1 files changed, 118 insertions, 0 deletions
diff --git a/packages/core/src/ide/ideContext.ts b/packages/core/src/ide/ideContext.ts
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+++ b/packages/core/src/ide/ideContext.ts
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+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { z } from 'zod';
+
+/**
+ * Zod schema for validating a cursor position.
+ */
+export const CursorSchema = z.object({
+  line: z.number(),
+  character: z.number(),
+});
+export type Cursor = z.infer<typeof CursorSchema>;
+
+/**
+ * Zod schema for validating an active file context from the IDE.
+ */
+export const OpenFilesSchema = z.object({
+  activeFile: z.string(),
+  selectedText: z.string().optional(),
+  cursor: CursorSchema.optional(),
+  recentOpenFiles: z
+    .array(
+      z.object({
+        filePath: z.string(),
+        timestamp: z.number(),
+      }),
+    )
+    .optional(),
+});
+export type OpenFiles = z.infer<typeof OpenFilesSchema>;
+
+/**
+ * Zod schema for validating the 'ide/openFilesChanged' notification from the IDE.
+ */
+export const OpenFilesNotificationSchema = z.object({
+  method: z.literal('ide/openFilesChanged'),
+  params: OpenFilesSchema,
+});
+
+type OpenFilesSubscriber = (openFiles: OpenFiles | undefined) => void;
+
+/**
+ * Creates a new store for managing the IDE's active file context.
+ * This factory function encapsulates the state and logic, allowing for the creation
+ * of isolated instances, which is particularly useful for testing.
+ *
+ * @returns An object with methods to interact with the active file context.
+ */
+export function createIdeContextStore() {
+  let openFilesContext: OpenFiles | undefined = undefined;
+  const subscribers = new Set<OpenFilesSubscriber>();
+
+  /**
+   * Notifies all registered subscribers about the current active file context.
+   */
+  function notifySubscribers(): void {
+    for (const subscriber of subscribers) {
+      subscriber(openFilesContext);
+    }
+  }
+
+  /**
+   * Sets the active file context and notifies all registered subscribers of the change.
+   * @param newOpenFiles The new active file context from the IDE.
+   */
+  function setOpenFilesContext(newOpenFiles: OpenFiles): void {
+    openFilesContext = newOpenFiles;
+    notifySubscribers();
+  }
+
+  /**
+   * Clears the active file context and notifies all registered subscribers of the change.
+   */
+  function clearOpenFilesContext(): void {
+    openFilesContext = undefined;
+    notifySubscribers();
+  }
+
+  /**
+   * Retrieves the current active file context.
+   * @returns The `OpenFiles` object if a file is active; otherwise, `undefined`.
+   */
+  function getOpenFilesContext(): OpenFiles | undefined {
+    return openFilesContext;
+  }
+
+  /**
+   * Subscribes to changes in the active file context.
+   *
+   * When the active file context changes, the provided `subscriber` function will be called.
+   * Note: The subscriber is not called with the current value upon subscription.
+   *
+   * @param subscriber The function to be called when the active file context changes.
+   * @returns A function that, when called, will unsubscribe the provided subscriber.
+   */
+  function subscribeToOpenFiles(subscriber: OpenFilesSubscriber): () => void {
+    subscribers.add(subscriber);
+    return () => {
+      subscribers.delete(subscriber);
+    };
+  }
+
+  return {
+    setOpenFilesContext,
+    getOpenFilesContext,
+    subscribeToOpenFiles,
+    clearOpenFilesContext,
+  };
+}
+
+/**
+ * The default, shared instance of the IDE context store for the application.
+ */
+export const ideContext = createIdeContextStore();