Payjoin-cli should cache ohttp-keys for re-use

This pr  adds the functionality of ohttp-keys
catching to payjoin-cli , ohttp-keys should not
be fetched each time and a cached key should be use.
Keys expire in 6 months .

Author: zealsham

payjoin-cli/src/app/v2/ohttp.rs

@@ -1,9 +1,16 @@
+use std::fs;
+use std::path::PathBuf;
 use std::sync::{Arc, Mutex};
+use std::time::{Duration, SystemTime};
 
 use anyhow::{anyhow, Result};
+use serde::{Deserialize, Serialize};
 
 use super::Config;
 
+// 6 months
+const CACHE_DURATION: Duration = Duration::from_secs(6 * 30 * 24 * 60 * 60);
+
 #[derive(Debug, Clone)]
 pub struct RelayManager {
     selected_relay: Option<url::Url>,
@@ -38,12 +45,12 @@ pub(crate) async fn unwrap_ohttp_keys_or_else_fetch(
             ohttp_keys,
             relay_url: config.v2()?.ohttp_relays[0].clone(),
         });
-    } else {
-        println!("Bootstrapping private network transport over Oblivious HTTP");
-        let fetched_keys = fetch_ohttp_keys(config, directory, relay_manager).await?;
-
-        Ok(fetched_keys)
     }
+
+    println!("Bootstrapping private network transport over Oblivious HTTP");
+    let fetched_keys = fetch_ohttp_keys(config, directory, relay_manager).await?;
+
+    Ok(fetched_keys)
 }
 
 async fn fetch_ohttp_keys(
@@ -77,6 +84,17 @@ async fn fetch_ohttp_keys(
             .expect("Lock should not be poisoned")
             .set_selected_relay(selected_relay.clone());
 
+        // try cache for this selected relay first
+        if let Some(cached) = read_cached_ohttp_keys(&selected_relay) {
+            println!("using Cached keys  for relay: {}", selected_relay);
+            if !is_expired(&cached) && cached.relay_url == selected_relay {
+                return Ok(ValidatedOhttpKeys {
+                    ohttp_keys: cached.keys,
+                    relay_url: cached.relay_url,
+                });
+            }
+        }
+
         let ohttp_keys = {
             #[cfg(feature = "_manual-tls")]
             {
@@ -101,8 +119,17 @@ async fn fetch_ohttp_keys(
         };
 
         match ohttp_keys {
-            Ok(keys) =>
-                return Ok(ValidatedOhttpKeys { ohttp_keys: keys, relay_url: selected_relay }),
+            Ok(keys) => {
+                // Cache the keys if they are not already cached for this relay
+                if read_cached_ohttp_keys(&selected_relay).is_none() {
+                    if let Err(e) = cache_ohttp_keys(&keys, &selected_relay) {
+                        tracing::debug!(
+                            "Failed to cache OHTTP keys for relay {selected_relay}: {e:?}"
+                        );
+                    }
+                }
+                return Ok(ValidatedOhttpKeys { ohttp_keys: keys, relay_url: selected_relay });
+            }
             Err(payjoin::io::Error::UnexpectedStatusCode(e)) => {
                 return Err(payjoin::io::Error::UnexpectedStatusCode(e).into());
             }
@@ -116,3 +143,49 @@ async fn fetch_ohttp_keys(
         }
     }
 }
+
+#[derive(Serialize, Deserialize, Debug)]
+struct CachedOhttpKeys {
+    keys: payjoin::OhttpKeys,
+    relay_url: payjoin::Url,
+    fetched_at: u64,
+}
+
+fn get_cache_file(relay_url: &payjoin::Url) -> PathBuf {
+    dirs::cache_dir()
+        .unwrap()
+        .join("payjoin-cli")
+        .join(relay_url.host_str().unwrap())
+        .join("ohttp-keys.json")
+}
+
+fn read_cached_ohttp_keys(relay_url: &payjoin::Url) -> Option<CachedOhttpKeys> {
+    let cache_file = get_cache_file(relay_url);
+    if !cache_file.exists() {
+        return None;
+    }
+    let data = fs::read_to_string(cache_file).ok().unwrap();
+    serde_json::from_str(&data).ok()
+}
+
+fn cache_ohttp_keys(ohttp_keys: &payjoin::OhttpKeys, relay_url: &payjoin::Url) -> Result<()> {
+    let cached = CachedOhttpKeys {
+        keys: ohttp_keys.clone(),
+        relay_url: relay_url.clone(),
+        fetched_at: SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap().as_secs(),
+    };
+
+    let serialized = serde_json::to_string(&cached)?;
+    let path = get_cache_file(relay_url);
+    fs::create_dir_all(path.parent().unwrap())?;
+    fs::write(path, serialized)?;
+    Ok(())
+}
+
+fn is_expired(cached_keys: &CachedOhttpKeys) -> bool {
+    let now = SystemTime::now()
+        .duration_since(SystemTime::UNIX_EPOCH)
+        .unwrap_or(Duration::ZERO)
+        .as_secs();
+    now.saturating_sub(cached_keys.fetched_at) > CACHE_DURATION.as_secs()
+}

payjoin-cli/tests/e2e.rs

@@ -64,6 +64,15 @@ mod e2e {
         res
     }
 
+    fn clear_payjoin_cache() -> std::io::Result<()> {
+        let cache_dir = dirs::cache_dir().unwrap().join("payjoin-cli");
+
+        if cache_dir.exists() {
+            std::fs::remove_dir_all(cache_dir)?;
+        }
+        Ok(())
+    }
+
     #[cfg(feature = "v1")]
     #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
     async fn send_receive_payjoin_v1() -> Result<(), BoxError> {
@@ -203,6 +212,8 @@ mod e2e {
         use tempfile::TempDir;
         use tokio::process::Child;
 
+        clear_payjoin_cache()?;
+
         type Result<T> = std::result::Result<T, BoxError>;
 
         init_tracing();