using System;

namespace Chronos.Extensions
{
    /// <summary>
    /// Extension methods for the DateTimeOffset data type.
    /// </summary>
    public static class DateTimeOffsetExtensions
    {
        #region · Extensions ·

        /// <summary>
        /// Indicates whether the date is today.
        /// </summary>
        /// <param name="dto">The date.</param>
        /// <returns>
        /// 	<c>true</c> if the specified date is today; otherwise, <c>false</c>.
        /// </returns>
        public static bool IsToday(this DateTimeOffset dto)
        {
            return (dto.Date.IsToday());
        }

        /// <summary>
        /// Sets the time on the specified DateTimeOffset value using the local system time zone.
        /// </summary>
        /// <param name="date">The base date.</param>
        /// <param name="hours">The hours to be set.</param>
        /// <param name="minutes">The minutes to be set.</param>
        /// <param name="seconds">The seconds to be set.</param>
        /// <returns>The DateTimeOffset including the new time value</returns>
        public static DateTimeOffset SetTime(this DateTimeOffset date, int hours, int minutes, int seconds)
        {
            return date.SetTime(new TimeSpan(hours, minutes, seconds));
        }

        /// <summary>
        /// Sets the time on the specified DateTime value using the local system time zone.
        /// </summary>
        /// <param name="date">The base date.</param>
        /// <param name="time">The TimeSpan to be applied.</param>
        /// <returns>
        /// The DateTimeOffset including the new time value
        /// </returns>
        public static DateTimeOffset SetTime(this DateTimeOffset date, TimeSpan time)
        {
            return date.SetTime(time, null);
        }

        /// <summary>
        /// Sets the time on the specified DateTime value using the specified time zone.
        /// </summary>
        /// <param name="date">The base date.</param>
        /// <param name="time">The TimeSpan to be applied.</param>
        /// <param name="localTimeZone">The local time zone.</param>
        /// <returns>/// The DateTimeOffset including the new time value/// </returns>
        public static DateTimeOffset SetTime(this DateTimeOffset date, TimeSpan time, TimeZoneInfo localTimeZone)
        {
            var localDate = date.ToLocalDateTime(localTimeZone);

            localDate.SetTime(time);
            
            return localDate.ToDateTimeOffset(localTimeZone);
        }

        /// <summary>
        /// Converts a DateTimeOffset into a DateTime using the local system time zone.
        /// </summary>
        /// <param name="dateTimeUtc">The base DateTimeOffset.</param>
        /// <returns>The converted DateTime</returns>
        public static DateTime ToLocalDateTime(this DateTimeOffset dateTimeUtc)
        {
            return dateTimeUtc.ToLocalDateTime(null);
        }

        /// <summary>
        /// Converts a DateTimeOffset into a DateTime using the specified time zone.
        /// </summary>
        /// <param name="dateTimeUtc">The base DateTimeOffset.</param>
        /// <param name="localTimeZone">The time zone to be used for conversion.</param>
        /// <returns>The converted DateTime</returns>
        public static DateTime ToLocalDateTime(this DateTimeOffset dateTimeUtc, TimeZoneInfo localTimeZone)
        {
            localTimeZone = (localTimeZone ?? TimeZoneInfo.Local);

            return TimeZoneInfo.ConvertTime(dateTimeUtc, localTimeZone).DateTime;
        }

        #endregion
    }
}