ethers-rs/ethers-contract/src/event.rs

#![allow(clippy::return_self_not_must_use)]

use crate::{log::LogMeta, stream::EventStream, ContractError, EthLogDecode};
use ethers_core::{
    abi::{Detokenize, RawLog},
    types::{BlockNumber, Filter, Log, Topic, H256},
};
use ethers_providers::{FilterWatcher, Middleware, PubsubClient, SubscriptionStream};
use std::{borrow::Cow, marker::PhantomData};

/// A trait for implementing event bindings
pub trait EthEvent: Detokenize + Send + Sync {
    /// The name of the event this type represents
    fn name() -> Cow<'static, str>;

    /// Retrieves the signature for the event this data corresponds to.
    /// This signature is the Keccak-256 hash of the ABI signature of
    /// this event.
    fn signature() -> H256;

    /// Retrieves the ABI signature for the event this data corresponds
    /// to.
    fn abi_signature() -> Cow<'static, str>;

    /// Decodes an Ethereum `RawLog` into an instance of the type.
    fn decode_log(log: &RawLog) -> Result<Self, ethers_core::abi::Error>
    where
        Self: Sized;

    /// Returns true if this is an anonymous event
    fn is_anonymous() -> bool;

    /// Returns an Event builder for the ethereum event represented by this types ABI signature.
    fn new<M: Middleware>(filter: Filter, provider: &M) -> Event<M, Self>
    where
        Self: Sized,
    {
        let filter = filter.event(&Self::abi_signature());
        Event { filter, provider, datatype: PhantomData }
    }
}

// Convenience implementation
impl<T: EthEvent> EthLogDecode for T {
    fn decode_log(log: &RawLog) -> Result<Self, ethers_core::abi::Error>
    where
        Self: Sized,
    {
        T::decode_log(log)
    }
}

/// Helper for managing the event filter before querying or streaming its logs
#[derive(Debug)]
#[must_use = "event filters do nothing unless you `query` or `stream` them"]
pub struct Event<'a, M, D> {
    /// The event filter's state
    pub filter: Filter,
    pub(crate) provider: &'a M,
    /// Stores the event datatype
    pub(crate) datatype: PhantomData<D>,
}

// TODO: Improve these functions
impl<M, D: EthLogDecode> Event<'_, M, D> {
    /// Sets the filter's `from` block
    #[allow(clippy::wrong_self_convention)]
    pub fn from_block<T: Into<BlockNumber>>(mut self, block: T) -> Self {
        self.filter = self.filter.from_block(block);
        self
    }

    /// Sets the filter's `to` block
    #[allow(clippy::wrong_self_convention)]
    pub fn to_block<T: Into<BlockNumber>>(mut self, block: T) -> Self {
        self.filter = self.filter.to_block(block);
        self
    }

    /// Sets the filter's `blockHash`. Setting this will override previously
    /// set `from_block` and `to_block` fields.
    #[allow(clippy::wrong_self_convention)]
    pub fn at_block_hash<T: Into<H256>>(mut self, hash: T) -> Self {
        self.filter = self.filter.at_block_hash(hash);
        self
    }

    /// Sets the filter's 0th topic (typically the event name for non-anonymous events)
    pub fn topic0<T: Into<Topic>>(mut self, topic: T) -> Self {
        self.filter.topics[0] = Some(topic.into());
        self
    }

    /// Sets the filter's 1st topic
    pub fn topic1<T: Into<Topic>>(mut self, topic: T) -> Self {
        self.filter.topics[1] = Some(topic.into());
        self
    }

    /// Sets the filter's 2nd topic
    pub fn topic2<T: Into<Topic>>(mut self, topic: T) -> Self {
        self.filter.topics[2] = Some(topic.into());
        self
    }

    /// Sets the filter's 3rd topic
    pub fn topic3<T: Into<Topic>>(mut self, topic: T) -> Self {
        self.filter.topics[3] = Some(topic.into());
        self
    }
}

