docs: readme with basic stuff and instructions

README.md

@@ -1 +1,66 @@
-# passport-keycloak-jwt-introspect
+# passport-keycloak-jwt-introspect
+
+By using [Keycloak](https://www.keycloak.org/), you can validate access tokens in different ways: online or offline.
+
+This [Passport](https://www.passportjs.org/) strategy allows you to perform an online validation of an access token by doing instrospect.
+
+
+## Installation
+```shell
+npm install passport-keycloak-jwt-introspect
+```
+
+## Usage
+
+#### Configuration
+```javascript
+passport.use(
+    new KeycloakJwtIntrospectStrategy(
+      {
+        clientId: KEYCLOAK_CLIENT_ID,
+        clientSecret: KEYCLOAK_CLIENT_SECRET,
+        introspectUrl: KEYCLOAK_INTROSPECT_URL,
+        passReqToCallback: true,
+      },
+      function (req, keycloakData, done) {
+        // You should always check that the token is active!
+        if (!keycloakData.active) return done(null, false);
+
+        // You can use all info. in jwtPayload to make your validations and create your user
+        return done(null, jwtPayload);
+      },
+    ),
+);
+```
+
+**KEYCLOAK_INTROSPECT_URL_EXAMPLE:**  http://localhost:8080/realms/YOUR_REALM/protocol/openid-connect/token/introspect
+
+Check out [Keycloak Data Example](doc/keycloak_data_example.json) JSON file to learn about all available attributes in the object.
+
+#### Request authentication
+Since this is a Bearer-like strategy, you don't have to use sessions. The token will be validated on every request.
+
+We could create a function to use as middleware and validate every request:
+```javascript
+export const checkAuth = (req: Request, res: Response, next: NextFunction) => {
+  passport.authenticate("keycloak-jwt-introspect", { session: false })(
+    req,
+    res,
+    next,
+  );
+};
+```
+
+Then, we can use it wherever we need to. For example, as a global middleware for our app:
+```javascript
+app.use(checkAuth);
+```
+
+## Examples
+Example usage cases and configuration are coming soon. Any help is appreciated, so feel free to contribute!
+
+## License
+[The MIT License](http://opensource.org/licenses/MIT)
+
+
+