From d85bf030113206c1464bc4cceb43436b7663ccbf Mon Sep 17 00:00:00 2001
From: Kai Vogelgesang <kai@leafbla.de>
Date: Sun, 25 Dec 2022 03:33:43 +0100
Subject: [PATCH] Implement WebSerial I/O

---
 webserial/src/serial/SerialConnection.svelte | 130 +++++++++++++++++++
 webserial/src/serial/SerialManager.svelte    |   6 +-
 webserial/src/serial/SerialReader.svelte     |  57 --------
 3 files changed, 133 insertions(+), 60 deletions(-)
 create mode 100644 webserial/src/serial/SerialConnection.svelte
 delete mode 100644 webserial/src/serial/SerialReader.svelte

diff --git a/webserial/src/serial/SerialConnection.svelte b/webserial/src/serial/SerialConnection.svelte
new file mode 100644
index 0000000..97a0e4a
--- /dev/null
+++ b/webserial/src/serial/SerialConnection.svelte
@@ -0,0 +1,130 @@
+<script lang="ts">
+    import { onMount } from "svelte";
+
+    export let port: SerialPort;
+    export let fps: number = 50;
+
+    const FRAME_TIME = 1000 / fps; // milliseconds
+
+    let lines = [];
+    let linesResolve: (value: string | PromiseLike<string>) => void = null;
+
+    function readLine(): Promise<string> {
+        if (lines.length > 0) {
+            return Promise.resolve(lines.shift());
+        } else {
+            // lines is empty, register callbacks
+            return new Promise((resolve) => {
+                linesResolve = resolve;
+            });
+        }
+    }
+
+    const handleLine = (line: string) => {
+        if (linesResolve !== null) {
+            linesResolve(line);
+            linesResolve = null;
+        } else {
+            lines.push(line);
+        }
+    };
+
+    let running = true;
+    async function readLoop() {
+        console.log("runner started");
+        await port.open({ baudRate: 500_000 });
+        let reader = port.readable.getReader();
+        let data = "";
+        try {
+            while (running) {
+                const { value, done } = await reader.read();
+                if (done) break;
+
+                const chunk = new TextDecoder().decode(value);
+                data += chunk;
+
+                const lines = data.split("\r\n");
+                data = lines.pop();
+                for (let line of lines) {
+                    handleLine(line);
+                }
+            }
+        } finally {
+            reader.releaseLock();
+        }
+        await port.close();
+        console.log("runner stopped");
+    }
+    let readLoopHandle: Promise<void> = null;
+
+    async function sync() {
+        while (running) {
+            const line = await readLine();
+            if (line === "Sync.") {
+                return;
+            }
+        }
+    }
+
+    let payload = new Uint8Array(512);
+
+    const sleep = (ms: number) =>
+        new Promise((resolve) => setTimeout(resolve, ms));
+
+    let lastLoopTime: number = null;
+
+    async function writeLoop() {
+        await sync();
+        while (running) {
+            const loopStart = performance.now();
+
+            // write out payload
+            let writer = port.writable.getWriter();
+            try {
+                await writer.write(payload);
+            } finally {
+                writer.releaseLock();
+            }
+
+            // read response
+            const response = await readLine();
+            if (response !== "Ack.") {
+                console.log(`received bad response: "${response}"`);
+                lastLoopTime = null;
+                await sync();
+                continue;
+            }
+
+            const loopTime = performance.now() - loopStart;
+            if (loopTime < FRAME_TIME) {
+                await sleep(FRAME_TIME - loopTime);
+            } else {
+                console.warn(`loop took too long (+${(loopTime - FRAME_TIME).toFixed(2)} ms)`);
+            }
+            lastLoopTime = loopTime;
+        }
+    }
+    let writeLoopHandle: Promise<void> = null;
+
+    onMount(() => {
+        console.log("mount");
+        readLoopHandle = readLoop();
+        writeLoopHandle = writeLoop();
+
+        return () => {
+            console.log("unmount");
+            running = false;
+            if (linesResolve !== null) {
+                linesResolve("");
+            }
+        };
+    });
+</script>
+
+<p>
+    {#if lastLoopTime !== null}
+        {lastLoopTime.toFixed(2).padStart(5)}
+    {:else}
+        syncing
+    {/if}
+</p>
diff --git a/webserial/src/serial/SerialManager.svelte b/webserial/src/serial/SerialManager.svelte
index 6926711..9214877 100644
--- a/webserial/src/serial/SerialManager.svelte
+++ b/webserial/src/serial/SerialManager.svelte
@@ -1,5 +1,5 @@
 <script lang="ts">
-    import SerialReader from "./SerialReader.svelte";
+    import SerialConnection from "./SerialConnection.svelte";
 
     let port: SerialPort = null;
 
@@ -14,9 +14,9 @@
 </script>
 
 {#if navigator.serial}
-    <p>serial baby</p>
+    <p>Serial available &#x1f680;</p>
     {#if port !== null}
-        <SerialReader {port}/>
+        <SerialConnection {port}/>
         <p><button on:click={disconnect}>disconnect</button></p>
     {:else}
         <p><button on:click={connect}>connect</button></p>
diff --git a/webserial/src/serial/SerialReader.svelte b/webserial/src/serial/SerialReader.svelte
deleted file mode 100644
index 1316e52..0000000
--- a/webserial/src/serial/SerialReader.svelte
+++ /dev/null
@@ -1,57 +0,0 @@
-<script lang="ts">
-    import { onMount } from "svelte";
-
-    export let port: SerialPort;
-
-    let lines = [];
-
-    const handleLine = (line: string) => {
-        lines.push(line);
-        if (lines.length > 10) lines.shift();
-        lines = lines;
-    }
-
-    let running = true;
-    async function runner() {
-        console.log("runner started");
-        await port.open({baudRate: 500_000});
-        let reader = port.readable.getReader();
-        let data = "";
-        try {
-            while (running) {
-                const { value, done } = await reader.read();
-                if (done) break;
-
-                const chunk = new TextDecoder().decode(value);
-                data += chunk;
-
-                const lines = data.split("\n");
-                data = lines.pop();
-                for (let line of lines) {
-                    handleLine(line);
-                }
-            }
-        } finally {
-            reader.releaseLock();
-        }
-        await port.close();
-        console.log("runner stopped");
-    }
-    let handle: Promise<void> = null;
-
-    onMount(() => {
-        console.log("mount");
-        handle = runner();
-
-        return () => {
-            console.log("unmount");
-            running = false;
-        };
-    });
-</script>
-
-<div>
-    {#each lines as line}
-        <div>{line}</div>
-    {/each}
-</div>