backups: add amazon s3 backup service.

app/logical/s3_backup_service.rb

@@ -0,0 +1,35 @@
+class S3BackupService < BackupService
+  attr_reader :client, :bucket
+
+  def initialize(client: nil, bucket: Danbooru.config.aws_s3_bucket_name)
+    @credentials = Aws::Credentials.new(Danbooru.config.aws_access_key_id, Danbooru.config.aws_secret_access_key)
+    @client = client || Aws::S3::Client.new(credentials: @credentials, region: "us-east-1", logger: Logger.new(STDOUT))
+    @bucket = bucket
+  end
+
+  def backup(file_path, type: nil, **options)
+    key = s3_key(file_path, type)
+    upload_to_s3(key, file_path)
+  end
+
+protected
+  def s3_key(file_path, type)
+    case type
+    when :original
+      "#{File.basename(file_path)}"
+    when :preview
+      "preview/#{File.basename(file_path)}"
+    when :large
+      "large/#{File.basename(file_path)}"
+    else
+      raise ArgumentError.new("Unknown type: #{type}")
+    end
+  end
+
+  def upload_to_s3(key, file_path)
+    File.open(file_path, "rb") do |body|
+      base64_md5 = Digest::MD5.base64digest(File.read(file_path))
+      client.put_object(bucket: bucket, key: key, body: body, content_md5: base64_md5)
+    end
+  end
+end