little added abstraction, c++ ffi shell

Cargo.toml

@@ -7,3 +7,6 @@ edition = "2021"
 axum = "0.8"
 serde = { version = "1", features = ["derive"] }
 tokio = { version = "1", features = ["full"] }
+
+[build-dependencies]
+cc = "1"

build.rs

@@ -0,0 +1,8 @@
+fn main() {
+    cc::Build::new()
+        .cpp(true)
+        .file("native/src/vector_engine_ffi.cpp")
+        .include("native/include")
+        .std("c++17")
+        .compile("vector_engine_ffi");
+}

native/include/vector_engine_ffi.h

@@ -0,0 +1,13 @@
+#ifndef VECTOR_ENGINE_FFI_H
+#define VECTOR_ENGINE_FFI_H
+
+struct NativeVectorEngine;
+
+extern "C" {
+
+NativeVectorEngine* native_vector_engine_new();
+void native_vector_engine_free(NativeVectorEngine* engine);
+
+}
+
+#endif

native/src/vector_engine_ffi.cpp

@@ -0,0 +1,11 @@
+#include "vector_engine_ffi.h"
+
+struct NativeVectorEngine {};
+
+extern "C" NativeVectorEngine* native_vector_engine_new() {
+    return new NativeVectorEngine();
+}
+
+extern "C" void native_vector_engine_free(NativeVectorEngine* engine) {
+    delete engine;
+}

src/api/handlers.rs

@@ -2,7 +2,6 @@ use axum::{extract::State, Json};
 
 use crate::{
     api::response::{bad_request, ApiError, ApiResult},
-    engine::VectorEngine,
     models::{
         DeleteRequest, InsertRequest, MessageResponse, SearchRequest, SearchResponse,
     },

src/engine.rs

@@ -4,6 +4,7 @@ pub trait VectorEngine {
     fn insert(&mut self, id: String, vector: Vec<f32>);
     fn search(&self, query: Vec<f32>, k: usize) -> Vec<SearchResult>;
     fn delete(&mut self, id: &str);
+    fn dimension(&self) -> Option<usize>;
 }
 
 #[derive(Default)]
@@ -15,10 +16,6 @@ impl FlatIndex {
     pub fn new() -> Self {
         Self::default()
     }
-
-    pub fn dimension(&self) -> Option<usize> {
-        self.vectors.first().map(|(_, vector)| vector.len())
-    }
 }
 
 impl VectorEngine for FlatIndex {
@@ -45,6 +42,10 @@ impl VectorEngine for FlatIndex {
     fn delete(&mut self, id: &str) {
         self.vectors.retain(|(stored_id, _)| stored_id != id);
     }
+
+    fn dimension(&self) -> Option<usize> {
+        self.vectors.first().map(|(_, vector)| vector.len())
+    }
 }
 
 fn cosine_similarity(left: &[f32], right: &[f32]) -> f32 {

src/state.rs

@@ -1,16 +1,16 @@
 use std::sync::{Arc, Mutex};
 
-use crate::engine::FlatIndex;
+use crate::engine::{FlatIndex, VectorEngine};
 
 #[derive(Clone)]
 pub struct AppState {
-    pub engine: Arc<Mutex<FlatIndex>>,
+    pub engine: Arc<Mutex<Box<dyn VectorEngine + Send>>>,
 }
 
 impl AppState {
     pub fn new() -> Self {
         Self {
-            engine: Arc::new(Mutex::new(FlatIndex::new())),
+            engine: Arc::new(Mutex::new(Box::new(FlatIndex::new()))),
         }
     }
 }