protocol: make it possible to send json key value pairs from the clie…

…nt to the server in the post body

html/app.js

@@ -915,6 +915,16 @@ export class SingerClient extends EventTarget {
     }
   }
 
+  send_kv(key, value) {
+    if (this.connection && this.hasConnectivity) {
+      this.connection.set_json_kv(key, value);
+    } else {
+      console.error(
+        "set_json_kv should never be sent before connection, dropping:",
+        key, value);
+    }
+  }
+
   send_telemetry(key, value, append) {
     // We're disabling this for now.
     return;
@@ -1226,6 +1236,10 @@ export class SingerClientConnection {
     }
   }
 
+  set_json_kv(key, value) {
+    this.server_connection.set_json_kv(key, value);
+  }
+
   send_telemetry(key, value, append) {
     var telemetry;
     if ("client_telemetry" in this.metadata_to_send) {

html/net.js

@@ -48,6 +48,7 @@ export class ServerConnection extends ServerConnectionBase {
     this.write_clock = null;
     this.userid = userid;
     this.send_metadata = {};
+    this.json_kvs = {}
     this.running = false;
     this.receive_cb = receive_cb;
     this.failure_cb = failure_cb;
@@ -83,6 +84,10 @@ export class ServerConnection extends ServerConnectionBase {
     this.send_metadata = send_metadata;
   }
 
+  set_json_kv(key, value) {
+    this.json_kvs[key] = value;
+  }
+
   send(chunk) {
     if (!this.running) {
       console.warn("Not sending to server because not running");
@@ -110,7 +115,12 @@ export class ServerConnection extends ServerConnectionBase {
     var saved_read_clock = this.read_clock;
     var saved_write_clock = this.write_clock;
 
-    samples_to_server(chunk_data, this.target_url, {
+    let json_kvs_str = JSON.stringify(this.json_kvs);
+    if (json_kvs_str === "{}") {
+      json_kvs_str = null;
+    }
+    this.json_kvs = {};
+    samples_to_server(chunk_data, this.target_url, json_kvs_str, {
       read_clock: this.read_clock,
       write_clock: this.write_clock,
       n_samples: chunk.length,
@@ -333,12 +343,25 @@ export async function query_server_clock(target_url) {
 }
 
 var xhrs_inflight = 0;
-export async function samples_to_server(outdata, target_url, send_metadata) {
-  console.debug("samples_to_server send_metadata:", send_metadata);
+export async function samples_to_server(
+     outdata, target_url, json_kvs_str, send_metadata) {
+  console.debug("samples_to_server send_metadata:", send_metadata,
+                "json_kvs_str", json_kvs_str);
   if (outdata === null) {
     outdata = new Uint8Array();
   }
 
+  if (json_kvs_str) {
+    const json_kvs_bytes = (new TextEncoder()).encode(json_kvs_str);
+    send_metadata.json_len = json_kvs_bytes.length;
+
+    const combined_outdata =
+          new Uint8Array(json_kvs_bytes.length + outdata.length);
+    combined_outdata.set(json_kvs_bytes);
+    combined_outdata.set(outdata, json_kvs_bytes.length);
+    outdata = combined_outdata;
+  }
+
   return new Promise((resolve, reject) => {
     var xhr = new XMLHttpRequest();
     xhr.onerror = () => {

server_wrapper.py

@@ -120,7 +120,16 @@ def handle_post(userid, n_samples, in_data_raw,
         dec = opuslib.Decoder(server.SAMPLE_RATE, CHANNELS)
         users[userid] = enc, dec
 
-    in_data = np.frombuffer(in_data_raw, dtype=np.uint8)
+    post_body = np.frombuffer(in_data_raw, dtype=np.uint8)
+    parsed_params = urllib.parse.parse_qs(query_string, strict_parsing=True)
+    json_len, = parsed_params.get("json_len", [None])
+    if json_len:
+        json_len = int(json_len)
+        json_kvs = json.loads(post_body[:json_len].tobytes().decode('utf8'))
+        in_data = post_body[json_len:]
+    else:
+        in_data = post_body
+        json_kvs = {}
 
     # If the user does not send us any data, we will treat it as silence of length n_samples. This is useful if they are just starting up.
     client_no_data = len(in_data)==0
@@ -148,7 +157,8 @@ def handle_post(userid, n_samples, in_data_raw,
     query_string += '&rms_volume=%s'%rms_volume
 
     data, x_audio_metadata = handle_json_post(
-        in_data, query_string, print_status, client_address=client_address)
+        in_data, query_string, json_kvs, print_status,
+        client_address=client_address)
 
     # Divide data into user_summary and raw audio data
     n_users_in_summary, = struct.unpack(">H", data[:2])
@@ -175,13 +185,14 @@ def handle_post(userid, n_samples, in_data_raw,
 
     return data.tobytes(), x_audio_metadata
 
-def handle_json_post(in_data, query_string, print_status, client_address=None):
-    in_json = {
+def handle_json_post(in_data, query_string, json_kvs, print_status,
+                     client_address=None):
+    json_kvs.update({
         "query_string": query_string,
         "print_status": print_status,
         "client_address": client_address,
-    }
-    out_json_raw, out_data = backend.handle_post(json.dumps(in_json), in_data)
+    })
+    out_json_raw, out_data = backend.handle_post(json.dumps(json_kvs), in_data)
 
     out_json = json.loads(out_json_raw)