use crsn::asm::data::literal::Value;
use crsn::asm::error::CrsnError;
use crsn::asm::instr::op::OpKind;
use crsn::asm::parse::arg_parser::TokenParser;
use crsn::module::{CrsnExtension, ParseRes, CrsnUniq};
use crsn::runtime::fault::Fault;
use crsn::runtime::run_thread::{RunState};
use crsn::sexp::SourcePosition;
use std::convert::TryFrom;
use std::io;
use crsn::asm::instr::cond::Flag;
use std::fmt;

mod console {
    use std::{io};
    use std::os::unix::io::RawFd;

    use std::ffi::c_void;
    use std::mem::{self, MaybeUninit};

    fn setup_fd(fd: RawFd) -> io::Result<libc::termios> {
        use libc::*;

        let mut tio = MaybeUninit::uninit();
        if 0 != unsafe { tcgetattr(fd, tio.as_mut_ptr()) } {
            return Err(io::Error::last_os_error());
        }
        let mut tio = unsafe { MaybeUninit::assume_init(tio) };
        let old_tio : termios = unsafe { mem::transmute_copy(&tio) };

        tio.c_iflag &= !(/*BRKINT |*/ /*ICRNL |*/ INPCK | ISTRIP | IXON);
        tio.c_oflag |= ONLCR;
        tio.c_cflag |= CS8;
        tio.c_lflag &= !(ECHO | ICANON | IEXTEN /*| ISIG*/);
        tio.c_cc[VMIN] = 1;
        tio.c_cc[VTIME] = 0;
        if 0 != unsafe { tcsetattr(fd, TCSANOW, &tio) } {
            return Err(io::Error::last_os_error());
        }

        Ok(old_tio)
    }

    pub fn init_io() -> io::Result<libc::termios> {
        setup_fd(libc::STDIN_FILENO)
    }

    pub fn read_byte() -> io::Result<u8> {
        let mut buf = 0u8;
        let len = unsafe { libc::read(libc::STDIN_FILENO, &mut buf as *mut u8 as *mut c_void, 1) };
        if len <= 0 {
            Err(io::Error::last_os_error())
        } else {
            Ok(buf as u8)
        }
    }

    pub fn write_byte(b : u8) -> io::Result<()> {
        let len = unsafe { libc::write(libc::STDOUT_FILENO, &b as *const u8 as *const c_void, 1) };
        if len <= 0 {
            Err(io::Error::last_os_error())
        } else {
            Ok(())
        }
    }

    pub fn write_char(c : char) -> io::Result<()> {
        let mut buf = [0u8; 4];
        for b in c.encode_utf8(&mut buf).as_bytes() {
            write_byte(*b)?;
        }
        Ok(())
    }

    pub fn read_char() -> io::Result<char> {
        let first = read_byte()?;

        if first & 0x80 == 0 {
            return Ok(first as char);
        }

        let mut bytes = [first, 0, 0, 0];

        let remain = if first & 0b1110_0000 == 0b1100_0000 {
            1
        } else if first & 0b1111_0000 == 0b1110_0000 {
            2
        } else /*if first & 0b1111_1000 == 0b1111_0000*/ {
            3
        };

        for n in 1..=remain {
            bytes[n] = read_byte()?;
        }

        std::str::from_utf8(&bytes[..=remain])
            .map(|s| s.chars().nth(0).unwrap())
            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
    }
}

#[derive(Clone)]
pub struct StdioOps {
    old_tio: Option<libc::termios>,
    hdl_stdin : Value,
    hdl_stdin_raw : Value,
    hdl_stdout : Value,
    hdl_stdout_raw : Value,
}

impl fmt::Debug for StdioOps {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("StdioOps")
            .field("hdl_stdin", &format_args!("0x{:08x}", self.hdl_stdin))
            .field("hdl_stdin_raw", &format_args!("0x{:08x}", self.hdl_stdin_raw))
            .field("hdl_stdout", &format_args!("0x{:08x}", self.hdl_stdout))
            .field("hdl_stdout_raw", &format_args!("0x{:08x}", self.hdl_stdout_raw))
            .finish()
    }
}

