use super::{Error, Receiver, Sender};
use crate::Channel;
use commonware_cryptography::PublicKey;
use futures::{
    channel::{mpsc, oneshot},
    SinkExt,
};
use rand_distr::Normal;
use std::time::Duration;

pub enum Message<P: PublicKey> {
    Register {
        public_key: P,
        channel: Channel,
        #[allow(clippy::type_complexity)]
        result: oneshot::Sender<Result<(Sender<P>, Receiver<P>), Error>>,
    },
    SetBandwidth {
        public_key: P,
        egress_bps: usize,
        ingress_bps: usize,
        result: oneshot::Sender<Result<(), Error>>,
    },
    AddLink {
        sender: P,
        receiver: P,
        sampler: Normal<f64>,
        success_rate: f64,
        result: oneshot::Sender<Result<(), Error>>,
    },
    RemoveLink {
        sender: P,
        receiver: P,
        result: oneshot::Sender<Result<(), Error>>,
    },
    Block {
        /// The public key of the peer sending the block request.
        from: P,
        /// The public key of the peer to block.
        to: P,
    },
    Blocked {
        result: oneshot::Sender<Result<Vec<(P, P)>, Error>>,
    },
}

/// Describes a connection between two peers.
///
/// Links are unidirectional (and must be set up in both directions
/// for a bidirectional connection).
#[derive(Clone)]
pub struct Link {
    /// Mean latency for the delivery of a message.
    pub latency: Duration,

    /// Standard deviation of the latency for the delivery of a message.
    pub jitter: Duration,

    /// Probability of a message being delivered successfully (in range \[0,1\]).
    pub success_rate: f64,
}

/// Interface for modifying the simulated network.
///
/// At any point, peers can be added/removed and links
/// between said peers can be modified.
#[derive(Clone)]
pub struct Oracle<P: PublicKey> {
    sender: mpsc::UnboundedSender<Message<P>>,
}

impl<P: PublicKey> Oracle<P> {
    /// Create a new instance of the oracle.
    pub(crate) fn new(sender: mpsc::UnboundedSender<Message<P>>) -> Self {
        Self { sender }
    }

    /// Spawn an individual control interface for a peer in the simulated network.
    pub fn control(&self, me: P) -> Control<P> {
        Control {
            me,
            sender: self.sender.clone(),
        }
    }

    /// Return a list of all blocked peers.
    pub async fn blocked(&mut self) -> Result<Vec<(P, P)>, Error> {
        let (s, r) = oneshot::channel();
        self.sender
            .send(Message::Blocked { result: s })
            .await
            .map_err(|_| Error::NetworkClosed)?;
        r.await.map_err(|_| Error::NetworkClosed)?
    }

    /// Register a new peer with the network that can interact over a given channel.
    ///
    /// By default, the peer will not be linked to any other peers. If a peer is already
    /// registered on a given channel, it will return an error.
    pub async fn register(
        &mut self,
        public_key: P,
        channel: Channel,
    ) -> Result<(Sender<P>, Receiver<P>), Error> {
        let (sender, receiver) = oneshot::channel();
        self.sender
            .send(Message::Register {
                public_key,
                channel,
                result: sender,
            })
            .await
            .map_err(|_| Error::NetworkClosed)?;
        receiver.await.map_err(|_| Error::NetworkClosed)?
    }

    /// Set bandwidth limits for a peer.
    ///
    /// Bandwidth is specified for the peer's egress (upload) and ingress (download)
    /// rates in bytes per second. Use `usize::MAX` for unlimited bandwidth.
    pub async fn set_bandwidth(
        &mut self,
        public_key: P,
        egress_bps: usize,
        ingress_bps: usize,
    ) -> Result<(), Error> {
        let (sender, receiver) = oneshot::channel();
        self.sender
            .send(Message::SetBandwidth {
                public_key,
                egress_bps,
                ingress_bps,
                result: sender,
            })
            .await
            .map_err(|_| Error::NetworkClosed)?;
        receiver.await.map_err(|_| Error::NetworkClosed)?
    }

    /// Create a unidirectional link between two peers.
    ///
    /// Link can be called multiple times for the same sender/receiver. The latest
    /// setting will be used.
    pub async fn add_link(&mut self, sender: P, receiver: P, config: Link) -> Result<(), Error> {
        // Sanity checks
        if sender == receiver {
            return Err(Error::LinkingSelf);
        }
        if config.success_rate < 0.0 || config.success_rate > 1.0 {
            return Err(Error::InvalidSuccessRate(config.success_rate));
        }

        // Convert Duration to milliseconds as f64 for the Normal distribution
        let latency_ms = config.latency.as_secs_f64() * 1000.0;
        let jitter_ms = config.jitter.as_secs_f64() * 1000.0;

        // Create distribution
        let sampler = Normal::new(latency_ms, jitter_ms).unwrap();

        // Wait for update to complete
        let (s, r) = oneshot::channel();
        self.sender
            .send(Message::AddLink {
                sender,
                receiver,
                sampler,
                success_rate: config.success_rate,
                result: s,
            })
            .await
            .map_err(|_| Error::NetworkClosed)?;
        r.await.map_err(|_| Error::NetworkClosed)?
    }

    /// Remove a unidirectional link between two peers.
    ///
    /// If no link exists, this will return an error.
    pub async fn remove_link(&mut self, sender: P, receiver: P) -> Result<(), Error> {
        // Sanity checks
        if sender == receiver {
            return Err(Error::LinkingSelf);
        }

        // Wait for update to complete
        let (s, r) = oneshot::channel();
        self.sender
            .send(Message::RemoveLink {
                sender,
                receiver,
                result: s,
            })
            .await
            .map_err(|_| Error::NetworkClosed)?;
        r.await.map_err(|_| Error::NetworkClosed)?
    }
}

/// Individual control interface for a peer in the simulated network.
#[derive(Clone)]
pub struct Control<P: PublicKey> {
    /// The public key of the peer this control interface is for.
    me: P,

    /// Sender for messages to the oracle.
    sender: mpsc::UnboundedSender<Message<P>>,
}

impl<P: PublicKey> crate::Blocker for Control<P> {
    type PublicKey = P;

    async fn block(&mut self, public_key: P) {
        let _ = self
            .sender
            .send(Message::Block {
                from: self.me.clone(),
                to: public_key,
            })
            .await;
    }
}