// 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/>.

#![warn(missing_docs)]

//! A simple client to get the current ETH price using an external API.

extern crate futures;
extern crate parity_runtime;
extern crate serde_json;

#[macro_use]
extern crate log;

#[cfg(test)]
extern crate fake_fetch;

pub extern crate fetch;

use std::{cmp, fmt, io, str};

use fetch::{Client as FetchClient, Fetch};
use futures::{
    future::{self, Either},
    Future, Stream,
};
use parity_runtime::Executor;
use serde_json::Value;

/// Current ETH price information.
#[derive(Debug)]
pub struct PriceInfo {
    /// Current ETH price in USD.
    pub ethusd: f32,
}

/// Price info error.
#[derive(Debug)]
pub enum Error {
    /// The API returned an unexpected status code.
    StatusCode(&'static str),
    /// The API returned an unexpected status content.
    UnexpectedResponse(Option<String>),
    /// There was an error when trying to reach the API.
    Fetch(fetch::Error),
    /// IO error when reading API response.
    Io(io::Error),
}

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

impl From<fetch::Error> for Error {
    fn from(err: fetch::Error) -> Self {
        Error::Fetch(err)
    }
}

/// A client to get the current ETH price using an external API.
pub struct Client<F = FetchClient> {
    pool: Executor,
    api_endpoint: String,
    fetch: F,
}

impl<F> fmt::Debug for Client<F> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.debug_struct("price_info::Client")
            .field("api_endpoint", &self.api_endpoint)
            .finish()
    }
}

impl<F> cmp::PartialEq for Client<F> {
    fn eq(&self, other: &Client<F>) -> bool {
        self.api_endpoint == other.api_endpoint
    }
}

impl<F: Fetch> Client<F> {
    /// Creates a new instance of the `Client` given a `fetch::Client`.
    pub fn new(fetch: F, pool: Executor, api_endpoint: String) -> Client<F> {
        Client {
            pool,
            api_endpoint,
            fetch,
        }
    }

    /// Gets the current ETH price and calls `set_price` with the result.
    pub fn get<G: FnOnce(PriceInfo) + Sync + Send + 'static>(&self, set_price: G) {
        let future = self
            .fetch
            .get(&self.api_endpoint, fetch::Abort::default())
            .from_err()
            .and_then(|response| {
                if !response.is_success() {
                    let s = Error::StatusCode(
                        response.status().canonical_reason().unwrap_or("unknown"),
                    );
                    return Either::A(future::err(s));
                }
                Either::B(response.concat2().from_err())
            })
            .and_then(move |body| {
                let body_str = str::from_utf8(&body).ok();
                let value: Option<Value> = body_str.and_then(|s| serde_json::from_str(s).ok());

                let ethusd = value
                    .as_ref()
                    .and_then(|value| value.pointer("/result/ethusd"))
                    .and_then(|obj| obj.as_str())
                    .and_then(|s| s.parse().ok());

                match ethusd {
                    Some(ethusd) => {
                        set_price(PriceInfo { ethusd });
                        Ok(())
                    }
                    None => Err(Error::UnexpectedResponse(body_str.map(From::from))),
                }
            })
            .map_err(|err| {
                warn!("Failed to auto-update latest ETH price: {:?}", err);
            });
        self.pool.spawn(future)
    }
}

#[cfg(test)]
mod test {
    use fake_fetch::FakeFetch;
    use parity_runtime::{Executor, Runtime};
    use std::sync::{
        atomic::{AtomicBool, Ordering},
        Arc,
    };
    use Client;

    fn price_info_ok(response: &str, executor: Executor) -> Client<FakeFetch<String>> {
        Client::new(
            FakeFetch::new(Some(response.to_owned())),
            executor,
            "fake_endpoint".to_owned(),
        )
    }

    fn price_info_not_found(executor: Executor) -> Client<FakeFetch<String>> {
        Client::new(
            FakeFetch::new(None::<String>),
            executor,
            "fake_endpoint".to_owned(),
        )
    }

    #[test]
    fn should_get_price_info() {
        let runtime = Runtime::with_thread_count(1);

        // given
        let response = r#"{
			"status": "1",
			"message": "OK",
			"result": {
				"ethbtc": "0.0891",
				"ethbtc_timestamp": "1499894236",
				"ethusd": "209.55",
				"ethusd_timestamp": "1499894229"
			}
		}"#;

        let price_info = price_info_ok(response, runtime.executor());

        // when
        price_info.get(|price| {
            // then
            assert_eq!(price.ethusd, 209.55);
        });
    }

    #[test]
    fn should_not_call_set_price_if_response_is_malformed() {
        let runtime = Runtime::with_thread_count(1);

        // given
        let response = "{}";

        let price_info = price_info_ok(response, runtime.executor());
        let b = Arc::new(AtomicBool::new(false));

        // when
        let bb = b.clone();
        price_info.get(move |_| {
            bb.store(true, Ordering::SeqCst);
        });

        // then
        assert_eq!(b.load(Ordering::SeqCst), false);
    }

    #[test]
    fn should_not_call_set_price_if_response_is_invalid() {
        let runtime = Runtime::with_thread_count(1);

        // given
        let price_info = price_info_not_found(runtime.executor());
        let b = Arc::new(AtomicBool::new(false));

        // when
        let bb = b.clone();
        price_info.get(move |_| {
            bb.store(true, Ordering::SeqCst);
        });

        // then
        assert_eq!(b.load(Ordering::SeqCst), false);
    }
}
