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use std::convert::TryFrom;
use error;
use std::fmt;

/// `Message`
#[derive(Debug, PartialEq, Clone)]
pub enum Message {
    Request(Op, Vec<u8>, Option<Payload>),
    Response(Op, Code, Option<Payload>),
}

pub fn request(op: Op, key: Vec<u8>, payload: Option<Payload>) -> Message {
    Message::Request(op, key, payload)
}

pub fn response(op: Op, code: Code, payload: Option<Payload>) -> Message {
    Message::Response(op, code, payload)
}

impl Message {
    pub fn key(&self) -> Option<&[u8]> {
        match *self {
            Message::Request(_, ref key, _) => Some(key.as_slice()),
            Message::Response(..) => None,
        }
    }

    pub fn op(&self) -> Op {
        match *self {
            Message::Request(op, ..) |
            Message::Response(op, ..) => op,
        }
    }

    pub fn code(&self) -> Code {
        match *self {
            Message::Request(..) => Code::Req,
            Message::Response(_, code, ..) => code,
        }
    }
    pub fn type_id(&self) -> Option<u32> {
        match *self {
            Message::Request(_, _, ref payload) => payload.as_ref().map(|p| p.type_id),
            Message::Response(_, _, ref payload) => payload.as_ref().map(|p| p.type_id),
        }
    }

    pub fn payload(&self) -> Option<&Payload> {
        match *self {
            Message::Request(_, _, ref payload) |
            Message::Response(_, _, ref payload) => payload.as_ref(),
        }
    }

    pub fn consume_request(self) -> Result<(Vec<u8>, Option<Payload>), error::Error> {
        match self {
            Message::Request(_, key, payload) => Ok((key, payload)),
            Message::Response(..) => Err(error::Error::new(
                error::ErrorKind::BadMessage,
                "expected a request, got a response",
            )),
        }
    }
    pub fn consume_response(self) -> Result<(Op, Code, Option<Payload>), error::Error> {
        match self {
            Message::Response(op, code, payload) => Ok((op, code, payload)),
            Message::Request(..) => Err(error::Error::new(
                error::ErrorKind::BadMessage,
                "expected a request, got a response",
            )),
        }
    }
}

impl fmt::Display for Message {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Message::Request(ref op, ref key, ref payload) => {
                match *payload {
                    Some(ref payload) => write!(f, "Request[Op={}, Key={:?}] {}", op, key, payload.clone()),
                    None => write!(f, "Request[Op={}, Key={:?}]", op, key),
                }
            }
            Message::Response(ref op, ref code, ref payload) => {
                match *payload {
                    Some(ref payload) => write!(f, "Response[Op={}, Code={}] {:?}", op, code, payload.clone()),
                    None => write!(f, "Request[Op={}, Code={}]", op, code),
                }
            }
        }
    }
}

/// `Payload`
#[derive(Debug, PartialEq, Clone)]
pub struct Payload {
    type_id: u32,
    data: Vec<u8>,
}

impl Payload {
    pub fn data(&self) -> &[u8] {
        self.data.as_slice()
    }
    pub fn type_id(&self) -> u32 {
        self.type_id
    }
}

pub fn payload(type_id: u32, data: Vec<u8>) -> Payload {
    Payload {
        type_id: type_id,
        data: data,
    }
}

impl fmt::Display for Payload {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "type_id: {}, data: {:?}", self.type_id, self.data)
    }
}

/// `Op`
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Op {
    Set = 0,
    Get = 1,
    Del = 2,
    Stats = 3,
}

impl fmt::Display for Op {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let s = match *self {
            Op::Set => "Set",
            Op::Get => "Get",
            Op::Del => "Del",
            Op::Stats => "Stats",
        };

        write!(f, "{}", s)
    }
}

impl TryFrom<u8> for Op {
    type Error = error::Error;

    fn try_from(i: u8) -> Result<Self, Self::Error> {
        match i {
            0 => Ok(Op::Set),
            1 => Ok(Op::Get),
            2 => Ok(Op::Del),
            3 => Ok(Op::Stats),
            _ => Err(error::Error::new(
                error::ErrorKind::UnknownOp,
                "got an unknown op code",
            )),
        }
    }
}

/// `Code`
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Code {
    Req = 0,
    Ok = 1,
    Miss = 2,
    Error = 3,
    Hit = 4,
}

impl fmt::Display for Code {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let s = match *self {
            Code::Req => "Req",
            Code::Ok => "Ok",
            Code::Miss => "Miss",
            Code::Error => "Error",
            Code::Hit => "Hit",
        };
        write!(f, "{}", s)
    }
}

impl TryFrom<u8> for Code {
    type Error = error::Error;

    fn try_from(i: u8) -> Result<Self, Self::Error> {
        match i {
            0 => Ok(Code::Req),
            1 => Ok(Code::Ok),
            2 => Ok(Code::Miss),
            3 => Ok(Code::Error),
            4 => Ok(Code::Hit),
            _ => Err(error::Error::new(
                error::ErrorKind::InvalidData,
                "unknown code",
            )),
        }
    }
}