use core::{alloc::Layout, time::Duration};

use bffs::path::Path;
use io::SeekFrom;

use crate::fs::File;

#[repr(u64)]
pub enum SysCall {
    Read = 0,
    Write = 1,
    Open = 2,
    Close = 3,
    Seek = 8,
    Alloc = 40,
    Dealloc = 41,
    Spawn = 58,
    ExecVE = 59,
    Exit = 60,
    NanoSleep = 101,
    WriteIntTemp = 998,
    WriteTemp = 999,
    Unimplemented = 1 << 31,
}

impl From<u64> for SysCall {
    fn from(value: u64) -> Self {
        match value {
            0 => SysCall::Read,
            1 => SysCall::Write,
            2 => SysCall::Open,
            3 => SysCall::Close,
            8 => SysCall::Seek,
            40 => SysCall::Alloc,
            41 => SysCall::Dealloc,
            58 => SysCall::Spawn,
            59 => SysCall::ExecVE,
            60 => SysCall::Exit,
            101 => SysCall::NanoSleep,
            998 => SysCall::WriteIntTemp,
            999 => SysCall::WriteTemp,
            _ => SysCall::Unimplemented,
        }
    }
}

#[allow(clippy::too_many_arguments)]
unsafe fn _syscall(
    syscall: SysCall,
    mut a1: u64,
    mut a2: u64,
    mut a3: u64,
    mut a4: u64,
    mut a5: u64,
    mut a6: u64,
    mut a7: u64,
) -> (u64, u64, u64, u64, u64, u64, u64, u64) {
    let mut a0 = syscall as u64;
    unsafe {
        core::arch::asm!(
            "ecall",
            inlateout("a0") a0,
            inlateout("a1") a1,
            inlateout("a2") a2,
            inlateout("a3") a3,
            inlateout("a4") a4,
            inlateout("a5") a5,
            inlateout("a6") a6,
            inlateout("a7") a7,
            clobber_abi("system")
        );
    }
    (a0, a1, a2, a3, a4, a5, a6, a7)
}

macro_rules! syscall {
    ($syscall:expr, $a1:expr, $a2:expr, $a3:expr, $a4:expr, $a5:expr, $a6:expr, $a7:expr) => {
        _syscall($syscall, $a1, $a2, $a3, $a4, $a5, $a6, $a7)
    };
    ($syscall:expr, $a1:expr, $a2:expr, $a3:expr, $a4:expr, $a5:expr, $a6:expr) => {
        syscall!($syscall, $a1, $a2, $a3, $a4, $a5, $a6, 0)
    };
    ($syscall:expr, $a1:expr, $a2:expr, $a3:expr, $a4:expr, $a5:expr) => {
        syscall!($syscall, $a1, $a2, $a3, $a4, $a5, 0)
    };
    ($syscall:expr, $a1:expr, $a2:expr, $a3:expr, $a4:expr) => {
        syscall!($syscall, $a1, $a2, $a3, $a4, 0)
    };
    ($syscall:expr, $a1:expr, $a2:expr, $a3:expr) => {
        syscall!($syscall, $a1, $a2, $a3, 0)
    };
    ($syscall:expr, $a1:expr, $a2:expr) => {
        syscall!($syscall, $a1, $a2, 0)
    };
    ($syscall:expr, $a1:expr) => {
        syscall!($syscall, $a1, 0)
    };
    ($syscall:expr) => {
        syscall!($syscall, 0)
    };
}

pub fn exit() {
    unsafe {
        syscall!(SysCall::Exit);
    }
}

pub fn sleep(duration: Duration) {
    unsafe {
        let (duration_secs, duration_nanos) = (duration.as_secs(), duration.subsec_nanos() as u64);
        syscall!(SysCall::NanoSleep, duration_secs, duration_nanos);
    }
}

pub fn write_string_temp(content: &str) {
    unsafe {
        syscall!(
            SysCall::WriteTemp,
            content.as_ptr() as u64,
            content.len() as u64
        );
    }
}
pub fn write_int_temp(content: u64) {
    unsafe {
        syscall!(SysCall::WriteIntTemp, content);
    }
}

pub fn alloc(layout: Layout) -> *mut u8 {
    unsafe {
        let size = layout.size();
        let align = layout.align();
        let (ptr, ..) = syscall!(SysCall::Alloc, size as u64, align as u64);
        ptr as *mut u8
    }
}
pub fn dealloc(ptr: *mut u8, layout: core::alloc::Layout) {
    unsafe {
        let size = layout.size();
        let align = layout.align();
        syscall!(SysCall::Dealloc, ptr as u64, size as u64, align as u64);
    }
}
pub fn open<P: AsRef<Path>>(path: P) -> File {
    unsafe {
        let path_str = path.as_ref().as_str();
        let ptr = path_str.as_ptr();
        let size = path_str.len();
        let (fd, ..) = syscall!(SysCall::Open, ptr as u64, size as u64);
        File::from_raw_fd(fd)
    }
}
pub fn close(file_descriptor: u64) {
    unsafe {
        syscall!(SysCall::Close, file_descriptor);
    }
}
pub fn write(file_descriptor: u64, buf: &[u8]) -> u64 {
    unsafe {
        let ptr = buf.as_ptr();
        let size = buf.len();
        let (len, ..) = syscall!(SysCall::Write, file_descriptor, ptr as u64, size as u64);
        len
    }
}
pub fn read(file_descriptor: u64, buf: &mut [u8]) -> u64 {
    unsafe {
        let ptr = buf.as_ptr();
        let size = buf.len();
        let (len, ..) = syscall!(SysCall::Read, file_descriptor, ptr as u64, size as u64);
        len
    }
}
pub fn seek(file_descriptor: u64, seek: SeekFrom) {
    unsafe {
        let (discriminant, value) = match seek {
            SeekFrom::Start(v) => (0, v),
            SeekFrom::End(v) => (1, v as u64),
            SeekFrom::Current(v) => (2, v as u64),
        };
        syscall!(SysCall::Seek, file_descriptor, discriminant, value);
    }
}
pub fn spawn<P: AsRef<Path>>(path: P) {
    unsafe {
        let path_str = path.as_ref().as_str();
        let ptr = path_str.as_ptr();
        let size = path_str.len();
        syscall!(SysCall::Spawn, ptr as u64, size as u64);
    }
}
pub fn execve<P: AsRef<Path>>(path: P) {
    unsafe {
        let path_str = path.as_ref().as_str();
        let ptr = path_str.as_ptr();
        let size = path_str.len();
        syscall!(SysCall::ExecVE, ptr as u64, size as u64);
    }
}