// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

use std::{
    collections::BTreeMap,
    fmt::{Debug, Error as FmtError, Formatter},
    io::{BufRead, BufReader},
    sync::{
        atomic::{AtomicUsize, Ordering},
        Arc,
    },
    thread, time,
};

use hash::keccak;
use parking_lot::Mutex;
use std::{fs::File, path::PathBuf};
use url::Url;

use ws::ws::{
    self, Error as WsError, ErrorKind as WsErrorKind, Handler, Handshake, Message, Request,
    Result as WsResult, Sender,
};

use serde::de::DeserializeOwned;
use serde_json::{self as json, Error as JsonError, Value as JsonValue};

use futures::{done, oneshot, Canceled, Complete, Future};

use jsonrpc_core::{
    request::MethodCall,
    response::{Failure, Output, Success},
    Error as JsonRpcError, Id, Params, Version,
};

use BoxFuture;

/// The actual websocket connection handler, passed into the
/// event loop of ws-rs
struct RpcHandler {
    pending: Pending,
    // Option is used here as temporary storage until connection
    // is setup and the values are moved into the new `Rpc`
    complete: Option<Complete<Result<Rpc, RpcError>>>,
    auth_code: String,
    out: Option<Sender>,
}

impl RpcHandler {
    fn new(out: Sender, auth_code: String, complete: Complete<Result<Rpc, RpcError>>) -> Self {
        RpcHandler {
            out: Some(out),
            auth_code: auth_code,
            pending: Pending::new(),
            complete: Some(complete),
        }
    }
}

impl Handler for RpcHandler {
    fn build_request(&mut self, url: &Url) -> WsResult<Request> {
        match Request::from_url(url) {
            Ok(mut r) => {
                let timestamp = time::UNIX_EPOCH
                    .elapsed()
                    .map_err(|err| WsError::new(WsErrorKind::Internal, format!("{}", err)))?;
                let secs = timestamp.as_secs();
                let hashed = keccak(format!("{}:{}", self.auth_code, secs));
                let proto = format!("{:x}_{}", hashed, secs);
                r.add_protocol(&proto);
                Ok(r)
            }
            Err(e) => Err(WsError::new(WsErrorKind::Internal, format!("{}", e))),
        }
    }
    fn on_error(&mut self, err: WsError) {
        match self.complete.take() {
            Some(c) => match c.send(Err(RpcError::WsError(err))) {
                Ok(_) => {}
                Err(_) => warn!(target: "rpc-client", "Unable to notify about error."),
            },
            None => warn!(target: "rpc-client", "unexpected error: {}", err),
        }
    }
    fn on_open(&mut self, _: Handshake) -> WsResult<()> {
        match (self.complete.take(), self.out.take()) {
            (Some(c), Some(out)) => {
                let res = c.send(Ok(Rpc {
                    out: out,
                    counter: AtomicUsize::new(0),
                    pending: self.pending.clone(),
                }));
                if let Err(_) = res {
                    warn!(target: "rpc-client", "Unable to open a connection.")
                }
                Ok(())
            }
            _ => {
                let msg = format!("on_open called twice");
                Err(WsError::new(WsErrorKind::Internal, msg))
            }
        }
    }
    fn on_message(&mut self, msg: Message) -> WsResult<()> {
        let ret: Result<JsonValue, JsonRpcError>;
        let response_id;
        let string = &msg.to_string();
        match json::from_str::<Output>(&string) {
            Ok(Output::Success(Success {
                result,
                id: Id::Num(id),
                ..
            })) => {
                ret = Ok(result);
                response_id = id as usize;
            }
            Ok(Output::Failure(Failure {
                error,
                id: Id::Num(id),
                ..
            })) => {
                ret = Err(error);
                response_id = id as usize;
            }
            Err(e) => {
                warn!(
                    target: "rpc-client",
                    "recieved invalid message: {}\n {:?}",
                    string,
                    e
                );
                return Ok(());
            }
            _ => {
                warn!(
                    target: "rpc-client",
                    "recieved invalid message: {}",
                    string
                );
                return Ok(());
            }
        }

        match self.pending.remove(response_id) {
            Some(c) => {
                if let Err(_) = c.send(ret.map_err(|err| RpcError::JsonRpc(err))) {
                    warn!(target: "rpc-client", "Unable to send response.")
                }
            }
            None => warn!(
                target: "rpc-client",
                "warning: unexpected id: {}",
                response_id
            ),
        }
        Ok(())
    }
}

