chrono-node/src/locales/en/parsers/ENWeekdayParser.ts

A natural language date parser in Javascript

import { ParsingContext } from "../../../chrono";
import { ParsingComponents } from "../../../results";
import { WEEKDAY_DICTIONARY } from "../constants";
import { matchAnyPattern } from "../../../utils/pattern";
import { AbstractParserWithWordBoundaryChecking } from "../../../common/parsers/AbstractParserWithWordBoundary";
import { createParsingComponentsAtWeekday } from "../../../common/calculation/weekdays";

const PATTERN = new RegExp(
    "(?:(?:\\,|\\(|\\（)\\s*)?" +
        "(?:on\\s*?)?" +
        "(?:(this|last|past|next)\\s*)?" +
        `(${matchAnyPattern(WEEKDAY_DICTIONARY)})` +
        "(?:\\s*(?:\\,|\\)|\\）))?" +
        "(?:\\s*(this|last|past|next)\\s*week)?" +
        "(?=\\W|$)",
    "i"
);

const PREFIX_GROUP = 1;
const WEEKDAY_GROUP = 2;
const POSTFIX_GROUP = 3;

export default class ENWeekdayParser extends AbstractParserWithWordBoundaryChecking {
    innerPattern(): RegExp {
        return PATTERN;
    }

    innerExtract(context: ParsingContext, match: RegExpMatchArray): ParsingComponents {
        const dayOfWeek = match[WEEKDAY_GROUP].toLowerCase();
        const weekday = WEEKDAY_DICTIONARY[dayOfWeek];
        const prefix = match[PREFIX_GROUP];
        const postfix = match[POSTFIX_GROUP];
        let modifierWord = prefix || postfix;
        modifierWord = modifierWord || "";
        modifierWord = modifierWord.toLowerCase();

        let modifier = null;
        if (modifierWord == "last" || modifierWord == "past") {
            modifier = "last";
        } else if (modifierWord == "next") {
            modifier = "next";
        } else if (modifierWord == "this") {
            modifier = "this";
        }

        return createParsingComponentsAtWeekday(context.reference, weekday, modifier);
    }
}