feat: add the tiktok integration

lib/auth.ts

@@ -32,6 +32,9 @@ export const { handlers, signIn, signOut, auth } = NextAuth({
     ],
     callbacks: {
         async session({ session, token }) {
+            if (token?.id && session.user) {
+                (session.user as { id?: string }).id = token.id as string;
+            }
             return session;
         },
         async jwt({ token, user }) {

lib/tiktok.ts

@@ -0,0 +1,150 @@
+const TIKTOK_AUTH_URL = "https://www.tiktok.com/v2/auth/authorize";
+const TIKTOK_TOKEN_URL = "https://open.tiktokapis.com/v2/oauth/token/";
+const TIKTOK_USER_INFO_URL = "https://open.tiktokapis.com/v2/user/info/";
+
+const CLIENT_KEY = process.env.TIKTOK_CLIENT_KEY!;
+const CLIENT_SECRET = process.env.TIKTOK_CLIENT_SECRET!;
+
+function getRedirectUri(): string {
+    return process.env.NODE_ENV === "production"
+        ? process.env.TIKTOK_REDIRECT_URI_PROD!
+        : process.env.TIKTOK_REDIRECT_URI_DEV!;
+}
+
+// ── PKCE helpers ──────────────────────────────────────────────
+export function generateCodeVerifier(): string {
+    const charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+    let result = "";
+    const array = new Uint8Array(64);
+    crypto.getRandomValues(array);
+    for (let i = 0; i < 64; i++) {
+        result += charset[array[i] % charset.length];
+    }
+    return result;
+}
+
+export async function generateCodeChallenge(verifier: string): Promise<string> {
+    const data = new TextEncoder().encode(verifier);
+    const digest = await globalThis.crypto.subtle.digest("SHA-256", data);
+    const bytes = Array.from(new Uint8Array(digest));
+    return btoa(bytes.map((b) => String.fromCharCode(b)).join(""))
+        .replace(/\+/g, "-")
+        .replace(/\//g, "_")
+        .replace(/=+$/, "");
+}
+// ──────────────────────────────────────────────────────────────
+
+export function getTikTokAuthUrl(state: string, codeChallenge: string): string {
+    const params = new URLSearchParams({
+        client_key: CLIENT_KEY,
+        response_type: "code",
+        scope: "user.info.basic,user.info.stats",
+        redirect_uri: getRedirectUri(),
+        state,
+        code_challenge: codeChallenge,
+        code_challenge_method: "S256",
+    });
+    return `${TIKTOK_AUTH_URL}?${params.toString()}`;
+}
+
+export interface TikTokTokenResponse {
+    access_token: string;
+    refresh_token: string;
+    open_id: string;
+    expires_in: number;
+    refresh_expires_in: number;
+    token_type: string;
+    scope: string;
+    error?: string;
+    error_description?: string;
+}
+
+export async function exchangeCodeForTokens(code: string, codeVerifier: string): Promise<TikTokTokenResponse> {
+    const body = new URLSearchParams({
+        client_key: CLIENT_KEY,
+        client_secret: CLIENT_SECRET,
+        code,
+        grant_type: "authorization_code",
+        redirect_uri: getRedirectUri(),
+        code_verifier: codeVerifier,
+    });
+
+    const res = await fetch(TIKTOK_TOKEN_URL, {
+        method: "POST",
+        headers: { "Content-Type": "application/x-www-form-urlencoded" },
+        body: body.toString(),
+    });
+
+    const data = await res.json();
+
+    if (!res.ok || data.error) {
+        throw new Error(data.error_description || data.error || "TikTok token exchange failed");
+    }
+
+    return data;
+}
+
+export async function refreshAccessToken(refreshToken: string): Promise<TikTokTokenResponse> {
+    const body = new URLSearchParams({
+        client_key: CLIENT_KEY,
+        client_secret: CLIENT_SECRET,
+        grant_type: "refresh_token",
+        refresh_token: refreshToken,
+    });
+
+    const res = await fetch(TIKTOK_TOKEN_URL, {
+        method: "POST",
+        headers: { "Content-Type": "application/x-www-form-urlencoded" },
+        body: body.toString(),
+    });
+
+    const data = await res.json();
+
+    if (!res.ok || data.error) {
+        throw new Error(data.error_description || data.error || "TikTok token refresh failed");
+    }
+
+    return data;
+}
+
+export interface TikTokUserStats {
+    followers: number;
+    likes: number;
+    videoCount: number;
+    username: string;
+    displayName: string;
+    avatarUrl: string;
+}
+
+export async function fetchUserStats(accessToken: string, openId: string): Promise<TikTokUserStats> {
+    const fields = "follower_count,following_count,likes_count,video_count,display_name,avatar_url";
+    const url = `${TIKTOK_USER_INFO_URL}?fields=${fields}`;
+
+    const res = await fetch(url, {
+        headers: {
+            Authorization: `Bearer ${accessToken}`,
+        },
+    });
+
+    const data = await res.json();
+
+    if (!res.ok || data.error?.code !== "ok") {
+        throw new Error(data.error?.message || "TikTok user info fetch failed");
+    }
+
+    const user = data.data?.user ?? {};
+
+    return {
+        followers: user.follower_count ?? 0,
+        likes: user.likes_count ?? 0,
+        videoCount: user.video_count ?? 0,
+        username: openId,
+        displayName: user.display_name ?? "",
+        avatarUrl: user.avatar_url ?? "",
+    };
+}
+
+
+
+
+