use nom::*;
use std::str;

use super::messages::{*, EngineMessage::*, UnsyncedEngineMessage::*, SyncedEngineMessage::*, ConfigEngineMessage::*, KeystrokeAction::*};

named!(length_specifier<&[u8], u16>, alt!(
    verify!(map!(take!(1), |a : &[u8]| a[0] as u16), |l| l < 64)
    | map!(take!(2), |a| (a[0] as u16 - 64) * 256 + a[1] as u16 + 64)
    )
);

named!(unrecognized_message<&[u8], EngineMessage>,
    do_parse!(rest >> (Unknown))
);

named!(string_tail<&[u8], String>, map!(map_res!(rest, str::from_utf8), String::from));

named!(synced_message<&[u8], SyncedEngineMessage>, alt!(
      do_parse!(tag!("+l") >> (Left(Press)))
));

named!(unsynced_message<&[u8], UnsyncedEngineMessage>, alt!(
      do_parse!(tag!("?") >> (Ping))
    | do_parse!(tag!("!") >> (Ping))
    | do_parse!(tag!("esay ") >> s: string_tail  >> (Say(s)))
));

named!(config_message<&[u8], ConfigEngineMessage>, alt!(
    do_parse!(tag!("C") >> (ConfigRequest))
));

named!(empty_message<&[u8], EngineMessage>,
    do_parse!(tag!("\0") >> (Empty))
);

named!(non_empty_message<&[u8], EngineMessage>, length_value!(length_specifier,
    alt!(
          map!(synced_message, |m| Synced(m, 0))
        | map!(unsynced_message, |m| Unsynced(m))
        | map!(config_message, |m| Config(m))
        | unrecognized_message
    )
));

named!(message<&[u8], EngineMessage>, alt!(
      empty_message
    | non_empty_message
    )
);

named!(pub extract_messages<&[u8], Vec<EngineMessage> >, many0!(complete!(message)));

#[test]
fn parse_length() {
    assert_eq!(length_specifier(b"\x01"), Ok((&b""[..], 1)));
    assert_eq!(length_specifier(b"\x00"), Ok((&b""[..], 0)));
    assert_eq!(length_specifier(b"\x3f"), Ok((&b""[..], 63)));
    assert_eq!(length_specifier(b"\x40\x00"), Ok((&b""[..], 64)));
    assert_eq!(length_specifier(b"\xff\xff"), Ok((&b""[..], 49215)));
}

#[test]
fn parse_synced_messages() {
    assert_eq!(message(b"\x04+l\x01\x01"), Ok((&b""[..], Synced(Left(Press), 0))));
}

#[test]
fn parse_unsynced_messages() {
    assert_eq!(message(b"\x0aesay hello"), Ok((&b""[..], Unsynced(Say(String::from("hello"))))));
}

#[test]
fn parse_incorrect_messages() {
    assert_eq!(message(b"\x00"), Ok((&b""[..], Empty)));
    assert_eq!(message(b"\x01\x00"), Ok((&b""[..], Unknown)));
}

#[test]
fn parse_config_messages() {
    assert_eq!(
        message(b"\x01C"),
        Ok((
            &b""[..],
            Config(ConfigRequest)
        ))
    );
}
#[test]
fn parse_test_general() {
    assert_eq!(string_tail(b"abc"), Ok((&b""[..], String::from("abc"))));
}