feat: prepare for logos module consumption

- add flake.nix for Nix builds (cdylib + header generation)
- switch crate-type from dylib to cdylib for C FFI
- replace placeholder delivery addresses with real derived addresses
- switch FFI inputs from owned to borrowed
- expose local_delivery_address() so caller knows where to subscribe

.gitignore

@@ -30,4 +30,8 @@ target
 # Temporary data folder
 tmp
 
+# Auto-generated C headers (regenerated by flake.nix build)
+libchat.h
+double_ratchet.h
+
 .DS_Store

core/conversations/Cargo.toml

@@ -4,7 +4,14 @@ version = "0.1.0"
 edition = "2024"
 
 [lib]
-crate-type = ["rlib","staticlib","dylib"]
+crate-type = ["rlib","staticlib","cdylib"]
+
+[features]
+headers = ["safer-ffi/headers"]
+
+[[bin]]
+name = "generate-libchat-headers"
+required-features = ["headers"]
 
 [dependencies]
 base64 = "0.22"

core/conversations/src/api.rs

@@ -49,9 +49,9 @@ pub struct ContextHandle(pub(crate) Context);
 /// # Returns
 /// Opaque handle to the store. Must be freed with destroy_context()
 #[ffi_export]
-pub fn create_context(name: repr_c::String) -> repr_c::Box<ContextHandle> {
+pub fn create_context(name: c_slice::Ref<'_, u8>) -> repr_c::Box<ContextHandle> {
-    // Deference name to to `str` and then borrow to &str
+    let name_str = std::str::from_utf8(name.as_slice()).unwrap_or("default");
-    Box::new(ContextHandle(Context::new_with_name(&*name))).into()
+    Box::new(ContextHandle(Context::new_with_name(name_str))).into()
 }
 
 /// Returns the friendly name of the contexts installation.
@@ -61,6 +61,13 @@ pub fn installation_name(ctx: &ContextHandle) -> repr_c::String {
     ctx.0.installation_name().to_string().into()
 }
 
+/// Returns the local delivery address (hex-encoded Blake2b-512 of the installation public key).
+/// This is the address other installations use to send messages to this context.
+#[ffi_export]
+pub fn local_delivery_address(ctx: &ContextHandle) -> repr_c::String {
+    ctx.0.local_delivery_address().to_string().into()
+}
+
 /// Destroys a conversation store and frees its memory
 ///
 /// # Safety
@@ -182,11 +189,12 @@ pub fn list_conversations(ctx: &mut ContextHandle) -> ListConvoResult {
 #[ffi_export]
 pub fn send_content(
     ctx: &mut ContextHandle,
-    convo_id: repr_c::String,
+    convo_id: c_slice::Ref<'_, u8>,
     content: c_slice::Ref<'_, u8>,
     out: &mut SendContentResult,
 ) {
-    let payloads = match ctx.0.send_content(&convo_id, &content) {
+    let convo_id_str = std::str::from_utf8(convo_id.as_slice()).unwrap_or("");
+    let payloads = match ctx.0.send_content(convo_id_str, &content) {
         Ok(p) => p,
         Err(_) => {
             *out = SendContentResult {

core/conversations/src/bin/generate-libchat-headers.rs

@@ -0,0 +1,3 @@
+fn main() -> std::io::Result<()> {
+    libchat::generate_headers()
+}

core/conversations/src/context.rs

@@ -65,6 +65,10 @@ impl Context {
         self._identity.get_name()
     }
 
+    pub fn local_delivery_address(&self) -> &str {
+        self.inbox.id()
+    }
+
     pub fn create_private_convo(
         &mut self,
         remote_bundle: &Introduction,

core/conversations/src/conversation/privatev1.rs

@@ -55,11 +55,12 @@ impl BaseConvoId {
 pub struct PrivateV1Convo {
     local_convo_id: String,
     remote_convo_id: String,
+    remote_delivery_address: String,
     dr_state: RatchetState,
 }
 
 impl PrivateV1Convo {
-    pub fn new_initiator(seed_key: SymmetricKey32, remote: PublicKey) -> Self {
+    pub fn new_initiator(seed_key: SymmetricKey32, remote: PublicKey, remote_delivery_address: String) -> Self {
         let base_convo_id = BaseConvoId::new(&seed_key);
         let local_convo_id = base_convo_id.id_for_participant(Role::Initiator);
         let remote_convo_id = base_convo_id.id_for_participant(Role::Responder);
@@ -73,11 +74,12 @@ impl PrivateV1Convo {
         Self {
             local_convo_id,
             remote_convo_id,
+            remote_delivery_address,
             dr_state,
         }
     }
 
