Implement edit and exit

src/vm/commands/edit.ts

@@ -1,7 +1,10 @@
-import {Command, ParseContext} from "./command.js";
+import {Command, ParseContext, wrapString} from "./command.js";
 import {LexInput} from "../lexer.js";
 import {StrVM} from "../vm.js";
 import {Awaitable} from "../../util/types.js";
+import fs from "node:fs/promises";
+import childProcess from "node:child_process";
+import {tempFile} from "../../util/fs.js";
 
 export class Edit extends Command<{}> {
     isParseCandidate(token: LexInput): boolean {
@@ -19,8 +22,17 @@ export class Edit extends Command<{}> {
     execute(vm: StrVM, data: {}): Awaitable<StrVM> {
         return vm.replaceContextMatchingTerm({
             string: async sub => {
+                await vm.control$.next({ cmd: 'close-prompt' })
 
-                return sub
+                const tmp = tempFile()
+                await fs.writeFile(tmp, sub, 'utf8')
+                const proc = childProcess.spawn(process.env.EDITOR || 'vim', [tmp], { stdio: 'inherit' })
+                await new Promise<void>(res => {
+                    proc.on('close', () => res())
+                })
+
+                await vm.control$.next({ cmd: 'restore-prompt' })
+                return (await fs.readFile(tmp, 'utf8')).toString()
             }
         })
     }