feat: add publishing & audio to ffi (#46)

- Divide FFI protocol into multiple files
- Audio support
- AV Streams/Sources
- Create tracks
- Use Dashmap to store handles
- Add a capture test
     - Ignored by GHA atm

livekit-ffi/src/lib.rs

@@ -1,5 +1,78 @@
+use livekit::prelude::*;
+use prost::Message;
+use std::any::Any;
+use thiserror::Error;
+
 mod proto {
     include!(concat!(env!("OUT_DIR"), "/livekit.rs"));
 }
-
+mod conversion;
 mod server;
+
+#[derive(Error, Debug)]
+pub enum FfiError {
+    #[error("the server is not configured")]
+    NotConfigured,
+    #[error("the server is already initialized")]
+    AlreadyInitialized,
+    #[error("room error {0}")]
+    Room(#[from] RoomError),
+    #[error("invalid request: {0}")]
+    InvalidRequest(&'static str),
+}
+
+/// # SAFTEY: The "C" callback must be threadsafe and not block
+pub type FfiCallbackFn = unsafe extern "C" fn(*const u8, usize);
+pub type FfiResult<T> = Result<T, FfiError>;
+pub type FfiAsyncId = usize;
+pub type FfiHandleId = usize;
+pub type FfiHandle = Box<dyn Any + Send + Sync>;
+
+pub const INVALID_HANDLE: FfiHandleId = 0;
+
+#[no_mangle]
+pub(crate) extern "C" fn livekit_ffi_request(
+    data: *const u8,
+    len: usize,
+    res_ptr: *mut *const u8,
+    res_len: *mut usize,
+) -> FfiHandleId {
+    let data = unsafe { std::slice::from_raw_parts(data, len) };
+    let res = match proto::FfiRequest::decode(data) {
+        Ok(res) => res,
+        Err(err) => {
+            eprintln!("failed to decode request: {}", err);
+            return INVALID_HANDLE;
+        }
+    };
+
+    let res = match server::FFI_SERVER.handle_request(res) {
+        Ok(res) => res,
+        Err(err) => {
+            eprintln!("failed to handle request: {}", err);
+            return INVALID_HANDLE;
+        }
+    }
+    .encode_to_vec();
+
+    unsafe {
+        *res_ptr = res.as_ptr();
+        *res_len = res.len();
+    }
+
+    let handle_id = server::FFI_SERVER.next_id();
+    server::FFI_SERVER
+        .ffi_handles()
+        .insert(handle_id, Box::new(res));
+
+    handle_id
+}
+
+#[no_mangle]
+pub(crate) extern "C" fn livekit_ffi_drop_handle(handle_id: FfiHandleId) -> bool {
+    // Free the memory
+    server::FFI_SERVER
+        .ffi_handles()
+        .remove(&handle_id)
+        .is_some()
+}