4 files changed, 162 insertions, 0 deletions
diff --git a/src/react-native-app/hooks/useColorScheme.ts b/src/react-native-app/hooks/useColorScheme.ts
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index 0000000..2a0bb61
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+++ b/src/react-native-app/hooks/useColorScheme.ts
@@ -0,0 +1,3 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+export { useColorScheme } from "react-native";
diff --git a/src/react-native-app/hooks/useColorScheme.web.ts b/src/react-native-app/hooks/useColorScheme.web.ts
new file mode 100644
index 0000000..fe92ccd
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+++ b/src/react-native-app/hooks/useColorScheme.web.ts
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+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+// NOTE: The default React Native styling doesn't support server rendering.
+// Server rendered styles should not change between the first render of the HTML
+// and the first render on the client. Typically, web developers will use CSS media queries
+// to render different styles on the client and server, these aren't directly supported in React Native
+// but can be achieved using a styling library like Nativewind.
+export function useColorScheme() {
+  return "light";
+}
diff --git a/src/react-native-app/hooks/useThemeColor.ts b/src/react-native-app/hooks/useThemeColor.ts
new file mode 100644
index 0000000..c7b9684
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+++ b/src/react-native-app/hooks/useThemeColor.ts
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+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+/**
+ * Learn more about light and dark modes:
+ * https://docs.expo.dev/guides/color-schemes/
+ */
+
+import { useColorScheme } from "react-native";
+
+import { Colors } from "@/constants/Colors";
+
+export function useThemeColor(
+  props: { light?: string; dark?: string },
+  colorName: keyof typeof Colors.light & keyof typeof Colors.dark,
+) {
+  const theme = useColorScheme() ?? "light";
+  const colorFromProps = props[theme];
+
+  if (colorFromProps) {
+    return colorFromProps;
+  } else {
+    return Colors[theme][colorName];
+  }
+}
diff --git a/src/react-native-app/hooks/useTracer.ts b/src/react-native-app/hooks/useTracer.ts
new file mode 100644
index 0000000..39d560a
--- /dev/null
+++ b/src/react-native-app/hooks/useTracer.ts
@@ -0,0 +1,125 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+import {
+  CompositePropagator,
+  W3CBaggagePropagator,
+  W3CTraceContextPropagator,
+} from "@opentelemetry/core";
+import { WebTracerProvider } from "@opentelemetry/sdk-trace-web";
+import {
+  BatchSpanProcessor,
+} from "@opentelemetry/sdk-trace-base";
+import { XMLHttpRequestInstrumentation } from "@opentelemetry/instrumentation-xml-http-request";
+import { FetchInstrumentation } from "@opentelemetry/instrumentation-fetch";
+import { registerInstrumentations } from "@opentelemetry/instrumentation";
+import { resourceFromAttributes } from "@opentelemetry/resources";
+import {
+  ATTR_DEVICE_ID,
+  ATTR_OS_NAME,
+  ATTR_OS_VERSION,
+  ATTR_SERVICE_NAME,
+  ATTR_SERVICE_VERSION,
+} from "@opentelemetry/semantic-conventions/incubating";
+import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-http";
+import { useEffect, useState } from "react";
+import {
+  getDeviceId,
+  getSystemVersion,
+  getVersion,
+} from "react-native-device-info";
+import { Platform } from "react-native";
+import { SessionIdProcessor } from "@/utils/SessionIdProcessor";
+import getFrontendProxyURL from "@/utils/Settings";
+
+export const setupTracerProvider = (proxyURL: string) => {
+  // TODO Should add a resource detector for React Native that provides this automatically
+  const resource = resourceFromAttributes({
+    [ATTR_SERVICE_NAME]: "react-native-app",
+    [ATTR_OS_NAME]: Platform.OS,
+    [ATTR_OS_VERSION]: getSystemVersion(),
+    [ATTR_SERVICE_VERSION]: getVersion(),
+    [ATTR_DEVICE_ID]: getDeviceId(),
+  });
+
+  // TODO Not obvious that the WebTracerProvider can be used for React Native, might be useful to have a thin
+  //  ReactNativeTracerProvider on top of it (or BasicTracerProvider) that makes this clear. Could also add some
+  //  protection against browser specific functionality being added to WebTracerProvider that breaks functionality
+  //  for React Native.
+  //  Alternatively could offer a TracerProvider that exposed a JS interface on top of the OTEL Android and Swift SDKS,
+  //  giving developers the option of collecting telemetry at the native mobile layer
+  return new WebTracerProvider({
+    resource,
+    spanProcessors: [
+      new BatchSpanProcessor(
+        new OTLPTraceExporter({
+          url: `${proxyURL}/otlp-http/v1/traces`,
+        }),
+        {
+          scheduledDelayMillis: 500,
+        },
+      ),
+      // TODO introduce a React Native session processor package that could be used here, taking into account mobile
+      // specific considerations for the session such as putting the app into the background
+      new SessionIdProcessor(),
+    ],
+  });
+}
+
+const Tracer = async () => {
+  const proxyURL = await getFrontendProxyURL();
+  const provider = setupTracerProvider(proxyURL);
+
+  provider.register({
+    propagator: new CompositePropagator({
+      propagators: [
+        new W3CBaggagePropagator(),
+        new W3CTraceContextPropagator(),
+      ],
+    }),
+  });
+
+  registerInstrumentations({
+    instrumentations: [
+      // TODO Some tiptoeing required here, propagateTraceHeaderCorsUrls is required to make the instrumentation
+      // work in the context of a mobile app even though we are not making CORS requests. `clearTimingResources` must
+      // be turned off to avoid using the web-only Performance API
+      // Overall wrapping or forking this and providing a React Native specific auto instrumentation will ease
+      // integration and make it less error-prone
+      new FetchInstrumentation({
+        propagateTraceHeaderCorsUrls: /.*/,
+        clearTimingResources: false,
+      }),
+
+      // The React Native implementation of fetch is simply a polyfill on top of XMLHttpRequest:
+      // https://github.com/facebook/react-native/blob/7ccc5934d0f341f9bc8157f18913a7b340f5db2d/packages/react-native/Libraries/Network/fetch.js#L17
+      // Because of this when making requests using `fetch` there will an additional span created for the underlying
+      // request made with XMLHttpRequest. Since in this demo calls to /api/ are made using fetch, turn off
+      // instrumentation for that path to avoid the extra spans.
+      new XMLHttpRequestInstrumentation({
+        ignoreUrls: [/\/api\/.*/],
+      }),
+    ],
+  });
+};
+
+export interface TracerResult {
+  loaded: boolean;
+}
+
+// TODO providing a wrapper similar to this that uses hooks over the full JS OTEL API would be nice to have for both
+// React Native and React development
+export const useTracer = (): TracerResult => {
+  const [loaded, setLoaded] = useState<boolean>(false);
+
+  useEffect(() => {
+    if (!loaded) {
+      Tracer()
+        .catch(() => console.warn("failed to setup tracer"))
+        .finally(() => setLoaded(true));
+    }
+  }, [loaded]);
+
+  return {
+    loaded,
+  };
+};