using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Globalization;

namespace TradeIdeas.MiscSupport
{
    /// <summary>
    /// This class has some routines for converting values between C# data types and the format required
    /// by the TI servers.
    /// </summary>
    public static class ServerFormats
    {
        /// <summary>
        /// The server always works with time in time_t format.  Messages to and from the server are
        /// typically in that format.  We have our own conversion that works better than any of
        /// the C# libraries for us.
        /// <seealso cref="ToTimeT"/> <seealso cref="FromTimeT"/> <seealso cref="DecodeServerTime"/>
        /// </summary>
        public static readonly DateTime UnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

        /// <summary>
        /// Takes a date in the current time zone (set in TI Pro) and converts it to UTC. ToUniversalTime() doesn't work
        /// since when the time zone in TI Pro is set to something other than local the date is incorrect.
        /// </summary>
        /// <param name="dt"></param>
        /// <returns></returns>
        public static DateTime ToUtc(this DateTime dt)
        {
            return TimeZoneInfo.ConvertTimeToUtc(dt, ServerFormats.CurrentTimeZone);
        }

        public static DateTime? ToUtc(this DateTime? dt)
        {
            if (!dt.HasValue) return dt;

            return TimeZoneInfo.ConvertTimeToUtc(dt.Value, ServerFormats.CurrentTimeZone);
        }

        public static DateTime FromUtc(this DateTime dt)
        {
            return TimeZoneInfo.ConvertTimeFromUtc(dt, ServerFormats.CurrentTimeZone);
        }

        public static DateTime? FromUtc(this DateTime? dt)
        {
            if (!dt.HasValue) return dt;

            return TimeZoneInfo.ConvertTimeFromUtc(dt.Value, ServerFormats.CurrentTimeZone);

        }

        /// <summary>
        /// Convert from a DateTime object to a time_t value.
        /// </summary>
        /// <param name="dt">The time to convert.  This must be in <see cref="CurrentTimeZone"/></param>
        /// <returns>The time in time_t format, or 0 if the input was null.</returns>
        public static long ToTimeT(DateTime? dt)
        {   // Interesting.  Converting the unix epoch to local time does not appear to work.  It was off by an
            // hour.  And just subtracting without converting did not work.  It appears that the subtraction
            // operation ignored the timezone (or "kind") of the two parameters.
            if (dt == null)
                return 0;
            DateTime usableDT = new DateTime(dt.Value.Ticks, DateTimeKind.Unspecified);
            // ConvertTime() and ConverTimeToUtc() both assert that the kind property matches the
            // source time zone property.  That's annoying and causes a lot of trouble.  We say
            // that it's on the caller to make sure that the input is in the CurrentTimeZone.
            // We then ignore the DateTimeKind of the input, which is consistent with most
            // operations, including the - operator.
            TimeSpan diff = TimeZoneInfo.ConvertTimeToUtc(usableDT, CurrentTimeZone) - UnixEpoch;
            return (long)Math.Round(diff.TotalSeconds);
        }

        /// <summary>
        /// Convert from the time_t format to a C# DateTime object.
        /// </summary>
        /// <param name="timeT">The time in time_t format.</param>
        /// <returns>The time, expressed in the <see cref="CurrentTimeZone"/>.  Or null if there is a problem.</returns>
        public static DateTime? FromTimeT(long timeT)
        {
            try
            {
                // Test conditions that may cause ArgumentOutOfRangeExceptions.
                if (timeT <= 0)
                    return null;
                long testTicks = timeT * TimeSpan.TicksPerSecond;
                if (testTicks > TimeSpan.MaxValue.Ticks)
                    return null;
                if (testTicks * TimeSpan.TicksPerSecond < TimeSpan.MinValue.Ticks)
                    return null;
                if (testTicks <= 0)  // Catch where the long multiplication returns a negative number because timeT is too big.
                    return null;
                TimeSpan timeSpan = new TimeSpan(testTicks);
                long testDateTicks = UnixEpoch.Ticks + timeSpan.Ticks;
                if (testDateTicks > DateTime.MaxValue.Ticks)
                    return null;
                if (testDateTicks < DateTime.MinValue.Ticks)
                    return null;
                DateTime testDate = UnixEpoch + timeSpan;
                return TimeZoneInfo.ConvertTimeFromUtc(testDate, CurrentTimeZone);
            }
            catch
            {
                return null;
            }
        }

