using Rubberduck.Parsing.Abstract;
using Rubberduck.Parsing.Grammar;
using Rubberduck.Parsing.Parsers;
using System.Globalization;

namespace Rubberduck.Parsing.Expressions;

public sealed class DateLiteralExpression : Expression
{
    private readonly IExpression _tokenText;

    public DateLiteralExpression(IExpression tokenText)
    {
        _tokenText = tokenText;
    }

    public override IValue Evaluate()
    {
        string literal = _tokenText.Evaluate().AsString;
        var parser = new VBADateLiteralParser();
        var dateLiteral = parser.Parse(literal);
        var dateOrTime = dateLiteral.dateOrTime();
        int year;
        int month;
        int day;
        int hours;
        int mins;
        int seconds;

        static bool legalMonth(int x) => x >= 0 && x <= 12;
        bool legalDay(int m, int d, int y)
        {
            bool legalYear = y >= 0 && y <= 32767;
            bool legalM = legalMonth(m);
            bool legalD = false;
            if (legalYear && legalM)
            {
                int daysInMonth = DateTime.DaysInMonth(y, m);
                legalD = d >= 1 && d <= daysInMonth;
            }
            return legalYear && legalM && legalD;
        }

        int yearFunc(int x)
        {
            if (x >= 0 && x <= 29)
            {
                return x + 2000;
            }
            else if (x >= 30 && x <= 99)
            {
                return x + 1900;
            }
            else
            {
                return x;
            }
        }

        int CY = DateTime.Now.Year;

