graph: Better comments

Author: incrypto32

core/src/subgraph/context/instance/mod.rs

@@ -22,14 +22,15 @@ pub(crate) struct SubgraphInstance<C: Blockchain, T: RuntimeHostBuilder<C>> {
     pub(super) static_data_sources: Arc<Vec<DataSource<C>>>,
     host_metrics: Arc<HostMetrics>,
 
-    /// The hosts represent the data sources in the subgraph. There is one host per data source.
+    /// The hosts represent the onchain data sources in the subgraph. There is one host per data source.
     /// Data sources with no mappings (e.g. direct substreams) have no host.
     ///
     /// Onchain hosts must be created in increasing order of block number. `fn hosts_for_trigger`
     /// will return the onchain hosts in the same order as they were inserted.
     onchain_hosts: OnchainHosts<C, T>,
 
-    // TODO(krishna): Describe subgraph_hosts
+    /// `subgraph_hosts` represent subgraph data sources declared in the manifest. These are a special
+    /// kind of data source that depends on the data from another source subgraph.
     subgraph_hosts: OnchainHosts<C, T>,
 
     offchain_hosts: OffchainHosts<C, T>,

graph/src/blockchain/block_stream.rs

@@ -315,6 +315,9 @@ impl<C: Blockchain> BlockWithTriggers<C> {
     }
 }
 
+/// The `TriggersAdapterWrapper` wraps the chain-specific `TriggersAdapter`, enabling chain-agnostic
+/// handling of subgraph datasource triggers. Without this wrapper, we would have to duplicate the same
+/// logic for each chain, increasing code repetition.
 pub struct TriggersAdapterWrapper<C: Blockchain> {
     pub adapter: Arc<dyn TriggersAdapter<C>>,
     pub source_subgraph_stores: Vec<(DeploymentHash, Arc<dyn ReadStore>)>,

graph/src/blockchain/mod.rs

@@ -248,6 +248,11 @@ impl From<web3::Error> for IngestorError {
     }
 }
 
+/// The `TriggerFilterWrapper` is a higher-level wrapper around the chain-specific `TriggerFilter`,
+/// enabling subgraph-based trigger filtering for subgraph datasources. This abstraction is necessary
+/// because subgraph filtering operates at a higher level than chain-based filtering. By using this wrapper,
+/// we reduce code duplication, allowing subgraph-based filtering to be implemented once, instead of
+/// duplicating it across different chains.
 #[derive(Debug)]
 pub struct TriggerFilterWrapper<C: Blockchain> {
     pub chain_filter: Arc<C::TriggerFilter>,