-    pub fn new_responder(seed_key: SymmetricKey32, dh_self: &PrivateKey) -> Self {
+    pub fn new_responder(seed_key: SymmetricKey32, dh_self: &PrivateKey, remote_delivery_address: String) -> Self {
         let base_convo_id = BaseConvoId::new(&seed_key);
         let local_convo_id = base_convo_id.id_for_participant(Role::Responder);
         let remote_convo_id = base_convo_id.id_for_participant(Role::Initiator);
@@ -92,6 +94,7 @@ impl PrivateV1Convo {
         Self {
             local_convo_id,
             remote_convo_id,
+            remote_delivery_address,
             dr_state,
         }
     }
@@ -179,7 +182,7 @@ impl Convo for PrivateV1Convo {
         let data = self.encrypt(frame);
 
         Ok(vec![AddressedEncryptedPayload {
-            delivery_address: "delivery_address".into(),
+            delivery_address: self.remote_delivery_address.clone(),
             data,
         }])
     }
@@ -236,8 +239,8 @@ mod tests {
         let seed_key_saro = SymmetricKey32::from(seed_key);
         let seed_key_raya = SymmetricKey32::from(seed_key);
         let send_content_bytes = vec![0, 2, 4, 6, 8];
-        let mut sr_convo = PrivateV1Convo::new_initiator(seed_key_saro, pub_raya);
+        let mut sr_convo = PrivateV1Convo::new_initiator(seed_key_saro, pub_raya, "test_addr".into());
-        let mut rs_convo = PrivateV1Convo::new_responder(seed_key_raya, &raya);
+        let mut rs_convo = PrivateV1Convo::new_responder(seed_key_raya, &raya, "test_addr".into());
 
         let send_frame = PrivateV1Frame {
             conversation_id: "_".into(),

core/conversations/src/inbox/handler.rs

@@ -16,12 +16,6 @@ use crate::inbox::handshake::InboxHandshake;
 use crate::proto;
 use crate::types::{AddressedEncryptedPayload, ContentData};
 
-/// Compute the deterministic Delivery_address for an installation
-fn delivery_address_for_installation(_: PublicKey) -> String {
-    // TODO: Implement Delivery Address
-    "delivery_address".into()
-}
-
 pub struct Inbox {
     ident: Rc<Identity>,
     local_convo_id: String,
@@ -78,13 +72,12 @@ impl Inbox {
         let (seed_key, ephemeral_pub) =
             InboxHandshake::perform_as_initiator(self.ident.secret(), &pkb, &mut rng);
 
-        let mut convo = PrivateV1Convo::new_initiator(seed_key, *remote_bundle.ephemeral_key());
+        let remote_delivery_addr = Inbox::inbox_identifier_for_key(*remote_bundle.installation_key());
+        let mut convo = PrivateV1Convo::new_initiator(seed_key, *remote_bundle.ephemeral_key(), remote_delivery_addr.clone());
 
         let mut payloads = convo.send_message(initial_message)?;
 
-        // Wrap First payload in Invite
         if let Some(first_message) = payloads.get_mut(0) {
-            // Take the the value of .data - it's being replaced at the end of this block
             let frame = Self::wrap_in_invite(std::mem::take(&mut first_message.data));
 
             // TODO: Encrypt frame
@@ -102,10 +95,7 @@ impl Inbox {
                 payload: Bytes::from_owner(ciphertext),
             };
 
-            // Update the address field with the Inbox delivery_Address
+            first_message.delivery_address = remote_delivery_addr;
-            first_message.delivery_address =
-                delivery_address_for_installation(*remote_bundle.installation_key());
-            // Update the data field with new Payload
             first_message.data = proto::EncryptedPayload {
                 encryption: Some(proto::Encryption::InboxHandshake(handshake)),
             };
@@ -128,12 +118,18 @@ impl Inbox {
         let key_index = hex::encode(header.responder_ephemeral.as_ref());
         let ephemeral_key = self.lookup_ephemeral_key(&key_index)?;
 
