Improve FAQ & video rendering, tighten homepage and CSS

server-rs/src/routes/stripe_webhook.rs

@@ -1,10 +1,13 @@
-use std::sync::Arc;
+use std::collections::VecDeque;
+use std::sync::{Arc, LazyLock};
 
 use axum::body::Bytes;
 use axum::extract::State;
 use axum::http::{HeaderMap, StatusCode};
 use axum::response::{IntoResponse, Response};
 use hmac::{Hmac, Mac};
+use parking_lot::Mutex;
+use rustc_hash::FxHashSet;
 use sha2::Sha256;
 use tracing::{info, warn};
 
@@ -13,6 +16,46 @@ use crate::state::SharedState;
 
 type HmacSha256 = Hmac<Sha256>;
 
+/// Process-local LRU of recently processed Stripe event IDs.
+/// Stripe retries deliver the same event ID; we drop duplicates so we don't
+/// re-run side effects (subscription writes, token cache invalidation, logs).
+/// Capacity is intentionally generous: at typical webhook volumes this covers
+/// far more than Stripe's retry window.
+struct EventDedup {
+    seen: FxHashSet<String>,
+    queue: VecDeque<String>,
+    capacity: usize,
+}
+
+impl EventDedup {
+    fn new(capacity: usize) -> Self {
+        Self {
+            seen: FxHashSet::default(),
+            queue: VecDeque::with_capacity(capacity),
+            capacity,
+        }
+    }
+
+    /// Returns `true` if this event ID is new (and records it),
+    /// `false` if it was already seen recently.
+    fn check_and_insert(&mut self, id: &str) -> bool {
+        if self.seen.contains(id) {
+            return false;
+        }
+        self.seen.insert(id.to_string());
+        self.queue.push_back(id.to_string());
+        if self.queue.len() > self.capacity {
+            if let Some(old) = self.queue.pop_front() {
+                self.seen.remove(&old);
+            }
+        }
+        true
+    }
+}
+
+static EVENT_DEDUP: LazyLock<Mutex<EventDedup>> =
+    LazyLock::new(|| Mutex::new(EventDedup::new(1024)));
+
 /// Verify Stripe webhook signature (v1 scheme).
 fn verify_signature(payload: &[u8], sig_header: &str, secret: &str) -> bool {
     // Parse timestamp and signature from header: "t=TIMESTAMP,v1=SIGNATURE"
@@ -95,7 +138,16 @@ pub async fn post_stripe_webhook(
     };
 
     let event_type = event["type"].as_str().unwrap_or("");
-    info!(event_type, "Received Stripe webhook");
+    let event_id = event["id"].as_str().unwrap_or("");
+
+    // Idempotency: drop replays/retries of an already-processed event.
+    // We always answer 200 so Stripe stops retrying.
+    if !event_id.is_empty() && !EVENT_DEDUP.lock().check_and_insert(event_id) {
+        info!(event_id, event_type, "Dropping duplicate Stripe webhook");
+        return StatusCode::OK.into_response();
+    }
+
+    info!(event_id, event_type, "Received Stripe webhook");
 
     if event_type == "checkout.session.completed" {
         let user_id = event["data"]["object"]["client_reference_id"]