refactor(client): introduce MithrilEraClient to improve extensibility for era-related features

- Update `Client` to expose a `MithrilEraClient`
- Remove public re-exports of `EraFetcher` and `FetchedEra` from `lib.rs`

Author: dlachaume

mithril-client-cli/src/utils/forced_era_fetcher.rs

@@ -1,6 +1,9 @@
 use async_trait::async_trait;
 
-use mithril_client::{EraFetcher, FetchedEra, MithrilResult};
+use mithril_client::{
+    MithrilResult,
+    era::{EraFetcher, FetchedEra},
+};
 
 pub struct ForcedEraFetcher {
     era: String,

mithril-client/src/client.rs

@@ -18,7 +18,7 @@ use crate::certificate_client::CertificateVerifierCache;
 use crate::certificate_client::{
     CertificateClient, CertificateVerifier, MithrilCertificateVerifier,
 };
-use crate::era::{AggregatorHttpEraFetcher, EraFetcher};
+use crate::era::{AggregatorHttpEraFetcher, EraFetcher, MithrilEraClient};
 use crate::feedback::{FeedbackReceiver, FeedbackSender};
 #[cfg(feature = "fs")]
 use crate::file_downloader::{
@@ -106,7 +106,7 @@ pub struct Client {
     cardano_database_client: Arc<CardanoDatabaseClient>,
     cardano_transaction_client: Arc<CardanoTransactionClient>,
     cardano_stake_distribution_client: Arc<CardanoStakeDistributionClient>,
-    era_fetcher: Arc<dyn EraFetcher>,
+    mithril_era_client: Arc<MithrilEraClient>,
 }
 
 impl Client {
@@ -147,8 +147,8 @@ impl Client {
     }
 
     /// Get the client that fetches the current Mithril era.
-    pub fn era_fetcher(&self) -> Arc<dyn EraFetcher> {
-        self.era_fetcher.clone()
+    pub fn mithril_era_client(&self) -> Arc<MithrilEraClient> {
+        self.mithril_era_client.clone()
     }
 }
 
@@ -166,10 +166,10 @@ pub struct ClientBuilder {
     http_file_downloader: Option<Arc<dyn FileDownloader>>,
     #[cfg(feature = "unstable")]
     certificate_verifier_cache: Option<Arc<dyn CertificateVerifierCache>>,
+    era_fetcher: Option<Arc<dyn EraFetcher>>,
     logger: Option<Logger>,
     feedback_receivers: Vec<Arc<dyn FeedbackReceiver>>,
     options: ClientOptions,
-    era_fetcher: Option<Arc<dyn EraFetcher>>,
 }
 
 impl ClientBuilder {
@@ -189,10 +189,10 @@ impl ClientBuilder {
             http_file_downloader: None,
             #[cfg(feature = "unstable")]
             certificate_verifier_cache: None,
+            era_fetcher: None,
             logger: None,
             feedback_receivers: vec![],
             options: ClientOptions::default(),
-            era_fetcher: None,
         }
     }
 
@@ -214,10 +214,10 @@ impl ClientBuilder {
             http_file_downloader: None,
             #[cfg(feature = "unstable")]
             certificate_verifier_cache: None,
+            era_fetcher: None,
             logger: None,
             feedback_receivers: vec![],
             options: ClientOptions::default(),
-            era_fetcher: None,
         }
     }
 
@@ -238,9 +238,11 @@ impl ClientBuilder {
             Some(client) => client,
         };
 
-        let era_fetcher = match self.era_fetcher {
-            None => Arc::new(AggregatorHttpEraFetcher::new(aggregator_client.clone())),
-            Some(era_fetcher) => era_fetcher,
+        let mithril_era_client = match self.era_fetcher {
+            None => Arc::new(MithrilEraClient::new(Arc::new(
+                AggregatorHttpEraFetcher::new(aggregator_client.clone()),
+            ))),
+            Some(era_fetcher) => Arc::new(MithrilEraClient::new(era_fetcher)),
         };
 
         let certificate_verifier = match self.certificate_verifier {
@@ -326,7 +328,7 @@ impl ClientBuilder {
             cardano_database_client,
             cardano_transaction_client,
             cardano_stake_distribution_client,
-            era_fetcher,
+            mithril_era_client,
         })
     }
 

mithril-client/src/era.rs

@@ -1,5 +1,8 @@
 //! A client to retrieve the current Mithril era.
 //!
+//! In order to do so it defines a [MithrilEraClient] which exposes the following features:
+//! - [fetch_current][MithrilEraClient::fetch_current]: fetch the current Mithril era using its [EraFetcher]
+//!
 //! This module defines the following components:
 //!
 //! - [EraFetcher]: defines an interface to retrieve the current Mithril era
@@ -16,7 +19,7 @@
 //!
 //! let client = ClientBuilder::aggregator("YOUR_AGGREGATOR_ENDPOINT", "YOUR_GENESIS_VERIFICATION_KEY").build()?;
 //!
-//! let fetched_era = client.era_fetcher().fetch_current_era().await?;
+//! let fetched_era = client.mithril_era_client().fetch_current().await?;
 //! match fetched_era.to_supported_era() {
 //!     Ok(supported_era) => println!("Current Mithril era: {supported_era}"),
 //!     Err(era) => println!(
@@ -41,6 +44,23 @@ use crate::{
     aggregator_client::{AggregatorClient, AggregatorRequest},
 };
 
+/// Client for retrieving the current Mithril era.
+pub struct MithrilEraClient {
+    era_fetcher: Arc<dyn EraFetcher>,
+}
+
+impl MithrilEraClient {
+    /// Constructs a new [MithrilEraClient].
+    pub fn new(era_fetcher: Arc<dyn EraFetcher>) -> Self {
+        Self { era_fetcher }
+    }
+
+    /// Fetches the current Mithril era.
+    pub async fn fetch_current(&self) -> MithrilResult<FetchedEra> {
+        self.era_fetcher.fetch_current_era().await
+    }
+}
+
 /// Wrapper around a raw Mithril era string.
 #[derive(Debug, PartialEq, Serialize, Deserialize)]
 pub struct FetchedEra {

mithril-client/src/lib.rs

@@ -12,7 +12,7 @@
 //! - [Cardano stake distribution][cardano_stake_distribution_client] list, get and get by epoch.
 //! - [Mithril stake distribution][mithril_stake_distribution_client] list and get.
 //! - [Certificates][certificate_client] list, get, and chain validation.
-//! - [EraFetcher][era_fetcher]: retrieve the current Mithril era.
+//! - [MithrilEraClient][era]: retrieve the current Mithril era.
 //!
 //! The [Client] aggregates the queries of all of those types.
 //!
@@ -139,7 +139,6 @@ mod type_alias;
 mod utils;
 
 pub use client::*;
-pub use era::{EraFetcher, FetchedEra};
 pub use message::*;
 pub use type_alias::*;