feat: add propagation interface

Author: ofrobots

packages/opencensus-core/src/trace/propagation/types.ts

@@ -0,0 +1,38 @@
+/**
+ * Copyright 2018, OpenCensus Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {SpanContext} from '../model/types';
+
+/**
+ * An transport and environment neutral API for getting request headers.
+ */
+export interface HeaderGetter {
+  getHeader(name: string): string|string[]|undefined;
+}
+
+/**
+ * A transport and environment neutral API for setting headers.
+ */
+export interface HeaderSetter { setHeader(name: string, value: string): void; }
+
+/**
+ *  Propagation interface
+ */
+export interface Propagation {
+  extract(getter: HeaderGetter): SpanContext|null;
+  inject(setter: HeaderSetter, spanContext: SpanContext): void;
+  generate(): SpanContext;
+}