web: introduce dynamic /updates endpoint

src/web/vks_updates.rs

@@ -0,0 +1,56 @@
+use std::io::{BufRead, BufReader};
+
+use rocket::http::hyper::header::{Expires, HttpDate};
+
+use crate::{database::updates::{Epoch, Manifest}, merge_util::merge_vectors};
+use crate::database::{Database, KeyDatabase};
+use crate::Result;
+
+const EPOCH_SERVE_LIMIT: u32 = 120;
+
+#[derive(Responder)]
+pub enum ManifestUpdateResponse {
+    #[response(status = 200, content_type = "application/pgp-keystore-update-manifest")]
+    Binary(Vec<u8>, Expires),
+    #[response(status = 404)]
+    NotFound(String),
+    #[response(status = 400)]
+    BadRequest(String),
+}
+
+#[get("/vks/v1/updates/<epoch>")]
+pub fn get_update_manifest(
+    db: rocket::State<KeyDatabase>,
+    epoch: u32,
+) -> ManifestUpdateResponse {
+    let epoch_now = Epoch::current().unwrap();
+    let epoch_since = Epoch::from(epoch);
+    if epoch_since >= epoch_now {
+        return ManifestUpdateResponse::BadRequest("Requested epoch must be in the past and completed".to_owned());
+    }
+    if epoch_now - epoch_since > (EPOCH_SERVE_LIMIT as i64) {
+        return ManifestUpdateResponse::NotFound(
+            format!("Updafe manifest data only available for the last {} epochs", EPOCH_SERVE_LIMIT));
+    }
+
+    let mut epoch_data: Vec<&[u32]> = Vec::with_capacity((epoch_now - epoch_since) as usize);
+    for e in epoch_since.until(epoch_now).expect("epoch_since is before epoch_now") {
+        match db.read_log_epoch(e) {
+            Err(e) => {
+                eprintln!("Error reading epoch: {:?}", e);
+                return ManifestUpdateResponse::NotFound(
+                    "No data found for requested update epoch".to_owned());
+            }
+            Ok(None) => {
+                return ManifestUpdateResponse::NotFound(
+                    "No data found for requested update epoch".to_owned());
+            }
+            Ok(Some(v)) => epoch_data.push(&v),
+        }
+    }
+
+    let prefixes = merge_vectors(epoch_data);
+    let manifest = Manifest::new(epoch_since, epoch_now.pred().unwrap(), prefixes).unwrap();
+    let expires = Expires(HttpDate(epoch_now.succ().expect("We're not at the end of time").into()));
+    ManifestUpdateResponse::Binary(manifest.to_vec(), expires)
+}