From bb33ca91749ba1693749d22d74a5b3abe8e93bcc Mon Sep 17 00:00:00 2001
From: James Mallon <me@jamesmallon.io>
Date: Tue, 2 Jan 2024 10:57:45 +0100
Subject: [PATCH] feat(block-fetcher-factory): added a factory for generating
 rpc clients

---
 src/networking/mod.rs | 139 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 src/networking/mod.rs

diff --git a/src/networking/mod.rs b/src/networking/mod.rs
new file mode 100644
index 0000000..8d283c3
--- /dev/null
+++ b/src/networking/mod.rs
@@ -0,0 +1,139 @@
+use crate::model::solana_block::SerializedSolanaBlock;
+use log::error;
+use solana_client::rpc_client::RpcClient;
+use std::thread;
+use std::time::Duration;
+
+/// A factory for creating instances of `BlockFetcher`.
+///
+/// This factory can create either a mock or a real Solana block fetcher based on the
+/// provided configuration. It abstracts the creation process of block fetchers,
+/// allowing for easy switching between mock and actual implementations.
+///
+/// # Fields
+/// - `use_mock`: A boolean flag indicating whether to use a mock implementation.
+/// - `rpc_url`: The URL of the Solana RPC client. Used when `use_mock` is `false`.
+pub struct BlockFetcherFactory {
+    use_mock: bool,
+    rpc_url: String,
+}
+
+impl BlockFetcherFactory {
+    /// Constructs a new `BlockFetcherFactory`.
+    ///
+    /// This method initializes a new factory with the specified configuration.
+    ///
+    /// # Parameters
+    /// - `use_mock`: A boolean flag indicating whether to use a mock implementation.
+    /// - `rpc_url`: A string slice representing the RPC URL for the Solana client.
+    ///
+    /// # Returns
+    /// Returns a new instance of `BlockFetcherFactory`.
+    pub fn new(use_mock: bool, rpc_url: &str) -> Self {
+        BlockFetcherFactory {
+            use_mock,
+            rpc_url: rpc_url.to_string(),
+        }
+    }
+
+    /// Creates a block fetcher based on the factory's configuration.
+    ///
+    /// This method generates either a mock or a real implementation of `BlockFetcher`
+    /// depending on the `use_mock` flag. It allows for flexible switching between
+    /// a testing (mock) environment and a production environment.
+    ///
+    /// # Returns
+    /// Returns a boxed object implementing `BlockFetcher` and `Send`.
+    /// This could either be a `MockSolanaClient` or a `SolanaClient` based on the configuration.
+    pub fn create_block_fetcher(&self) -> Box<dyn BlockFetcher + Send> {
+        if self.use_mock {
+            Box::new(MockSolanaClient::new())
+        } else {
+            Box::new(SolanaClient::new(&self.rpc_url))
+        }
+    }
+}
+
+pub trait BlockFetcher {
+    /// Fetches a block from the blockchain by its slot number.
+    ///
+    /// Implementations of this method should retrieve the block corresponding
+    /// to the provided slot number and return it in a serialized form.
+    /// The method varies in its actual behavior based on the implementing struct.
+    ///
+    /// # Parameters
+    /// - `slot`: The slot number of the block to fetch.
+    ///
+    /// # Returns
+    /// Returns a `Result` containing either a `SerializedSolanaBlock` on success
+    /// or a `GetBlockError` on failure.
+    fn get_block(&self, slot: u64) -> Result<SerializedSolanaBlock, GetBlockError>;
+}
+
+pub struct SolanaClient {
+    rpc_client: RpcClient,
+}
+
+impl BlockFetcher for SolanaClient {
+    fn get_block(&self, slot: u64) -> Result<SerializedSolanaBlock, GetBlockError> {
+        let block = self.rpc_client.get_block(slot).map_err(|err| {
+            error!("Could not retrieve block {} due to error: {}", slot, err);
+            GetBlockError::RpcError
+        })?;
+
+        let data = serde_json::to_string(&block).map_err(|err| {
+            error!("An error occurred serializing a Solana block: {}, Error: {}", slot, err);
+            GetBlockError::SerializationError
+        })?;
+
+        Ok(SerializedSolanaBlock {
+            slot_number: block.parent_slot as u64,
+            data,
+        })
+    }
+}
+
+impl SolanaClient {
+    fn new(rpc_url: &str) -> Self {
+        SolanaClient {
+            rpc_client: RpcClient::new(rpc_url),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum GetBlockError {
+    RpcError,
+    SerializationError,
+}
+
+// mocking
+pub struct MockSolanaClient {
+    error: Option<GetBlockError>,
+    get_block_returns: SerializedSolanaBlock,
+}
+
+impl BlockFetcher for MockSolanaClient {
+    fn get_block(&self, _: u64) -> Result<SerializedSolanaBlock, GetBlockError> {
+        // simulate the latency for a network call
+        thread::sleep(Duration::from_millis(250));
+        if self.error.is_some() {
+            let clone = self.error.clone().unwrap();
+            Err(clone)
+        } else {
+            Ok(self.get_block_returns.clone())
+        }
+    }
+}
+
+impl MockSolanaClient {
+    pub fn new() -> Self {
+        MockSolanaClient {
+            error: None,
+            get_block_returns: SerializedSolanaBlock {
+                slot_number: 123,
+                data: "{ \"name\": \"hello_world\" }".to_string(),
+            },
+        }
+    }
+}