Clean subdir api (#228)

There were a couple of functions with similar names that confused me.
Some weren't even used. This cleans them up

- first commit repalces unnecessary functions with a well named
conversion fn
- second encapsulates a similarly named private conversion function in
the right place
-  third removes a helper function with no apparent use

Author: DanGould

payjoin/src/receive/v2.rs

@@ -56,17 +56,9 @@ impl Enroller {
         }
     }
 
-    pub fn subdirectory(&self) -> String {
-        let pubkey = &self.s.public_key().serialize();
-        let b64_config = base64::Config::new(base64::CharacterSet::UrlSafe, false);
-        base64::encode_config(pubkey, b64_config)
-    }
-
-    pub fn payjoin_subdir(&self) -> String { format!("{}/{}", self.subdirectory(), "payjoin") }
-
     pub fn extract_req(&mut self) -> Result<(Request, ohttp::ClientResponse), Error> {
         let url = self.ohttp_relay.clone();
-        let subdirectory = self.subdirectory();
+        let subdirectory = subdir_path_from_pubkey(&self.s.public_key());
         let (body, ctx) = crate::v2::ohttp_encapsulate(
             &mut self.ohttp_keys,
             "POST",
@@ -97,7 +89,7 @@ impl Enroller {
     }
 }
 
-fn subdirectory(pubkey: &bitcoin::secp256k1::PublicKey) -> String {
+fn subdir_path_from_pubkey(pubkey: &bitcoin::secp256k1::PublicKey) -> String {
     let pubkey = pubkey.serialize();
     let b64_config = base64::Config::new(base64::CharacterSet::UrlSafe, false);
     base64::encode_config(pubkey, b64_config)
@@ -268,8 +260,6 @@ impl Enrolled {
         Ok(crate::v2::ohttp_encapsulate(&mut self.ohttp_keys, "GET", &fallback_target, None)?)
     }
 
-    pub fn pubkey(&self) -> [u8; 33] { self.s.public_key().serialize() }
-
     pub fn fallback_target(&self) -> String {
         let pubkey = &self.s.public_key().serialize();
         let b64_config = base64::Config::new(base64::CharacterSet::UrlSafe, false);
@@ -518,7 +508,7 @@ impl PayjoinProposal {
         let post_payjoin_target = format!(
             "{}{}/payjoin",
             self.context.directory.as_str(),
-            subdirectory(&self.context.s.public_key())
+            subdir_path_from_pubkey(&self.context.s.public_key())
         );
         log::debug!("Payjoin post target: {}", post_payjoin_target.as_str());
         let (body, ctx) = crate::v2::ohttp_encapsulate(

payjoin/src/send/mod.rs

@@ -28,6 +28,8 @@ use std::str::FromStr;
 
 use bitcoin::address::NetworkChecked;
 use bitcoin::psbt::Psbt;
+#[cfg(feature = "v2")]
+use bitcoin::secp256k1::PublicKey;
 use bitcoin::{FeeRate, Script, ScriptBuf, Sequence, TxOut, Weight};
 pub use error::{CreateRequestError, ResponseError, ValidationError};
 pub(crate) use error::{InternalCreateRequestError, InternalValidationError};
@@ -323,16 +325,7 @@ impl RequestContext {
         &mut self,
         ohttp_relay: Url,
     ) -> Result<(Request, ContextV2), CreateRequestError> {
-        let rs_base64 = crate::v2::subdir(self.endpoint.as_str()).to_string();
-        log::debug!("rs_base64: {:?}", rs_base64);
-        let b64_config =
-            bitcoin::base64::Config::new(bitcoin::base64::CharacterSet::UrlSafe, false);
-        let rs = bitcoin::base64::decode_config(rs_base64, b64_config)
-            .map_err(InternalCreateRequestError::SubdirectoryNotBase64)?;
-        log::debug!("rs: {:?}", rs.len());
-        let rs = bitcoin::secp256k1::PublicKey::from_slice(&rs)
-            .map_err(InternalCreateRequestError::SubdirectoryInvalidPubkey)?;
-
+        let rs = Self::rs_pubkey_from_dir_endpoint(&self.endpoint)?;
         let url = self.endpoint.clone();
         let body = serialize_v2_body(
             &self.psbt,
@@ -368,6 +361,32 @@ impl RequestContext {
             },
         ))
     }
+
+    #[cfg(feature = "v2")]
+    fn rs_pubkey_from_dir_endpoint(endpoint: &Url) -> Result<PublicKey, CreateRequestError> {
+        let path_and_query: String;
+
+        if let Some(pos) = endpoint.as_str().rfind('/') {
+            path_and_query = endpoint.as_str()[pos + 1..].to_string();
+        } else {
+            path_and_query = endpoint.to_string();
+        }
+
+        let subdirectory: String;
+
+        if let Some(pos) = path_and_query.find('?') {
+            subdirectory = path_and_query[..pos].to_string();
+        } else {
+            subdirectory = path_and_query;
+        }
+
+        let b64_config =
+            bitcoin::base64::Config::new(bitcoin::base64::CharacterSet::UrlSafe, false);
+        let pubkey_bytes = bitcoin::base64::decode_config(subdirectory, b64_config)
+            .map_err(InternalCreateRequestError::SubdirectoryNotBase64)?;
+        Ok(bitcoin::secp256k1::PublicKey::from_slice(&pubkey_bytes)
+            .map_err(InternalCreateRequestError::SubdirectoryInvalidPubkey)?)
+    }
 }
 
 #[cfg(feature = "v2")]

payjoin/src/v2.rs

@@ -8,25 +8,6 @@ use chacha20poly1305::{AeadCore, ChaCha20Poly1305, Nonce};
 
 pub const PADDED_MESSAGE_BYTES: usize = 7168; // 7KB
 
-pub fn subdir(path: &str) -> String {
-    let subdirectory: String;
-
-    if let Some(pos) = path.rfind('/') {
-        subdirectory = path[pos + 1..].to_string();
-    } else {
-        subdirectory = path.to_string();
-    }
-
-    let pubkey_id: String;
-
-    if let Some(pos) = subdirectory.find('?') {
-        pubkey_id = subdirectory[..pos].to_string();
-    } else {
-        pubkey_id = subdirectory;
-    }
-    pubkey_id
-}
-
 /// crypto context
 ///
 /// <- Receiver S