Throttle inactive user emails

app/mailers/user_mailer.rb

@@ -1,13 +1,18 @@
 class UserMailer < ApplicationMailer
   default from: "Covidliste <[email protected]>"
 
+  MIN_SEND_INTERVAL = 7.days
+
   def send_inactive_user_unsubscription_request
-    user = User.find(params[:user_id])
+    @user = User.find(params[:user_id])
+
+    return if @user.email.blank?
+    return if @user.last_inactive_user_email_sent_at && @user.last_inactive_user_email_sent_at >= MIN_SEND_INTERVAL.ago
 
-    return if user.email.blank?
+    @user.touch(:last_inactive_user_email_sent_at)
 
     mail(
-      to: user.email,
+      to: @user.email,
       subject: "Attendez-vous toujours une dose de vaccin ?"
     )
   end

app/models/user.rb

@@ -156,6 +156,7 @@ def anonymize!
     self.birthdate = nil
     self.grid_i = nil
     self.grid_j = nil
+    self.last_inactive_user_email_sent_at = nil
     self.anonymized_at = Time.now.utc
     save(validate: false)
   end

db/migrate/20210530071920_add_last_inactive_user_email_sent_at.rb

@@ -0,0 +1,5 @@
+class AddLastInactiveUserEmailSentAt < ActiveRecord::Migration[6.1]
+  def change
+    add_column :users, :last_inactive_user_email_sent_at, :datetime
+  end
+end

spec/mailers/user_mailer_spec.rb

@@ -0,0 +1,27 @@
+require "rails_helper"
+
+RSpec.describe UserMailer, type: :mailer do
+  describe "#send_inactive_user_unsubscription_request" do
+    let(:mail) { described_class.with(user_id: user.id).send_inactive_user_unsubscription_request }
+    let(:user) { create(:user) }
+
+    it "renders the headers" do
+      expect(mail.subject).to eq("Attendez-vous toujours une dose de vaccin ?")
+      expect(mail.to).to eq([user.email])
+      expect(mail.from).to eq(["[email protected]"])
+    end
+
+    it "updates the last_inactive_user_email_sent_at" do
+      expect { mail.deliver_now }
+        .to change { user.reload.last_inactive_user_email_sent_at }
+        .from(nil)
+        .to(be_within(1.minute).of(Time.zone.now))
+    end
+
+    it "includes a signed link to the confirm_destroy_profile URL" do
+      match_data = mail.body.encoded.match(%r{/users/profile/confirm_destroy\?authentication_token=([^"]+)"})
+      token = CGI.unescape(match_data.captures.first)
+      expect(User.find_signed(token, purpose: "users.destroy")).to eq(user)
+    end
+  end
+end