str/src/vm/commands/line.ts

import {Command, CommandData, ParseContext} from "./command.js";
import {Executable} from "../parse.js";
import {LexInput} from "../lexer.js";
import {StrVM} from "../vm.js";
import {Awaitable} from "../../util/types.js";
import {Lines} from "./lines.js";
import {Each} from "./each.js";
import {Join} from "./join.js";

export type LineData = {
    exec: Executable<CommandData>,
}

export class Line extends Command<LineData> {
    async attemptParse(context: ParseContext): Promise<LineData> {
        return {
            exec: await context.popExecutable(),
        }
    }

    getDisplayName(): string {
        return 'line'
    }

    isParseCandidate(token: LexInput): boolean {
        return this.isKeyword(token, 'line')
    }

    execute(vm: StrVM, data: LineData): Awaitable<StrVM> {
        // `line <cmd>` is equivalent to `lines` -> `each <cmd>` -> `join`, so just do that
        return vm.tapInPlace(ctx =>
            ctx.replaceSubject(async sub =>
                vm.runInChild(async (child, ctx) => {
                    await (new Lines).execute(child, {})
                    await (new Each).execute(child, { exec: data.exec })
                    await (new Join).execute(child, {})
                    return ctx.getSubject()
                })))
    }
}