// Copyright (c) Microsoft Corporation
// The Microsoft Corporation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Text;
using System.Text.RegularExpressions;
using Microsoft.PowerToys.Run.Plugin.TimeDate.Properties;

[assembly: InternalsVisibleTo("Microsoft.PowerToys.Run.Plugin.TimeDate.UnitTests")]

namespace Microsoft.PowerToys.Run.Plugin.TimeDate.Components
{
    internal static class TimeAndDateHelper
    {
        private static readonly Regex _regexSpecialInputFormats = new Regex(@"^.*(::)?(u|ums|ft|oa|exc|exf)[+-]\d");
        private static readonly Regex _regexCustomDateTimeFormats = new Regex(@"(?<!\\)(DOW|DIM|WOM|WOY|EAB|WFT|UXT|UMS|OAD|EXC|EXF)");
        private static readonly Regex _regexCustomDateTimeDow = new Regex(@"(?<!\\)DOW");
        private static readonly Regex _regexCustomDateTimeDim = new Regex(@"(?<!\\)DIM");
        private static readonly Regex _regexCustomDateTimeWom = new Regex(@"(?<!\\)WOM");
        private static readonly Regex _regexCustomDateTimeWoy = new Regex(@"(?<!\\)WOY");
        private static readonly Regex _regexCustomDateTimeEab = new Regex(@"(?<!\\)EAB");
        private static readonly Regex _regexCustomDateTimeWft = new Regex(@"(?<!\\)WFT");
        private static readonly Regex _regexCustomDateTimeUxt = new Regex(@"(?<!\\)UXT");
        private static readonly Regex _regexCustomDateTimeUms = new Regex(@"(?<!\\)UMS");
        private static readonly Regex _regexCustomDateTimeOad = new Regex(@"(?<!\\)OAD");
        private static readonly Regex _regexCustomDateTimeExc = new Regex(@"(?<!\\)EXC");
        private static readonly Regex _regexCustomDateTimeExf = new Regex(@"(?<!\\)EXF");

        private const long UnixTimeSecondsMin = -62135596800;
        private const long UnixTimeSecondsMax = 253402300799;
        private const long UnixTimeMillisecondsMin = -62135596800000;
        private const long UnixTimeMillisecondsMax = 253402300799999;
        private const long WindowsFileTimeMin = 0;
        private const long WindowsFileTimeMax = 2650467707991000000;
        private const double OADateMin = -657434.99999999;
        private const double OADateMax = 2958465.99999999;
        private const double Excel1900DateMin = 1;
        private const double Excel1900DateMax = 2958465.99998843;
        private const double Excel1904DateMin = 0;
        private const double Excel1904DateMax = 2957003.99998843;

        /// <summary>
        /// Get the format for the time string
        /// </summary>
        /// <param name="targetFormat">Type of format</param>
        /// <param name="timeLong">Show date with weekday and name of month (long format)</param>
        /// <param name="dateLong">Show time with seconds (long format)</param>
        /// <returns>String that identifies the time/date format (<see href="https://learn.microsoft.com/dotnet/api/system.datetime.tostring"/>)</returns>
        internal static string GetStringFormat(FormatStringType targetFormat, bool timeLong, bool dateLong)
        {
            switch (targetFormat)
            {
                case FormatStringType.Time:
                    return timeLong ? "T" : "t";
                case FormatStringType.Date:
                    return dateLong ? "D" : "d";
                case FormatStringType.DateTime:
                    if (timeLong & dateLong)
                    {
                        return "F"; // Friday, October 31, 2008 5:04:32 PM
                    }
                    else if (timeLong & !dateLong)
                    {
                        return "G"; // 10/31/2008 5:04:32 PM
                    }
                    else if (!timeLong & dateLong)
                    {
                        return "f"; // Friday, October 31, 2008 5:04 PM
                    }
                    else
                    {
                        // (!timeLong & !dateLong)
                        return "g"; // 10/31/2008 5:04 PM
                    }

                default:
                    return string.Empty; // Windows default based on current culture settings
            }
        }

        /// <summary>
        /// Returns the number week in the month (Used code from 'David Morton' from <see href="https://social.msdn.microsoft.com/Forums/vstudio/bf504bba-85cb-492d-a8f7-4ccabdf882cb/get-week-number-for-month"/>)
        /// </summary>
        /// <param name="date">date</param>
        /// <param name="formatSettingFirstDayOfWeek">Setting for the first day in the week.</param>
        /// <returns>Number of week in the month</returns>
        internal static int GetWeekOfMonth(DateTime date, DayOfWeek formatSettingFirstDayOfWeek)
        {
            int weekCount = 1;

            for (int i = 1; i <= date.Day; i++)
            {
                DateTime d = new(date.Year, date.Month, i);

