From c1b117d1572543c62b16f2cbc43a85d0272225cc Mon Sep 17 00:00:00 2001
From: Daniel Khan <daniel@khan.io>
Date: Tue, 9 Jul 2019 19:17:17 +0200
Subject: [PATCH] Add Tracer API

Closes #28
---
 .../opentelemetry-types/src/trace/tracer.ts   | 110 ++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 packages/opentelemetry-types/src/trace/tracer.ts

diff --git a/packages/opentelemetry-types/src/trace/tracer.ts b/packages/opentelemetry-types/src/trace/tracer.ts
new file mode 100644
index 00000000000..45cc37d26ff
--- /dev/null
+++ b/packages/opentelemetry-types/src/trace/tracer.ts
@@ -0,0 +1,110 @@
+/**
+ * Copyright 2019, OpenTelemetry 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
+ *
+ *      https://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 { Span } from './span';
+import { Attributes } from './attributes';
+import { SpanKind } from './span_kind';
+import { SpanContext } from './span_context';
+
+/**
+ * Options needed for span creation
+ *
+ * @todo: Move into module of its own
+ */
+export interface SpanOptions {
+  /**
+   * The SpanKind of a span
+   */
+  kind?: SpanKind;
+
+  /**
+   * A spans attributes
+   */
+  attributes?: Attributes;
+
+  /**
+   * Indicates that events are being recorded for a span
+   */
+  isRecordingEvents?: boolean;
+
+  /**
+   * The parent span
+   */
+  parent?: Span | SpanContext;
+
+  /**
+   * The start timestamp of a span
+   */
+  startTime?: number;
+}
+
+/**
+ * Tracer provides an interface for creating spans and propagating context in-process.
+ */
+export interface Tracer {
+  /**
+   * Returns the current Span from the current context if available.
+   *
+   * If there is no Span associated with the current context, a default Span
+   * with invalid SpanContext is returned.
+   *
+   * @returns Span The currently active Span
+   */
+  getCurrentSpan(): Span;
+
+  /**
+   *
+   * @param name The name of the span
+   * @param [options] SpanOptions used for span creation
+   * @returns Span The newly created span
+   */
+  start(name: string, options?: SpanOptions): Span;
+
+  /**
+   * Executes the function given by fn within the context provided by Span
+   *
+   * @param span The span that provides the context
+   * @param fn The function to be eexcuted inside the provided context
+   */
+  withSpan<T extends (...args: unknown[]) => unknown>(
+    span: Span,
+    fn: T
+  ): ReturnType<T>;
+
+  /**
+   * Send a pre-populated span object to the exporter.
+   * Sampling and recording decisions as well as other collection optimizations
+   * are the responsibility of a caller.
+   *
+   * @todo: Pending API discussion. Revisit if Span or SpanData should be passed
+   *        in here once this is sorted out.
+   * @param span
+   */
+  recordSpanData(span: Span): void;
+
+  /**
+   * Returns the binary format interface which can serialize/deserialize Spans.
+   * @todo: Change return type once BinaryFormat is available
+   */
+  getBinaryFormat(): unknown;
+
+  /**
+   * Returns the HTTP text format interface which can inject/extract Spans.
+   *
+   * @todo: Change return type once HttpTextFormat is available
+   */
+  getHttpTextFormat: unknown;
+}