        if (dateOrTime.dateValue() == null)
        {
            year = 1899;
            month = 12;
            day = 30;
        }
        else
        {
            var dateValue = dateOrTime.dateValue();
            var txt = dateOrTime.GetText();
            var L = dateValue.dateValuePart()[0];
            var M = dateValue.dateValuePart()[1];
            VBADateParser.DateValuePartContext R = null;
            if (dateValue.dateValuePart().Length == 3)
            {
                R = dateValue.dateValuePart()[2];
            }
            // "If L and M are numbers and R is not present:"
            if (L.dateValueNumber() != null && M.dateValueNumber() != null && R == null)
            {
                var LNumber = int.Parse(L.GetText(), CultureInfo.InvariantCulture);
                var MNumber = int.Parse(M.GetText(), CultureInfo.InvariantCulture);
                if (legalMonth(LNumber) && legalDay(LNumber, MNumber, CY))
                {
                    month = LNumber;
                    day = MNumber;
                    year = CY;
                }
                else if (legalMonth(MNumber) && legalDay(MNumber, LNumber, CY))
                {
                    month = MNumber;
                    day = LNumber;
                    year = CY;
                }
                else if (legalMonth(LNumber))
                {
                    month = LNumber;
                    day = 1;
                    year = MNumber;
                }
                else if (legalMonth(MNumber))
                {
                    month = MNumber;
                    day = 1;
                    year = LNumber;
                }
                else
                {
                    throw new Exception("Invalid date: " + dateLiteral.GetText());
                }
            }
            // "If L, M, and R are numbers:"
            else if (L.dateValueNumber() != null && M.dateValueNumber() != null && R != null && R.dateValueNumber() != null)
            {
                var LNumber = int.Parse(L.GetText(), CultureInfo.InvariantCulture);
                var MNumber = int.Parse(M.GetText(), CultureInfo.InvariantCulture);
                var RNumber = int.Parse(R.GetText(), CultureInfo.InvariantCulture);
                if (legalMonth(LNumber) && legalDay(LNumber, MNumber, yearFunc(RNumber)))
                {
                    month = LNumber;
                    day = MNumber;
                    year = yearFunc(RNumber);
                }
                else if (legalMonth(MNumber) && legalDay(MNumber, RNumber, yearFunc(LNumber)))
                {
                    month = MNumber;
                    day = RNumber;
                    year = yearFunc(LNumber);
                }
                else if (legalMonth(MNumber) && legalDay(MNumber, LNumber, yearFunc(RNumber)))
                {
                    month = MNumber;
                    day = LNumber;
                    year = yearFunc(RNumber);
                }
                else
                {
                    throw new Exception("Invalid date: " + dateLiteral.GetText());
                }
            }
            // "If either L or M is not a number and R is not present:"
            else if ((L.dateValueNumber() == null || M.dateValueNumber() == null) && R == null)
            {
                int N;
                string monthName;
                if (L.dateValueNumber() != null)
                {
                    N = int.Parse(L.GetText(), CultureInfo.InvariantCulture);
                    monthName = M.GetText();
                }
                else
                {
                    N = int.Parse(M.GetText(), CultureInfo.InvariantCulture);
                    monthName = L.GetText();
                }
                int monthNameNumber;
                if (monthName.Length == 3)
                {
                    monthNameNumber = DateTime.ParseExact(monthName, "MMM", CultureInfo.InvariantCulture).Month;
                }
                else
                {
                    monthNameNumber = DateTime.ParseExact(monthName, "MMMM", CultureInfo.InvariantCulture).Month;
                }
                if (legalDay(monthNameNumber, N, CY))
                {
                    month = monthNameNumber;
                    day = N;
                    year = CY;
                }
                else
                {
                    month = monthNameNumber;
                    day = 1;
                    year = N;
                }
            }
            // "Otherwise, R is present and one of L, M, and R is not a number:"
            else
            {
                int N1;
                int N2;
                string monthName;
                if (L.dateValueNumber() == null)
                {
                    monthName = L.GetText();
                    N1 = int.Parse(M.GetText(), CultureInfo.InvariantCulture);
                    N2 = int.Parse(R.GetText(), CultureInfo.InvariantCulture);
                }
                else if (M.dateValueNumber() == null)
                {
                    monthName = M.GetText();
                    N1 = int.Parse(L.GetText(), CultureInfo.InvariantCulture);
                    N2 = int.Parse(R.GetText(), CultureInfo.InvariantCulture);
                }
                else
                {
                    monthName = R.GetText();
                    N1 = int.Parse(L.GetText(), CultureInfo.InvariantCulture);
                    N2 = int.Parse(M.GetText(), CultureInfo.InvariantCulture);
                }
                int monthNameNumber;
                if (monthName.Length == 3)
                {
                    monthNameNumber = DateTime.ParseExact(monthName, "MMM", CultureInfo.InvariantCulture).Month;
                }
                else
                {
                    monthNameNumber = DateTime.ParseExact(monthName, "MMMM", CultureInfo.InvariantCulture).Month;
                }
                if (legalDay(monthNameNumber, N1, yearFunc(N2)))
                {
                    month = monthNameNumber;
                    day = N1;
                    year = yearFunc(N2);
                }
                else if (legalDay(monthNameNumber, N2, yearFunc(N1)))
                {
                    month = monthNameNumber;
                    day = N2;
                    year = yearFunc(N1);
                }
                else
                {
                    throw new Exception("Invalid date: " + dateLiteral.GetText());
                }
            }
        }

        if (dateOrTime.timeValue() == null)
        {
            hours = 0;
            mins = 0;
            seconds = 0;
        }
        else
        {
            var timeValue = dateOrTime.timeValue();
            hours = int.Parse(timeValue.timeValuePart()[0].GetText(), CultureInfo.InvariantCulture);
            if (timeValue.timeValuePart().Length == 1)
            {
                mins = 0;
            }
            else
            {
                mins = int.Parse(timeValue.timeValuePart()[1].GetText(), CultureInfo.InvariantCulture);
            }
            if (timeValue.timeValuePart().Length < 3)
            {
                seconds = 0;
            }
            else
            {
                seconds = int.Parse(timeValue.timeValuePart()[2].GetText(), CultureInfo.InvariantCulture);
            }
            var amPm = timeValue.AMPM();
            if (amPm != null && (amPm.GetText().ToUpper() == "P" || amPm.GetText().ToUpper() == "PM") && hours >= 0 && hours <= 11)
            {
                hours += 12;
            }
            else if (amPm != null && (amPm.GetText().ToUpper() == "A" || amPm.GetText().ToUpper() == "AM") && hours == 12)
            {
                hours = 0;
            }
        }
        return new DateValue(new DateTime(year, month, day, hours, mins, seconds));
    }
}
