api: initial subtitles functionality with youtube support

this took way more effort than i expected it to do, mostly because of youtube locking everything down to shit

local processing doesn't function with subtitles yet, wasm needs to be updated

api/src/stream/manage.js

@@ -41,7 +41,10 @@ export function createStream(obj) {
             audioFormat: obj.audioFormat,
 
             isHLS: obj.isHLS || false,
-            originalRequest: obj.originalRequest
+            originalRequest: obj.originalRequest,
+
+            // url to a subtitle file
+            subtitles: obj.subtitles,
         };
 
     // FIXME: this is now a Promise, but it is not awaited
@@ -94,6 +97,18 @@ export function createProxyTunnels(info) {
         );
     }
 
+    if (info.subtitles) {
+        proxyTunnels.push(
+            createStream({
+                url: info.subtitles,
+                type: "proxy",
+                service: `${info?.service}-subtitles`,
+                headers: info?.headers,
+                requestIP: info?.requestIP
+            })
+        );
+    }
+
     return proxyTunnels;
 }
 
@@ -111,7 +126,7 @@ export function getInternalTunnelFromURL(url) {
     return getInternalTunnel(id);
 }
 
-export function createInternalStream(url, obj = {}) {
+export function createInternalStream(url, obj = {}, isSubtitles) {
     assert(typeof url === 'string');
 
     let dispatcher = obj.dispatcher;
@@ -132,9 +147,12 @@ export function createInternalStream(url, obj = {}) {
         headers = new Map(Object.entries(obj.headers));
     }
 
+    // subtitles don't need special treatment unlike big media files
+    const service = isSubtitles ? `${obj.service}-subtitles` : obj.service;
+
     internalStreamCache.set(streamID, {
         url,
-        service: obj.service,
+        service,
         headers,
         controller,
         dispatcher,
@@ -245,6 +263,14 @@ function wrapStream(streamInfo) {
         }
     } else throw 'invalid urls';
 
+    if (streamInfo.subtitles) {
+        streamInfo.subtitles = createInternalStream(
+            streamInfo.subtitles,
+            streamInfo,
+            /*isSubtitles=*/true
+        );
+    }
+
     return streamInfo;
 }