                // Count week number +1 if day is the first day of a week and not day 1 of the month.
                // (If we count on day one of a month we would start the month with week number 2.)
                if (i > 1 && d.DayOfWeek == formatSettingFirstDayOfWeek)
                {
                    weekCount += 1;
                }
            }

            return weekCount;
        }

        /// <summary>
        /// Returns the number of the day in the week
        /// </summary>
        /// <param name="date">Date</param>
        /// <returns>Number of the day in the week</returns>
        internal static int GetNumberOfDayInWeek(DateTime date, DayOfWeek formatSettingFirstDayOfWeek)
        {
            int daysInWeek = 7;
            int adjustment = 1; // We count from 1 to 7 and not from 0 to 6

            return ((date.DayOfWeek + daysInWeek - formatSettingFirstDayOfWeek) % daysInWeek) + adjustment;
        }

        internal static double ConvertToOleAutomationFormat(DateTime date, OADateFormats type)
        {
            double v = date.ToOADate();

            switch (type)
            {
                case OADateFormats.Excel1904:
                    // Excel with base 1904: Adjust by -1462
                    v -= 1462;

                    // Date starts at 1/1/1904 = 0
                    if (Math.Truncate(v) < 0)
                    {
                        throw new ArgumentOutOfRangeException("Not a valid Excel date.", innerException: null);
                    }

                    return v;
                case OADateFormats.Excel1900:
                    // Excel with base 1900: Adjust by -1 if v < 61
                    v = v < 61 ? v - 1 : v;

                    // Date starts at 1/1/1900 = 1
                    if (Math.Truncate(v) < 1)
                    {
                        throw new ArgumentOutOfRangeException("Not a valid Excel date.", innerException: null);
                    }

                    return v;
                default:
                    // OLE Automation date: Return as is.
                    return v;
            }
        }

        /// <summary>
        /// Convert input string to a <see cref="DateTime"/> object in local time
        /// </summary>
        /// <param name="input">String with date/time</param>
        /// <param name="timestamp">The new <see cref="DateTime"/> object</param>
        /// <param name="inputParsingErrorMsg">Error message shown to the user</param>
        /// <returns>True on success; otherwise, false</returns>
        internal static bool ParseStringAsDateTime(in string input, out DateTime timestamp, out string inputParsingErrorMsg)
        {
            inputParsingErrorMsg = string.Empty;
            CompositeFormat errorMessage = CompositeFormat.Parse(Resources.Microsoft_plugin_timedate_InvalidInput_SupportedRange);

            if (DateTime.TryParse(input, out timestamp))
            {
                // Known date/time format
                return true;
            }
            else if (Regex.IsMatch(input, @"^u[\+-]?\d+$"))
            {
                // Unix time stamp
                // We use long instead of int, because int is too small after 03:14:07 UTC 2038-01-19
                var canParse = long.TryParse(input.TrimStart('u'), out var secondsU);

                // Value has to be in the range from -62135596800 to 253402300799
                if (!canParse || secondsU < UnixTimeSecondsMin || secondsU > UnixTimeSecondsMax)
                {
                    inputParsingErrorMsg = string.Format(CultureInfo.CurrentCulture, errorMessage, Resources.Microsoft_plugin_timedate_Unix, UnixTimeSecondsMin, UnixTimeSecondsMax);
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                timestamp = DateTimeOffset.FromUnixTimeSeconds(secondsU).LocalDateTime;
                return true;
            }
            else if (Regex.IsMatch(input, @"^ums[\+-]?\d+$"))
            {
                // Unix time stamp in milliseconds
                // We use long instead of int because int is too small after 03:14:07 UTC 2038-01-19
                var canParse = long.TryParse(input.TrimStart("ums".ToCharArray()), out var millisecondsUms);

                // Value has to be in the range from -62135596800000 to 253402300799999
                if (!canParse || millisecondsUms < UnixTimeMillisecondsMin || millisecondsUms > UnixTimeMillisecondsMax)
                {
                    inputParsingErrorMsg = string.Format(CultureInfo.CurrentCulture, errorMessage, Resources.Microsoft_plugin_timedate_Unix_Milliseconds, UnixTimeMillisecondsMin, UnixTimeMillisecondsMax);
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                timestamp = DateTimeOffset.FromUnixTimeMilliseconds(millisecondsUms).LocalDateTime;
                return true;
            }
            else if (Regex.IsMatch(input, @"^ft\d+$"))
            {
                var canParse = long.TryParse(input.TrimStart("ft".ToCharArray()), out var secondsFt);

