//! Internal module describing the exchange flow
//!
//! Implements the flow of sending and receiving messages.
//! This includes the custom workflow of binding RPC methods
//! before being able to use them.

use std::{collections::HashMap, fmt};

use crate::{
    message::{self, Receive, Send},
    DFHackError,
};
use num_enum::TryFromPrimitiveError;

#[derive(PartialEq, Eq, Hash)]
pub struct Method {
    pub plugin: String,
    pub name: String,
}

impl Method {
    fn new(plugin: String, name: String) -> Self {
        Method { plugin, name }
    }
}

pub struct Protocol {
    stream: std::net::TcpStream,
    bindings: HashMap<Method, i16>,
}

const MAGIC_QUERY: &str = "DFHack?\n";
const MAGIC_REPLY: &str = "DFHack!\n";
const VERSION: i32 = 1;

const BIND_METHOD_ID: i16 = 0;
const RUN_COMMAND_ID: i16 = 1;

impl dfhack_proto::ProtocolTrait<crate::DFHackError> for Protocol {
    fn request<TRequest, TReply>(
        &mut self,
        plugin: std::string::String,
        name: std::string::String,
        request: TRequest,
    ) -> crate::DFHackResult<TReply>
    where
        TRequest: protobuf::Message,
        TReply: protobuf::Message,
    {
        let method = Method::new(plugin, name);

        // did not manage to use the entry api due to borrow checker
        let maybe_id = self.bindings.get(&method);
        let id: i16;

        if maybe_id.is_none() {
            id = self.bind_method::<TRequest, TReply>(&method)?;
            self.bindings.insert(method, id);
        } else {
            id = *maybe_id.unwrap();
        }
        self.request_raw(id, request)
    }
}

impl Protocol {
    pub fn connect() -> crate::DFHackResult<Self> {
        let port = match std::env::var("DFHACK_PORT") {
            Ok(p) => p,
            Err(_) => "5000".to_string(),
        };
        Self::connect_to(&format!("127.0.0.1:{}", port))
    }

    pub fn connect_to(address: &str) -> crate::DFHackResult<Protocol> {
        log::info!("Connecting to {}", address);
        let mut client = Protocol {
            stream: std::net::TcpStream::connect(address)?,
            bindings: HashMap::new(),
        };

        client.bindings.insert(
            Method::new("".to_string(), "BindMethod".to_string()),
            BIND_METHOD_ID,
        );
        client.bindings.insert(
            Method::new("".to_string(), "RunCommand".to_string()),
            RUN_COMMAND_ID,
        );

        let handshake_request = message::Handshake::new(MAGIC_QUERY.to_string(), VERSION);
        handshake_request.send(&mut client.stream)?;
        let handshake_reply = message::Handshake::receive(&mut client.stream)?;

        if handshake_reply.magic != MAGIC_REPLY {
            return Err(DFHackError::BadMagicFailure(handshake_reply.magic));
        }

        if handshake_reply.version != VERSION {
            return Err(DFHackError::BadVersionFailure(handshake_reply.version));
        }

        Ok(client)
    }

    pub fn request_raw<TIN: protobuf::Message, TOUT: protobuf::Message>(
        &mut self,
        id: i16,
        message: TIN,
    ) -> crate::DFHackResult<TOUT> {
        let request = message::Request::new(id, message);
        request.send(&mut self.stream)?;

        loop {
            let reply: message::Reply<TOUT> = message::Reply::receive(&mut self.stream)?;
            match reply {
                message::Reply::Text(text) => {
                    for fragment in text.get_fragments() {
                        println!("{}", fragment.get_text());
                    }
                }
                message::Reply::Result(result) => return Ok(result),
                message::Reply::Failure(_) => return Err(DFHackError::RpcError()),
            }
        }
    }

    pub fn bind_method<TIN: protobuf::Message, TOUT: protobuf::Message>(
        &mut self,
        method: &Method,
    ) -> crate::DFHackResult<i16> {
        log::debug!("Binding the method {}:{}", method.plugin, method.name);
        let mut request = crate::CoreBindRequest::new();
        let input_msg = TIN::descriptor_static().full_name();
        let output_msg = TOUT::descriptor_static().full_name();
        request.set_method(method.name.to_owned());
        request.set_input_msg(input_msg.to_string());
        request.set_output_msg(output_msg.to_string());
        request.set_plugin(method.plugin.to_owned());
        let reply: crate::CoreBindReply = self.request_raw(BIND_METHOD_ID, request)?;
        Ok(reply.get_assigned_id() as i16)
    }
}

impl Drop for Protocol {
    fn drop(&mut self) {
        let quit = message::Quit::new();
        let res = quit.send(&mut self.stream);
        if let Err(failure) = res {
            println!(
                "Warning: failed to close the connection to dfhack-remote: {}",
                failure
            );
        }
    }
}

impl fmt::Display for DFHackError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
        match self {
            DFHackError::BadMagicFailure(magic) => {
                write!(f, "Handshake failed: bad magic {magic}.")
            }
            DFHackError::BadVersionFailure(version) => {
                write!(f, "Handshake failed: unsupported version {version}.")
            }
            DFHackError::CommunicationFailure(error) => {
                write!(f, "Communication failure: {error}")
            }
            DFHackError::ProtobufError(error) => {
                write!(f, "Protobuf error: {error}")
            }
            DFHackError::UnknownReplyCode(code) => {
                write!(f, "Unknown DFHack reply code: {code}")
            }
            DFHackError::RpcError() => {
                write!(f, "RPC Error")
            }
        }
    }
}

impl From<std::io::Error> for DFHackError {
    fn from(err: std::io::Error) -> Self {
        Self::CommunicationFailure(err)
    }
}

impl From<protobuf::ProtobufError> for DFHackError {
    fn from(err: protobuf::ProtobufError) -> Self {
        Self::ProtobufError(err)
    }
}

impl From<TryFromPrimitiveError<message::RpcReplyCode>> for DFHackError {
    fn from(err: TryFromPrimitiveError<message::RpcReplyCode>) -> Self {
        Self::UnknownReplyCode(err.number)
    }
}