Refactor WS subprotocol handling

asciinema · Jan 22, 2025 · 12087c3 · 12087c3
1 parent 0506708
commit 12087c3
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Showing 4 changed files with 179 additions and 138 deletions.
diff --git a/src/driver/websocket.js b/src/driver/websocket.js
@@ -21,6 +21,7 @@ function websocket(
   let successfulConnectionTimeout;
   let stop = false;
   let wasOnline = false;
+  let initTimeout;
 
   function connect() {
     socket = new WebSocket(url, ["v1.alis", "v2.asciicast", "raw"]);
@@ -33,11 +34,11 @@ function websocket(
       logger.info(`activating ${proto} protocol handler`);
 
       if (proto === "v1.alis") {
-        socket.onmessage = onMessage(alisHandler);
+        socket.onmessage = onMessage(alisHandler(logger));
       } else if (proto === "v2.asciicast") {
-        socket.onmessage = onMessage(jsonHandler);
+        socket.onmessage = onMessage(jsonHandler());
       } else if (proto === "raw") {
-        socket.onmessage = onMessage(rawHandler);
+        socket.onmessage = onMessage(rawHandler());
       }
 
       successfulConnectionTimeout = setTimeout(() => {
@@ -46,6 +47,7 @@ function websocket(
     };
 
     socket.onclose = (event) => {
+      clearTimeout(initTimeout);
       stopBuffer();
 
       if (stop || event.code === 1000 || event.code === 1005) {
@@ -67,7 +69,7 @@ function websocket(
   }
 
   function onMessage(handler) {
-    const initialHandler = handler;
+    initTimeout = setTimeout(enterOfflineMode, 5000);
 
     return function (event) {
       const result = handler(event.data);
@@ -78,31 +80,34 @@ function websocket(
         } else if (typeof result === "string") {
           buf.pushText(result);
         } else if (result === false) {
-          stopBuffer();
-          handleOfflineMessage();
-          handler = initialHandler;
+          // EOT
+          enterOfflineMode();
         } else if (result !== undefined) {
           throw `unexpected value from protocol handler: ${result}`;
         }
       } else {
         if (typeof result === "object" && !Array.isArray(result)) {
-          const { cols, rows, time, init, theme } = result.meta;
-          initStream(cols, rows, time, init, theme);
-          handler = result.handler;
-        } else if (result === false) {
-          handleOfflineMessage();
-          handler = initialHandler;
-        } else if (result !== undefined) {
+          const { time, term } = result;
+          const { size, init, theme } = term;
+          const { cols, rows } = size;
+          enterOnlineMode(cols, rows, time, init, theme);
+          clearTimeout(initTimeout);
+        } else if (result === undefined) {
+          clearTimeout(initTimeout);
+          initTimeout = setTimeout(enterOfflineMode, 1000);
+        } else {
+          clearTimeout(initTimeout);
           throw `unexpected value from protocol handler: ${result}`;
         }
       }
     };
   }
 
-  function initStream(cols, rows, time, init, theme) {
+  function enterOnlineMode(cols, rows, time, init, theme) {
     logger.debug(`stream init (${cols}x${rows} @${time})`);
     setState("playing");
-    initBuffer(time);
+    stopBuffer();
+    buf = getBuffer(bufferTime, feed, resize, (t) => clock.setTime(t), time, minFrameTime, logger);
     reset(cols, rows, init, theme);
     clock = new Clock();
     wasOnline = true;
@@ -112,26 +117,14 @@ function websocket(
     }
   }
 
-  function initBuffer(baseStreamTime) {
+  function enterOfflineMode() {
     stopBuffer();
 