+        // Extract initiator's identity key for delivery address before header is consumed
+        let initiator_static_bytes: [u8; 32] = header.initiator_static.as_ref()
+            .try_into()
+            .map_err(|_| ChatError::BadBundleValue("wrong size - initiator static".into()))?;
+        let remote_delivery_addr = Inbox::inbox_identifier_for_key(PublicKey::from(initiator_static_bytes));
+
         // Perform handshake and decrypt frame
         let (seed_key, frame) = self.perform_handshake(ephemeral_key, header, handshake.payload)?;
 
         match frame.frame_type.unwrap() {
             proto::inbox_v1_frame::FrameType::InvitePrivateV1(_invite_private_v1) => {
-                let mut convo = PrivateV1Convo::new_responder(seed_key, ephemeral_key);
+                let mut convo = PrivateV1Convo::new_responder(seed_key, ephemeral_key, remote_delivery_addr);
 
                 let Some(enc_payload) = _invite_private_v1.initial_message else {
                     return Err(ChatError::Protocol("missing initial encpayload".into()));

core/conversations/src/lib.rs

@@ -14,6 +14,13 @@ pub use api::*;
 pub use context::{Context, Introduction};
 pub use errors::ChatError;
 
+#[cfg(feature = "headers")]
+pub fn generate_headers() -> std::io::Result<()> {
+    safer_ffi::headers::builder()
+        .to_file("libchat.h")?
+        .generate()
+}
+
 #[cfg(test)]
 mod tests {
 
@@ -24,8 +31,8 @@ mod tests {
 
     #[test]
     fn test_message_roundtrip() {
-        let mut saro = create_context("saro".into());
+        let mut saro = create_context(b"saro".as_slice().into());
-        let mut raya = create_context("raya".into());
+        let mut raya = create_context(b"raya".as_slice().into());
 
         // Raya Creates Bundle and Sends to Saro
         let mut intro_result = CreateIntroResult {

flake.nix

@@ -0,0 +1,95 @@
+{
+  description = "libchat - Logos Chat cryptographic library";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, rust-overlay }:
+    let
+      systems = [ "aarch64-darwin" "x86_64-darwin" "aarch64-linux" "x86_64-linux" ];
+      forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f {
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ rust-overlay.overlays.default ];
+        };
+      });
+    in
+    {
+      packages = forAllSystems ({ pkgs }:
+        let
+          rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust_toolchain.toml;
+          rustPlatform = pkgs.makeRustPlatform {
+            cargo = rustToolchain;
+            rustc = rustToolchain;
+          };
+        in
+        {
+          default = rustPlatform.buildRustPackage {
+            pname = "libchat";
+            version = "0.1.0";
+            src = pkgs.lib.cleanSourceWith {
+              src = ./.;
+              filter = path: type:
+                let base = builtins.baseNameOf path;
+                in !(builtins.elem base [ "target" "nim-bindings" ".git" ".github" "tmp" ]);
+            };
+
+            cargoLock = {
+              lockFile = ./Cargo.lock;
+              outputHashes = {
+                "chat-proto-0.1.0" = "sha256-aCl80VOIkd/GK3gnmRuFoSAvPBfeE/FKCaNlLt5AbUU=";
+              };
+            };
+
+            # perl: required by openssl-sys (transitive dep)
+            nativeBuildInputs = [ pkgs.perl pkgs.pkg-config pkgs.cmake ];
+            doCheck = false; # tests require network access unavailable in nix sandbox
+
+            postBuild = ''
+              cargo run --release --bin generate-libchat-headers --features headers
+            '';
+
+            installPhase = ''
+              runHook preInstall
+              mkdir -p $out/lib $out/include
+
+              # Copy shared library
+              cp target/release/liblibchat.so    $out/lib/ 2>/dev/null || true
+              cp target/release/liblibchat.dylib $out/lib/ 2>/dev/null || true
+              cp target/release/liblibchat.a     $out/lib/ 2>/dev/null || true
+
+              # Copy generated header
+              cp libchat.h $out/include/
+
+              runHook postInstall
+            '';
+
+            meta = with pkgs.lib; {
+              description = "Logos Chat cryptographic library (C FFI)";
+              platforms = platforms.unix;
+            };
+          };
+        }
+      );
+
+      devShells = forAllSystems ({ pkgs }:
+        let
+          rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust_toolchain.toml;
+        in
+        {
+          default = pkgs.mkShell {
+            nativeBuildInputs = [
+              rustToolchain
+              pkgs.pkg-config
+              pkgs.cmake
+            ];
+          };
+        }
+      );
+    };
+}