// 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/>.

//! A map of subscribers.

use ethereum_types::H64;
use jsonrpc_pubsub::{
    typed::{Sink, Subscriber},
    SubscriptionId,
};
use std::{collections::HashMap, ops, str};

#[derive(Debug, Clone, Hash, Eq, PartialEq)]
pub struct Id(H64);
impl str::FromStr for Id {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s.starts_with("0x") {
            Ok(Id(s[2..].parse().map_err(|e| format!("{}", e))?))
        } else {
            Err("The id must start with 0x".into())
        }
    }
}
impl Id {
    // TODO: replace `format!` see [#10412](https://github.com/openethereum/openethereum/issues/10412)
    pub fn as_string(&self) -> String {
        format!("{:?}", self.0)
    }
}

#[cfg(not(test))]
mod random {
    use rand::rngs::OsRng;
    pub type Rng = rand::rngs::OsRng;
    pub fn new() -> Rng {
        OsRng
    }
}

#[cfg(test)]
mod random {
    extern crate rand_xorshift;
    use self::rand_xorshift::XorShiftRng;
    use rand::SeedableRng;
    const RNG_SEED: [u8; 16] = [0u8; 16];
    pub type Rng = XorShiftRng;
    pub fn new() -> Rng {
        Rng::from_seed(RNG_SEED)
    }
}

pub struct Subscribers<T> {
    rand: random::Rng,
    subscriptions: HashMap<Id, T>,
}

impl<T> Default for Subscribers<T> {
    fn default() -> Self {
        Subscribers {
            rand: random::new(),
            subscriptions: HashMap::new(),
        }
    }
}

impl<T> Subscribers<T> {
    fn next_id(&mut self) -> Id {
        let data = H64::random_using(&mut self.rand);
        Id(data)
    }

    /// Insert new subscription and return assigned id.
    pub fn insert(&mut self, val: T) -> SubscriptionId {
        let id = self.next_id();
        debug!(target: "pubsub", "Adding subscription id={:?}", id);
        let s = id.as_string();
        self.subscriptions.insert(id, val);
        SubscriptionId::String(s)
    }

    /// Removes subscription with given id and returns it (if any).
    pub fn remove(&mut self, id: &SubscriptionId) -> Option<T> {
        trace!(target: "pubsub", "Removing subscription id={:?}", id);
        match *id {
            SubscriptionId::String(ref id) => match id.parse() {
                Ok(id) => self.subscriptions.remove(&id),
                Err(_) => None,
            },
            _ => None,
        }
    }
}

impl<T> Subscribers<Sink<T>> {
    /// Assigns id and adds a subscriber to the list.
    pub fn push(&mut self, sub: Subscriber<T>) {
        let id = self.next_id();
        if let Ok(sink) = sub.assign_id(SubscriptionId::String(id.as_string())) {
            debug!(target: "pubsub", "Adding subscription id={:?}", id);
            self.subscriptions.insert(id, sink);
        }
    }
}

impl<T, V> Subscribers<(Sink<T>, V)> {
    /// Assigns id and adds a subscriber to the list.
    pub fn push(&mut self, sub: Subscriber<T>, val: V) {
        let id = self.next_id();
        if let Ok(sink) = sub.assign_id(SubscriptionId::String(id.as_string())) {
            debug!(target: "pubsub", "Adding subscription id={:?}", id);
            self.subscriptions.insert(id, (sink, val));
        }
    }
}

impl<T> ops::Deref for Subscribers<T> {
    type Target = HashMap<Id, T>;

    fn deref(&self) -> &Self::Target {
        &self.subscriptions
    }
}
