feat(slack): refactor state decoding logic for custom bot handling

Author: yuriassuncx

slack/actions/oauth/callback.ts

@@ -1,5 +1,6 @@
 import { AppContext } from "../../mod.ts";
 import { SlackOAuthResponse } from "../../utils/client.ts";
+import { decodeCustomBotState } from "../../utils/state-helpers.ts";
 
 export interface Props {
   code: string;
@@ -19,15 +20,6 @@ export interface Props {
   state?: string;
 }
 
-function decodeState(state: string) {
-  try {
-    const decoded = atob(decodeURIComponent(state));
-    return JSON.parse(decoded);
-  } catch {
-    return {};
-  }
-}
-
 /**
  * @name SLACK_OAUTH_CALLBACK
  * @title Slack OAuth Callback
@@ -54,7 +46,7 @@ export default async function callback(
   let finalBotName = botName;
 
   if (state) {
-    const stateData = decodeState(state);
+    const stateData = decodeCustomBotState(state);
     if (stateData.isCustomBot) {
       finalClientSecret = stateData.customClientSecret || clientSecret;
       finalBotName = stateData.customBotName || botName;

slack/loaders/oauth/start.ts

@@ -1,5 +1,6 @@
 import { OAUTH_URL_AUTH, SCOPES } from "../../utils/constants.ts";
 import { generateBotSelectionPage } from "../../utils/ui-templates/page-generator.ts";
+import { decodeState } from "../../utils/state-helpers.ts";
 
 export interface Props {
   clientId: string;
@@ -12,15 +13,6 @@ export interface Props {
   botName?: string;
 }
 
-function decodeState(state: string) {
-  try {
-    const decoded = atob(decodeURIComponent(state));
-    return JSON.parse(decoded);
-  } catch {
-    return {};
-  }
-}
-
 export default function start(props: Props, req: Request) {
   const url = new URL(req.url);
   const useDecoChatBot = url.searchParams.get("useDecoChatBot");

slack/utils/state-helpers.ts

@@ -0,0 +1,27 @@
+/**
+ * Decodes a base64-encoded state parameter from OAuth flow
+ * @param state - The base64-encoded state string
+ * @returns The decoded state object or empty object if decoding fails
+ */
+export function decodeState(state: string): Record<string, unknown> {
+  try {
+    const decoded = atob(decodeURIComponent(state));
+    return JSON.parse(decoded);
+  } catch {
+    return {};
+  }
+}
+
+/**
+ * Type-safe version of decodeState for custom bot state
+ */
+export interface CustomBotState {
+  customClientSecret?: string;
+  customBotName?: string;
+  isCustomBot?: boolean;
+  [key: string]: unknown;
+}
+
+export function decodeCustomBotState(state: string): CustomBotState {
+  return decodeState(state) as CustomBotState;
+}