
    // Redox and Linux threads are 1:1, not M:N.
    1
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_getcpuclockid.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_getcpuclockid(
    thread: pthread_t,
    clock_out: *mut clockid_t,
) -> c_int {
    match pthread::get_cpu_clkid(unsafe { &*thread.cast() }) {
        Ok(clock) => {
            unsafe { clock_out.write(clock) };
            0
        }
        Err(Errno(error)) => error,
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_getschedparam.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_getschedparam(
    thread: pthread_t,
    policy_out: *mut c_int,
    param_out: *mut sched_param,
) -> c_int {
    match pthread::get_sched_param(unsafe { &*thread.cast() }) {
        Ok((policy, param)) => {
            unsafe { policy_out.write(policy) };
            unsafe { param_out.write(param) };
            0
        }
        Err(Errno(error)) => error,
    }
}

pub mod tls;
pub use tls::*;

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_join.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_join(thread: pthread_t, retval: *mut *mut c_void) -> c_int {
    match unsafe { pthread::join(&*thread.cast()) } {
        Ok(pthread::Retval(ret)) => {
            if !retval.is_null() {
                unsafe { core::ptr::write(retval, ret) };
            }
            0
        }
        Err(Errno(error)) => error,
    }
}

pub mod mutex;
pub use self::mutex::*;

pub mod once;
pub use self::once::*;

pub mod rwlock;
pub use self::rwlock::*;

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_self.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_self() -> pthread_t {
    (unsafe { pthread::current_thread().unwrap_unchecked() }) as *const _ as *mut _
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_setcancelstate.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_setcancelstate(state: c_int, oldstate: *mut c_int) -> c_int {
    match pthread::set_cancel_state(state) {
        Ok(old) => {
            // POSIX doesn't imply oldstate can be NULL anywhere, but a lot of C code probably
            // relies on it...
            if let Some(oldstate) = NonNull::new(oldstate) {
                unsafe { oldstate.write(old) };
            }
            0
        }
        Err(Errno(error)) => error,
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_setcancelstate.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_setcanceltype(ty: c_int, oldty: *mut c_int) -> c_int {
    match pthread::set_cancel_type(ty) {
        Ok(old) => {
            // POSIX doesn't imply oldty can be NULL anywhere, but a lot of C code probably relies
            // on it...
            if let Some(oldty) = NonNull::new(oldty) {
                unsafe { oldty.write(old) };
            }
            0
        }
        Err(Errno(error)) => error,
    }
}

// Not in latest POSIX, mark as depreciated?
/// See <https://pubs.opengroup.org/onlinepubs/000095399/functions/pthread_setconcurrency.html>.
#[unsafe(no_mangle)]
pub extern "C" fn pthread_setconcurrency(concurrency: c_int) -> c_int {
    // Redox and Linux threads are 1:1, not M:N.
    0
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_setschedparam.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_setschedparam(
    thread: pthread_t,
    policy: c_int,
    param: *const sched_param,
) -> c_int {
    e(pthread::set_sched_param(
        unsafe { &*thread.cast() },
        policy,
        unsafe { &*param },
    ))
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_setschedprio.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_setschedprio(thread: pthread_t, prio: c_int) -> c_int {
    e(pthread::set_sched_priority(
        unsafe { &*thread.cast() },
        prio,
    ))
}

pub mod spin;
pub use self::spin::*;

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_setcancelstate.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn pthread_testcancel() {
    unsafe { pthread::testcancel() };
}

// Must be the same struct as defined in the pthread_cleanup_push macro.
#[repr(C)]
pub(crate) struct CleanupLinkedListEntry {
    routine: extern "C" fn(*mut c_void),
    arg: *mut c_void,
    prev: *const c_void,
}

#[thread_local]
pub(crate) static CLEANUP_LL_HEAD: Cell<*const CleanupLinkedListEntry> =
    Cell::new(core::ptr::null());

// TODO: unwind? setjmp/longjmp?

#[unsafe(no_mangle)]
pub unsafe extern "C" fn __relibc_internal_pthread_cleanup_push(new_entry: *mut c_void) {
    let new_entry = unsafe { &mut *new_entry.cast::<CleanupLinkedListEntry>() };

    new_entry.prev = CLEANUP_LL_HEAD.get().cast();
    CLEANUP_LL_HEAD.set(new_entry);
}
#[unsafe(no_mangle)]
pub unsafe extern "C" fn __relibc_internal_pthread_cleanup_pop(execute: c_int) {
    let prev_head = unsafe { CLEANUP_LL_HEAD.get().read() };
    CLEANUP_LL_HEAD.set(prev_head.prev.cast());

    if execute != 0 {
        (prev_head.routine)(prev_head.arg);
    }
}

pub(crate) unsafe fn run_destructor_stack() {
    unsafe { crate::cxa::__cxa_thread_finalize() };

    let mut ptr = CLEANUP_LL_HEAD.get();

    while !ptr.is_null() {
        let entry = unsafe { ptr.read() };
        ptr = entry.prev.cast();

        (entry.routine)(entry.arg);
    }
}