        /// <summary>
        /// Convert a time from the server into a DateTime object in the <see cref="CurrentTimeZone"/>.
        /// 
        /// This can return null for a number of reasons.  The input could be complete invalid.
        /// The input could be empty.  The input could be 0.
        /// 
        /// Most of the time the server will send us values in the time_t format, and converted to
        /// a string.  However, that is not the only valid format.  Use this function to do the
        /// conversion, in case it is in another format.
        /// </summary>
        /// <param name="source">The input from the server.</param>
        /// <returns>The time.</returns>
        public static DateTime? DecodeServerTime(string source)
        {   // The preferred format for time is time_t.  Over the wire it is usually converted
            // between an integer and a string in the obvious way.  The other option is to send
            // the time in Eastern time.  In that case time is sent the time as a mysql string.
            // We store it as if it were local time.  That is to say that we store it in C# as
            // if we were in the eastern timezone.  And we lie and say that it is local time.
            long asNumber;
            double asDouble;
            if (long.TryParse(source, out asNumber))
                return FromTimeT(asNumber);
            else if (double.TryParse(source, out asDouble))
                return FromTimeT((int)asDouble);
            // This is currently a placeholder.  See the Delphi version of DecodeServerTime()
            // for more details.
            // TODO Add the second format.
            return null;
        }

        /// <summary>
        /// The standard dot net library will let you read but not set the current time zone.
        /// So we make our own variable.  Everyone should use ServerFormats.TimeZoneInfo rather
        /// than TimeZoneInfo.Local or TimeZone.CurrentTimeZone.  Most people only use the 
        /// timezone indirectly, so that's not a huge problem.  Use <see cref="ToTimeT"/>, <see cref="FromTimeT"/>, or <see cref="DecodeServerTime"/>
        /// to translate a time between "local" time and the server format.  And use
        /// ServerFormats.Now rather than DateTime.Now.  That should cover everything.
        /// </summary>
        static public TimeZoneInfo CurrentTimeZone = TimeZoneInfo.Local;

        /// <summary>
        /// Use this to get the current time in the same timezone as all of the data from the server.
        /// If you compare DateTime.Now to a time that this library creates, the results will make no
        /// sense.
        /// </summary>
        static public DateTime Now
        {
            get
            {
                return TimeZoneInfo.ConvertTime(DateTime.Now, CurrentTimeZone);
            }
        }

        /// <summary>
        /// Use this to get the current date in the same timezone as all of the data from the server.
        /// <seealso cref="Now"/>
        /// </summary>
        static public DateTime Today
        {
            get
            {
                DateTime saveNow = Now;
                return new DateTime(saveNow.Year, saveNow.Month, saveNow.Day);
            }
        }

        /// <summary>
        /// Use this to parse floating point numbers from the server.
        /// 
        /// Floating point numbers are the most obvious case to fail if you use the wrong culture.  Is
        /// "1,002" one thousand and two, or one and one five hundreth?  When talking to the server we always want
        /// a period to mean the decimal point.  We allow commas as number seperators,
        /// because they are used in a few places.
        /// </summary>
        /// <param name="source">A string from the server.</param>
        /// <param name="result">The result of the conversion or 0 on failure.</param>
        /// <returns>True if we were able to do the parsing.</returns>
        public static bool TryParse(string source, out double result)
        {
            return Double.TryParse(source, NumberStyles.Float | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out result);
        }

