Compute dashboard stats

Track open rate for new post notifications (user clicked the button in
the link or not). No data about the user is collected during the
process, it only uses an ID inserted by the issue delivery worker.

src/issue_delivery_worker.rs

@@ -1,4 +1,7 @@
-use crate::{configuration::Settings, domain::SubscriberEmail, email_client::EmailClient};
+use crate::{
+    configuration::Settings, domain::SubscriberEmail, email_client::EmailClient, routes::EmailType,
+};
+use anyhow::Context;
 use sqlx::{Executor, PgPool, Postgres, Row, Transaction, postgres::PgPoolOptions};
 use std::time::Duration;
 use tracing::{Span, field::display};
@@ -41,10 +44,10 @@ pub async fn try_execute_task(
     email_client: &EmailClient,
 ) -> Result<ExecutionOutcome, anyhow::Error> {
     let task = dequeue_task(connection_pool).await?;
-    if task.is_none() {
-        return Ok(ExecutionOutcome::EmptyQueue);
-    }
-    let (transaction, task) = task.unwrap();
+    let (mut transaction, task) = match task {
+        Some((transaction, task)) => (transaction, task),
+        None => return Ok(ExecutionOutcome::EmptyQueue),
+    };
     Span::current()
         .record("newsletter_issue_id", display(task.newsletter_issue_id))
         .record("subscriber_email", display(&task.subscriber_email));
@@ -52,6 +55,9 @@ pub async fn try_execute_task(
         Ok(email) => {
             let mut issue = get_issue(connection_pool, task.newsletter_issue_id).await?;
             issue.inject_unsubscribe_token(&task.unsubscribe_token);
+            if task.kind == EmailType::NewPost.to_string() {
+                issue.create_tracking_info(&mut transaction).await?;
+            }
             if let Err(e) = email_client
                 .send_email(
                     &email,
@@ -85,6 +91,7 @@ pub async fn try_execute_task(
 }
 
 struct NewsletterIssue {
+    newsletter_issue_id: Uuid,
     title: String,
     text_content: String,
     html_content: String,
@@ -95,6 +102,28 @@ impl NewsletterIssue {
         self.text_content = self.text_content.replace("UNSUBSCRIBE_TOKEN", token);
         self.html_content = self.html_content.replace("UNSUBSCRIBE_TOKEN", token);
     }
+
+    async fn create_tracking_info(
+        &mut self,
+        transaction: &mut Transaction<'static, Postgres>,
+    ) -> Result<(), anyhow::Error> {
+        let email_id = Uuid::new_v4();
+        let query = sqlx::query!(
+            r#"
+            INSERT INTO notifications_delivered (email_id, newsletter_issue_id)
+            VALUES ($1, $2)
+            "#,
+            email_id,
+            self.newsletter_issue_id
+        );
+        transaction
+            .execute(query)
+            .await
+            .context("Failed to store email tracking info.")?;
+        self.text_content = self.text_content.replace("EMAIL_ID", &email_id.to_string());
+        self.html_content = self.html_content.replace("EMAIL_ID", &email_id.to_string());
+        Ok(())
+    }
 }
 
 #[tracing::instrument(skip_all)]
@@ -105,7 +134,7 @@ async fn get_issue(
     let issue = sqlx::query_as!(
         NewsletterIssue,
         r#"
-        SELECT title, text_content, html_content
+        SELECT newsletter_issue_id, title, text_content, html_content
         FROM newsletter_issues
         WHERE newsletter_issue_id = $1
         "#,
@@ -120,6 +149,7 @@ pub struct Task {
     pub newsletter_issue_id: Uuid,
     pub subscriber_email: String,
     pub unsubscribe_token: String,
+    pub kind: String,
 }
 
 #[tracing::instrument(skip_all)]
@@ -129,7 +159,7 @@ async fn dequeue_task(
     let mut transaction = connection_pool.begin().await?;
     let query = sqlx::query!(
         r#"
-        SELECT newsletter_issue_id, subscriber_email, unsubscribe_token
+        SELECT newsletter_issue_id, subscriber_email, unsubscribe_token, kind
         FROM issue_delivery_queue
         FOR UPDATE
         SKIP LOCKED
@@ -142,6 +172,7 @@ async fn dequeue_task(
             newsletter_issue_id: row.get("newsletter_issue_id"),
             subscriber_email: row.get("subscriber_email"),
             unsubscribe_token: row.get("unsubscribe_token"),
+            kind: row.get("kind"),
         };
         Ok(Some((transaction, task)))
     } else {