import { ParsingContext, Refiner } from "../../chrono";
import { ParsingResult } from "../../results";

const TIMEZONE_OFFSET_PATTERN = new RegExp("^\\s*(?:\\(?(?:GMT|UTC)\\s?)?([+-])(\\d{1,2})(?::?(\\d{2}))?\\)?", "i");
const TIMEZONE_OFFSET_SIGN_GROUP = 1;
const TIMEZONE_OFFSET_HOUR_OFFSET_GROUP = 2;
const TIMEZONE_OFFSET_MINUTE_OFFSET_GROUP = 3;

export default class ExtractTimezoneOffsetRefiner implements Refiner {
    refine(context: ParsingContext, results: ParsingResult[]): ParsingResult[] {
        results.forEach(function (result) {
            if (result.start.isCertain("timezoneOffset")) {
                return;
            }

            const suffix = context.text.substring(result.index + result.text.length);
            const match = TIMEZONE_OFFSET_PATTERN.exec(suffix);
            if (!match) {
                return;
            }

            context.debug(() => {
                console.log(`Extracting timezone: '${match[0]}' into : ${result}`);
            });

            const hourOffset = parseInt(match[TIMEZONE_OFFSET_HOUR_OFFSET_GROUP]);
            const minuteOffset = parseInt(match[TIMEZONE_OFFSET_MINUTE_OFFSET_GROUP] || "0");
            let timezoneOffset = hourOffset * 60 + minuteOffset;
            // No timezones have offsets greater than 14 hours, so disregard this match
            if (timezoneOffset > 14 * 60) {
                return;
            }
            if (match[TIMEZONE_OFFSET_SIGN_GROUP] === "-") {
                timezoneOffset = -timezoneOffset;
            }

            if (result.end != null) {
                result.end.assign("timezoneOffset", timezoneOffset);
            }

            result.start.assign("timezoneOffset", timezoneOffset);
            result.text += match[0];
        });

        return results;
    }
}