using Grand.Business.Core.Interfaces.Common.Directory;
using Grand.Domain.Directory;
using System.Collections.ObjectModel;
using System.Diagnostics;

namespace Grand.Business.Common.Services.Directory
{
    /// <summary>
    /// Represents a datetime service
    /// </summary>
    public class DateTimeService : IDateTimeService
    {
        private readonly DateTimeSettings _dateTimeSettings;
        private TimeZoneInfo _timeZoneInfo;
        /// <summary>
        /// Ctor
        /// </summary>
        /// <param name="dateTimeSettings">Datetime settings</param>
        public DateTimeService(
            DateTimeSettings dateTimeSettings)
        {
            _dateTimeSettings = dateTimeSettings;
        }

        /// <summary>
        /// Retrieves a System.TimeZoneInfo object from the registry based on its identifier.
        /// </summary>
        /// <param name="id">The time zone identifier, which corresponds to the System.TimeZoneInfo.Id property.</param>
        /// <returns>A System.TimeZoneInfo object whose identifier is the value of the id parameter.</returns>
        public virtual TimeZoneInfo FindTimeZoneById(string id)
        {
            return TimeZoneInfo.FindSystemTimeZoneById(id);
        }

        /// <summary>
        /// Returns a sorted collection of all the time zones
        /// </summary>
        /// <returns>A read-only collection of System.TimeZoneInfo objects.</returns>
        public virtual ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones()
        {
            return TimeZoneInfo.GetSystemTimeZones();
        }

        /// <summary>
        /// Converts the date and time to current user date and time
        /// </summary>
        /// <param name="dt">The date and time (represents local system time or UTC time) to convert.</param>
        /// <returns>A DateTime value that represents time that corresponds to the dateTime parameter in customer time zone.</returns>
        public virtual DateTime ConvertToUserTime(DateTime dt)
        {
            return ConvertToUserTime(dt, dt.Kind);
        }

        /// <summary>
        /// Converts the date and time to current user date and time
        /// </summary>
        /// <param name="dt">The date and time (represents local system time or UTC time) to convert.</param>
        /// <param name="sourceDateTimeKind">The source datetime kind</param>
        /// <returns>A DateTime value that represents time that corresponds to the dateTime parameter in customer time zone.</returns>
        public virtual DateTime ConvertToUserTime(DateTime dt, DateTimeKind sourceDateTimeKind)
        {
            dt = DateTime.SpecifyKind(dt, sourceDateTimeKind);
            var currentUserTimeZoneInfo = this.CurrentTimeZone;
            return TimeZoneInfo.ConvertTime(dt, currentUserTimeZoneInfo);
        }

        /// <summary>
        /// Converts the date and time to current user date and time
        /// </summary>
        /// <param name="dt">The date and time to convert.</param>
        /// <param name="sourceTimeZone">The time zone of dateTime.</param>
        /// <param name="destinationTimeZone">The time zone to convert dateTime to.</param>
        /// <returns>A DateTime value that represents time that corresponds to the dateTime parameter in customer time zone.</returns>
        public virtual DateTime ConvertToUserTime(DateTime dt, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
        {
            return TimeZoneInfo.ConvertTime(dt, sourceTimeZone, destinationTimeZone);
        }

        /// <summary>
        /// Converts the date and time to Coordinated Universal Time (UTC)
        /// </summary>
        /// <param name="dt">The date and time (represents local system time or UTC time) to convert.</param>
        /// <returns>A DateTime value that represents the Coordinated Universal Time (UTC) that corresponds to the dateTime parameter. The DateTime value's Kind property is always set to DateTimeKind.Utc.</returns>
        public virtual DateTime ConvertToUtcTime(DateTime dt)
        {
            return ConvertToUtcTime(dt, dt.Kind);
        }

        /// <summary>
        /// Converts the date and time to Coordinated Universal Time (UTC)
        /// </summary>
        /// <param name="dt">The date and time (represents local system time or UTC time) to convert.</param>
        /// <param name="sourceDateTimeKind">The source datetime kind</param>
        /// <returns>A DateTime value that represents the Coordinated Universal Time (UTC) that corresponds to the dateTime parameter. The DateTime value's Kind property is always set to DateTimeKind.Utc.</returns>
        public virtual DateTime ConvertToUtcTime(DateTime dt, DateTimeKind sourceDateTimeKind)
        {
            dt = DateTime.SpecifyKind(dt, sourceDateTimeKind);
            return TimeZoneInfo.ConvertTimeToUtc(dt, TimeZoneInfo.Utc);
        }

        /// <summary>
        /// Converts the date and time to Coordinated Universal Time (UTC)
        /// </summary>
        /// <param name="dt">The date and time to convert.</param>
        /// <param name="sourceTimeZone">The time zone of dateTime.</param>
        /// <returns>A DateTime value that represents the Coordinated Universal Time (UTC) that corresponds to the dateTime parameter. The DateTime value's Kind property is always set to DateTimeKind.Utc.</returns>
        public virtual DateTime ConvertToUtcTime(DateTime dt, TimeZoneInfo sourceTimeZone)
        {
            if (sourceTimeZone.IsInvalidTime(dt))
            {
                //could not convert
                return dt;
            }
            return dt.Kind == DateTimeKind.Utc ? dt : TimeZoneInfo.ConvertTimeToUtc(dt, sourceTimeZone);
        }

        /// <summary>
        /// Gets the current user time zone
        /// </summary>
        public virtual TimeZoneInfo CurrentTimeZone {
            get {
                if (_timeZoneInfo != null) return _timeZoneInfo;
                try
                {
                    if (!string.IsNullOrEmpty(_dateTimeSettings.DefaultStoreTimeZoneId))
                        _timeZoneInfo = FindTimeZoneById(_dateTimeSettings.DefaultStoreTimeZoneId);
                }
                catch (Exception exc)
                {
                    Debug.Write(exc.ToString());
                }

                return _timeZoneInfo ??= TimeZoneInfo.Local;

            }
        }
    }
}