1 files changed, 59 insertions, 0 deletions
diff --git a/app/models/user_interacted_project.rb b/app/models/user_interacted_project.rb
new file mode 100644
index 00000000000..dd55a6acb79
--- /dev/null
+++ b/app/models/user_interacted_project.rb
@@ -0,0 +1,59 @@
+class UserInteractedProject < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :project
+
+  validates :project_id, presence: true
+  validates :user_id, presence: true
+
+  CACHE_EXPIRY_TIME = 1.day
+
+  # Schema version required for this model
+  REQUIRED_SCHEMA_VERSION = 20180223120443
+
+  class << self
+    def track(event)
+      # For events without a project, we simply don't care.
+      # An example of this is the creation of a snippet (which
+      # is not related to any project).
+      return unless event.project_id
+
+      attributes = {
+        project_id: event.project_id,
+        user_id: event.author_id
+      }
+
+      cached_exists?(attributes) do
+        transaction(requires_new: true) do
+          begin
+            where(attributes).select(1).first || create!(attributes)
+            true # not caching the whole record here for now
+          rescue ActiveRecord::RecordNotUnique
+            # Note, above queries are not atomic and prone
+            # to race conditions (similar like #find_or_create!).
+            # In the case where we hit this, the record we want
+            # already exists - shortcut and return.
+            true
+          end
+        end
+      end
+    end
+
+    # Check if we can safely call .track (table exists)
+    def available?
+      @available_flag ||= ActiveRecord::Migrator.current_version >= REQUIRED_SCHEMA_VERSION # rubocop:disable Gitlab/PredicateMemoization
+    end
+
+    # Flushes cached information about schema
+    def reset_column_information
+      @available_flag = nil
+      super
+    end
+
+    private
+
+    def cached_exists?(project_id:, user_id:, &block)
+      cache_key = "user_interacted_projects:#{project_id}:#{user_id}"
+      Rails.cache.fetch(cache_key, expires_in: CACHE_EXPIRY_TIME, &block)
+    end
+  end
+end