Implement output/clipboard interfaces, stub implementations, and implement execute()s for Copy and Paste

src/vm/output.ts

@@ -1,4 +1,5 @@
 import {StrRVal} from "./commands/command.js";
+import {Awaitable} from "../util/types.js";
 
 export const getSubjectDisplay = (sub: StrRVal): string => {
     if ( sub.term === 'string' ) {
@@ -11,3 +12,39 @@ export const getSubjectDisplay = (sub: StrRVal): string => {
 
     return JSON.stringify(sub.value, null, '\t')  // fixme
 }
+
+export type Display = {
+    showSubject(sub: StrRVal): Awaitable<unknown>
+}
+
+export class ConsoleDisplay implements Display {
+    showSubject(sub: StrRVal) {
+        console.log(`\n---------------\n${getSubjectDisplay(sub)}\n---------------\n`)
+    }
+}
+
+export class NullDisplay implements Display {
+    showSubject() {}
+}
+
+export type Clipboard = {
+    read(): Awaitable<string>
+    overwrite(sub: string): Awaitable<unknown>
+}
+
+export class FakeClipboard {
+    private val = ''
+
+    read() {
+        return this.val
+    }
+
+    overwrite(sub: string) {
+        this.val = sub
+    }
+}
+
+export type OutputManager = {
+    display: Display,
+    clipboard: Clipboard,
+}