using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace CAPI.Custom
{
    public class LeadTime : IComparable<LeadTime>
    {
        public string OriginalValue { get; protected set; }
        public string Unit { get; protected set; }
        public int Value {get; protected set; }

        public LeadTime(string stringValue)
        {
            OriginalValue = stringValue?.Trim();
            Value = LeadTimeUnits.ParseValue(stringValue);
            Unit = LeadTimeUnits.ParseUnit(stringValue);

            if (Value == 0) Unit = LeadTimeUnits.Stock;
        }

        public override string ToString()
        {
            if (LeadTimeUnits.Stock.Equals(Unit)) return Unit;

            var postfix = Value == 1 ? string.Empty : "s";
            return $"{Value} {Unit}{postfix}";
        }

        public int CompareTo(LeadTime other)
        {
            return this.ToTimeSpan().CompareTo(other.ToTimeSpan());
        }

        public TimeSpan ToTimeSpan()
        {
            return LeadTimeUnits.GetTimeSpanFromUnit(Unit)
                .Multiply(Value);
        }
    }

    public class LeadTimeUnits
    {
        public static string Stock => "STOCK";
        public static string Hours => "Hour";
        public static string Days => "Day";
        public static string Weeks => "Week";
        public static string Months => "Month";
        public static string[] GetSorted => new string[] { Stock, Hours, Days, Weeks, Months };

        static Dictionary<string, LeadTimeUnitInfo> unitInfos = new Dictionary<string, LeadTimeUnitInfo>()
        {
            { Months, new LeadTimeUnitInfo { Name = Months, Alternates = new string[]{ "mos", "m" } } },
            { Weeks, new LeadTimeUnitInfo { Name = Weeks, Alternates = new string[]{ "w" }, TimeSpan = new TimeSpan(days: 7, 0, 0, 0) } },
            { Days, new LeadTimeUnitInfo { Name = Days, Alternates = new string[]{ "d" }, TimeSpan = new TimeSpan(days: 1, 0, 0, 0) } },
            { Hours, new LeadTimeUnitInfo { Name = Hours, Alternates = new string[]{ "hrs", "hr", "h" }, TimeSpan = new TimeSpan(hours: 1, 0, 0) } },
            { Stock, new LeadTimeUnitInfo { Name = Stock, Alternates = new string[]{ }, TimeSpan = new TimeSpan() } }
        };

        public static TimeSpan GetTimeSpanFromUnit(string unit)
        {
            if (!GetSorted.Contains(unit)) return new TimeSpan();

            if (Months.Equals(unit, StringComparison.OrdinalIgnoreCase))
            {
                return DateTime.Today.AddMonths(1).Subtract(DateTime.Today);
            }

            return unitInfos[unit].TimeSpan;
        }

        static Regex regexInt = new Regex(@"\d+");
        public static int ParseValue(string value)
        {
            var matches = regexInt.Matches(value)
                .Cast<Match>()
                .Select(m => m.Value.TryParseInt())
                .Where(p => p.HasValue);

            return matches.Max().GetValueOrDefault();
        }

        public static string ParseUnit(string value)
        {
            string result = string.Empty;

            if (value.IsEmpty()) return Stock;

            foreach (var key in LeadTimeUnits.GetSorted.Reverse())
            {
                if (result.IsEmpty())
                {
                    if (value.ToLower().Contains(key.ToLower()))
                    {
                        result = key;
                    }
                    else
                    {
                        foreach(var alt in unitInfos[key].Alternates)
                        {
                            if (result.IsEmpty() && value.ToLower().Contains(alt.ToLower()))
                            {
                                result = key;
                            }
                        }
                    }
                }
            }

            if (result.IsEmpty()) result = Stock;

            return result;
        }

        class LeadTimeUnitInfo
        {
            public string Name { get; set; }
            public string[] Alternates { get; set; }
            public TimeSpan TimeSpan { get; set; }
        }
    }
}