parjs/src/internal/parsers/int.ts

Library for building parsers using combinators.

import { ParserDefinitionError } from "../../errors";
import { defaults } from "../../utils";
import type { Parjser } from "../parjser";
import { ParjserBase } from "../parser";
import { ResultKind } from "../result";
import type { ParsingState } from "../state";
import { NumericHelpers } from "./numeric-helpers";

/** A set of options for parsing integers. */
export interface IntOptions {
    allowSign: boolean;
    base: number;
}

const defaultOptions: IntOptions = {
    allowSign: true,
    base: 10
};

class Int extends ParjserBase<number> {
    type = "int";

    constructor(
        readonly options: IntOptions,
        readonly expecting: string
    ) {
        super();
    }

    _apply(ps: ParsingState): void {
        const { allowSign, base } = this.options;
        let { position } = ps;
        const { input } = ps;
        const initPos = ps.position;
        let sign = allowSign ? NumericHelpers.parseSign(ps) : 0;
        let parsedSign = false;
        if (sign !== 0) {
            parsedSign = true;
        } else {
            sign = 1;
        }
        position = ps.position;
        NumericHelpers.parseDigitsInBase(ps, base);
        const value = parseInt(input.substring(initPos, ps.position), base);

        if (ps.position === position) {
            ps.kind = parsedSign ? ResultKind.HardFail : ResultKind.SoftFail;
        } else {
            ps.value = value;
            ps.kind = ResultKind.Ok;
        }
    }
}

/**
 * Returns a parser that will parse a single integer, with the options given by `options`.
 *
 * @param pOptions A set of options for parsing integers.
 */
export function int(pOptions?: Partial<IntOptions>): Parjser<number> {
    const options = defaults(pOptions, defaultOptions);
    if (options.base > 36) {
        throw new ParserDefinitionError("int", "invalid base");
    }
    const expecting = `expecting a ${options.allowSign ? "signed" : "unsigned"} integer in base ${
        options.base
    }`;
    return new Int(options, expecting);
}