-    buf = getBuffer(
-      bufferTime,
-      feed,
-      resize,
-      (t) => clock.setTime(t),
-      baseStreamTime,
-      minFrameTime,
-      logger,
-    );
-  }
-
-  function handleOfflineMessage() {
-    logger.info("stream offline");
-
     if (wasOnline) {
+      logger.info("stream ended");
       setState("offline", { message: "Stream ended" });
     } else {
+      logger.info("stream offline");
       setState("offline", { message: "Stream offline" });
     }
 

diff --git a/src/driver/websocket/alis.js b/src/driver/websocket/alis.js
@@ -1,94 +1,115 @@
-function alisHandler(buffer) {
+function alisHandler(logger) {
   const outputDecoder = new TextDecoder();
   const inputDecoder = new TextDecoder();
-  const arr = new Uint8Array(buffer);
+  let handler = parseMagicString;
 
-  if (!(arr[0] == 0x41 && arr[1] == 0x4c && arr[2] == 0x69 && arr[3] == 0x53 && arr[4] === 1)) {
-    // not 'ALiS\x01'
-    throw "not an ALiS v1 live stream";
-  }
+  function parseMagicString(buffer) {
+    const text = (new TextDecoder()).decode(buffer);
 
-  const view = new DataView(buffer);
-  let offset = 5;
-  const cols = view.getUint16(offset, true);
-  offset += 2;
-  const rows = view.getUint16(offset, true);
-  offset += 2;
-  const time = view.getFloat32(offset, true);
-  offset += 4;
-  const themeFormat = view.getUint8(offset);
-  offset += 1;
-  let theme;
-
-  if (themeFormat === 8) {
-    const len = (2 + 8) * 3;
-    theme = parseTheme(new Uint8Array(buffer, offset, len));
-    offset += len;
-  } else if (themeFormat === 16) {
-    const len = (2 + 16) * 3;
-    theme = parseTheme(new Uint8Array(buffer, offset, len));
-    offset += len;
-  } else if (themeFormat !== 0) {
-    logger.warn(`unsupported theme format (${themeFormat})`);
-    socket.close();
-    return;
+    if (text === "ALiS\x01") {
+      handler = parseInitFrame;
+    } else {
+      throw "not an ALiS v1 live stream";
+    }
   }
 
-  const initLen = view.getUint32(offset, true);
-  offset += 4;
-
-  let init;
+  function parseInitFrame(buffer) {
+    const view = new DataView(buffer);
+    const type = view.getUint8(0);
+
+    if (type !== 0x01) throw `expected init (0x01) frame, got ${type}`;
+
+    let offset = 1;
+    const cols = view.getUint16(offset, true);
+    offset += 2;
+    const rows = view.getUint16(offset, true);
+    offset += 2;
+    const time = view.getFloat32(offset, true);
+    offset += 4;
+    const themeFormat = view.getUint8(offset);
+    offset += 1;
+    let theme;
+
+    if (themeFormat === 8) {
+      const len = (2 + 8) * 3;
+      theme = parseTheme(new Uint8Array(buffer, offset, len));
+      offset += len;
+    } else if (themeFormat === 16) {
+      const len = (2 + 16) * 3;
+      theme = parseTheme(new Uint8Array(buffer, offset, len));
+      offset += len;
+    } else if (themeFormat !== 0) {
+      logger.warn(`alis: unsupported theme format (${themeFormat})`);
+      socket.close();
+      return;
+    }
+
+    const initLen = view.getUint32(offset, true);
+    offset += 4;
+
+    let init;
+
+    if (initLen > 0) {
+      init = outputDecoder.decode(new Uint8Array(buffer, offset, initLen));
+      offset += initLen;
+    }
+
+    handler = parseEventFrame;
+
+    return {
+      time,
+      term: {
+        size: { cols, rows },
+        theme,
+        init
+      }
+    }
+  }
 
