From 5d88dbc92ce470c951717debe246e182b3fe5656 Mon Sep 17 00:00:00 2001
From: Sampras Lopes <lsampras@pm.me>
Date: Mon, 16 Oct 2023 18:20:23 +0530
Subject: [PATCH] feat(events): add basic event handler to collect application
 events (#2602)

---
 crates/router/src/events.rs              | 25 ++++++++++++++++++++++++
 crates/router/src/events/event_logger.rs | 15 ++++++++++++++
 crates/router/src/lib.rs                 |  1 +
 crates/router/src/routes/app.rs          | 13 +++++++++++-
 4 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 crates/router/src/events.rs
 create mode 100644 crates/router/src/events/event_logger.rs

diff --git a/crates/router/src/events.rs b/crates/router/src/events.rs
new file mode 100644
index 000000000000..f573a4970b25
--- /dev/null
+++ b/crates/router/src/events.rs
@@ -0,0 +1,25 @@
+use serde::Serialize;
+
+pub mod event_logger;
+
+pub trait EventHandler: Sync + Send + dyn_clone::DynClone {
+    fn log_event<T: Event>(&self, event: T, previous: Option<T>);
+}
+
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum EventType {
+    PaymentIntent,
+    PaymentAttempt,
+    Refund,
+    ApiLogs,
+}
+
+pub trait Event
+where
+    Self: Serialize,
+{
+    fn event_type() -> EventType;
+
+    fn key(&self) -> String;
+}
diff --git a/crates/router/src/events/event_logger.rs b/crates/router/src/events/event_logger.rs
new file mode 100644
index 000000000000..d8254b2cc4e9
--- /dev/null
+++ b/crates/router/src/events/event_logger.rs
@@ -0,0 +1,15 @@
+use super::{Event, EventHandler};
+use crate::services::logger;
+
+#[derive(Clone, Debug, Default)]
+pub struct EventLogger {}
+
+impl EventHandler for EventLogger {
+    fn log_event<T: Event>(&self, event: T, previous: Option<T>) {
+        if let Some(prev) = previous {
+            logger::info!(previous = ?serde_json::to_string(&prev).unwrap_or(r#"{ "error": "Serialization failed" }"#.to_string()), current = ?serde_json::to_string(&event).unwrap_or(r#"{ "error": "Serialization failed" }"#.to_string()), event_type =? T::event_type(), event_id =? event.key(), log_type = "event");
+        } else {
+            logger::info!(current = ?serde_json::to_string(&event).unwrap_or(r#"{ "error": "Serialization failed" }"#.to_string()), event_type =? T::event_type(), event_id =? event.key(), log_type = "event");
+        }
+    }
+}
diff --git a/crates/router/src/lib.rs b/crates/router/src/lib.rs
index 5cea2a012335..11efec64055b 100644
--- a/crates/router/src/lib.rs
+++ b/crates/router/src/lib.rs
@@ -15,6 +15,7 @@ pub(crate) mod macros;
 pub mod routes;
 pub mod workflows;
 
+pub mod events;
 pub mod middleware;
 pub mod openapi;
 pub mod services;
diff --git a/crates/router/src/routes/app.rs b/crates/router/src/routes/app.rs
index 7f18220438c4..5ebafe9a66e0 100644
--- a/crates/router/src/routes/app.rs
+++ b/crates/router/src/routes/app.rs
@@ -25,15 +25,17 @@ use super::{ephemeral_key::*, payment_methods::*, webhooks::*};
 use crate::{
     configs::settings,
     db::{StorageImpl, StorageInterface},
+    events::{event_logger::EventLogger, EventHandler},
     routes::cards_info::card_iin_info,
     services::get_store,
 };
 
 #[derive(Clone)]
-pub struct AppState {
+pub struct AppStateBase<E: EventHandler> {
     pub flow_name: String,
     pub store: Box<dyn StorageInterface>,
     pub conf: Arc<settings::Settings>,
+    pub event_handler: E,
     #[cfg(feature = "email")]
     pub email_client: Arc<dyn EmailClient>,
     #[cfg(feature = "kms")]
@@ -41,6 +43,8 @@ pub struct AppState {
     pub api_client: Box<dyn crate::services::ApiClient>,
 }
 
+pub type AppState = AppStateBase<EventLogger>;
+
 impl scheduler::SchedulerAppState for AppState {
     fn get_db(&self) -> Box<dyn SchedulerInterface> {
         self.store.get_scheduler_db()
@@ -48,8 +52,10 @@ impl scheduler::SchedulerAppState for AppState {
 }
 
 pub trait AppStateInfo {
+    type Event: EventHandler;
     fn conf(&self) -> settings::Settings;
     fn store(&self) -> Box<dyn StorageInterface>;
+    fn event_handler(&self) -> &Self::Event;
     #[cfg(feature = "email")]
     fn email_client(&self) -> Arc<dyn EmailClient>;
     fn add_request_id(&mut self, request_id: Option<String>);
@@ -59,6 +65,7 @@ pub trait AppStateInfo {
 }
 
 impl AppStateInfo for AppState {
+    type Event = EventLogger;
     fn conf(&self) -> settings::Settings {
         self.conf.as_ref().to_owned()
     }
@@ -69,6 +76,9 @@ impl AppStateInfo for AppState {
     fn email_client(&self) -> Arc<dyn EmailClient> {
         self.email_client.to_owned()
     }
+    fn event_handler(&self) -> &Self::Event {
+        &self.event_handler
+    }
     fn add_request_id(&mut self, request_id: Option<String>) {
         self.api_client.add_request_id(request_id);
     }
@@ -137,6 +147,7 @@ impl AppState {
             #[cfg(feature = "kms")]
             kms_secrets: Arc::new(kms_secrets),
             api_client,
+            event_handler: EventLogger::default(),
         }
     }