parjs/src/internal/combinators/exactly.ts

A parser-combinator library for JavaScript.

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

import {ParsingState} from "../state";
import {ResultKind} from "../result";
import {ParjsCombinator} from "../../index";
import {defineCombinator} from "./combinator";
import {ParjserBase} from "../parser";

/**
 * Applies the source parser exactly `count` times, and yields all the results in an array.
 * @param count The number of times to apply the source parser.
 */
export function exactly<T>(count: number)
    : ParjsCombinator<T, T[]>;

export function exactly(count: number) {
    return defineCombinator(source => {
        return new class Exactly extends ParjserBase {
            type = "exactly";
            expecting = source.expecting;
            _apply(ps: ParsingState): void {
                let arr = [] as any[];
                for (let i = 0; i < count; i++) {
                    source.apply(ps);
                    if (!ps.isOk) {
                        if (ps.kind === ResultKind.SoftFail && i > 0) {
                            ps.kind = ResultKind.HardFail;
                        }
                        // fail because the inner parser has failed.
                        return;
                    }
                    arr.push(ps.value);
                }
                ps.value = arr;
            }
        }();
    });
}