                // Windows file time
                // Value has to be in the range from 0 to 2650467707991000000
                if (!canParse || secondsFt < WindowsFileTimeMin || secondsFt > WindowsFileTimeMax)
                {
                    inputParsingErrorMsg = string.Format(CultureInfo.CurrentCulture, errorMessage, Resources.Microsoft_plugin_timedate_WindowsFileTime, WindowsFileTimeMin, WindowsFileTimeMax);
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                // DateTime.FromFileTime returns as local time.
                timestamp = DateTime.FromFileTime(secondsFt);
                return true;
            }
            else if (Regex.IsMatch(input, @"^oa[+-]?\d+[,.0-9]*$"))
            {
                var canParse = double.TryParse(input.TrimStart("oa".ToCharArray()), out var oADate);

                // OLE Automation date
                // Input has to be in the range from -657434.99999999 to 2958465.99999999
                // DateTime.FromOADate returns as local time.
                if (!canParse || oADate < OADateMin || oADate > OADateMax)
                {
                    inputParsingErrorMsg = string.Format(CultureInfo.CurrentCulture, errorMessage, Resources.Microsoft_plugin_timedate_OADate, OADateMin, OADateMax);
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                timestamp = DateTime.FromOADate(oADate);
                return true;
            }
            else if (Regex.IsMatch(input, @"^exc[+-]?\d+[,.0-9]*$"))
            {
                var canParse = double.TryParse(input.TrimStart("exc".ToCharArray()), out var excDate);

                // Excel's 1900 date value
                // Input has to be in the range from 1 (0 = Fake date) to 2958465.99998843 and not 60 whole number
                // Because of a bug in Excel and the way it behaves before 3/1/1900 we have to adjust all inputs lower than 61 for +1
                // DateTime.FromOADate returns as local time.
                if (!canParse || excDate < 0 || excDate > Excel1900DateMax)
                {
                    // For the if itself we use 0 as min value that we can show a special message if input is 0.
                    inputParsingErrorMsg = string.Format(CultureInfo.CurrentCulture, errorMessage, Resources.Microsoft_plugin_timedate_Excel1900, Excel1900DateMin, Excel1900DateMax);
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                if (Math.Truncate(excDate) == 0 || Math.Truncate(excDate) == 60)
                {
                    inputParsingErrorMsg = Resources.Microsoft_plugin_timedate_InvalidInput_FakeExcel1900;
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                excDate = excDate <= 60 ? excDate + 1 : excDate;
                timestamp = DateTime.FromOADate(excDate);
                return true;
            }
            else if (Regex.IsMatch(input, @"^exf[+-]?\d+[,.0-9]*$"))
            {
                var canParse = double.TryParse(input.TrimStart("exf".ToCharArray()), out var exfDate);

                // Excel's 1904 date value
                // Input has to be in the range from 0 to 2957003.99998843
                // Because Excel uses 01/01/1904 as base we need to adjust for +1462
                // DateTime.FromOADate returns as local time.
                if (!canParse || exfDate < Excel1904DateMin || exfDate > Excel1904DateMax)
                {
                    inputParsingErrorMsg = string.Format(CultureInfo.CurrentCulture, errorMessage, Resources.Microsoft_plugin_timedate_Excel1904, Excel1904DateMin, Excel1904DateMax);
                    timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                    return false;
                }

                timestamp = DateTime.FromOADate(exfDate + 1462);
                return true;
            }
            else
            {
                timestamp = new DateTime(1, 1, 1, 1, 1, 1);
                return false;
            }
        }

        /// <summary>
        /// Test if input is special parsing for Unix time, Unix time in milliseconds, file time, ...
        /// </summary>
        /// <param name="input">String with date/time</param>
        /// <returns>True if yes; otherwise, false</returns>
        internal static bool IsSpecialInputParsing(string input)
        {
            return _regexSpecialInputFormats.IsMatch(input);
        }

        /// <summary>
        /// Converts a DateTime object based on the format string
        /// </summary>
        /// <param name="date">Date/time object.</param>
        /// <param name="unix">Value for replacing "Unix Time Stamp".</param>
        /// <param name="unixMilliseconds">Value for replacing "Unix Time Stamp in milliseconds".</param>
        /// <param name="calWeek">Value for relacing calendar week.</param>
        /// <param name="eraShortFormat">Era abbreviation.</param>
        /// <param name="format">Format definition.</param>
        /// <returns>Formated date/time string.</returns>
        internal static string ConvertToCustomFormat(DateTime date, long unix, long unixMilliseconds, int calWeek, string eraShortFormat, string format, CalendarWeekRule firstWeekRule, DayOfWeek firstDayOfTheWeek)
        {
            string result = format;

