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use std::io;

use tokio::io::{AsyncWrite, AsyncWriteExt};

pub(crate) const MAGIC: u8 = 0x07;
pub(crate) const TERMINATOR: u8 = 0x21;
pub(crate) const SEPARATOR: u8 = 0x20;

#[derive(Debug)]
pub(crate) enum Packet {
    SetNicknameRequest(Vec<u8>),
    SetNickname(Vec<u8>),
    ChangeNicknameRequest(Vec<u8>),
    ChangeNickname(Vec<u8>),
    UserListRequest,
    UserListResponse(Vec<Vec<u8>>),
    SendWord { sender: Vec<u8>, recipients: Vec<Vec<u8>>, word: Vec<u8> },
    DeliverWord { sender: Vec<u8>, word: Vec<u8> },
    SendInstructions { sender: Vec<u8>, recipients: Vec<Vec<u8>>, instructions: Vec<u8> },
    DeliverInstructions { sender: Vec<u8>, instructions: Vec<u8> },
    SendList { sender: Vec<u8>, recipients: Vec<Vec<u8>>, list: Vec<Vec<u8>> },
    DeliverList { sender: Vec<u8>, list: Vec<Vec<u8>> },
    SendImage { sender: Vec<u8>, recipients: Vec<Vec<u8>>, bytes: Vec<u8> },
    DeliverImage { sender: Vec<u8>, bytes: Vec<u8> },
    SendObject { sender: Vec<u8>, recipients: Vec<Vec<u8>>, bytes: Vec<u8> },
    DeliverObject { sender: Vec<u8>, bytes: Vec<u8> },
}

impl Packet {
    fn opcode(&self) -> Opcode {
        match self {
            Self::SetNicknameRequest(_) => Opcode::SetNicknameRequest,
            Self::SetNickname(_) => Opcode::SetNickname,
            Self::ChangeNicknameRequest(_) => Opcode::ChangeNicknameRequest,
            Self::ChangeNickname(_) => Opcode::ChangeNickname,
            Self::UserListRequest => Opcode::UserListRequest,
            Self::UserListResponse(_) => Opcode::UserListResponse,
            Self::SendWord { .. } => Opcode::SendWord,
            Self::DeliverWord { .. } => Opcode::DeliverWord,
            Self::SendInstructions { .. } => Opcode::SendInstructions,
            Self::DeliverInstructions { .. } => Opcode::DeliverInstructions,
            Self::SendList { .. } => Opcode::SendList,
            Self::DeliverList { .. } => Opcode::DeliverList,
            Self::SendImage { .. } => Opcode::SendImage,
            Self::DeliverImage { .. } => Opcode::DeliverImage,
            Self::SendObject { .. } => Opcode::SendObject,
            Self::DeliverObject { .. } => Opcode::DeliverObject,
        }
    }

    // TODO: Don't clone?
    fn users(&self) -> Vec<Vec<u8>> {
        match self {
            Self::SetNicknameRequest(_)
            | Self::SetNickname(_)
            | Self::ChangeNicknameRequest(_)
            | Self::ChangeNickname(_)
            | Self::UserListRequest => Vec::new(),
            Self::UserListResponse(users) => users.clone(),
            Self::SendWord { sender, recipients, .. }
            | Self::SendInstructions { sender, recipients, .. }
            | Self::SendList { sender, recipients, .. }
            | Self::SendImage { sender, recipients, .. }
            | Self::SendObject { sender, recipients, .. } => {
                let mut result = vec![sender.clone()];
                result.extend_from_slice(recipients);
                result
            },
            Self::DeliverWord { sender, .. }
            | Self::DeliverInstructions { sender, .. }
            | Self::DeliverList { sender, .. }
            | Self::DeliverImage { sender, .. }
            | Self::DeliverObject { sender, .. } => vec![sender.clone()],
        }
    }

