Optimized business hours rendering of raw 📖StadtKatalog entries

times.js

const Calendar = java.util.Calendar;
const weekdayKeys = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"];

const equalTimeFrames = function(a, b) {
    if (a.length !== b.length) {
        return false;
    }

    for (let i = 0; i < a.length; i++) {
        if (a[i] !== b[i]) {
            return false;
        }
    }

    return true;
};

const findSimpleRanges = function(week) {
    const reduced = [0];
    for (let i = 1; i < weekdayKeys.length; i++) {
        let prevDay = week[weekdayKeys[i - 1]],
            currDay = week[weekdayKeys[i]];

        reduced[i] = (equalTimeFrames(prevDay, currDay) ? reduced[i - 1] : i);
    }
    return reduced;
};

const eliminateEqualRanges = function(week, weekRanges) {
    const dedupedRanges = [];
    for (let i = weekRanges.length - 1; i >= 0; i--) {
        let lowestMatchingRange = -1;

        for (let u = 0; u < i && lowestMatchingRange < 0; u++) {
            if (equalTimeFrames(week[weekdayKeys[u]], week[weekdayKeys[i]])) {
                lowestMatchingRange = u;
            }
        }

        dedupedRanges[i] = (lowestMatchingRange >= 0 ? lowestMatchingRange : weekRanges[i]);
    }

    return dedupedRanges;
};

exports.reduceTimeRanges = function reduceTimeRanges(week) {
    return eliminateEqualRanges(week, findSimpleRanges(week));
};

const createRangeBag = function(reducedTimeRange) {
    const rangeBag = Object.create(null);

    reducedTimeRange.forEach(function(rangeNumber, index) {
        const slot = String(rangeNumber);
        if (!rangeBag[slot]) {
            rangeBag[slot] = [index];
        } else {
            rangeBag[slot].push(index);
        }
    });

    return rangeBag;
};

const canFoldIntoDayRange = function(range) {
    return range.every(function(dayNumber, idx, arr) {
        return !idx || dayNumber === arr[idx - 1] || dayNumber === arr[idx - 1] + 1;
    })
};

exports.foldDayNames = function(week, reducedTimeRange, rangeHyphen, rangeDelimiter, languageTag) {
    const locale = java.util.Locale.forLanguageTag(languageTag);
    const dfs = new java.text.DateFormatSymbols(locale);
    const dfsWeekdays = dfs.getShortWeekdays();
    const shortWeekdays = [
        dfsWeekdays[Calendar.MONDAY],
        dfsWeekdays[Calendar.TUESDAY],
        dfsWeekdays[Calendar.WEDNESDAY],
        dfsWeekdays[Calendar.THURSDAY],
        dfsWeekdays[Calendar.FRIDAY],
        dfsWeekdays[Calendar.SATURDAY],
        dfsWeekdays[Calendar.SUNDAY]
    ];

    const rangeStrings = [];

    const rangeBag = createRangeBag(reducedTimeRange);
    Object.keys(rangeBag).sort().map(function(rangeNumber) {
        const bagOfDays = rangeBag[rangeNumber];

        if (canFoldIntoDayRange(bagOfDays) && bagOfDays.length > 1) {
            rangeStrings.push({
                days: shortWeekdays[bagOfDays[0]] + rangeHyphen + shortWeekdays[bagOfDays.slice(-1)],
                timeFrames: week[weekdayKeys[rangeNumber]]
            });
        } else {
            rangeStrings.push({
                days: bagOfDays.map(function(dayIndex) {
                    return shortWeekdays[dayIndex];
                }).join(rangeDelimiter),
                timeFrames: week[weekdayKeys[rangeNumber]]
            });
        }
    });

    return rangeStrings;
};

exports.formatTimeFrames = function(timeFrames, format, delimiter, placeholder) {
    if (timeFrames.length === 0) {
        return placeholder || "";
    }

    const frameStr = [];
    for (let i = 0; i < timeFrames.length; i += 2) {
        frameStr.push(
            format.replace("{start}", timeFrames[i]).replace("{end}", timeFrames[i + 1] || "max. 24:00")
        );
    }

    return frameStr.join(delimiter);
};