lang: Add Event utility type to get events from bytes

lang/attribute/program/src/declare_program/mod.rs

@@ -10,7 +10,7 @@ use common::gen_docs;
 use mods::{
     accounts::gen_accounts_mod, client::gen_client_mod, constants::gen_constants_mod,
     cpi::gen_cpi_mod, events::gen_events_mod, internal::gen_internal_mod, program::gen_program_mod,
-    types::gen_types_mod,
+    types::gen_types_mod, utils::gen_utils_mod,
 };
 
 pub struct DeclareProgram {
@@ -66,6 +66,9 @@ fn gen_program(idl: &Idl, name: &syn::Ident) -> proc_macro2::TokenStream {
     let client_mod = gen_client_mod(idl);
     let internal_mod = gen_internal_mod(idl);
 
+    // Utils
+    let utils_mod = gen_utils_mod(idl);
+
     quote! {
         #docs
         pub mod #name {
@@ -82,6 +85,8 @@ fn gen_program(idl: &Idl, name: &syn::Ident) -> proc_macro2::TokenStream {
             #cpi_mod
             #client_mod
             #internal_mod
+
+            #utils_mod
         }
     }
 }

lang/attribute/program/src/declare_program/mods/mod.rs

@@ -6,5 +6,6 @@ pub mod events;
 pub mod internal;
 pub mod program;
 pub mod types;
+pub mod utils;
 
 use super::common;

lang/attribute/program/src/declare_program/mods/utils.rs

@@ -0,0 +1,61 @@
+use anchor_idl::types::Idl;
+use quote::{format_ident, quote};
+
+use super::common::gen_discriminator;
+
+pub fn gen_utils_mod(idl: &Idl) -> proc_macro2::TokenStream {
+    let event = gen_event(idl);
+
+    quote! {
+        /// Program utilities.
+        pub mod utils {
+            #event
+        }
+    }
+}
+
+fn gen_event(idl: &Idl) -> proc_macro2::TokenStream {
+    let variants = idl
+        .events
+        .iter()
+        .map(|ev| format_ident!("{}", ev.name))
+        .map(|name| quote! { #name(#name) });
+    let match_arms = idl.events.iter().map(|ev| {
+        let disc = gen_discriminator(&ev.discriminator);
+        let name = format_ident!("{}", ev.name);
+        let event = quote! { #name::try_from_slice(value).map(Self::#name) };
+        quote! { #disc => #event }
+    });
+
+    quote! {
+        use super::{*, events::*};
+
+        /// An enum that includes all events of the declared program as a tuple variant.
+        ///
+        /// See [`Self::try_from_bytes`] to create an instance from bytes.
+        pub enum Event {
+            #(#variants,)*
+        }
+
+        impl Event {
+            /// Try to create an event based on the given bytes.
+            ///
+            /// This method returns an error if the discriminator of the given bytes don't match
+            /// with any of the existing events, or if the deserialization fails.
+            pub fn try_from_bytes(bytes: &[u8]) -> std::io::Result<Self> {
+                Self::try_from(bytes)
+            }
+        }
+
+        impl TryFrom<&[u8]> for Event {
+            type Error = std::io::Error;
+
+            fn try_from(value: &[u8]) -> std::io::Result<Self> {
+                match &value[..8] {
+                    #(#match_arms,)*
+                    _ => Err(std::io::ErrorKind::NotFound.into()),
+                }
+            }
+        }
+    }
+}