-  if (initLen > 0) {
-    init = outputDecoder.decode(new Uint8Array(buffer, offset, initLen));
-    offset += initLen;
+  function parseEventFrame(buffer) {
+    const view = new DataView(buffer);
+    const type = view.getUint8(0);
+
+    if (type === 0x6f) {
+      // 'o' - output
+      const time = view.getFloat32(1, true);
+      const len = view.getUint32(5, true);
+      const text = outputDecoder.decode(new Uint8Array(buffer, 9, len));
+
+      return [time, "o", text];
+    } else if (type === 0x69) {
+      // 'i' - input
+      const time = view.getFloat32(1, true);
+      const len = view.getUint32(5, true);
+      const text = inputDecoder.decode(new Uint8Array(buffer, 9, len));
+
+      return [time, "i", text];
+    } else if (type === 0x72) {
+      // 'r' - resize
+      const time = view.getFloat32(1, true);
+      const cols = view.getUint16(5, true);
+      const rows = view.getUint16(7, true);
+
+      return [time, "r", { cols, rows }];
+    } else if (type === 0x6d) {
+      // 'm' - marker
+      const time = view.getFloat32(1, true);
+      const len = view.getUint32(5, true);
+      const decoder = new TextDecoder();
+      const text = decoder.decode(new Uint8Array(buffer, 9, len));
+
+      return [time, "m", text];
+    } else if (type === 0x04) {
+      // EOT
+      handler = parseInitFrame;
+      return false;
+    } else {
+      logger.debug(`alis: unknown frame type: ${type}`);
+    }
   }
 
-  const meta = { cols, rows, time, init, theme };
-
-  return {
-    meta,
-
-    handler: function(buffer) {
-      const view = new DataView(buffer);
-      const type = view.getUint8(0);
-
-      if (type === 0x6f) {
-        // 'o' - output
-        const time = view.getFloat32(1, true);
-        const len = view.getUint32(5, true);
-        const text = outputDecoder.decode(new Uint8Array(buffer, 9, len));
-
-        return [time, "o", text];
-      } else if (type === 0x69) {
-        // 'i' - input
-        const time = view.getFloat32(1, true);
-        const len = view.getUint32(5, true);
-        const text = inputDecoder.decode(new Uint8Array(buffer, 9, len));
-
-        return [time, "i", text];
-      } else if (type === 0x72) {
-        // 'r' - resize
-        const time = view.getFloat32(1, true);
-        const cols = view.getUint16(5, true);
-        const rows = view.getUint16(7, true);
-
-        return [time, "r", { cols, rows }];
-      } else if (type === 0x6d) {
-        // 'm' - marker
-        const time = view.getFloat32(1, true);
-        const len = view.getUint32(5, true);
-        const decoder = new TextDecoder();
-        const text = decoder.decode(new Uint8Array(buffer, 9, len));
-
-        return [time, "m", text];
-      } else if (type === 0x04) {
-        // offline (EOT)
-        return false; // go offline
-      } else {
-        logger.debug(`unknown event type: ${type}`);
-      }
-    },
+  return function(buffer) {
+    return handler(buffer);
   };
 }
 

diff --git a/src/driver/websocket/json.js b/src/driver/websocket/json.js
@@ -1,26 +1,40 @@
-function jsonHandler(buffer) {
-  const header = JSON.parse(buffer);
+function jsonHandler() {
+  let parse = parseHeader;
 
-  if (header.version !== 2) {
-    throw "not an asciicast v2 stream";
-  }
-
-  const meta = { cols: header.width, rows: header.height, time: 0.0 };
+  function parseHeader(buffer) {
+    const header = JSON.parse(buffer);
 
-  return {
-    meta,
+    if (header.version !== 2) {
+      throw "not an asciicast v2 stream";
+    }
 
-    handler: function(buffer) {
-      const event = JSON.parse(buffer);
+    parse = parseEvent;
 
-      if (event[1] === "r") {
-        const [cols, rows] = event[2].split("x");
-        return [event[0], "r", { cols, rows }];
-      } else {
-        return event;
+    return {
+      time: 0.0,
+      term: {
+        size: {
+          cols: header.width,
+          rows: header.height
+        }
       }
+    };
+  }
+
+  function parseEvent(buffer) {
+    const event = JSON.parse(buffer);
+
+    if (event[1] === "r") {
+      const [cols, rows] = event[2].split("x");
+      return [event[0], "r", { cols, rows }];
+    } else {
+      return event;
     }
   }
+
+  return function(buffer) {
+    return parse(buffer);
+  };
 }
 
 export { jsonHandler };