//! A unified API for abstracting over various exchanges.

pub mod binance;
pub mod gdax;
pub mod hitbtc;
pub mod errors;
pub mod timestamp;
pub mod symbol;
pub mod order_book;
mod query_string;
mod wss;

use futures::prelude::*;
use std::collections::HashMap;
use serde_derive::{Serialize, Deserialize};
use bitflags::bitflags;
use crate::Side;
use crate::tick::{TickUnit, Tickable};
use crate::order_book::LimitUpdate;

use self::timestamp::Timestamped;
use self::symbol::{Symbol, WithSymbol};

pub use self::gdax as coinbase_pro; // Just rename GDAX to its new name.

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// Params needed for an API client.
pub struct Params {
    /// Streaming API address (usually over WebSocket).
    pub streaming_endpoint: String,

    /// REST API endpoint (usually over HTTP).
    pub rest_endpoint: String,
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// See https://www.investopedia.com/terms/t/timeinforce.asp.
pub enum TimeInForce {
    /// The order stays on the exchange until it is executed on canceled.
    GoodTilCanceled,

    /// The order must partially fill immediately, the remaining unfilled quantity
    /// is canceled.
    ImmediateOrCancel,

    /// If the order cannot be filled immediately in its entierety, it is rejected.
    FillOrKilll,
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// Order type.
pub enum OrderType {
    /// A normal limit order.
    Limit,

    /// A limit order which cannot take liquidity, i.e. an error would be returned by
    /// the exchange if the order crosses the other side of the book.
    LimitMaker,
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// An order to be sent through the API.
pub struct Order {
    price: Tickable,
    size: Tickable,
    side: Side,
    #[serde(rename = "type")]
    type_: OrderType,
    time_in_force: TimeInForce,
    time_window: u64,
    order_id: Option<String>,
}

impl Order {
    /// Return a new `Order`, with:
    /// * `price` being the order price
    /// * `size` being the order size
    /// * `side` being `Side::Bid` (buy) or `Side::Ask` (sell)
    pub fn new<T, U>(price: T, size: U, side: Side) -> Self
        where T: Into<Tickable>, U: Into<Tickable>
    {
        Order {
            price: price.into(),
            size: size.into(),
            side,
            type_: OrderType::Limit,
            time_in_force: TimeInForce::GoodTilCanceled,
            time_window: 5000,
            order_id: None,
        }
    }

    /// Set the order type.
    pub fn with_order_type(mut self, order_type: OrderType) -> Self {
        self.type_ = order_type;
        self
    }

    /// Time in force, see https://www.investopedia.com/terms/t/timeinforce.asp.
    pub fn with_time_in_force(mut self, time_in_force: TimeInForce) -> Self {
        self.time_in_force = time_in_force;
        self
    }

    /// Delay until the order becomes invalid if not treated by the server, in ms.
    ///
    /// # Note
    /// Usable only on binance. On Coinbase Pro, the exchange forces the time window
    /// to be 30s. I don't know about HitBTC.
    pub fn with_time_window(mut self, time_window: u64) -> Self {
        self.time_window = time_window;
        self
    }

    /// Generate an id for identifying this order. When possible, the order id will
    /// be equal to `hint`, otherwise it is assured that all ids generated by a call to
    /// this method are distinct.
    pub fn with_order_id<C: ApiClient>(mut self, hint: &str) -> Self {
        self.order_id = Some(C::new_order_id(hint));
        self
    }

    /// Return the order id if one was provided.
    pub fn order_id(&self) -> Option<&str> {
        self.order_id.as_ref().map(|s| s.as_ref())
    }

    /// Return the order price.
    pub fn price(&self) -> &Tickable {
        &self.price
    }

    /// Return the order size.
    pub fn size(&self) -> &Tickable {
        &self.size
    }

    /// Return the order type.
    pub fn order_type(&self) -> OrderType {
        self.type_
    }

    /// Return the chosen time in force.
    pub fn time_in_force(&self) -> TimeInForce {
        self.time_in_force
    }

    /// Return the chosen validity time window.
    pub fn time_window(&self) -> u64 {
        self.time_window
    }
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// An order to cancel a previous order.
pub struct Cancel {
    order_id: String,
    time_window: u64,
}

impl Cancel {
    /// Return a new `Cancel`, with `order_id` identifying the order to cancel.
    pub fn new(order_id: String) -> Self {
        Cancel {
            order_id,
            time_window: 5000,
        }
    }

    /// Delay until the cancel order becomes invalid if not treated by the server, in ms.
    ///
    /// # Note
    /// Usable only on binance. On Coinbase Pro, the exchange forces the time window
    /// to be 30s. I don't know about HitBTC.
    pub fn with_time_window(mut self, time_window: u64) -> Self {
        self.time_window = time_window;
        self
    }

    /// Return the order id to cancel.
    pub fn order_id(&self) -> &str {
        &self.order_id
    }

    /// Return the chosen validity time window.
    pub fn time_window(&self) -> u64 {
        self.time_window
    }
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// An acknowledgment that an order has been treated by the server.
pub struct OrderAck {
    /// ID identifiying the order.
    pub order_id: String,
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// An acknowledgment that a cancel order has been treated by the server.
pub struct CancelAck;