impl StdioOps {
    pub fn new() -> Box<dyn CrsnExtension> {
        Box::new(Self {
            old_tio: None,
            hdl_stdin: 0,
            hdl_stdin_raw: 0,
            hdl_stdout: 0,
            hdl_stdout_raw: 0,
        })
    }
}

impl Drop for StdioOps {
    fn drop(&mut self) {
        // Un-break the terminal
        if let Some(tio) = self.old_tio.take() {
            let _ = unsafe { libc::tcsetattr(libc::STDIN_FILENO, libc::TCSANOW, &tio) };
        }
    }
}

impl CrsnExtension for StdioOps {
    fn init(&mut self, uniq: &CrsnUniq) {
        self.hdl_stdin = uniq.unique_handle();
        self.hdl_stdin_raw = uniq.unique_handle();
        self.hdl_stdout = uniq.unique_handle();
        self.hdl_stdout_raw = uniq.unique_handle();

        // This can fail if the input is not a tty
        if let Ok(tio) = console::init_io() {
            self.old_tio = Some(tio);
        }
    }

    /// Get value of an extension-provided constant.
    /// This constant may be an object handle, or a constant value used as argument in some other instruction.
    fn get_constant_value<'a>(&self, name: &str) -> Option<Value>
    {
        match name {
            "cin" => Some(self.hdl_stdin),
            "cin_r" => Some(self.hdl_stdin_raw),
            "cout" => Some(self.hdl_stdout),
            "cout_r" => Some(self.hdl_stdout_raw),
            _ => None
        }
    }

    fn name(&self) -> &'static str {
        "stdio"
    }

    fn parse_op<'a>(&self, _pos: &SourcePosition, _keyword: &str, args: TokenParser<'a>) -> Result<ParseRes<'a, OpKind>, CrsnError> {
        Ok(ParseRes::Unknown(args))
    }

    /// Run-time method called to read an object (using the object handle syntax)
    fn read_obj(&self, state: &mut RunState, handle: Value)
                -> Result<Option<Value>, Fault>
    {
        if handle == self.hdl_stdin {
            match console::read_char() {
                Ok(c) => {
                    return Ok(Some(c as Value));
                }
                Err(e) => {
                    state.set_flag(Flag::Invalid, true);
                    if e.kind() != io::ErrorKind::InvalidData {
                        state.set_flag(Flag::Eof, true);
                    }
                    return Ok(Some(0));
                }
            }
        }

        if handle == self.hdl_stdin_raw {
            match console::read_byte() {
                Ok(b) => {
                    return Ok(Some(b as Value));
                }
                Err(_e) => {
                    state.set_flag(Flag::Invalid, true);
                    state.set_flag(Flag::Eof, true);
                    return Ok(Some(0));
                }
            }
        }

        if handle == self.hdl_stdout || handle == self.hdl_stdout_raw {
            state.set_flag(Flag::Invalid, true);
            return Ok(Some(0));
        }

        Ok(None)
    }

    /// Run-time method called to write an object (using the object handle syntax)
    fn write_obj(&self, state: &mut RunState, handle: Value, value: Value) -> Result<Option<()>, Fault>
    {
        state.clear_status();

        if handle == self.hdl_stdout {
            if let Ok(a_char) = char::try_from((value & 0xFFFF_FFFF) as u32) {
                if console::write_char(a_char).is_err() {
                        state.set_flag(Flag::Eof, true);
                }
            } else {
                state.set_flag(Flag::Invalid, true);
            }
            return Ok(Some(()));
        }

        if handle == self.hdl_stdout_raw {
            if console::write_byte((value & 0xFF) as u8).is_err() {
                state.set_flag(Flag::Eof, true);
            }
            return Ok(Some(()));
        }

        if handle == self.hdl_stdin || handle == self.hdl_stdin_raw {
            state.set_flag(Flag::Invalid, true);
            return Ok(Some(()));
        }

        Ok(None)
    }
}