use aya_bpf::{helpers::{bpf_get_current_task_btf, bpf_probe_read_kernel, bpf_probe_read_kernel_str_bytes, bpf_probe_read_user_str_bytes}, cty::{c_char, c_int, c_long}, maps::PerCpuArray};

use crate::{*, vmlinux::{task_struct, umode_t}};

const AT_FDCWD: c_int = -100;
const MAX_PATH: usize = 4096;

#[repr(C)]
pub struct Buffer<> {
    pub buf: [u8; MAX_PATH],
}

#[map]
static mut PATH_BUF: PerCpuArray<Buffer> = PerCpuArray::with_max_entries(1, 0);

#[map]
static mut TMP_BUF: PerCpuArray<Buffer> = PerCpuArray::with_max_entries(1, 0);

pub fn handle_sys_open(ctx: TracePointContext, syscall_type: SyscallType) -> Result<c_long, c_long> {
    //info!(&ctx, "called");
    match syscall_type {
        SyscallType::Enter => unsafe { handle_sys_open_enter(ctx) },
        SyscallType::Exit => unsafe { handle_sys_open_exit(ctx) },
    }
}

unsafe fn handle_sys_open_enter(ctx: TracePointContext) -> Result<c_long, c_long> {
    //info!(&ctx, "handle_sys_open_enter start");
    let mut task = bpf_get_current_task_btf() as *mut task_struct;

    #[repr(C)]
    #[derive(Clone, Copy)]
    struct OpenAtSyscallArgs {
        dfd: c_int,
        filename: *const c_char,
        flags: c_int,
        mode: umode_t,
    }

    let args = ctx.read_at::<OpenAtSyscallArgs>(16)?;

    if args.dfd != AT_FDCWD {
        return Err(1)
    }

    info!(&ctx, "relative call!");
    let pwd = get_task_pwd(&ctx, task)?;
    
    info!(&ctx, "PWD: {}", pwd);
    
    let buf = get_buf(&PATH_BUF)?;
    let filename = unsafe {
        core::str::from_utf8_unchecked(bpf_probe_read_user_str_bytes(
            args.filename as *const u8,
            &mut buf.buf,
        ).unwrap_unchecked())
    };

    info!(
        &ctx,
        "filename: {} dfd: {}",
        filename,
        args.dfd
    );
 
    Ok(0)
}

unsafe fn handle_sys_open_exit(ctx: TracePointContext) -> Result<c_long, c_long> {
    //info!(&ctx, "handle_sys_open_exit start");
    let ret = ctx.read_at::<c_long>(16)?; //TODO: We cant use unwrap, thats why we couldnt use the aya helper fns

    let tgid = ctx.tgid();
    if let Some(syscall) = SYSCALL_ENTERS.get(&tgid) {
        let SyscallInfo::Write(mut syscall_write) = syscall;
        syscall_write.ret = ret;
        EVENTS.output(&ctx, &SyscallInfo::Write(syscall_write), 0);
        let _ = SYSCALL_ENTERS.remove(&tgid);
        return Ok(0);
    }

    Err(0)
}

unsafe fn get_task_pwd<'a>(ctx: &TracePointContext, task: *const task_struct) -> Result<&'a str, c_long> {
    let result = get_buf(&PATH_BUF)?;
    let fs = bpf_probe_read_kernel(&(*task).fs)?;
    let pwd = bpf_probe_read_kernel(&(*fs).pwd)?;
    let rwada = bpf_probe_read_kernel(&pwd.dentry)?;
    let tmp_buf = get_buf(&TMP_BUF)?;
    let iname = bpf_probe_read_kernel_str_bytes(&(*rwada).d_iname as *const u8, &mut tmp_buf.buf)?;
    for i in 0..iname.len() {
        *result.buf.as_mut_ptr().add(i) = iname[i];
    }
    *result.buf.as_mut_ptr().add(iname.len()) = 0; //idk why we have to index like this

    Ok(str_from_u8_nul_utf8_unchecked(&result.buf))
}

unsafe fn get_buf<'a>(buf: &PerCpuArray<Buffer>) -> Result<&'a mut Buffer, i64>{
    let ptr = buf.get_ptr_mut(0).ok_or(1)?;
    Ok(&mut *ptr)
}

unsafe fn str_from_u8_nul_utf8_unchecked(utf8_src: &[u8]) -> &str {
    let mut nul_range_end = utf8_src.len();
    for i in 0..utf8_src.len() {
        if i > 200 { //satisfy the verifier
            break;
        }
        if utf8_src[i] == b'\0' {
            nul_range_end = i;
            break;
        }
    }

    str::from_utf8_unchecked(&utf8_src[0..nul_range_end])
}