Move description dictionary to a new file

actions-expressions/src/completion/descriptionDictionary.ts

@@ -0,0 +1,32 @@
+import {Dictionary} from "../data/dictionary";
+import {ExpressionData, Kind, Pair} from "../data/expressiondata";
+
+export type DescriptionPair = Pair & {description?: string};
+
+export function isDescriptionDictionary(x: ExpressionData): x is DescriptionDictionary {
+  return x.kind === Kind.Dictionary && x instanceof DescriptionDictionary;
+}
+
+export class DescriptionDictionary extends Dictionary {
+  private readonly descriptions = new Map<string, string>();
+
+  constructor(...pairs: DescriptionPair[]) {
+    super();
+
+    for (const p of pairs) {
+      this.add(p.key, p.value, p.description);
+    }
+  }
+
+  override add(key: string, value: ExpressionData, description?: string): void {
+    super.add(key, value);
+    if (description) {
+      this.descriptions.set(key, description);
+    }
+  }
+
+  override pairs(): DescriptionPair[] {
+    const pairs = super.pairs();
+    return pairs.map(p => ({...p, description: this.descriptions.get(p.key)}));
+  }
+}