use libc::ioctl;
use libc::{c_ushort, STDIN_FILENO, STDOUT_FILENO, TIOCGWINSZ};
use nix::sys::termios;
use nix::sys::termios::{
    ControlFlags, InputFlags, LocalFlags, OutputFlags, SpecialCharacterIndices, Termios,
};
use std::os::unix::io::RawFd;

#[derive(Debug)]
pub struct TermSize {
    /// number of rows
    pub rows: u16,
    /// number of columns
    pub cols: u16,
}

#[repr(C)]
#[derive(Debug)]
struct UnixTermSize {
    /// number of rows
    pub rows: c_ushort,
    /// number of columns
    pub cols: c_ushort,
    x: c_ushort,
    y: c_ushort,
}

/// Convert Ctrl+letter chords to their
/// ASCII table equivalents
#[inline]
pub fn ctrl_key(c: char) -> char {
    let key = c as u8;

    if !c.is_ascii() {
        panic!("CTRL_KEY only accepts ASCII characters");
    }

    // Intentionally "overflow" u8 to wrap around to the
    // beginning of the ASCII table. Ctrl+a is 1, Ctrl+b is 2, etc.
    (key & 0x1f) as char
}

/// Get a `Termios` struct, for getting/setting terminal flags
pub fn get_termios(fd: RawFd) -> Termios {
    termios::tcgetattr(fd).unwrap()
}

/// Put terminal into raw mode so there is full control of terminal output
pub fn enable_raw_mode() {
    let mut raw = get_termios(STDIN_FILENO);

    raw.input_flags.remove(
        InputFlags::BRKINT
            | InputFlags::ICRNL
            | InputFlags::INPCK
            | InputFlags::ISTRIP
            | InputFlags::IXON,
    );

    raw.output_flags.remove(OutputFlags::OPOST);

    // 8 bit characters
    raw.control_flags |= ControlFlags::CS8;

    raw.local_flags
        .remove(LocalFlags::ECHO | LocalFlags::ICANON | LocalFlags::IEXTEN | LocalFlags::ISIG);

    raw.control_chars[SpecialCharacterIndices::VMIN as usize] = 0;
    raw.control_chars[SpecialCharacterIndices::VTIME as usize] = 1;

    // Raw mode or bust!
    termios::tcsetattr(STDIN_FILENO, termios::SetArg::TCSAFLUSH, &raw).unwrap();
}

/// Restore terminal to "cooked"/canonical mode
pub fn disable_raw_mode(original: &Termios) {
    termios::tcsetattr(STDIN_FILENO, termios::SetArg::TCSAFLUSH, original).unwrap();
}

/// Attempt to get the size of the terminal (in rows and columns) from an `ioctl` call
pub fn get_term_size() -> Option<TermSize> {
    let raw = UnixTermSize {
        rows: 0,
        cols: 0,
        x: 0,
        y: 0,
    };

    let r = unsafe { ioctl(STDOUT_FILENO, TIOCGWINSZ.into(), &raw) };

    if r == 0 {
        Some(TermSize {
            rows: raw.rows,
            cols: raw.cols,
        })
    } else {
        None
    }
}