1 files changed, 71 insertions, 0 deletions
diff --git a/shared/components/src/utils/uniqueId.ts b/shared/components/src/utils/uniqueId.ts
new file mode 100644
index 0000000..3a6d21d
--- /dev/null
+++ b/shared/components/src/utils/uniqueId.ts
@@ -0,0 +1,71 @@
+import { getContext } from 'svelte';
+
+export const UNIQUE_ID_CONTEXT_NAME = 'amp-web-unique-id';
+
+interface UniqueContext {
+    nextId: number;
+}
+
+// TODO: rdar://84029606 (Extract logger into shared util)
+interface Logger {
+    warn(...args: any[]): string;
+}
+interface LoggerFactory {
+    loggerFor(name: string): Logger;
+}
+
+export function initializeUniqueIdContext(
+    context: Map<string, unknown>,
+    loggerFactory: LoggerFactory,
+): void {
+    const logger = loggerFactory.loggerFor('uniqueIdContext');
+
+    if (context.has(UNIQUE_ID_CONTEXT_NAME)) {
+        logger.warn(
+            `${UNIQUE_ID_CONTEXT_NAME} context has already been created. Cannot be created more than once`,
+        );
+    } else {
+        const INITAL_STATE: UniqueContext = { nextId: 0 };
+        context.set(UNIQUE_ID_CONTEXT_NAME, INITAL_STATE);
+    }
+}
+
+/**
+ * Creates a unique Id string based on string provided
+ *
+ * @returns unique id string
+ */
+export type UniqueIdGenerator = () => string;
+
+// Custom elements most likely will not be used in an environment has that initialized the Svelte
+// context. Components that are later wrapped by a custom element should use this function so that
+// they can generate unique ids automatically when used inside a Svelte app, but not throw an error
+// when used in other contexts.
+//
+export function maybeGetUniqueIdGenerator(): UniqueIdGenerator | undefined {
+    const UNIQUE_ID_PREFIX = 'uid-';
+    const state: UniqueContext = getContext(UNIQUE_ID_CONTEXT_NAME);
+    const isNextIdANumber = typeof state?.nextId === 'number';
+
+    if (!isNextIdANumber) {
+        return;
+    }
+
+    return () => {
+        const id = `${UNIQUE_ID_PREFIX}${state.nextId}`;
+        state.nextId += 1;
+        return id;
+    };
+}
+
+export function getUniqueIdGenerator(): UniqueIdGenerator {
+    const uniqueIdGenerator = maybeGetUniqueIdGenerator();
+
+    if (!uniqueIdGenerator) {
+        throw new Error(
+            `${UNIQUE_ID_CONTEXT_NAME} context has not been initialized. Initialize at application bootstrap.`,
+        );
+    }
+
+    return uniqueIdGenerator;
+}