Implement diff viewers

14 files changed, 232 insertions, 0 deletions

diff --git a/app/models/diff_viewer/added.rb b/app/models/diff_viewer/added.rb
new file mode 100644
index 00000000000..1909e6ef9d8
--- /dev/null
+++ b/app/models/diff_viewer/added.rb
@@ -0,0 +1,8 @@
+module DiffViewer
+  class Added < Base
+    include Simple
+    include Static
+
+    self.partial_name = 'added'
+  end
+end
diff --git a/app/models/diff_viewer/base.rb b/app/models/diff_viewer/base.rb
new file mode 100644
index 00000000000..0cbe714288d
--- /dev/null
+++ b/app/models/diff_viewer/base.rb
@@ -0,0 +1,87 @@
+module DiffViewer
+  class Base
+    PARTIAL_PATH_PREFIX = 'projects/diffs/viewers'.freeze
+
+    class_attribute :partial_name, :type, :extensions, :file_types, :binary, :switcher_icon, :switcher_title
+
+    # These limits relate to the sum of the old and new blob sizes.
+    # Limits related to the actual size of the diff are enforced in Gitlab::Diff::File.
+    class_attribute :collapse_limit, :size_limit
+
+    delegate :partial_path, :loading_partial_path, :rich?, :simple?, :text?, :binary?, to: :class
+
+    attr_reader :diff_file
+
+    delegate :project, to: :diff_file
+
+    def initialize(diff_file)
+      @diff_file = diff_file
+      @initially_binary = diff_file.binary?
+    end
+
+    def self.partial_path
+      File.join(PARTIAL_PATH_PREFIX, partial_name)
+    end
+
+    def self.rich?
+      type == :rich
+    end
+
+    def self.simple?
+      type == :simple
+    end
+
+    def self.binary?
+      binary
+    end
+
+    def self.text?
+      !binary?
+    end
+
+    def self.can_render?(diff_file, verify_binary: true)
+      can_render_blob?(diff_file.old_blob, verify_binary: verify_binary) &&
+        can_render_blob?(diff_file.new_blob, verify_binary: verify_binary)
+    end
+
+    def self.can_render_blob?(blob, verify_binary: true)
+      return true if blob.nil?
+      return false if verify_binary && binary? != blob.binary?
+      return true if extensions&.include?(blob.extension)
+      return true if file_types&.include?(blob.file_type)
+
+      false
+    end
+
+    def collapsed?
+      return @collapsed if defined?(@collapsed)
+      return @collapsed = true if diff_file.collapsed?
+
+      @collapsed = !diff_file.expanded? && collapse_limit && diff_file.raw_size > collapse_limit
+    end
+
+    def too_large?
+      return @too_large if defined?(@too_large)
+      return @too_large = true if diff_file.too_large?
+
+      @too_large = size_limit && diff_file.raw_size > size_limit
+    end
+
+    def binary_detected_after_load?
+      !@initially_binary && diff_file.binary?
+    end
+
+    # This method is used on the server side to check whether we can attempt to
+    # render the diff_file at all. Human-readable error messages are found in the
+    # `BlobHelper#diff_render_error_reason` helper.
+    def render_error
+      if too_large?
+        :too_large
+      end
+    end
+
+    def prepare!
+      # To be overridden by subclasses
+    end
+  end
+end
diff --git a/app/models/diff_viewer/client_side.rb b/app/models/diff_viewer/client_side.rb
new file mode 100644
index 00000000000..cf41d07f8eb
--- /dev/null
+++ b/app/models/diff_viewer/client_side.rb
@@ -0,0 +1,10 @@
+module DiffViewer
+  module ClientSide
+    extend ActiveSupport::Concern
+
+    included do
+      self.collapse_limit = 1.megabyte
+      self.size_limit = 10.megabytes
+    end
+  end
+end
diff --git a/app/models/diff_viewer/deleted.rb b/app/models/diff_viewer/deleted.rb
new file mode 100644
index 00000000000..9c129bac694
--- /dev/null
+++ b/app/models/diff_viewer/deleted.rb
@@ -0,0 +1,8 @@
+module DiffViewer
+  class Deleted < Base
+    include Simple
+    include Static
+
+    self.partial_name = 'deleted'
+  end
+end
diff --git a/app/models/diff_viewer/image.rb b/app/models/diff_viewer/image.rb
new file mode 100644
index 00000000000..759d9a36ebb
--- /dev/null
+++ b/app/models/diff_viewer/image.rb
@@ -0,0 +1,12 @@
+module DiffViewer
+  class Image < Base
+    include Rich
+    include ClientSide
+
+    self.partial_name = 'image'
+    self.extensions = UploaderHelper::IMAGE_EXT
+    self.binary = true
+    self.switcher_icon = 'picture-o'
+    self.switcher_title = 'image diff'
+  end
+end
diff --git a/app/models/diff_viewer/mode_changed.rb b/app/models/diff_viewer/mode_changed.rb
