add KethEvent to encode state (#189)

Part of #139

crates/exex/src/model/event.rs

@@ -0,0 +1,31 @@
+use super::primitives::KethPointer;
+use serde::{Deserialize, Serialize};
+
+/// Represents an Ethereum event in the Keth model.
+///
+/// Events are used in the Ethereum Virtual Machine (EVM) to log information during contract
+/// execution. They are composed of `topics` and `data`, where:
+/// - `topics`: A list of indexed fields that can be used for efficient filtering and querying.
+/// - `data`: Additional unindexed information related to the event.
+///
+/// This struct provides a Keth-compatible representation of Ethereum events, where both `topics`
+/// and `data` are stored as `KethPointer` to ensure compatibility with the Cairo VM's constraints.
+#[derive(Debug, Eq, Ord, Hash, PartialEq, PartialOrd, Clone, Serialize, Deserialize)]
+pub struct KethEvent {
+    /// The indexed topics associated with the event.
+    ///
+    /// Topics allow filtering of events based on specific criteria. Each topic is typically a
+    /// 256-bit value represented as a [`KethPointer`] to ensure compatibility with Cairo VM
+    /// constraints.
+    ///
+    /// In the Cairo VM, topics are an array of Felts.
+    pub topics: KethPointer,
+
+    /// The unindexed data associated with the event.
+    ///
+    /// This field contains the raw data emitted by the event, which is not indexed but can
+    /// provide additional context about the event.
+    ///
+    /// The data is stored as a [`KethPointer`] (an array of Felts in the Cairo VM).
+    pub data: KethPointer,
+}

crates/exex/src/model/mod.rs

@@ -1,4 +1,5 @@
 pub mod block;
+pub mod event;
 pub mod header;
 pub mod payload;
 pub mod primitives;