create session class and refactor js to use it

client/javascript/session.js

@@ -0,0 +1,98 @@
+class CurlSession {
+  constructor(options={}) {
+    check_loaded(true);
+
+    this.options = options;
+    this.session_ptr = _session_create();
+    this.active_requests = 0;
+    this.event_loop = null;
+    this.requests_list = [];
+  }
+
+  assert_ready() {
+    if (!this.session_ptr) {
+      throw "session has been removed";
+    }
+  }
+
+  set_connections(connections_limit, cache_limit) {
+    this.assert_ready();
+    _session_set_options(this.session_ptr, connections_limit, cache_limit);
+  }
+
+  create_request(url, js_data_callback, js_end_callback, js_headers_callback) {
+    this.assert_ready();
+    let end_callback_ptr;
+    let data_callback_ptr;
+    let headers_callback_ptr;
+  
+    let end_callback = (error) => {
+      Module.removeFunction(end_callback_ptr);
+      Module.removeFunction(data_callback_ptr);
+      Module.removeFunction(headers_callback_ptr);
+      
+      this.active_requests--;
+      js_end_callback(error);
+    }
+  
+    let data_callback = (chunk_ptr, chunk_size) => {
+      let data = Module.HEAPU8.subarray(chunk_ptr, chunk_ptr + chunk_size);
+      let chunk = new Uint8Array(data);
+      js_data_callback(chunk);
+    }
+  
+    let headers_callback = () => {
+      js_headers_callback();
+    }
+  
+    end_callback_ptr = Module.addFunction(end_callback, "vi");
+    headers_callback_ptr = Module.addFunction(headers_callback, "v");
+    data_callback_ptr = Module.addFunction(data_callback, "vii");
+    let request_ptr = c_func(_create_request, [url, data_callback_ptr, end_callback_ptr, headers_callback_ptr]);
+    
+    return request_ptr;
+  }
+
+  remove_request(request_ptr) {
+    this.assert_ready();
+    _session_remove_request(this.session_ptr, request_ptr);
+
+    let request_index = this.requests_list.indexOf(request_ptr);
+    if (request_index !== -1) {
+      this.requests_list.splice(request_index, 1);
+    }
+  }
+
+  start_request(request_ptr) {
+    this.assert_ready();
+    _session_add_request(this.session_ptr, request_ptr);
+    _session_perform(this.session_ptr);
+
+    this.active_requests++;
+    this.requests_list.push(request_ptr);
+  
+    if (this.event_loop) {
+      return;
+    }
+    
+    this.event_loop = setInterval(() => {
+      let libcurl_active = _session_get_active(this.session_ptr);
+      if (libcurl_active || this.active_requests) {
+        _session_perform(this.session_ptr);
+      }
+      else {
+        clearInterval(this.event_loop);
+        this.event_loop = null;
+      }
+    }, 0);
+  }
+
+  close() {
+    this.assert_ready();
+    for (let request_ptr of this.requests_list) {
+      this.remove_request(request_ptr);
+    }
+    _session_cleanup(this.session_ptr);
+    this.session_ptr = null;
+  }
+}