Add mode support (#333)

* Add mode support

* update "as any" with proper "as unknwon as ModeName" casting

* Add documentation to README and registry.ts

* Add  tests for differen event types, integration flows, and error conditions

* Clean up some tests

* Minor test fix

* Minor formatting test + switch from interface to type

* correct the order of mkdir call

* always configureGitAuth as there's already a fallback to handle null users by using the bot ID

* simplify registry setup

---------

Co-authored-by: km-anthropic <km-anthropic@users.noreply.github.com>

src/modes/registry.ts

@@ -0,0 +1,52 @@
+/**
+ * Mode Registry for claude-code-action
+ *
+ * This module provides access to all available execution modes.
+ *
+ * To add a new mode:
+ * 1. Add the mode name to VALID_MODES below
+ * 2. Create the mode implementation in a new directory (e.g., src/modes/review/)
+ * 3. Import and add it to the modes object below
+ * 4. Update action.yml description to mention the new mode
+ */
+
+import type { Mode } from "./types";
+import { tagMode } from "./tag/index";
+
+export const DEFAULT_MODE = "tag" as const;
+export const VALID_MODES = ["tag"] as const;
+export type ModeName = (typeof VALID_MODES)[number];
+
+/**
+ * All available modes.
+ * Add new modes here as they are created.
+ */
+const modes = {
+  tag: tagMode,
+} as const satisfies Record<ModeName, Mode>;
+
+/**
+ * Retrieves a mode by name.
+ * @param name The mode name to retrieve
+ * @returns The requested mode
+ * @throws Error if the mode is not found
+ */
+export function getMode(name: ModeName): Mode {
+  const mode = modes[name];
+  if (!mode) {
+    const validModes = VALID_MODES.join("', '");
+    throw new Error(
+      `Invalid mode '${name}'. Valid modes are: '${validModes}'. Please check your workflow configuration.`,
+    );
+  }
+  return mode;
+}
+
+/**
+ * Type guard to check if a string is a valid mode name.
+ * @param name The string to check
+ * @returns True if the name is a valid mode name
+ */
+export function isValidMode(name: string): name is ModeName {
+  return VALID_MODES.includes(name as ModeName);
+}

src/modes/tag/index.ts

@@ -0,0 +1,40 @@
+import type { Mode } from "../types";
+import { checkContainsTrigger } from "../../github/validation/trigger";
+
+/**
+ * Tag mode implementation.
+ *
+ * The traditional implementation mode that responds to @claude mentions,
+ * issue assignments, or labels. Creates tracking comments showing progress
+ * and has full implementation capabilities.
+ */
+export const tagMode: Mode = {
+  name: "tag",
+  description: "Traditional implementation mode triggered by @claude mentions",
+
+  shouldTrigger(context) {
+    return checkContainsTrigger(context);
+  },
+
+  prepareContext(context, data) {
+    return {
+      mode: "tag",
+      githubContext: context,
+      commentId: data?.commentId,
+      baseBranch: data?.baseBranch,
+      claudeBranch: data?.claudeBranch,
+    };
+  },
+
+  getAllowedTools() {
+    return [];
+  },
+
+  getDisallowedTools() {
+    return [];
+  },
+
+  shouldCreateTrackingComment() {
+    return true;
+  },
+};

src/modes/types.ts

@@ -0,0 +1,56 @@
+import type { ParsedGitHubContext } from "../github/context";
+import type { ModeName } from "./registry";
+
+export type ModeContext = {
+  mode: ModeName;
+  githubContext: ParsedGitHubContext;
+  commentId?: number;
+  baseBranch?: string;
+  claudeBranch?: string;
+};
+
+export type ModeData = {
+  commentId?: number;
+  baseBranch?: string;
+  claudeBranch?: string;
+};
+
+/**
+ * Mode interface for claude-code-action execution modes.
+ * Each mode defines its own behavior for trigger detection, prompt generation,
+ * and tracking comment creation.
+ *
+ * Future modes might include:
+ * - 'review': Optimized for code reviews without tracking comments
+ * - 'freeform': For automation with no trigger checking
+ */
+export type Mode = {
+  name: ModeName;
+  description: string;
+
+  /**
+   * Determines if this mode should trigger based on the GitHub context
+   */
+  shouldTrigger(context: ParsedGitHubContext): boolean;
+
+  /**
+   * Prepares the mode context with any additional data needed for prompt generation
+   */
+  prepareContext(context: ParsedGitHubContext, data?: ModeData): ModeContext;
+
+  /**
+   * Returns additional tools that should be allowed for this mode
+   * (base GitHub tools are always included)
+   */
+  getAllowedTools(): string[];
+
+  /**
+   * Returns tools that should be disallowed for this mode
+   */
+  getDisallowedTools(): string[];
+
+  /**
+   * Determines if this mode should create a tracking comment
+   */
+  shouldCreateTrackingComment(): boolean;
+};