str/src/vm/commands/contains.ts

import { LexInput } from "../lexer.js";
import {Command, ParseContext, StrTerm, unwrapString} from "./command.js";
import {StrVM} from "../vm.js";
import {Awaitable} from "../../util/types.js";

export class Contains extends Command<{ find: StrTerm }> {
    attemptParse(context: ParseContext): { find: StrTerm } {
        return {
            find: context.popTerm(),
        }
    }

    getDisplayName(): string {
        return 'contains'
    }

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

    execute(vm: StrVM, data: { find: StrTerm }): Awaitable<StrVM> {
        return vm.inPlace(ctx =>
            ctx.replaceSubject(sub =>
                sub.emptyUnlessCondition(s =>
                    s.includes(ctx.resolveString(data.find)))))
    }
}