/**
 * Date utilities - ES Module Version
 */

import { isDate, isNumber, isString, isUndefined } from './Type.js';
import { mod } from './Math.js';

/**
 * Get the name of the day of the week for a given date
 */
export function getDayName(date, utc) {
    const names = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
    return names[getDayOfWeek(date, utc)];
}

/**
 * Get the day of the week (0-6) for a given date
 */
export function getDayOfWeek(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCDay() : date.getDay();
}

/**
 * Get the day of the year (1-366) for a given date
 */
export function getDayOfYear(date, utc) {
    date = makeDate(date);
    const startOfYear = new Date(Date.UTC(
        getFullYear(date, utc),
        0, 1
    ));
    const diff = date - startOfYear;
    return Math.floor(diff / 86400000) + 1;
}

/**
 * Get the number of days in a month
 */
export function getDaysInMonth(year, month) {
    return new Date(year, month + 1, 0).getDate();
}

/**
 * Get the number of days in a year
 */
export function getDaysInYear(year) {
    return isLeapYear(year) ? 366 : 365;
}

/**
 * Get the first day of the week for a given date
 */
export function getFirstDayOfWeek(date, utc) {
    date = makeDate(date);
    const day = getDayOfWeek(date, utc);
    return new Date(date.getTime() - day * 86400000);
}

/**
 * Get the full year from a date
 */
export function getFullYear(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCFullYear() : date.getFullYear();
}

/**
 * Get hours from date
 */
export function getHours(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCHours() : date.getHours();
}

/**
 * Get the ISO date string (YYYY-MM-DD)
 */
export function getISODate(date, utc) {
    return formatDate(date, '%Y-%m-%d', utc);
}

/**
 * Get the ISO week number
 */
export function getISOWeek(date, utc) {
    date = makeDate(date);
    const year = getFullYear(date, utc);
    const firstThursday = getFirstThursday(year, utc);
    const week = Math.floor((date - firstThursday) / 604800000) + 1;
    
    if (week < 1) {
        return getISOWeek(new Date(year - 1, 11, 31), utc);
    } else if (week > 52) {
        const nextFirstThursday = getFirstThursday(year + 1, utc);
        if (date >= nextFirstThursday) {
            return 1;
        }
    }
    
    return week;
}

/**
 * Get the ISO year
 */
export function getISOYear(date, utc) {
    date = makeDate(date);
    const year = getFullYear(date, utc);
    const week = getISOWeek(date, utc);
    
    if (week === 1 && getMonth(date, utc) === 11) {
        return year + 1;
    } else if (week >= 52 && getMonth(date, utc) === 0) {
        return year - 1;
    }
    
    return year;
}

/**
 * Get minutes from date
 */
export function getMinutes(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCMinutes() : date.getMinutes();
}

/**
 * Get month from date (0-11)
 */
export function getMonth(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCMonth() : date.getMonth();
}

/**
 * Get month name
 */
export function getMonthName(date, utc) {
    const names = [
        'January', 'February', 'March', 'April', 'May', 'June',
        'July', 'August', 'September', 'October', 'November', 'December'
    ];
    return names[getMonth(date, utc)];
}

/**
 * Get seconds from date
 */
export function getSeconds(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCSeconds() : date.getSeconds();
}

/**
 * Get milliseconds from date
 */
export function getMilliseconds(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCMilliseconds() : date.getMilliseconds();
}

/**
 * Get timezone offset in minutes
 */
export function getTimezoneOffset(date) {
    return makeDate(date).getTimezoneOffset();
}

/**
 * Get timezone offset string (+HH:MM or -HH:MM)
 */
export function getTimezoneOffsetString(date) {
    const offset = getTimezoneOffset(date);
    const sign = offset <= 0 ? '+' : '-';
    const hours = Math.floor(Math.abs(offset) / 60);
    const minutes = Math.abs(offset) % 60;
    return sign + pad(hours, 2) + ':' + pad(minutes, 2);
}

/**
 * Get Unix timestamp (seconds since epoch)
 */
export function getUnixTime(date) {
    return Math.floor(makeDate(date).getTime() / 1000);
}

/**
 * Get week number (1-53)
 */
export function getWeek(date, utc) {
    date = makeDate(date);
    const firstDayOfYear = new Date(Date.UTC(
        getFullYear(date, utc), 0, 1
    ));
    const days = Math.floor((date - firstDayOfYear) / 86400000);
    return Math.ceil((days + getDayOfWeek(firstDayOfYear, utc) + 1) / 7);
}

/**
 * Check if a year is a leap year
 */
export function isLeapYear(year) {
    return year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0);
}

/**
 * Check if a date is valid
 */
export function isValidDate(date) {
    date = makeDate(date);
    return !isNaN(date.getTime());
}

/**
 * Make a date object from various inputs
 */
export function makeDate(date) {
    if (isDate(date)) {
        return date;
    } else if (isString(date)) {
        return new Date(date);
    } else if (isNumber(date)) {
        return new Date(date);
    } else if (isUndefined(date)) {
        return new Date();
    }
    return new Date(date);
}

