sounisi5011/ts-peg

import {
    ParseFailureResult,
    Parser,
    ParseResult,
    ParserGenerator,
    ParseSuccessResult,
} from '../../internal';

export type CustomizableParserParseFunc<TResult> = (
    input: string,
    offsetStart: number,
    stopOffset: number,
) =>
    | ParseSuccessResult<TResult>
    | { offsetEnd: number; valueGetter(): TResult }
    | undefined;

export class CustomizableParser<TResult> extends Parser<TResult> {
    private readonly __parseFunc: CustomizableParserParseFunc<TResult>;

    constructor(
        parseFunc: CustomizableParserParseFunc<TResult>,
        parserGenerator: ParserGenerator,
    ) {
        super(parserGenerator);
        this.__parseFunc = parseFunc;
    }

    protected __parse(
        input: string,
        offsetStart: number,
        stopOffset: number,
    ): ParseResult<TResult> {
        const result = this.__parseFunc(input, offsetStart, stopOffset);
        if (result && result.offsetEnd <= stopOffset) {
            return result instanceof ParseSuccessResult
                ? result
                : new ParseSuccessResult({
                      offsetEnd: result.offsetEnd,
                      dataGenerator: result.valueGetter,
                      allowCache: true,
                  });
        }
        return new ParseFailureResult({ allowCache: true });
    }
}