Add CodeMirror langauge definition

Author: hjr265

README.md

@@ -384,3 +384,17 @@ ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 defer cancel()
 values, err := eval.Evaluate(source, input, eval.WithContext(ctx))
 ```
+
+## Editor Support
+
+A CodeMirror 6 language definition for Scanspec syntax highlighting is available at [`contrib/codemirror/scanspec.js`](contrib/codemirror/scanspec.js).
+
+``` javascript
+import { scanspec } from "./scanspec.js"
+import { EditorView, basicSetup } from "codemirror"
+
+new EditorView({
+  extensions: [basicSetup, scanspec],
+  parent: document.getElementById("editor"),
+})
+```

contrib/codemirror/scanspec.js

@@ -0,0 +1,42 @@
+import { StreamLanguage } from "@codemirror/language"
+
+export const scanspec = StreamLanguage.define({
+  token(stream, state) {
+    // Comments
+    if (stream.match("#")) {
+      stream.skipToEnd()
+      return "comment"
+    }
+
+    // Strings
+    if (stream.match('"')) {
+      while (!stream.eol()) {
+        if (stream.next() === "\\") stream.next()
+        else if (stream.current().endsWith('"') && stream.current().length > 1) break
+      }
+      return "string"
+    }
+
+    // Numbers (float before int)
+    if (stream.match(/\d+\.\d*/)) return "number"
+    if (stream.match(/\d+/)) return "number"
+
+    // Operators
+    if (stream.match(/\*\*|==|!=|<=|>=|&&|\|\|/)) return "operator"
+    if (stream.match(/[+\-*/<>=!]/)) return "operator"
+
+    // Keywords, types, and identifiers
+    if (stream.match(/[a-zA-Z_][a-zA-Z0-9_]*/)) {
+      const word = stream.current()
+      if (/^(check|else|end|eof|eol|for|if|scan|scanln|var)$/.test(word))
+        return "keyword"
+      if (/^(bool|int|int64|float32|float64|string)$/.test(word))
+        return "typeName"
+      return "variableName"
+    }
+
+    // Skip whitespace and punctuation
+    stream.next()
+    return null
+  },
+})