impl<'a, M, D> Event<'a, M, D>
where
    M: Middleware,
    D: EthLogDecode,
{
    /// Turns this event filter into `Stream` that yields decoded events.
    ///
    /// This will first install a new logs filter via [`eth_newFilter`](https://docs.alchemy.com/alchemy/apis/ethereum/eth-newfilter) using the configured `filter` object. See also [`FilterWatcher`](ethers_providers::FilterWatcher).
    ///
    /// Once the filter is created, this will periodically call [`eth_getFilterChanges`](https://docs.alchemy.com/alchemy/apis/ethereum/eth-getfilterchanges) to get the newest logs and decode them
    ///
    /// **Note:** Compared to [`Self::subscribe`], which is only available on `PubsubClient`s, such
    /// as Websocket, this is a poll-based subscription, as the node does not notify us when a new
    /// matching log is available, instead we have to actively ask for new logs using additional RPC
    /// requests, and this is done on an interval basis.
    ///
    /// # Example
    ///
    /// ```
    /// # async fn test<M:ethers_providers::Middleware>(contract: ethers_contract::Contract<M>) {
    /// # use ethers_core::types::*;
    /// # use futures_util::stream::StreamExt;
    /// # use ethers_contract::{Contract, EthEvent};
    ///
    /// // The event we want to get
    /// #[derive(Clone, Debug, EthEvent)]
    /// pub struct Approval {
    ///     #[ethevent(indexed)]
    ///     pub token_owner: Address,
    ///     #[ethevent(indexed)]
    ///     pub spender: Address,
    ///     pub tokens: U256,
    /// }
    ///
    /// let ev = contract.event::<Approval>().from_block(1337).to_block(2000);
    /// let mut event_stream = ev.stream().await.unwrap();
    ///
    ///  while let Some(Ok(approval)) = event_stream.next().await {
    ///      let Approval{token_owner,spender,tokens} = approval;
    /// }
    ///
    /// # }
    /// ```
    pub async fn stream(
        &'a self,
    ) -> Result<
        // Wraps the FilterWatcher with a mapping to the event
        EventStream<'a, FilterWatcher<'a, M::Provider, Log>, D, ContractError<M>>,
        ContractError<M>,
    > {
        let filter =
            self.provider.watch(&self.filter).await.map_err(ContractError::MiddlewareError)?;
        Ok(EventStream::new(filter.id, filter, Box::new(move |log| self.parse_log(log))))
    }

    /// As [`Self::stream`], but does not discard [`Log`] metadata.
    pub async fn stream_with_meta(
        &'a self,
    ) -> Result<
        // Wraps the FilterWatcher with a mapping to the event
        EventStream<'a, FilterWatcher<'a, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
        ContractError<M>,
    > {
        let filter =
            self.provider.watch(&self.filter).await.map_err(ContractError::MiddlewareError)?;
        Ok(EventStream::new(
            filter.id,
            filter,
            Box::new(move |log| {
                let meta = LogMeta::from(&log);
                Ok((self.parse_log(log)?, meta))
            }),
        ))
    }
}

impl<'a, M, D> Event<'a, M, D>
where
    M: Middleware,
    <M as Middleware>::Provider: PubsubClient,
    D: EthLogDecode,
{
    /// Returns a subscription for the event
    ///
    /// See also [Self::stream()].
    pub async fn subscribe(
        &'a self,
    ) -> Result<
        // Wraps the SubscriptionStream with a mapping to the event
        EventStream<'a, SubscriptionStream<'a, M::Provider, Log>, D, ContractError<M>>,
        ContractError<M>,
    > {
        let filter = self
            .provider
            .subscribe_logs(&self.filter)
            .await
            .map_err(ContractError::MiddlewareError)?;
        Ok(EventStream::new(filter.id, filter, Box::new(move |log| self.parse_log(log))))
    }

    pub async fn subscribe_with_meta(
        &'a self,
    ) -> Result<
        // Wraps the SubscriptionStream with a mapping to the event
        EventStream<'a, SubscriptionStream<'a, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
        ContractError<M>,
    > {
        let filter = self
            .provider
            .subscribe_logs(&self.filter)
            .await
            .map_err(ContractError::MiddlewareError)?;
        Ok(EventStream::new(
            filter.id,
            filter,
            Box::new(move |log| {
                let meta = LogMeta::from(&log);
                Ok((self.parse_log(log)?, meta))
            }),
        ))
    }
}

impl<M, D> Event<'_, M, D>
where
    M: Middleware,
    D: EthLogDecode,
{
    /// Queries the blockchain for the selected filter and returns a vector of matching
    /// event logs
    pub async fn query(&self) -> Result<Vec<D>, ContractError<M>> {
        let logs =
            self.provider.get_logs(&self.filter).await.map_err(ContractError::MiddlewareError)?;
        let events = logs
            .into_iter()
            .map(|log| self.parse_log(log))
            .collect::<Result<Vec<_>, ContractError<M>>>()?;
        Ok(events)
    }

    /// Queries the blockchain for the selected filter and returns a vector of logs
    /// along with their metadata
    pub async fn query_with_meta(&self) -> Result<Vec<(D, LogMeta)>, ContractError<M>> {
        let logs =
            self.provider.get_logs(&self.filter).await.map_err(ContractError::MiddlewareError)?;
        let events = logs
            .into_iter()
            .map(|log| {
                let meta = LogMeta::from(&log);
                let event = self.parse_log(log)?;
                Ok((event, meta))
            })
            .collect::<Result<_, ContractError<M>>>()?;
        Ok(events)
    }

    pub fn parse_log(&self, log: Log) -> Result<D, ContractError<M>> {
        D::decode_log(&RawLog { topics: log.topics, data: log.data.to_vec() }).map_err(From::from)
    }
}