extern crate libc;
extern crate serde;
extern crate serde_json;

use libc::syscall;

use std::io::prelude::*;
use std::error::Error;
use std::fs::File;
use std::io::{ErrorKind, Read};

use std::mem::size_of;
use std::ffi::CString;


fn main() -> Result<(), Box<dyn Error>> {
    // TODO: Get the rootfs key and other parameters through RA/LA or PAL
    let rootfs_key = b"c7-32-b3-ed-44-df-ec-7b-25-2d-9a-32-38-8d-58-61";
    let rootfs_upper_layer = "../gen_rootfs_instance/mnt_unionfs/upper";
    let rootfs_lower_layer = "../gen_rootfs_instance/mnt_unionfs/lower";
    let rootfs_entry = "/bin";

    // Get the key of FS image if needed
    let key = {
        // TODO: Get the key through RA or LA
        let mut file = File::create("/etc/image_key")?;
       // Writes key.
        file.write(rootfs_key)?;

        const IMAGE_KEY_FILE: &str = "/etc/image_key";
        let key_str = load_key(IMAGE_KEY_FILE)?;
        let mut key: sgx_key_128bit_t = Default::default();
        parse_str_to_bytes(&key_str, &mut key)?;
        Some(key)
    };

    let key_ptr = key
        .as_ref()
        .map(|key| key as *const sgx_key_128bit_t)
        .unwrap_or(std::ptr::null());

    // Mount the image
    const SYS_MOUNT_FS: i64 = 363;

    // Set rootfs parameters
    let upper_layer_path =
        CString::new(rootfs_upper_layer).expect("CString::new failed");
    let lower_layer_path =
        CString::new(rootfs_lower_layer).expect("CString::new failed");
    let entry_point = CString::new(rootfs_entry).expect("CString::new failed");
    let hostfs_source = CString::new("/tmp").expect("CString::new failed");

    // Example envs. must end with null
    let env1 = CString::new("TEST=1234").unwrap();
    let env2 = CString::new("OCCLUM=NO").unwrap();
    let env3 = CString::new("TEST2=5678").unwrap();
    let envp = [env1.as_ptr(), env2.as_ptr(), env3.as_ptr(), std::ptr::null()];

    let rootfs_config: user_rootfs_config = user_rootfs_config {
        len: size_of::<user_rootfs_config>(),
        upper_layer_path: upper_layer_path.as_ptr(),
        lower_layer_path: lower_layer_path.as_ptr(),
        entry_point: entry_point.as_ptr(),
        hostfs_source: hostfs_source.as_ptr(),
        hostfs_target: std::ptr::null(),
        envp: envp.as_ptr()
    };

    let ret = unsafe { syscall(
        SYS_MOUNT_FS,
        key_ptr,
        &rootfs_config)
    };
    if ret < 0 {
        return Err(Box::new(std::io::Error::last_os_error()));
    }

    Ok(())
}

#[allow(non_camel_case_types)]
type sgx_key_128bit_t = [u8; 16];

#[repr(C)]
#[derive(Debug, Copy, Clone)]
#[allow(non_camel_case_types)]
struct user_rootfs_config {
    // length of the struct
    len: usize,
    // UnionFS type rootfs upper layer, read-write layer
    upper_layer_path: *const i8,
    // UnionFS type rootfs lower layer, read-only layer
    lower_layer_path: *const i8,
    entry_point: *const i8,
    // HostFS source path
    hostfs_source: *const i8,
    // HostFS target path, default value is "/host"
    hostfs_target: *const i8,
    // An array of pointers to null-terminated strings
    // and must be terminated by a null pointer
    envp: *const *const i8,
}

fn load_key(key_path: &str) -> Result<String, Box<dyn Error>> {
    let mut key_file = File::open(key_path)?;
    let mut key = String::new();
    key_file.read_to_string(&mut key)?;
    Ok(key.trim_end_matches(|c| c == '\r' || c == '\n').to_string())
}

fn parse_str_to_bytes(arg_str: &str, bytes: &mut [u8]) -> Result<(), Box<dyn Error>> {
    let bytes_str_vec = {
        let bytes_str_vec: Vec<&str> = arg_str.split('-').collect();
        if bytes_str_vec.len() != bytes.len() {
            return Err(Box::new(std::io::Error::new(
                ErrorKind::InvalidData,
                "The length or format of Key/MAC string is invalid",
            )));
        }
        bytes_str_vec
    };

    for (byte_i, byte_str) in bytes_str_vec.iter().enumerate() {
        bytes[byte_i] = u8::from_str_radix(byte_str, 16)?;
    }
    Ok(())
}