/// Keeping track of issued requests to be matched up with responses
#[derive(Clone)]
struct Pending(Arc<Mutex<BTreeMap<usize, Complete<Result<JsonValue, RpcError>>>>>);

impl Pending {
    fn new() -> Self {
        Pending(Arc::new(Mutex::new(BTreeMap::new())))
    }
    fn insert(&mut self, k: usize, v: Complete<Result<JsonValue, RpcError>>) {
        self.0.lock().insert(k, v);
    }
    fn remove(&mut self, k: usize) -> Option<Complete<Result<JsonValue, RpcError>>> {
        self.0.lock().remove(&k)
    }
}

fn get_authcode(path: &PathBuf) -> Result<String, RpcError> {
    if let Ok(fd) = File::open(path) {
        if let Some(Ok(line)) = BufReader::new(fd).lines().next() {
            let mut parts = line.split(';');
            let token = parts.next();

            if let Some(code) = token {
                return Ok(code.into());
            }
        }
    }
    Err(RpcError::NoAuthCode)
}

/// The handle to the connection
pub struct Rpc {
    out: Sender,
    counter: AtomicUsize,
    pending: Pending,
}

impl Rpc {
    /// Blocking, returns a new initialized connection or RpcError
    pub fn new(url: &str, authpath: &PathBuf) -> Result<Self, RpcError> {
        let rpc = Self::connect(url, authpath).map(|rpc| rpc).wait()?;
        rpc
    }

    /// Non-blocking, returns a future
    pub fn connect(url: &str, authpath: &PathBuf) -> BoxFuture<Result<Self, RpcError>, Canceled> {
        let (c, p) = oneshot::<Result<Self, RpcError>>();
        match get_authcode(authpath) {
            Err(e) => return Box::new(done(Ok(Err(e)))),
            Ok(code) => {
                let url = String::from(url);
                // The ws::connect takes a FnMut closure, which means c cannot
                // be moved into it, since it's consumed on complete.
                // Therefore we wrap it in an option and pick it out once.
                let mut once = Some(c);
                thread::spawn(move || {
                    let conn = ws::connect(url, |out| {
                        // this will panic if the closure is called twice,
                        // which it should never be.
                        let c = once.take().expect("connection closure called only once");
                        RpcHandler::new(out, code.clone(), c)
                    });
                    match conn {
                        Err(err) => {
                            // since ws::connect is only called once, it cannot
                            // both fail and succeed.
                            let c = once.take().expect("connection closure called only once");
                            let _ = c.send(Err(RpcError::WsError(err)));
                        }
                        // c will complete on the `on_open` event in the Handler
                        _ => (),
                    }
                });
                Box::new(p)
            }
        }
    }

    /// Non-blocking, returns a future of the request response
    pub fn request<T>(
        &mut self,
        method: &'static str,
        params: Vec<JsonValue>,
    ) -> BoxFuture<Result<T, RpcError>, Canceled>
    where
        T: DeserializeOwned + Send + Sized,
    {
        let (c, p) = oneshot::<Result<JsonValue, RpcError>>();

        let id = self.counter.fetch_add(1, Ordering::Relaxed);
        self.pending.insert(id, c);

        let request = MethodCall {
            jsonrpc: Some(Version::V2),
            method: method.to_owned(),
            params: Params::Array(params),
            id: Id::Num(id as u64),
        };

        let serialized = json::to_string(&request).expect("request is serializable");
        let _ = self.out.send(serialized);

        Box::new(p.map(|result| match result {
            Ok(json) => {
                let t: T = json::from_value(json)?;
                Ok(t)
            }
            Err(err) => Err(err),
        }))
    }
}

pub enum RpcError {
    WrongVersion(String),
    ParseError(JsonError),
    MalformedResponse(String),
    JsonRpc(JsonRpcError),
    WsError(WsError),
    Canceled(Canceled),
    UnexpectedId,
    NoAuthCode,
}

impl Debug for RpcError {
    fn fmt(&self, f: &mut Formatter) -> Result<(), FmtError> {
        match *self {
            RpcError::WrongVersion(ref s) => write!(f, "Expected version 2.0, got {}", s),
            RpcError::ParseError(ref err) => write!(f, "ParseError: {}", err),
            RpcError::MalformedResponse(ref s) => write!(f, "Malformed response: {}", s),
            RpcError::JsonRpc(ref json) => write!(f, "JsonRpc error: {:?}", json),
            RpcError::WsError(ref s) => write!(f, "Websocket error: {}", s),
            RpcError::Canceled(ref s) => write!(f, "Futures error: {:?}", s),
            RpcError::UnexpectedId => write!(f, "Unexpected response id"),
            RpcError::NoAuthCode => write!(f, "No authcodes available"),
        }
    }
}

impl From<JsonError> for RpcError {
    fn from(err: JsonError) -> RpcError {
        RpcError::ParseError(err)
    }
}

impl From<WsError> for RpcError {
    fn from(err: WsError) -> RpcError {
        RpcError::WsError(err)
    }
}

impl From<Canceled> for RpcError {
    fn from(err: Canceled) -> RpcError {
        RpcError::Canceled(err)
    }
}