♻️ Extracted tokenData and twitch authentication

To be finished

src/backend/helpers/tokenData.ts

@@ -0,0 +1,51 @@
+import { TokenData } from "../../interfaces/TokenData";
+import {promises as fs} from "fs";
+import { resolve } from "path";
+
+const TOKENS_FILE = "tokens.json";
+const LOG_PREFIX = "[TokenData] ";
+
+export {
+  getTokenData,
+  saveTokenData
+}
+
+function getTokenDataFilePath(): string {
+  return resolve(process.cwd(), TOKENS_FILE);
+}
+
+async function getTokenData(): Promise<TokenData> {
+  const tokenDataFilePath = getTokenDataFilePath();
+  let buffer: Buffer;
+
+  try {
+    buffer = await fs.readFile(tokenDataFilePath);
+  } catch (e) {
+    console.error(`${LOG_PREFIX}${TOKENS_FILE} not found on ${tokenDataFilePath}.`);
+    process.exit(1);
+  }
+
+  const tokenData = await JSON.parse(buffer.toString());
+
+  checkTokenData(tokenData);
+
+  return tokenData;
+}
+
+async function saveTokenData(tokenData: TokenData): Promise<void> {
+  const tokenDataFilePath = getTokenDataFilePath();
+  const jsonTokenData = JSON.stringify(tokenData);
+
+  await fs.writeFile(tokenDataFilePath, jsonTokenData);
+  console.log(`${LOG_PREFIX}Token data saved`);
+}
+
+function checkTokenData(tokenData: TokenData) {
+  if (
+    !tokenData.access_token ||
+    !tokenData.refresh_token
+  ) {
+    console.error(`${LOG_PREFIX}Missing refresh_token or access_token in ${TOKENS_FILE}.`);
+    process.exit(1);
+  }
+}

src/backend/helpers/twitch.ts

@@ -0,0 +1,96 @@
+import { AccessToken, RefreshableAuthProvider, StaticAuthProvider } from "twitch-auth";
+import { getTokenData, saveTokenData } from "./tokenData";
+
+import { ApiClient } from "twitch";
+import { TokenData } from "../../interfaces/TokenData";
+
+const LOG_PREFIX = "[Twitch] ";
+
+let refreshAuthProvider: RefreshableAuthProvider;
+
+export {
+  getAuthProvider,
+  getApiClient
+}
+
+interface ClientCredentials {
+  clientId: string;
+  clientSecret: string;
+}
+
+function getClientCredentials(): ClientCredentials {
+  if (
+    !process.env.TWITCH_CLIENT_ID ||
+    !process.env.TWITCH_CLIENT_SECRET
+  ) {
+		console.error(
+			`${LOG_PREFIX}Missing environment parameters TWITCH_CLIENT_ID or TWITCH_CLIENT_SECRET`
+		);
+    process.exit(1);
+  }
+
+  return {
+    clientId: process.env.TWITCH_CLIENT_ID,
+    clientSecret: process.env.TWITCH_CLIENT_SECRET
+  };
+}
+
+async function createStaticAuthProvider(): Promise<StaticAuthProvider> {
+  let tokenData = await getTokenData();
+  const credentials = getClientCredentials();
+
+  return new StaticAuthProvider(
+    credentials.clientId,
+    tokenData.access_token
+  );
+}
+
+async function getAuthProvider(): Promise<RefreshableAuthProvider> {
+  if (refreshAuthProvider) {
+    return refreshAuthProvider;
+  }
+
+  let tokenData = await getTokenData();
+
+  const staticAuthProvider = await createStaticAuthProvider();
+  const credentials = getClientCredentials();
+
+  const expiry = tokenData.expiryTimestamp === null
+    ? null
+    : new Date(tokenData.expiryTimestamp);
+
+  refreshAuthProvider = new RefreshableAuthProvider(
+		staticAuthProvider,
+		{
+      clientSecret: credentials.clientSecret,
+      refreshToken: tokenData.refresh_token,
+			expiry,
+      onRefresh: onRefresh
+    }
+  ) as RefreshableAuthProvider;
+
+  return refreshAuthProvider;
+}
+
+async function onRefresh(refreshData: AccessToken): Promise<void> {
+  const { accessToken, refreshToken, expiryDate } = refreshData;
+  console.log(`${LOG_PREFIX}Tokens refreshed`);
+
+  const expiryTimestamp = expiryDate === null
+    ? 0
+    : expiryDate.getTime()
+
+  const newTokenData: TokenData = {
+    access_token: accessToken,
+    refresh_token: refreshToken,
+    expiryTimestamp
+  };
+
+  await saveTokenData(newTokenData);
+}
+
+async function getApiClient() {
+  const authProvider = await getAuthProvider();
+
+  return new ApiClient({ authProvider });
+}