104 lines
3.7 KiB
Rust
104 lines
3.7 KiB
Rust
use std::collections::HashMap;
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use ethabi::ethereum_types::Address;
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use substreams_ethereum::{
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pb::eth::v2::{self as eth},
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Event,
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};
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use crate::common::HasAddresser;
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/// Utility struct to easily filter events and assign them handlers.
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///
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/// Usage:
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/// ```
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/// let eh = EventHandler::new(&block);
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/// eh.filter_by_address(store); // This is optional, if omitted it will handle all events that match the type, independently of the emitting contract.
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/// eh.on::<Transfer, _>(&mut on_transfer);
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/// eh.on::<Approval, _>(&mut on_approval);
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/// eh.on::<Mint, _>(&mut on_mint);
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/// eh.on::<Burn, _>(&mut on_burn);
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/// eh.handle_events(); // this will run all handlers
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/// ```
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///
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/// You'll likely want to mutate some value from the handlers that is in the current scope.
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/// For that, make your handlers be closures, that close over the variable you want to mutate, and
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/// have the whole EventHandler block of code in its own scope (either by wrapping it in an aux
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/// function or by wrapping it in {...})
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///
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/// Like so:
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/// ```
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/// let mut balances : Vec<Balance> = vec![];
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/// {
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/// let mut on_transfer = |/*...*/| {
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/// // this handler modifies `balances`
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/// balances.push(some_balance);
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/// };
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/// let eh = EventHandler::new(&block);
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/// eh.on::<Transfer, _>(&mut on_transfer);
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/// eh.handle_events();
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/// }
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///
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/// // do whatever else with `balances` here.
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/// ```
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pub struct EventHandler<'a> {
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block: &'a eth::Block,
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#[allow(clippy::type_complexity)]
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handlers: HashMap<&'static str, Box<dyn FnMut(ð::Log, ð::TransactionTrace) + 'a>>,
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addresses: Option<Box<dyn HasAddresser + 'a>>,
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}
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impl<'a> EventHandler<'a> {
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pub fn new(block: &'a eth::Block) -> Self {
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Self { block, handlers: HashMap::new(), addresses: None }
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}
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/// Sets the HasAddresser as a filter for which events to handle.
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/// Only one at a time can be set. Setting it twice will remove the first one.
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/// Addresses found in the `HasAddresser` will be the ones we'll handle events from.
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pub fn filter_by_address(&mut self, addresser: impl HasAddresser + 'a) {
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self.addresses = Some(Box::new(addresser));
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}
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/// Registers a handler to be run on a given event. The handler should have the signature:
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/// `|ev: SomeEvent, tx: &pbeth::v2::TransactionTrace, log: &pbeth::v2::Log|`.
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/// You can only assign one handler to each Event type.
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/// Handlers are keyed by the name of the event they are handling, so be careful to not assign
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/// handlers for 2 different events named equal.
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pub fn on<E: Event, F>(&mut self, mut handler: F)
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where
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F: FnMut(E, ð::TransactionTrace, ð::Log) + 'a,
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{
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self.handlers.insert(
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E::NAME,
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Box::new(move |log: ð::Log, tx: ð::TransactionTrace| {
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if let Some(event) = E::match_and_decode(log) {
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handler(event, tx, log);
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}
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}),
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);
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}
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/// Will run all registered handlers for all events present on the block that match the given
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/// filters. You'll likely want to run this just once.
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pub fn handle_events(&mut self) {
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// Here we don't need to filter out failed transactions because logs only exist for
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// successful ones.
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for log in self.block.logs() {
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if self.addresses.is_some() &&
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!&self
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.addresses
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.as_ref()
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.unwrap()
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.has_address(Address::from_slice(log.log.address.as_slice()))
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{
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continue;
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}
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for handler in self.handlers.values_mut() {
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handler(log.log, log.receipt.transaction);
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}
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}
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}
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}
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