1 files changed, 99 insertions, 0 deletions
diff --git a/app/models/blob_viewer/base.rb b/app/models/blob_viewer/base.rb
new file mode 100644
index 00000000000..35965d01692
--- /dev/null
+++ b/app/models/blob_viewer/base.rb
@@ -0,0 +1,99 @@
+module BlobViewer
+  class Base
+    PARTIAL_PATH_PREFIX = 'projects/blob/viewers'.freeze
+
+    class_attribute :partial_name, :loading_partial_name, :type, :extensions, :file_types, :load_async, :binary, :switcher_icon, :switcher_title, :collapse_limit, :size_limit
+
+    self.loading_partial_name = 'loading'
+
+    delegate :partial_path, :loading_partial_path, :rich?, :simple?, :load_async?, :text?, :binary?, to: :class
+
+    attr_reader :blob
+
+    delegate :project, to: :blob
+
+    def initialize(blob)
+      @blob = blob
+      @initially_binary = blob.binary?
+    end
+
+    def self.partial_path
+      File.join(PARTIAL_PATH_PREFIX, partial_name)
+    end
+
+    def self.loading_partial_path
+      File.join(PARTIAL_PATH_PREFIX, loading_partial_name)
+    end
+
+    def self.rich?
+      type == :rich
+    end
+
+    def self.simple?
+      type == :simple
+    end
+
+    def self.auxiliary?
+      type == :auxiliary
+    end
+
+    def self.load_async?
+      load_async
+    end
+
+    def self.binary?
+      binary
+    end
+
+    def self.text?
+      !binary?
+    end
+
+    def self.can_render?(blob, verify_binary: true)
+      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)
+
+      @collapsed = !blob.expanded? && collapse_limit && blob.raw_size > collapse_limit
+    end
+
+    def too_large?
+      return @too_large if defined?(@too_large)
+
+      @too_large = size_limit && blob.raw_size > size_limit
+    end
+
+    def binary_detected_after_load?
+      !@initially_binary && blob.binary?
+    end
+
+    # This method is used on the server side to check whether we can attempt to
+    # render the blob at all. Human-readable error messages are found in the
+    # `BlobHelper#blob_render_error_reason` helper.
+    #
+    # This method does not and should not load the entire blob contents into
+    # memory, and should not be overridden to do so in order to validate the
+    # format of the blob.
+    #
+    # Prefer to implement a client-side viewer, where the JS component loads the
+    # binary from `blob_raw_url` and does its own format validation and error
+    # rendering, especially for potentially large binary formats.
+    def render_error
+      if too_large?
+        :too_large
+      elsif collapsed?
+        :collapsed
+      end
+    end
+
+    def prepare!
+      # To be overridden by subclasses
+    end
+  end
+end