perf: avoid expensive doc stringification for autocomplete

Refactored the autocomplete variable matching logic in `src/ui/editor.ts` to iterate through document lines using CodeMirror's `iterLines()` instead of allocating the entire document string in memory with `toString()`. Also pulled the regex up and introduced a quick `.includes("=")` bailout to skip the regex engine completely for most lines.

Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>

benchmark_editor.ts

@@ -0,0 +1,51 @@
+import { EditorState } from "@codemirror/state";
+
+const lines = [];
+for (let i = 0; i < 500000; i++) {
+    lines.push(`some_var_${i} = ${i * 10} + 5`);
+}
+const text = lines.join('\n');
+const state = EditorState.create({ doc: text });
+
+function benchmarkOld() {
+    const start = performance.now();
+    const options = [];
+    const docText = state.doc.toString();
+    for (const m of docText.matchAll(/^\s*([\p{L}_][\p{L}\d_]*)\s*=/gmu)) {
+        options.push({ label: m[1], type: "variable" });
+    }
+    const end = performance.now();
+    return end - start;
+}
+
+const pattern = /^\s*([\p{L}_][\p{L}\d_]*)\s*=/u;
+function benchmarkRegexPerLine() {
+    const start = performance.now();
+    const options = [];
+    const iter = state.doc.iterLines();
+    for (let next = iter.next(); !next.done; next = iter.next()) {
+        const line = next.value;
+        // Optimization: checking '=' first is significantly faster than firing regex blindly
+        if (line.includes('=')) {
+            const m = pattern.exec(line);
+            if (m) {
+                options.push({ label: m[1], type: "variable" });
+            }
+        }
+    }
+    const end = performance.now();
+    return end - start;
+}
+
+benchmarkOld();
+benchmarkRegexPerLine();
+
+let oldTotal = 0;
+let newTotal = 0;
+for (let i = 0; i < 10; i++) {
+    oldTotal += benchmarkOld();
+    newTotal += benchmarkRegexPerLine();
+}
+
+console.log(`Old avg: ${oldTotal / 10} ms`);
+console.log(`Regex per line with '=' check avg: ${newTotal / 10} ms`);

src/ui/editor.ts

@@ -170,6 +170,7 @@ export class SumEditor {
     this.resultsEl = resultsEl;
 
     let engineOptions: { label: string; type: string; detail?: string }[] | null = null;
+    const varPattern = /^\s*([\p{L}_][\p{L}\d_]*)\s*=/u;
     const completionSource = (ctx: CompletionContext): CompletionResult | null => {
       const word = ctx.matchBefore(/[\p{L}_]+$/u);
       if (!word || (word.from === word.to && !ctx.explicit)) return null;
@@ -182,10 +183,16 @@ export class SumEditor {
       }));
       const options = [...engineOptions];
       // document variables
-      const text = ctx.state.doc.toString();
+      const iter = ctx.state.doc.iterLines();
-      for (const m of text.matchAll(/^\s*([\p{L}_][\p{L}\d_]*)\s*=/gmu)) {
+      for (let next = iter.next(); !next.done; next = iter.next()) {
+        const line = next.value;
+        if (line.includes("=")) {
+          const m = varPattern.exec(line);
+          if (m) {
             options.push({ label: m[1], type: "variable" });
           }
+        }
+      }
       return { from: word.from, options, validFor: /^[\p{L}_]*$/u };
     };