//
// DateField.cs: text entry for date
//
// Author: Barry Nolte
//
// Licensed under the MIT license
//
using System;
using System.Globalization;
using System.Linq;
using NStack;

namespace Terminal.Gui {

	/// <summary>
	///   Date edit widget
	/// </summary>
	/// <remarks>
	///   This widget provides date editing functionality, and mouse support.
	/// </remarks>
	public class DateField : TextField {
		bool isShort;

		int longFieldLen = 10;
		int shortFieldLen = 8;
		int FieldLen { get { return isShort ? shortFieldLen : longFieldLen; } }
		string sepChar;
		string longFormat;
		string shortFormat;
		string Format { get { return isShort ? shortFormat : longFormat; } }


		/// <summary>
		///    Public constructor that creates a date edit field at an absolute position and fixed size.
		/// </summary>
		/// <param name="x">The x coordinate.</param>
		/// <param name="y">The y coordinate.</param>
		/// <param name="date">Initial date contents.</param>
		/// <param name="isShort">If true, shows only two digits for the year.</param>
		public DateField(int x, int y, DateTime date, bool isShort = false) : base(x, y, isShort ? 10 : 12, "")
		{
			CultureInfo cultureInfo = CultureInfo.CurrentCulture;
			sepChar = cultureInfo.DateTimeFormat.DateSeparator;
			longFormat = $" {cultureInfo.DateTimeFormat.ShortDatePattern}";
			shortFormat = GetShortFormat(longFormat);
			this.isShort = isShort;
			CursorPosition = 1;
			Date = date;
			Changed += DateField_Changed;
		}

		void DateField_Changed(object sender, ustring e)
		{
			if (!DateTime.TryParseExact(Text.ToString(), Format, CultureInfo.CurrentCulture, DateTimeStyles.None, out DateTime result))
				Text = e;
		}

		string GetShortFormat(string lf)
		{
			return lf.Replace("yyyy", "yy");
		}

		/// <summary>
		///   Gets or sets the date in the widget.
		/// </summary>
		/// <remarks>
		/// </remarks>
		public DateTime Date {
			get {
				if (!DateTime.TryParseExact(Text.ToString(), Format, CultureInfo.CurrentCulture, DateTimeStyles.None, out DateTime result)) return new DateTime();
				return result;
			}
			set {
				this.Text = value.ToString(Format);
			}
		}

		bool SetText(Rune key)
		{
			var text = TextModel.ToRunes(Text);
			var newText = text.GetRange(0, CursorPosition);
			newText.Add(key);
			if (CursorPosition < FieldLen)
				newText = newText.Concat(text.GetRange(CursorPosition + 1, text.Count - (CursorPosition + 1))).ToList();
			return SetText(ustring.Make(newText));
		}

		bool SetText(ustring text)
		{
			ustring[] vals = text.Split(ustring.Make(sepChar));
			ustring[] frm = ustring.Make(Format).Split(ustring.Make(sepChar));
			bool isValidDate = true;
			int idx = GetFormatIndex(frm, "y");
			int year = Int32.Parse(vals[idx].ToString());
			int month;
			int day;
			idx = GetFormatIndex(frm, "M");
			if (Int32.Parse(vals[idx].ToString()) < 1) {
				isValidDate = false;
				month = 1;
				vals[idx] = "1";
			} else if (Int32.Parse(vals[idx].ToString()) > 12) {
				isValidDate = false;
				month = 12;
				vals[idx] = "12";
			} else
				month = Int32.Parse(vals[idx].ToString());
			idx = GetFormatIndex(frm, "d");
			if (Int32.Parse(vals[idx].ToString()) < 1) {
				isValidDate = false;
				day = 1;
				vals[idx] = "1";
			} else if (Int32.Parse(vals[idx].ToString()) > 31) {
				isValidDate = false;
				day = DateTime.DaysInMonth(year, month);
				vals[idx] = day.ToString();
			} else
				day = Int32.Parse(vals[idx].ToString());
			string date = GetData(month, day, year, frm);
			Text = date;

			if (!DateTime.TryParseExact(date, Format, CultureInfo.CurrentCulture, DateTimeStyles.None, out DateTime result) ||
				!isValidDate)
				return false;
			return true;
		}

		string GetData(int month, int day, int year, ustring[] fm)
		{
			string data = " ";
			for (int i = 0; i < fm.Length; i++) {
				if (fm[i].Contains("M"))
					data += $"{month,2:00}";
				else if (fm[i].Contains("d"))
					data += $"{day,2:00}";
				else
					data += isShort ? $"{year,2:00}" : $"{year,4:0000}";
				if (i < 2)
					data += $"{sepChar}";
			}
			return data;
		}

		int GetFormatIndex(ustring[] fm, string t)
		{
			int idx = -1;
			for (int i = 0; i < fm.Length; i++) {
				if (fm[i].Contains(t)) {
					idx = i;
					break;
				}
			}
			return idx;
		}

		void IncCursorPosition()
		{
			if (CursorPosition == FieldLen)
				return;
			if (Text[++CursorPosition] == sepChar.ToCharArray()[0])
				CursorPosition++;
		}

		void DecCursorPosition()
		{
			if (CursorPosition == 1)
				return;
			if (Text[--CursorPosition] == sepChar.ToCharArray()[0])
				CursorPosition--;
		}

		void AdjCursorPosition()
		{
			if (Text[CursorPosition] == sepChar.ToCharArray()[0])
				CursorPosition++;
		}

		public override bool ProcessKey(KeyEvent kb)
		{
			switch (kb.Key) {
			case Key.DeleteChar:
			case Key.ControlD:
				SetText('0');
				break;

			case Key.Delete:
			case Key.Backspace:
				SetText('0');
				DecCursorPosition();
				break;

			// Home, C-A
			case Key.Home:
			case Key.ControlA:
				CursorPosition = 1;
				break;

			case Key.CursorLeft:
			case Key.ControlB:
				DecCursorPosition();
				break;

			case Key.End:
			case Key.ControlE: // End
				CursorPosition = FieldLen;
				break;

			case Key.CursorRight:
			case Key.ControlF:
				IncCursorPosition();
				break;

			default:
				// Ignore non-numeric characters.
				if (kb.Key < (Key)((int)'0') || kb.Key > (Key)((int)'9'))
					return false;
				if (SetText(TextModel.ToRunes(ustring.Make((uint)kb.Key)).First()))
					IncCursorPosition();
				return true;
			}
			return true;
		}

		public override bool MouseEvent(MouseEvent ev)
		{
			if (!ev.Flags.HasFlag(MouseFlags.Button1Clicked))
				return false;
			if (!HasFocus)
				SuperView.SetFocus(this);

			var point = ev.X;
			if (point > FieldLen)
				point = FieldLen;
			if (point < 1)
				point = 1;
			CursorPosition = point;
			AdjCursorPosition();
			return true;
		}
	}
}