erdos 0.4.0

ERDOS is a platform for developing self-driving cars and robotics applications.
Documentation 
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use std::fmt::Debug;

use abomonation_derive::Abomonation;
use serde::{Deserialize, Serialize};

use crate::dataflow::time::Timestamp;

/// Trait for valid message data. The data must be clonable, sendable between threads and
/// serializable.
// TODO: somehow add the deserialize requirement.
pub trait Data: 'static + Clone + Send + Sync + Debug + Serialize {}
/// Any type that is clonable, sendable, and can be serialized and dereserialized implements `Data`.
impl<T> Data for T where
    for<'a> T: 'static + Clone + Send + Sync + Debug + Serialize + Deserialize<'a>
{
}

/// Operators send messages on streams. A message can be either a `Watermark` or a `TimestampedData`.
#[derive(Clone, Debug, Serialize, Deserialize, Abomonation)]
pub enum Message<D: Data> {
    TimestampedData(TimestampedData<D>),
    Watermark(Timestamp),
}

impl<D: Data> Message<D> {
    /// Creates a new `TimestampedData` message.
    pub fn new_message(timestamp: Timestamp, data: D) -> Message<D> {
        Self::TimestampedData(TimestampedData::new(timestamp, data))
    }

    /// Creates a new `Watermark` message.
    pub fn new_watermark(timestamp: Timestamp) -> Message<D> {
        Self::Watermark(timestamp)
    }

    pub fn is_top_watermark(&self) -> bool {
        if let Self::Watermark(t) = self {
            t.is_top()
        } else {
            false
        }
    }

    pub fn data(&self) -> Option<&D> {
        match self {
            Self::TimestampedData(d) => Some(&d.data),
            _ => None,
        }
    }

    pub fn timestamp(&self) -> &Timestamp {
        match self {
            Self::TimestampedData(d) => &d.timestamp,
            Self::Watermark(t) => t,
        }
    }
}

impl<D: Data + PartialEq> PartialEq for Message<D> {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Self::TimestampedData(d1), Self::TimestampedData(d2)) => d1 == d2,
            (Self::Watermark(w1), Self::Watermark(w2)) => w1 == w2,
            _ => false,
        }
    }
}

/// Data message which operators send along streams.
#[derive(Debug, Clone, Serialize, Deserialize, Abomonation)]
pub struct TimestampedData<D: Data> {
    /// Timestamp of the message.
    pub timestamp: Timestamp,
    /// Data is an option in case one wants to send null messages.
    pub data: D,
}

impl<D: Data> TimestampedData<D> {
    pub fn new(timestamp: Timestamp, data: D) -> Self {
        Self { timestamp, data }
    }
}

impl<D: Data + PartialEq> PartialEq for TimestampedData<D> {
    fn eq(&self, other: &Self) -> bool {
        self.timestamp == other.timestamp && self.data == other.data
    }
}