            // DOW: Number of day in week
            result = _regexCustomDateTimeDow.Replace(result, GetNumberOfDayInWeek(date, firstDayOfTheWeek).ToString(CultureInfo.CurrentCulture));

            // DIM: Days in Month
            result = _regexCustomDateTimeDim.Replace(result, DateTime.DaysInMonth(date.Year, date.Month).ToString(CultureInfo.CurrentCulture));

            // WOM: Week of Month
            result = _regexCustomDateTimeWom.Replace(result, GetWeekOfMonth(date, firstDayOfTheWeek).ToString(CultureInfo.CurrentCulture));

            // WOY: Week of Year
            result = _regexCustomDateTimeWoy.Replace(result, calWeek.ToString(CultureInfo.CurrentCulture));

            // EAB: Era abbreviation
            result = _regexCustomDateTimeEab.Replace(result, eraShortFormat);

            // WFT: Week of Month
            if (_regexCustomDateTimeWft.IsMatch(result))
            {
                // Special handling as very early dates can't convert.
                result = _regexCustomDateTimeWft.Replace(result, date.ToFileTime().ToString(CultureInfo.CurrentCulture));
            }

            // UXT: Unix time stamp
            result = _regexCustomDateTimeUxt.Replace(result, unix.ToString(CultureInfo.CurrentCulture));

            // UMS: Unix time stamp milli seconds
            result = _regexCustomDateTimeUms.Replace(result, unixMilliseconds.ToString(CultureInfo.CurrentCulture));

            // OAD: OLE Automation date
            result = _regexCustomDateTimeOad.Replace(result, ConvertToOleAutomationFormat(date, OADateFormats.OLEAutomation).ToString(CultureInfo.CurrentCulture));

            // EXC: Excel date value with base 1900
            if (_regexCustomDateTimeExc.IsMatch(result))
            {
                // Special handling as very early dates can't convert.
                result = _regexCustomDateTimeExc.Replace(result, ConvertToOleAutomationFormat(date, OADateFormats.Excel1900).ToString(CultureInfo.CurrentCulture));
            }

            // EXF: Excel date value with base 1904
            if (_regexCustomDateTimeExf.IsMatch(result))
            {
                // Special handling as very early dates can't convert.
                result = _regexCustomDateTimeExf.Replace(result, ConvertToOleAutomationFormat(date, OADateFormats.Excel1904).ToString(CultureInfo.CurrentCulture));
            }

            return result;
        }

        /// <summary>
        /// Test a string for our custom date and time format syntax
        /// </summary>
        /// <param name="str">String to test.</param>
        /// <returns>True if yes and otherwise false</returns>
        internal static bool StringContainsCustomFormatSyntax(string str)
        {
            return _regexCustomDateTimeFormats.IsMatch(str);
        }

        /// <summary>
        /// Returns a CalendarWeekRule enum value based on the plugin setting.
        /// </summary>
        internal static CalendarWeekRule GetCalendarWeekRule(int pluginSetting)
        {
            switch (pluginSetting)
            {
                case 0:
                    return CalendarWeekRule.FirstDay;
                case 1:
                    return CalendarWeekRule.FirstFullWeek;
                case 2:
                    return CalendarWeekRule.FirstFourDayWeek;
                default:
                    // Wrong json value and system setting (-1).
                    return DateTimeFormatInfo.CurrentInfo.CalendarWeekRule;
            }
        }

        /// <summary>
        /// Returns a DayOfWeek enum value based on the FirstDayOfWeek plugin setting.
        /// </summary>
        internal static DayOfWeek GetFirstDayOfWeek(int pluginSetting)
        {
            switch (pluginSetting)
            {
                case 0:
                    return DayOfWeek.Sunday;
                case 1:
                    return DayOfWeek.Monday;
                case 2:
                    return DayOfWeek.Tuesday;
                case 3:
                    return DayOfWeek.Wednesday;
                case 4:
                    return DayOfWeek.Thursday;
                case 5:
                    return DayOfWeek.Friday;
                case 6:
                    return DayOfWeek.Saturday;
                default:
                    // Wrong json value and system setting (-1).
                    return DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek;
            }
        }
    }

    /// <summary>
    /// Type of time/date format
    /// </summary>
    internal enum FormatStringType
    {
        Time,
        Date,
        DateTime,
    }

    /// <summary>
    /// Different versions of Date formats based on OLE Automation date
    /// </summary>
    internal enum OADateFormats
    {
        OLEAutomation,
        Excel1900,
        Excel1904,
    }
}