feat: add block provider trait (#90)

* feat: add block provider trait

* rustmft

* rename BlockInfo to ChainInfo

crates/interfaces/src/error.rs

@@ -0,0 +1,13 @@
+/// Result alias for `Error`
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Core error variants possible when interacting with the blockchain
+#[derive(Debug, thiserror::Error)]
+#[allow(missing_docs)]
+pub enum Error {
+    #[error(transparent)]
+    Execution(#[from] crate::executor::Error),
+
+    #[error(transparent)]
+    Consensus(#[from] crate::consensus::Error),
+}

crates/interfaces/src/lib.rs

@@ -12,3 +12,11 @@ pub mod executor;
 
 /// Consensus traits.
 pub mod consensus;
+
+/// Traits that provide chain access.
+pub mod provider;
+
+/// Possible errors when interacting with the chain.
+mod error;
+
+pub use error::{Error, Result};

crates/interfaces/src/provider/block.rs

@@ -0,0 +1,71 @@
+use crate::Result;
+use reth_primitives::{
+    rpc::{BlockId, BlockNumber},
+    Block, H256, U256,
+};
+
+/// Client trait for fetching `Block` related data.
+pub trait BlockProvider: Send + Sync {
+    /// Returns the current info for the chain.
+    fn chain_info(&self) -> Result<ChainInfo>;
+
+    /// Returns the block. Returns `None` if block is not found.
+    fn block(&self, id: BlockId) -> Result<Option<Block>>;
+
+    /// Converts the `BlockNumber` variants.
+    fn convert_block_number(
+        &self,
+        num: BlockNumber,
+    ) -> Result<Option<reth_primitives::BlockNumber>> {
+        let num = match num {
+            BlockNumber::Latest => self.chain_info()?.best_number,
+            BlockNumber::Earliest => 0,
+            BlockNumber::Pending => return Ok(None),
+            BlockNumber::Number(num) => num.as_u64(),
+        };
+        Ok(Some(num))
+    }
+
+    /// Get the hash of the block by matching the given id.
+    fn block_hash_for_id(&self, block_id: BlockId) -> Result<Option<H256>> {
+        match block_id {
+            BlockId::Hash(hash) => Ok(Some(hash)),
+            BlockId::Number(num) => {
+                if matches!(num, BlockNumber::Latest) {
+                    return Ok(Some(self.chain_info()?.best_hash))
+                }
+                self.convert_block_number(num)?
+                    .map(|num| self.block_hash(num.into()))
+                    .transpose()
+                    .map(|maybe_hash| maybe_hash.flatten())
+            }
+        }
+    }
+
+    /// Get the number of the block by matching the given id.
+    fn block_number_for_id(
+        &self,
+        block_id: BlockId,
+    ) -> Result<Option<reth_primitives::BlockNumber>> {
+        match block_id {
+            BlockId::Hash(hash) => self.block_number(hash),
+            BlockId::Number(num) => self.convert_block_number(num),
+        }
+    }
+
+    /// Gets the `Block` for the given hash. Returns `None` if no block with this hash exists.
+    fn block_number(&self, hash: H256) -> Result<Option<reth_primitives::BlockNumber>>;
+
+    /// Get the hash of the block with the given number. Returns `None` if no block with this number
+    /// exists.
+    fn block_hash(&self, number: U256) -> Result<Option<H256>>;
+}
+
+/// Current status of the blockchain's head.
+#[derive(Debug, Eq, PartialEq)]
+pub struct ChainInfo {
+    /// Best block hash.
+    pub best_hash: H256,
+    /// Best block number.
+    pub best_number: reth_primitives::BlockNumber,
+}

crates/interfaces/src/provider/mod.rs

@@ -0,0 +1,3 @@
+mod block;
+
+pub use block::BlockProvider;