Begin work on the new RPC for the new node

substrate/node/src/rpc/blockchain.rs

@@ -0,0 +1,52 @@
+use std::{sync::Arc, ops::Deref, collections::HashSet};
+
+use rand_core::{RngCore, OsRng};
+
+use sp_core::Encode;
+use sp_blockchain::{Error as BlockchainError, HeaderMetadata, HeaderBackend};
+use sp_block_builder::BlockBuilder;
+use sp_api::ProvideRuntimeApi;
+
+use serai_abi::{primitives::prelude::*, SubstrateBlock as Block};
+use serai_runtime::*;
+
+use jsonrpsee::RpcModule;
+
+use sc_client_api::BlockBackend;
+
+pub(crate) fn module<
+  C: 'static
+    + Send
+    + Sync
+    + HeaderMetadata<Block, Error = BlockchainError>
+    + HeaderBackend<Block>
+    + BlockBackend<Block>
+    + ProvideRuntimeApi<Block>,
+>(
+  client: Arc<C>,
+) -> Result<RpcModule<impl 'static + Send + Sync>, Box<dyn std::error::Error + Send + Sync>> {
+  let mut module = RpcModule::new(client);
+  module.register_async_method("serai_block", |params, client, _ext| async move {
+    let [block_hash]: [String; 1] = params.parse()?;
+    let Some(block_hash) = hex::decode(&block_hash).ok().and_then(|bytes| {
+      <[u8; 32]>::try_from(bytes.as_slice())
+        .map(<Block as sp_runtime::traits::Block>::Hash::from)
+        .ok()
+    }) else {
+      return Err(jsonrpsee::types::error::ErrorObjectOwned::owned(
+        -1,
+        "requested block hash wasn't a valid hash",
+        Option::<()>::None,
+      ));
+    };
+    let Some(block) = client.block(block_hash).ok().flatten() else {
+      return Err(jsonrpsee::types::error::ErrorObjectOwned::owned(
+        -2,
+        "couldn't find requested block",
+        Option::<()>::None,
+      ));
+    };
+    Ok(hex::encode(block.block.encode()))
+  })?;
+  Ok(module)
+}