Extract tree summary logic out of RefsController#logs_tree

1 files changed, 115 insertions, 0 deletions

diff --git a/lib/gitlab/tree_summary.rb b/lib/gitlab/tree_summary.rb
new file mode 100644
index 00000000000..b05d408b1c0
--- /dev/null
+++ b/lib/gitlab/tree_summary.rb
@@ -0,0 +1,115 @@
+module Gitlab
+  class TreeSummary
+    include ::Gitlab::Utils::StrongMemoize
+
+    attr_reader :commit, :project, :path, :offset, :limit
+
+    attr_reader :resolved_commits
+    private :resolved_commits
+
+    def initialize(commit, project, params = {})
+      @commit = commit
+      @project = project
+
+      @path = params.fetch(:path, nil).presence
+      @offset = params.fetch(:offset, 0).to_i
+      @limit = (params.fetch(:limit, 25) || 25).to_i
+
+      # Ensure that if multiple tree entries share the same last commit, they share
+      # a ::Commit instance. This prevents us from rendering the same commit title
+      # multiple times
+      @resolved_commits = {}
+    end
+
+    # Creates a summary of the tree entries for a commit, within the window of
+    # entries defined by the offset and limit parameters. This consists of two
+    # return values:
+    #
+    #     - An Array of Hashes containing the following keys:
+    #         - file_name:   The full path of the tree entry
+    #         - type:        One of :blob, :tree, or :submodule
+    #         - commit:      The last ::Commit to touch this entry in the tree
+    #         - commit_path: URI of the commit in the web interface
+    #     - An Array of the unique ::Commit objects in the first value
+    def summarize
+      summary = contents
+        .map { |content| build_entry(content) }
+        .tap { |summary| fill_last_commits!(summary) }
+
+      [summary, commits]
+    end
+
+    # Does the tree contain more entries after the given offset + limit?
+    def more?
+      all_contents[next_offset].present?
+    end
+
+    # The offset of the next batch of tree entries. If more? returns false, this
+    # batch will be empty
+    def next_offset
+      [all_contents.size + 1, offset + limit].min
+    end
+
+    private
+
+    def contents
+      all_contents[offset, limit]
+    end
+
+    def commits
+      resolved_commits.values
+    end
+
+    def repository
+      project.repository
+    end
+
+    def entry_path(entry)
+      File.join(*[path, entry[:file_name]].compact)
+    end
+
+    def build_entry(entry)
+      { file_name: entry.name, type: entry.type }
+    end
+
+    def fill_last_commits!(entries)
+      # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37433
+      Gitlab::GitalyClient.allow_n_plus_1_calls do
+        entries.each do |entry|
+          raw_commit = repository.last_commit_for_path(commit.id, entry_path(entry))
+
+          if raw_commit
+            commit = resolve_commit(raw_commit)
+
+            entry[:commit] = commit
+            entry[:commit_path] =  commit_path(commit)
+          end
+        end
+      end
+    end
+
+    def resolve_commit(raw_commit)
+      return nil unless raw_commit.present?
+
+      resolved_commits[raw_commit.id] ||= ::Commit.new(raw_commit, project)
+    end
+
+    def commit_path(commit)
+      Gitlab::Routing.url_helpers.project_commit_path(project, commit)
+    end
+
+    def all_contents
+      strong_memoize(:all_contents) do
+        [
+          *tree.trees,
+          *tree.blobs,
+          *tree.submodules
+        ]
+      end
+    end
+
+    def tree
+      strong_memoize(:tree) { repository.tree(commit.id, path) }
+    end
+  end
+end