commit 00e6045482dee54286893aeeb01695530251db25
Author: Holly McFarland <me@hollymcfarland.com>
Date:   Tue Aug 18 16:15:02 2026 -0400

    initial commit

diff --git a/README.md b/README.md
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+1. Install Tampermonkey or something in your browser
+2. Open [dscrtc.user.js](https://git.hollymcfarland.com/monorail/DSCRTC/src/branch/main/dscrtc.user.js#bypass=true) and read until you're comfortable that I'm not stealing your credit card data or whatever
+3. Click "Raw" near the top to bring up the install screen
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diff --git a/dscrtc.user.js b/dscrtc.user.js
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+// ==UserScript==
+// @name         Deep Space Communications Relay Tab Completion
+// @namespace    https://hollymcfarland.com
+// @version      2026-08-16
+// @description  Tab complete known definitions
+// @author       You
+// @match        https://dscr.dixonary.co.uk/
+// @grant        none
+// ==/UserScript==
+
+(function() {
+    'use strict';
+
+    document.addEventListener("keydown", (event) => {
+        // Only listen to tab
+        if (event.key !== "Tab") return;
+
+        // Only listen when message box focused
+        const inputEl = document.querySelector("#message-input");
+        if (document.activeElement !== inputEl) return;
+
+        // Don't tab out of input box
+        event.preventDefault();
+
+        const input = inputEl.value;
+        const cursorPos = inputEl.selectionStart;
+
+        // I don't even want to _think_ about how to handle tab completion if you have a range selected
+        if (cursorPos !== inputEl.selectionEnd) return;
+
+        // Character behind cursor should be non-whitespace
+        // Character after cursor should at least not be a letter
+        // Hopefully this accounts for _most_ reasonable signal definitions
+        if (!(/\S/.test(input[cursorPos-1]) && (input.length === cursorPos || /[^A-Z]/.test(input[cursorPos])))) return;
+
+        // Everything from most recent word boundary to the cursor position should be a reasonable estimate of "current signal"
+        const currentSignal = /[\w-_]+?$/.exec(input.slice(0, cursorPos).toUpperCase())[0];
+
+        const signals = JSON.parse(localStorage.getItem("dict")).map((s) => (s.value));
+
+        const matches = signals.filter((s) => (s.startsWith(currentSignal)));
+
+        // Give up if current signal isn't a prefix of any signal
+        if (!matches.length) return;
+
+        // Longest common prefix algorithm
+        // After loop, i contains number of additional characters (after currentSignal.length) that are shared by all matches
+        matches.sort();
+        console.log(matches);
+        let i = 0;
+        for (; i<matches[0].length; i++) {
+            const idx = i + currentSignal.length;
+            const [first, last] = [matches[0][idx], matches[matches.length-1][idx]];
+            if (first === undefined || last === undefined || first !== last) break;
+        }
+
+        const addedCharacters = matches[0].slice(currentSignal.length, currentSignal.length+i);
+
+        // Put new computed value back into text box and reposition cursor to match
+        inputEl.value = input.slice(0, cursorPos) + addedCharacters + input.slice(cursorPos);
+        inputEl.selectionStart = cursorPos + i;
+        inputEl.selectionEnd = cursorPos + i;
+    });
+})();
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