    fn to_bytes(self) -> Vec<u8> {
        let mut body = {
            let users = self.users();
            let mut content = Vec::new();
            content.push(self.opcode() as u8);
            content.extend_from_slice(users.len().to_string().as_bytes());
            content.push(TERMINATOR);
            for mut user in users {
                content.extend_from_slice(user.len().to_string().as_bytes());
                content.push(TERMINATOR);
                content.append(&mut user);
            }
            content.append(&mut match self {
                Packet::SetNicknameRequest(nickname)
                | Packet::SetNickname(nickname)
                | Packet::ChangeNicknameRequest(nickname)
                | Packet::ChangeNickname(nickname) => nickname,
                Packet::UserListRequest
                | Packet::UserListResponse(_) => Vec::new(),
                Packet::SendWord { word, .. }
                | Packet::DeliverWord { word, .. } => word,
                Packet::SendInstructions { instructions, .. }
                | Packet::DeliverInstructions { instructions, .. } => instructions,
                Packet::SendList { mut list, .. }
                | Packet::DeliverList { mut list, .. } => {
                    let mut content = Vec::new();
                    let mut list_iter = list.iter_mut().peekable();
                    while let Some(word) = list_iter.next() {
                        content.append(word);
                        if list_iter.peek().is_some() {
                            content.push(SEPARATOR);
                        }
                    }
                    content
                },
                Packet::SendImage { bytes, .. }
                | Packet::DeliverImage { bytes, .. }
                | Packet::SendObject { bytes, .. }
                | Packet::DeliverObject { bytes, .. } => bytes,
            });
            content
        };

        {
            let mut data = Vec::new();
            data.push(MAGIC);
            data.extend_from_slice(body.len().to_string().as_bytes());
            data.push(TERMINATOR);
            data.append(&mut body);
            data
        }
    }

    pub(crate) async fn async_write<W>(self, writer: &mut W) -> Result<(), io::Error>
        where W: AsyncWrite + Unpin
    {
        writer.write_all(&self.to_bytes()).await?;
        Ok(())
    }
}

#[derive(Debug)]
pub enum Error {
    InvalidOpcode,
}

pub(crate) enum Opcode {
    SetNicknameRequest = 0x61,
    SetNickname = 0x62,
    ChangeNicknameRequest = 0x58,
    ChangeNickname = 0x79,
    UserListRequest = 0x55,
    UserListResponse = 0x76,
    SendWord = 0x57,
    DeliverWord = 0x77,
    SendInstructions = 0x52,
    DeliverInstructions = 0x72,
    SendList = 0x4c,
    DeliverList = 0x6c,
    SendImage = 0x49,
    DeliverImage = 0x69,
    SendObject = 0x6f,
    DeliverObject = 0x4f,
}

impl TryFrom<u8> for Opcode {
    type Error = Error;

    fn try_from(v: u8) -> Result<Self, Self::Error> {
        match v {
            v if v == Self::SetNicknameRequest as u8 => Ok(Self::SetNicknameRequest),
            v if v == Self::SetNickname as u8 => Ok(Self::SetNickname),
            v if v == Self::ChangeNicknameRequest as u8 => Ok(Self::ChangeNicknameRequest),
            v if v == Self::ChangeNickname as u8 => Ok(Self::ChangeNickname),
            v if v == Self::UserListRequest as u8 => Ok(Self::UserListRequest),
            v if v == Self::UserListResponse as u8 => Ok(Self::UserListResponse),
            v if v == Self::SendWord as u8 => Ok(Self::SendWord),
            v if v == Self::DeliverWord as u8 => Ok(Self::DeliverWord),
            v if v == Self::SendInstructions as u8 => Ok(Self::SendInstructions),
            v if v == Self::DeliverInstructions as u8 => Ok(Self::DeliverInstructions),
            v if v == Self::SendList as u8 => Ok(Self::SendList),
            v if v == Self::DeliverList as u8 => Ok(Self::DeliverList),
            v if v == Self::SendImage as u8 => Ok(Self::SendImage),
            v if v == Self::DeliverImage as u8 => Ok(Self::DeliverImage),
            v if v == Self::SendObject as u8 => Ok(Self::SendObject),
            v if v == Self::DeliverObject as u8 => Ok(Self::DeliverObject),
            _ => Err(Error::InvalidOpcode),
        }
    }
}