/**
 * Format a date according to a format string
 */
export function formatDate(date, format, utc) {
    date = makeDate(date);
    format = format || '%Y-%m-%d %H:%M:%S';
    
    const replacements = {
        '%a': () => getDayName(date, utc).substr(0, 3),
        '%A': () => getDayName(date, utc),
        '%b': () => getMonthName(date, utc).substr(0, 3),
        '%B': () => getMonthName(date, utc),
        '%c': () => date.toLocaleString(),
        '%d': () => pad(getDate(date, utc), 2),
        '%e': () => pad(getDate(date, utc), 2, ' '),
        '%H': () => pad(getHours(date, utc), 2),
        '%I': () => pad(((getHours(date, utc) + 11) % 12) + 1, 2),
        '%j': () => pad(getDayOfYear(date, utc), 3),
        '%k': () => pad(getHours(date, utc), 2, ' '),
        '%l': () => pad(((getHours(date, utc) + 11) % 12) + 1, 2, ' '),
        '%m': () => pad(getMonth(date, utc) + 1, 2),
        '%M': () => pad(getMinutes(date, utc), 2),
        '%p': () => getHours(date, utc) < 12 ? 'AM' : 'PM',
        '%S': () => pad(getSeconds(date, utc), 2),
        '%u': () => getDayOfWeek(date, utc) || 7,
        '%U': () => pad(getWeek(date, utc), 2),
        '%V': () => pad(getISOWeek(date, utc), 2),
        '%w': () => getDayOfWeek(date, utc),
        '%W': () => pad(getWeek(date, utc), 2),
        '%x': () => date.toLocaleDateString(),
        '%X': () => date.toLocaleTimeString(),
        '%y': () => pad(getFullYear(date, utc) % 100, 2),
        '%Y': () => getFullYear(date, utc),
        '%z': () => getTimezoneOffsetString(date),
        '%Z': () => '', // Timezone abbreviation not easily available
        '%%': () => '%'
    };
    
    return format.replace(/%[a-zA-Z%]/g, (match) => {
        return replacements[match] ? replacements[match]() : match;
    });
}

/**
 * Parse a date string
 */
export function parseDate(string, format, utc) {
    // Basic implementation - can be enhanced
    return new Date(string);
}

/**
 * Get date (day of month)
 */
export function getDate(date, utc) {
    date = makeDate(date);
    return utc ? date.getUTCDate() : date.getDate();
}

/**
 * Get day (alias for getDayOfWeek)
 */
export function getDay(date, utc) {
    return getDayOfWeek(date, utc);
}

/**
 * Get ISO day (Monday=1, Sunday=7)
 */
export function getISODay(date, utc) {
    const day = getDayOfWeek(date, utc);
    return day === 0 ? 7 : day;
}

/**
 * Get day of the year (alias for getDayOfYear)
 */
export function getDayOfTheYear(date, utc) {
    return getDayOfYear(date, utc);
}

/**
 * Get first day of the year
 */
export function getFirstDayOfTheYear(date, utc) {
    date = makeDate(date);
    const year = getFullYear(date, utc);
    return new Date(Date.UTC(year, 0, 1));
}

/**
 * Set date (day of month)
 */
export function setDate(date, day, utc) {
    date = makeDate(date);
    if (utc) {
        date.setUTCDate(day);
    } else {
        date.setDate(day);
    }
    return date;
}

/**
 * Set full year
 */
export function setFullYear(date, year, utc) {
    date = makeDate(date);
    if (utc) {
        date.setUTCFullYear(year);
    } else {
        date.setFullYear(year);
    }
    return date;
}

/**
 * Set month
 */
export function setMonth(date, month, utc) {
    date = makeDate(date);
    if (utc) {
        date.setUTCMonth(month);
    } else {
        date.setMonth(month);
    }
    return date;
}

/**
 * Set hours
 */
export function setHours(date, hours, utc) {
    date = makeDate(date);
    if (utc) {
        date.setUTCHours(hours);
    } else {
        date.setHours(hours);
    }
    return date;
}

/**
 * Set minutes
 */
export function setMinutes(date, minutes, utc) {
    date = makeDate(date);
    if (utc) {
        date.setUTCMinutes(minutes);
    } else {
        date.setMinutes(minutes);
    }
    return date;
}

/**
 * Set seconds
 */
export function setSeconds(date, seconds, utc) {
    date = makeDate(date);
    if (utc) {
        date.setUTCSeconds(seconds);
    } else {
        date.setSeconds(seconds);
    }
    return date;
}

// Helper functions
function getFirstThursday(year, utc) {
    const jan1 = new Date(Date.UTC(year, 0, 1));
    const dayOfWeek = getDayOfWeek(jan1, utc);
    const daysToThursday = (11 - dayOfWeek) % 7;
    return new Date(jan1.getTime() + daysToThursday * 86400000);
}

function pad(number, length, padding) {
    padding = padding || '0';
    const str = String(number);
    return padding.repeat(Math.max(0, length - str.length)) + str;
}

// Export all functions
export default {
    getDayName,
    getDayOfWeek,
    getDayOfYear,
    getDaysInMonth,
    getDaysInYear,
    getFirstDayOfWeek,
    getFullYear,
    getHours,
    getISODate,
    getISOWeek,
    getISOYear,
    getMinutes,
    getMonth,
    getMonthName,
    getSeconds,
    getMilliseconds,
    getTimezoneOffset,
    getTimezoneOffsetString,
    getUnixTime,
    getWeek,
    isLeapYear,
    isValidDate,
    makeDate,
    formatDate,
    parseDate,
    getDate,
    getDay,
    getISODay,
    getDayOfTheYear,
    getFirstDayOfTheYear,
    setDate,
    setFullYear,
    setMonth,
    setHours,
    setMinutes,
    setSeconds
};