Added IssueCollection

This class can be used to reduce a list of issues down to a subset based
on user permissions. This class operates in such a way that it can
reduce issues using as few queries as possible, if any at all.

1 files changed, 40 insertions, 0 deletions

diff --git a/app/models/issue_collection.rb b/app/models/issue_collection.rb
new file mode 100644
index 00000000000..df36252a5b1
--- /dev/null
+++ b/app/models/issue_collection.rb
@@ -0,0 +1,40 @@
+# IssueCollection can be used to reduce a list of issues down to a subset.
+#
+# IssueCollection is not meant to be some sort of Enumerable, instead it's meant
+# to take a list of issues and return a new list of issues based on some
+# criteria. For example, given a list of issues you may want to return a list of
+# issues that can be read or updated by a given user.
+class IssueCollection
+  attr_reader :collection
+
+  def initialize(collection)
+    @collection = collection
+  end
+
+  # Returns all the issues that can be updated by the user.
+  def updatable_by_user(user)
+    return collection if user.admin?
+
+    # Given all the issue projects we get a list of projects that the current
+    # user has at least reporter access to.
+    projects_with_reporter_access = user.
+      projects_with_reporter_access_limited_to(project_ids).
+      pluck(:id)
+
+    collection.select do |issue|
+      if projects_with_reporter_access.include?(issue.project_id)
+        true
+      elsif issue.is_a?(Issue)
+        issue.assignee_or_author?(user)
+      else
+        false
+      end
+    end
+  end
+
+  private
+
+  def project_ids
+    @project_ids ||= collection.map(&:project_id).uniq
+  end
+end