#![no_std]
#![feature(asm)]
#![feature(linkage)]
#![feature(panic_info_message)]
#![feature(alloc_error_handler)]

#[macro_use]
pub mod console;
mod lang_items;
mod syscall;

extern crate alloc;
extern crate core;
#[macro_use]
extern crate bitflags;

use buddy_system_allocator::LockedHeap;
pub use console::{flush, STDIN, STDOUT};
pub use syscall::*;

const USER_HEAP_SIZE: usize = 16384;

static mut HEAP_SPACE: [u8; USER_HEAP_SIZE] = [0; USER_HEAP_SIZE];

#[global_allocator]
static HEAP: LockedHeap = LockedHeap::empty();

#[alloc_error_handler]
pub fn handle_alloc_error(layout: core::alloc::Layout) -> ! {
    panic!("Heap allocation error, layout = {:?}", layout);
}

#[no_mangle]
#[link_section = ".text.entry"]
pub extern "C" fn _start() -> ! {
    unsafe {
        HEAP.lock()
            .init(HEAP_SPACE.as_ptr() as usize, USER_HEAP_SIZE);
    }
    exit(main());
}

#[linkage = "weak"]
#[no_mangle]
fn main() -> i32 {
    panic!("Cannot find main!");
}

bitflags! {
    pub struct OpenFlags: u32 {
        const RDONLY = 0;
        const WRONLY = 1 << 0;
        const RDWR = 1 << 1;
        const CREATE = 1 << 9;
        const TRUNC = 1 << 10;
    }
}

#[repr(C)]
#[derive(Debug, Default)]
pub struct TimeVal {
    pub sec: usize,
    pub usec: usize,
}

impl TimeVal {
    pub fn new() -> Self {
        Self::default()
    }
}

#[repr(C)]
#[derive(Debug)]
pub struct Stat {
    /// ID of device containing file
    pub dev: u64,
    /// inode number
    pub ino: u64,
    /// file type and mode
    pub mode: StatMode,
    /// number of hard links
    pub nlink: u32,
    /// unused pad
    pad: [u64; 7],
}

impl Stat {
    pub fn new() -> Self {
        Stat {
            dev: 0,
            ino: 0,
            mode: StatMode::NULL,
            nlink: 0,
            pad: [0; 7],
        }
    }
}

impl Default for Stat {
    fn default() -> Self {
        Self::new()
    }
}

bitflags! {
    pub struct StatMode: u32 {
        const NULL  = 0;
        /// directory
        const DIR   = 0o040000;
        /// ordinary regular file
        const FILE  = 0o100000;
    }
}

const AT_FDCWD: isize = -100;

pub fn open(path: &str, flags: OpenFlags) -> isize {
    sys_openat(AT_FDCWD as usize, path, flags.bits, OpenFlags::RDWR.bits)
}

pub fn close(fd: usize) -> isize {
    if fd == STDOUT {
        console::flush();
    }
    sys_close(fd)
}

pub fn read(fd: usize, buf: &mut [u8]) -> isize {
    sys_read(fd, buf)
}

pub fn write(fd: usize, buf: &[u8]) -> isize {
    sys_write(fd, buf)
}

pub fn link(old_path: &str, new_path: &str) -> isize {
    sys_linkat(AT_FDCWD as usize, old_path, AT_FDCWD as usize, new_path, 0)
}

pub fn unlink(path: &str) -> isize {
    sys_unlinkat(AT_FDCWD as usize, path, 0)
}

pub fn fstat(fd: usize, st: &Stat) -> isize {
    sys_fstat(fd, st)
}

pub fn mail_read(buf: &mut [u8]) -> isize {
    sys_mail_read(buf)
}

pub fn mail_write(pid: usize, buf: &[u8]) -> isize {
    sys_mail_write(pid, buf)
}

pub fn exit(exit_code: i32) -> ! {
    console::flush();
    sys_exit(exit_code);
}

pub fn yield_() -> isize {
    sys_yield()
}

pub fn get_time() -> isize {
    let time = TimeVal::new();
    match sys_get_time(&time, 0) {
        0 => ((time.sec & 0xffff) * 1000 + time.usec / 1000) as isize,
        _ => -1,
    }
}

pub fn getpid() -> isize {
    sys_getpid()
}

pub fn fork() -> isize {
    sys_fork()
}

pub fn exec(path: &str) -> isize {
    sys_exec(path)
}

pub fn set_priority(prio: isize) -> isize {
    sys_set_priority(prio)
}

pub fn wait(exit_code: &mut i32) -> isize {
    loop {
        match sys_waitpid(-1, exit_code as *mut _) {
            -2 => {
                sys_yield();
            }
            n => {
                return n;
            }
        }
    }
}

pub fn waitpid(pid: usize, exit_code: &mut i32) -> isize {
    loop {
        match sys_waitpid(pid as isize, exit_code as *mut _) {
            -2 => {
                sys_yield();
            }
            n => {
                return n;
            }
        }
    }
}

pub fn sleep(period_ms: usize) {
    let start = get_time();
    while get_time() < start + period_ms as isize {
        sys_yield();
    }
}

pub fn mmap(start: usize, len: usize, prot: usize) -> isize {
    sys_mmap(start, len, prot)
}

pub fn munmap(start: usize, len: usize) -> isize {
    sys_munmap(start, len)
}

pub fn spawn(path: &str) -> isize {
    sys_spawn(path)
}

pub fn dup(fd: usize) -> isize {
    sys_dup(fd)
}
pub fn pipe(pipe_fd: &mut [usize]) -> isize {
    sys_pipe(pipe_fd)
}