// Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.

// SPDX-License-Identifier: BSD-3-Clause

//! Wrapper for interpreting syscall exit codes.

use std::os::raw::c_int;

/// Wrapper to interpret syscall exit codes and provide a rustacean `io::Result`.

#[derive(Debug)]

pub struct SyscallReturnCode<T: From<i8> + Eq = c_int>(pub T);

impl<T: From<i8> + Eq> SyscallReturnCode<T> {

    /// Returns the last OS error if value is -1 or Ok(value) otherwise.

    pub fn into_result(self) -> std::io::Result<T> {

        if self.0 == T::from(-1) {

            Err(std::io::Error::last_os_error())

        } else {

            Ok(self.0)

        }

    }

    /// Returns the last OS error if value is -1 or Ok(()) otherwise.

    pub fn into_empty_result(self) -> std::io::Result<()> {

        self.into_result().map(|_| ())

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn test_syscall_ops() {

        let mut syscall_code = SyscallReturnCode(1);

        match syscall_code.into_result() {

            Ok(_value) => (),

            _ => unreachable!(),

        }

        syscall_code = SyscallReturnCode(-1);

        assert!(syscall_code.into_result().is_err());

        syscall_code = SyscallReturnCode(1);

        match syscall_code.into_empty_result() {

            Ok(()) => (),

            _ => unreachable!(),

        }

        syscall_code = SyscallReturnCode(-1);

        assert!(syscall_code.into_empty_result().is_err());

        let mut syscall_code_long = SyscallReturnCode(1i64);

        match syscall_code_long.into_result() {

            Ok(_value) => (),

            _ => unreachable!(),

        }

        syscall_code_long = SyscallReturnCode(-1i64);

        assert!(syscall_code_long.into_result().is_err());

    }

}