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// A notification that some order has been updated, i.e. a trade crossed through this order.
pub struct OrderUpdate {
    /// ID identifying the order being updated.
    pub order_id: String,

    /// Size just consumed by last trade.
    pub consumed_size: TickUnit,

    /// Total remaining size for this order (can be maintained in a standalone way
    /// using the size of the order at insertion time, `consumed_size` and `commission`).
    pub remaining_size: TickUnit,

    /// Price at which the last trade happened.
    pub consumed_price: TickUnit,

    /// Commission amount (warning: for binance this may not be in the same currency as
    /// the traded asset).
    pub commission: TickUnit,
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// A liquidity consuming order.
pub struct Trade {
    /// Price in ticks.
    pub price: TickUnit,

    /// Size consumed by the trade.
    pub size: TickUnit,

    /// Side of the maker:
    /// * if `Ask`, then the maker was providing liquidity on the ask side,
    ///   i.e. the consumer bought to the maker
    /// * if `Bid`, then the maker was providing liquidity on the bid side,
    ///   i.e. the consumer sold to the maker
    pub maker_side: Side,
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// A notification that some order has expired or was canceled.
pub struct OrderExpiration {
    /// Expired order.
    pub order_id: String,
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
/// A notification that some order has been received by the exchange.
pub struct OrderConfirmation {
    /// Unique order id.
    pub order_id: String,

    /// Price at which the order was inserted.
    pub price: TickUnit,

    /// Size at which the order was inserted.
    pub size: TickUnit,

    /// Side of the order.
    pub side: Side,
}

#[derive(Clone, PartialEq, Eq, Debug, Serialize, Deserialize)]
/// A notification that some event happened.
pub enum Notification {
    /// A trade was executed.
    Trade(Timestamped<Trade>),

    /// The limit order book has changed and should be updated.
    LimitUpdates(Vec<Timestamped<LimitUpdate>>),

    /// An order has been inserted.
    OrderConfirmation(Timestamped<OrderConfirmation>),

    /// An order has been updated.
    OrderUpdate(Timestamped<OrderUpdate>),

    /// An order has expired or was canceled.
    OrderExpiration(Timestamped<OrderExpiration>),
}

bitflags! {
    /// Bit flags indicating which type of notification to forward.
    pub struct NotificationFlags: u8 {
        /// Forward limit updates of the order book.
        const ORDER_BOOK = 0b0001;

        /// Forward trades.
        const TRADES = 0b0010;

        /// Forward order confirmations and updates.
        const ORDERS = 0b0100;

        /// Forward all notifications.
        const ALL = Self::ORDER_BOOK.bits | Self::TRADES.bits | Self::ORDERS.bits;
    }
}

/// Generate order ids.
pub trait GenerateOrderId {
    /// Use `hint` for generating an order id. Except for
    /// GDAX, this should just be `== to_owned`.
    fn new_order_id(hint: &str) -> String;
}

#[derive(Clone, PartialEq, Eq, Hash, Debug, Deserialize)]
/// Account balance for one asset.
pub struct Balance {
    /// Available amount, unticked.
    pub free: String,

    /// Locked amount, unticked.
    pub locked: String,
}

/// A wrapper over a (currency name) => (balance) `HashMap`.
pub type Balances = HashMap<String, Balance>;

/// A trait implemented by clients of various exchanges API.
pub trait ApiClient: GenerateOrderId {
    /// Type returned by the `stream` implementor, used for continuously receiving
    /// notifications.
    type Stream: Stream<Item = Notification, Error = ()> + Send + 'static;

    /// Find a symbol by name.
    fn find_symbol(&self, symbol: &str) -> Option<Symbol>;

    /// Start streaming notifications, only forward those indicated by `flags`.
    fn stream_with_flags(&self, symbol: Symbol, flags: NotificationFlags) -> Self::Stream;

    /// Start streaming notifications.
    fn stream(&self, symbol: Symbol) -> Self::Stream {
        self.stream_with_flags(symbol, NotificationFlags::ALL)
    }

    /// Send an order to the exchange.
    fn order(&self, order: WithSymbol<&Order>)
        -> Box<dyn Future<Item = Timestamped<OrderAck>, Error = errors::OrderError> + Send + 'static>;

    /// Send a cancel order to the exchange.
    ///
    /// # Note
    /// Do no try to cancel an order if said order has not yet been confirmed by the exchange.
    fn cancel(&self, cancel: WithSymbol<&Cancel>)
        -> Box<dyn Future<Item = Timestamped<CancelAck>, Error = errors::CancelError> + Send + 'static>;

    /// Send a ping to the exchange. This can be used to measure the whole roundtrip time,
    /// including authentication and passage through the various software layers. For binance,
    /// the exchange must be pinged regularly in order to keep the listen key alive.
    ///
    /// # Note
    /// Only work for binance right now.
    fn ping(&self)
        -> Box<dyn Future<Item = Timestamped<()>, Error = errors::Error> + Send + 'static>;

    /// Retrieve balances for this account.
    fn balances(&self)
        -> Box<dyn Future<Item = Balances, Error = errors::Error> + Send + 'static>;
}