parjs/src/internal/combinators/then-pick.ts

A parser-combinator library for JavaScript.

/**
 * @module parjs/combinators
 */
/** */

import {ParjsCombinator, Parjser, ParjsProjection} from "../parjser";
import {ParjserBase} from "../parser";
import {defineCombinator} from "./combinator";
import {ParsingState} from "../state";
import {ImplicitParjser} from "../scalar-converter";

/**
 * Applies the source parser, and then applies a selector on the source parser's
 * result and user state to choose or create the parser to apply next.
 * @param selector
 */
export function thenPick<A, B>(selector: ParjsProjection<A, ImplicitParjser<B>>):
    ParjsCombinator<A, B> {
    return defineCombinator(source => {
        return new class ThenPick extends ParjserBase {
            expecting = source.expecting;
            type = "then-pick";

            _apply(ps: ParsingState): void {
                source.apply(ps);
                if (!ps.isOk) {
                    return;
                }
                let firstVal = ps.value;
                let nextParser = selector(ps.value, ps.userState) as ParjserBase;
                nextParser.apply(ps);
                if (ps.isOk) {
                    return;
                }
                if (ps.isSoft) {
                    ps.kind = "Hard";
                }
            }

        }();
    });
}