feat(plasma): Online Plasma Input Fetcher (#167)

* feat(plasma): Online Plasma Input Fetcher Stub

* Update crates/plasma/src/lib.rs

Co-authored-by: clabby <ben@clab.by>

---------

Co-authored-by: clabby <ben@clab.by>

crates/plasma/Cargo.toml

@@ -17,18 +17,36 @@ alloy-primitives = { workspace = true, features = ["rlp"] }
 async-trait.workspace = true
 
 # Local
-kona-primitives = { path = "../primitives" }
-kona-derive = { path = "../derive" }
+kona-primitives = { path = "../primitives", version = "0.0.1" }
+kona-derive = { path = "../derive", version = "0.0.1" }
 
 # `serde` feature dependencies
 serde = { version = "1.0.203", default-features = false, features = ["derive"], optional = true }
 
+# `online` feature dependencies
+alloy-transport-http = { git = "https://github.com/alloy-rs/alloy", rev = "cb95183", optional = true } 
+alloy-provider = { git = "https://github.com/alloy-rs/alloy", rev = "cb95183", default-features = false, optional = true }
+reqwest = { version = "0.12", default-features = false, optional = true }
+
 [dev-dependencies]
 kona-derive = { path = "../derive", features = ["test-utils"] }
-tracing-subscriber = "0.3.18"
 serde_json = { version = "1.0.117", default-features = false }
 tokio = { version = "1.38", features = ["full"] }
+tracing-subscriber = "0.3.18"
 
 [features]
 default = ["serde"]
-serde = ["dep:serde", "kona-primitives/serde"]
+serde = [
+  "dep:serde",
+  "kona-primitives/serde",
+  "alloy-primitives/serde",
+  "alloy-consensus/serde",
+  "kona-derive/serde",
+]
+online = [
+  "dep:alloy-provider",
+  "dep:alloy-transport-http",
+  "dep:reqwest",
+  "alloy-provider/reqwest",
+  "alloy-consensus/serde",
+]

crates/plasma/src/lib.rs

@@ -11,5 +11,10 @@ pub mod source;
 pub mod traits;
 pub mod types;
 
+#[cfg(feature = "online")]
+mod online;
+#[cfg(feature = "online")]
+pub use online::OnlinePlasmaInputFetcher;
+
 #[cfg(test)]
 pub mod test_utils;

crates/plasma/src/online.rs

@@ -0,0 +1,54 @@
+//! Module contains an online implementation of the Plasma Input Fetcher.
+
+use crate::{
+    traits::PlasmaInputFetcher,
+    types::{FinalizedHeadSignal, PlasmaError},
+};
+use alloc::boxed::Box;
+use alloy_primitives::Bytes;
+use async_trait::async_trait;
+use kona_derive::online::AlloyChainProvider;
+use kona_primitives::{
+    block::{BlockID, BlockInfo},
+    system_config::SystemConfig,
+};
+
+/// An Online Plasma Input Fetcher.
+#[derive(Debug, Clone)]
+pub struct OnlinePlasmaInputFetcher {}
+
+#[async_trait]
+impl PlasmaInputFetcher<AlloyChainProvider> for OnlinePlasmaInputFetcher {
+    async fn get_input(
+        &mut self,
+        _fetcher: &AlloyChainProvider,
+        _commitment: Bytes,
+        _block: BlockID,
+    ) -> Option<Result<Bytes, PlasmaError>> {
+        unimplemented!()
+    }
+
+    async fn advance_l1_origin(
+        &mut self,
+        _fetcher: &AlloyChainProvider,
+        _block: BlockID,
+    ) -> Option<Result<(), PlasmaError>> {
+        unimplemented!()
+    }
+
+    async fn reset(
+        &mut self,
+        _block_number: BlockInfo,
+        _cfg: SystemConfig,
+    ) -> Option<Result<(), PlasmaError>> {
+        unimplemented!()
+    }
+
+    async fn finalize(&mut self, _block_number: BlockInfo) -> Option<Result<(), PlasmaError>> {
+        unimplemented!()
+    }
+
+    fn on_finalized_head_signal(&mut self, _callback: FinalizedHeadSignal) {
+        unimplemented!()
+    }
+}