chore: Copy the in-mem logging functions to the FFI crate

rust/pact_ffi/src/log/inmem_buffer.rs

@@ -1,10 +1,14 @@
 //! In-memory buffer for logging output.
 
+use std::collections::HashMap;
 use std::io;
 use std::io::Write;
-use tracing_subscriber::fmt::MakeWriter;
+use std::sync::Mutex;
 
-use pact_matching::logging::write_to_log_buffer;
+use bytes::{BufMut, Bytes, BytesMut};
+use lazy_static::lazy_static;
+use tokio::task_local;
+use tracing_subscriber::fmt::MakeWriter;
 
 /// In-memory buffer for logging output. Sends output to global static `LOG_BUFFER` in the pact_matching
 /// crate. If there is a task local ID found, will accumulate against that ID, otherwise will
@@ -31,3 +35,38 @@ impl <'a> MakeWriter<'a> for InMemBuffer {
     *self
   }
 }
+
+lazy_static! {
+  /// Memory buffer for the buffer logger. This is needed here because there is no
+  /// way to get the logger sync from the Dispatch struct. The buffer will be emptied
+  /// when the contents is fetched via an FFI call.
+  ///
+  /// Accumulates the log entries against a task local ID. If the ID is not set, accumulates against
+  /// the "global" ID.
+  /// cbindgen:ignore
+  static ref LOG_BUFFER: Mutex<HashMap<String, BytesMut>> = Mutex::new(HashMap::new());
+}
+
+task_local! {
+  /// Log ID to accumulate logs against
+  #[allow(missing_docs)]
+  pub static LOG_ID: String;
+}
+
+/// Fetches the contents from the id scoped in-memory buffer and empties the buffer.
+pub fn fetch_buffer_contents(id: &str) -> Bytes {
+  let mut inner = LOG_BUFFER.lock().unwrap();
+  let buffer = inner.entry(id.to_string())
+    .or_insert_with(|| BytesMut::with_capacity(256));
+  buffer.split().freeze()
+}
+
+/// Writes the provided bytes to the task local ID scoped in-memory buffer. If there is no
+/// task local ID set, will write to the "global" buffer.
+pub fn write_to_log_buffer(buf: &[u8]) {
+  let id = LOG_ID.try_with(|id| id.clone()).unwrap_or_else(|_| "global".into());
+  let mut inner = LOG_BUFFER.lock().unwrap();
+  let buffer = inner.entry(id)
+    .or_insert_with(|| BytesMut::with_capacity(256));
+  buffer.put(buf);
+}