        /// <summary>
        /// Use this to parse integers from the server.
        /// This is not as interesting as parsing a floating point number, but we still
        /// want to allow a comma as a number
        /// seperator.  Sometimes the server will send things that way.  Also, if the user
        /// types a number, this will allow us to parse it the same way that the server
        /// would.
        /// </summary>
        /// <param name="source">The input from the server.</param>
        /// <param name="result">The result, or 0 if there was a problem.</param>
        /// <returns>True if the parse succeeded.</returns>
        public static bool TryParse(string source, out int result)
        {
            return Int32.TryParse(source, NumberStyles.Integer | NumberStyles.AllowThousands,
                                  CultureInfo.InvariantCulture, out result);
        }

        /// <summary>
        /// Use this to parse 64 bit integers from the server.
        /// This is not as interesting as parsing a floating point number, but we still
        /// want to allow a comma as a number
        /// seperator.  Sometimes the server will send things that way.  Also, if the user
        /// types a number, this will allow us to parse it the same way that the server
        /// would.
        /// </summary>
        /// <param name="source">The input from the server.</param>
        /// <param name="result">The result, or 0 if there was a problem.</param>
        /// <returns>True if the parse succeeded.</returns>
        public static bool TryParse(string source, out Int64 result)
        {
            return Int64.TryParse(source, NumberStyles.Integer | NumberStyles.AllowThousands,
                                  CultureInfo.InvariantCulture, out result);
        }

        /// <summary>
        /// Convert a double into a string that the server will understand.
        /// </summary>
        /// <param name="source">The number to convert.</param>
        /// <returns>The number as the server wants to see it.</returns>
        public static string ToString(double source)
        {   // This one doesn't have to be used in a lot of places.  You can send a double
            // as part of a message, and TalkWithServer.CreateMessageFromArray will call
            // this function.
            return source.ToString(CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Convert a double? into a string that the server will understand.
        /// If double? is null return empty string.
        /// </summary>
        /// <param name="source">The number to convert.</param>
        /// <returns>The number as the server wants to see it.</returns>
        public static string ToString(double? source)
        {   // This one doesn't have to be used in a lot of places.  Currently used in 
            // OddsMakerConfig when saving config settings.
            if (source == null)
                return "";
            double sourceDouble = (double)source;
            return sourceDouble.ToString(CultureInfo.InvariantCulture);
        }

        /// <summary>
        /// Convert text with abreviations to a double.
        /// Abbreviatoins K (thousands), M (millions), and B (billions).
        /// </summary>
        /// <param name="source">The string user entered.</param>
        /// <param name="result">The result, or 0 if there was a problem. </param>
        /// <returns>True if the parse succeeded.</returns>
        public static bool TryParseWithAbreviations(string source, out double result)
        {
            string textValue = source.ToUpperInvariant();
            // List of characters to exclude.
            char[] charSeparators = new char[] { ' ', 'K', 'M', 'B' };
            string[] splitText;
            double value;
            result = 0;
            // We are going to separate the text value from the blank spaces and abbreviations the user enters.
            splitText = textValue.Split(charSeparators, StringSplitOptions.RemoveEmptyEntries);
            if (splitText.Length == 1)
            {
                double factor = FactorTextBoxText(textValue);
                if (double.TryParse(splitText[0], out value))
                {
                    result = value * factor;
                    return true;
                }
            }
            return false;
        }

        /// <summary>
        /// Returns the factor associated with abbreviations for thousands, millions, and billions.
        /// If no abbreviations are found we return 1.
        /// </summary>
        /// <param name="text">The string that may </param>
        /// <returns>Factor associated with using abbreviations.</returns>
        private static double FactorTextBoxText(string text)
        {
            text = text.ToUpperInvariant();
            double factor = 1.0;
            if (text.Contains("K"))
                factor = 1000.0;
            else if (text.Contains("M"))
                factor = 1000000.0;
            else if (text.Contains("B"))
                factor = 1000000000.0;
            return factor;
        }
    }
}