// Copyright 2015-2018 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity 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.

// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.

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

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

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

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

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

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

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: Some(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)
	}
}