From a9b0e2f49a5ae011dd879ecdd25c5ffea55ba28e Mon Sep 17 00:00:00 2001
From: Paul-Christian Volkmer <code@pcvolkmer.de>
Date: Fri, 22 Dec 2023 04:51:27 +0100
Subject: [PATCH] feat: extract user ID from client token

---
 Cargo.toml    |  1 +
 src/client.rs | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index 6f2f574..390246e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,6 +21,7 @@ serde_json = "1.0"
 tokio = { version = "1.35", features = ["rt-multi-thread", "macros"], default-features = false }
 tokio-tungstenite = { version = "0.21", features = ["connect", "rustls-tls-webpki-roots"], default-features = false }
 url = "2.5"
+base64 = "0.21"
 
 [profile.release]
 opt-level = "s"
diff --git a/src/client.rs b/src/client.rs
index 9cf0329..86e14b4 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -22,9 +22,12 @@ use std::fmt::{Display, Formatter};
 use std::marker::PhantomData;
 use std::time::Duration;
 
+use base64::engine::general_purpose::STANDARD_NO_PAD;
+use base64::Engine;
 use futures_util::{SinkExt, StreamExt};
 use reqwest::{IntoUrl, StatusCode};
 use serde::Deserialize;
+use serde_json::json;
 use tokio::join;
 use tokio::sync::mpsc::Sender;
 use tokio_tungstenite::connect_async;
@@ -41,6 +44,11 @@ struct LoginResponse {
     token: String,
 }
 
+#[derive(Deserialize, Debug)]
+struct TokenClaim {
+    sub: String,
+}
+
 #[derive(Deserialize, Debug)]
 struct MembershipResponse {
     #[serde(rename = "id")]
@@ -252,6 +260,27 @@ impl Client<LoggedOut> {
 }
 
 impl Client<LoggedIn> {
+    /// Get user ID extracted from client token
+    ///
+    /// This method fails if the token cannot be parsed
+    fn get_user_id(&self) -> Result<String, ClientError> {
+        let token = self.token.clone().unwrap_or_default();
+        let mut token_parts = token.split('.');
+
+        match token_parts.nth(1) {
+            None => Err(ParserError("Unparsable token".into())),
+            Some(part) => match STANDARD_NO_PAD.decode(part) {
+                Ok(d) => match serde_json::from_str::<TokenClaim>(
+                    &String::from_utf8(d).unwrap_or_default(),
+                ) {
+                    Ok(claim) => Ok(claim.sub),
+                    Err(err) => Err(ParserError(format!("Unparsable token claim: {}", err))),
+                },
+                Err(err) => Err(ParserError(format!("Unparsable token: {}", err))),
+            },
+        }
+    }
+
     /// Logout the client and discard existing token if not logged in
     ///
     /// If successful the result will be of type `Client<LoggedOut>`