new file mode 100644
index 00000000000..d487d996f8d
--- /dev/null
+++ b/app/models/diff_viewer/mode_changed.rb
@@ -0,0 +1,8 @@
+module DiffViewer
+  class ModeChanged < Base
+    include Simple
+    include Static
+
+    self.partial_name = 'mode_changed'
+  end
+end
diff --git a/app/models/diff_viewer/no_preview.rb b/app/models/diff_viewer/no_preview.rb
new file mode 100644
index 00000000000..5455fee4490
--- /dev/null
+++ b/app/models/diff_viewer/no_preview.rb
@@ -0,0 +1,9 @@
+module DiffViewer
+  class NoPreview < Base
+    include Simple
+    include Static
+
+    self.partial_name = 'no_preview'
+    self.binary = true
+  end
+end
diff --git a/app/models/diff_viewer/not_diffable.rb b/app/models/diff_viewer/not_diffable.rb
new file mode 100644
index 00000000000..4f9638626ea
--- /dev/null
+++ b/app/models/diff_viewer/not_diffable.rb
@@ -0,0 +1,9 @@
+module DiffViewer
+  class NotDiffable < Base
+    include Simple
+    include Static
+
+    self.partial_name = 'not_diffable'
+    self.binary = true
+  end
+end
diff --git a/app/models/diff_viewer/renamed.rb b/app/models/diff_viewer/renamed.rb
new file mode 100644
index 00000000000..f1fbfd8c6d5
--- /dev/null
+++ b/app/models/diff_viewer/renamed.rb
@@ -0,0 +1,8 @@
+module DiffViewer
+  class Renamed < Base
+    include Simple
+    include Static
+
+    self.partial_name = 'renamed'
+  end
+end
diff --git a/app/models/diff_viewer/rich.rb b/app/models/diff_viewer/rich.rb
new file mode 100644
index 00000000000..3b0ca6e4cff
--- /dev/null
+++ b/app/models/diff_viewer/rich.rb
@@ -0,0 +1,11 @@
+module DiffViewer
+  module Rich
+    extend ActiveSupport::Concern
+
+    included do
+      self.type = :rich
+      self.switcher_icon = 'file-text-o'
+      self.switcher_title = 'rendered diff'
+    end
+  end
+end
diff --git a/app/models/diff_viewer/server_side.rb b/app/models/diff_viewer/server_side.rb
new file mode 100644
index 00000000000..aed1a0791b1
--- /dev/null
+++ b/app/models/diff_viewer/server_side.rb
@@ -0,0 +1,26 @@
+module DiffViewer
+  module ServerSide
+    extend ActiveSupport::Concern
+
+    included do
+      self.collapse_limit = 1.megabyte
+      self.size_limit = 5.megabytes
+    end
+
+    def prepare!
+      diff_file.old_blob&.load_all_data!
+      diff_file.new_blob&.load_all_data!
+    end
+
+    def render_error
+      # Files that are not stored in the repository, like LFS files and
+      # build artifacts, can only be rendered using a client-side viewer,
+      # since we do not want to read large amounts of data into memory on the
+      # server side. Client-side viewers use JS and can fetch the file from
+      # `diff_file_blob_raw_path` and `diff_file_old_blob_raw_path` using AJAX.
+      return :server_side_but_stored_externally if diff_file.stored_externally?
+
+      super
+    end
+  end
+end
diff --git a/app/models/diff_viewer/simple.rb b/app/models/diff_viewer/simple.rb
new file mode 100644
index 00000000000..65750996ee4
--- /dev/null
+++ b/app/models/diff_viewer/simple.rb
@@ -0,0 +1,11 @@
+module DiffViewer
+  module Simple
+    extend ActiveSupport::Concern
+
+    included do
+      self.type = :simple
+      self.switcher_icon = 'code'
+      self.switcher_title = 'source diff'
+    end
+  end
+end
diff --git a/app/models/diff_viewer/static.rb b/app/models/diff_viewer/static.rb
new file mode 100644
index 00000000000..d761328b3f6
--- /dev/null
+++ b/app/models/diff_viewer/static.rb
@@ -0,0 +1,10 @@
+module DiffViewer
+  module Static
+    extend ActiveSupport::Concern
+
+    # We can always render a static viewer, even if the diff is too large.
+    def render_error
+      nil
+    end
+  end
+end
diff --git a/app/models/diff_viewer/text.rb b/app/models/diff_viewer/text.rb
new file mode 100644
index 00000000000..98f4b2aea2a
--- /dev/null
+++ b/app/models/diff_viewer/text.rb
@@ -0,0 +1,15 @@
+module DiffViewer
+  class Text < Base
+    include Simple
+    include ServerSide
+
+    self.partial_name = 'text'
+    self.binary = false
+
+    # Since the text diff viewer doesn't render the old and new blobs in full,
+    # we only need the limits related to the actual size of the diff which are
+    # already enforced in Gitlab::Diff::File.
+    self.collapse_limit = nil
+    self.size_limit = nil
+  end
+end