//
// TimeField.cs: text entry for time
//
// Author: Jörg Preiß
//
// Licensed under the MIT license
using System;
using System.Globalization;
using System.Linq;
using NStack;

namespace Terminal.Gui {
	/// <summary>
	///   Time editing <see cref="View"/>
	/// </summary>
	/// <remarks>
	///   The <see cref="TimeField"/> <see cref="View"/> provides time editing functionality with mouse support.
	/// </remarks>
	public class TimeField : TextField {
		TimeSpan time;
		bool isShort;

		int longFieldLen = 8;
		int shortFieldLen = 5;
		string sepChar;
		string longFormat;
		string shortFormat;

		int fieldLen => isShort ? shortFieldLen : longFieldLen;
		string format => isShort ? shortFormat : longFormat;

		/// <summary>
		///   TimeChanged event, raised when the Date has changed.
		/// </summary>
		/// <remarks>
		///   This event is raised when the <see cref="Time"/> changes.
		/// </remarks>
		/// <remarks>
		///   The passed <see cref="EventArgs"/> is a <see cref="DateTimeEventArgs{T}"/> containing the old value, new value, and format string.
		/// </remarks>
		public event EventHandler<DateTimeEventArgs<TimeSpan>> TimeChanged;

		/// <summary>
		///    Initializes a new instance of <see cref="TimeField"/> using <see cref="LayoutStyle.Absolute"/> positioning.
		/// </summary>
		/// <param name="x">The x coordinate.</param>
		/// <param name="y">The y coordinate.</param>
		/// <param name="time">Initial time.</param>
		/// <param name="isShort">If true, the seconds are hidden. Sets the <see cref="IsShortFormat"/> property.</param>
		public TimeField (int x, int y, TimeSpan time, bool isShort = false) : base (x, y, isShort ? 7 : 10, "")
		{
			Initialize (time, isShort);
		}

		/// <summary>
		///    Initializes a new instance of <see cref="TimeField"/> using <see cref="LayoutStyle.Computed"/> positioning.
		/// </summary>
		/// <param name="time">Initial time</param>
		public TimeField (TimeSpan time) : base (string.Empty)
		{
			Width = fieldLen + 2;
			Initialize (time);
		}

		/// <summary>
		///    Initializes a new instance of <see cref="TimeField"/> using <see cref="LayoutStyle.Computed"/> positioning.
		/// </summary>
		public TimeField () : this (time: TimeSpan.MinValue) { }

		void Initialize (TimeSpan time, bool isShort = false)
		{
			CultureInfo cultureInfo = CultureInfo.CurrentCulture;
			sepChar = cultureInfo.DateTimeFormat.TimeSeparator;
			longFormat = $" hh\\{sepChar}mm\\{sepChar}ss";
			shortFormat = $" hh\\{sepChar}mm";
			this.isShort = isShort;
			Time = time;
			CursorPosition = 1;
			TextChanged += TextField_TextChanged;

			// Things this view knows how to do
			AddCommand (Command.DeleteCharRight, () => { DeleteCharRight (); return true; });
			AddCommand (Command.DeleteCharLeft, () => { DeleteCharLeft (); return true; });
			AddCommand (Command.LeftHome, () => MoveHome ());
			AddCommand (Command.Left, () => MoveLeft ());
			AddCommand (Command.RightEnd, () => MoveEnd ());
			AddCommand (Command.Right, () => MoveRight ());

			// Default keybindings for this view
			AddKeyBinding (Key.DeleteChar, Command.DeleteCharRight);
			AddKeyBinding (Key.D | Key.CtrlMask, Command.DeleteCharRight);

			AddKeyBinding (Key.Delete, Command.DeleteCharLeft);
			AddKeyBinding (Key.Backspace, Command.DeleteCharLeft);

			AddKeyBinding (Key.Home, Command.LeftHome);
			AddKeyBinding (Key.A | Key.CtrlMask, Command.LeftHome);

			AddKeyBinding (Key.CursorLeft, Command.Left);
			AddKeyBinding (Key.B | Key.CtrlMask, Command.Left);

			AddKeyBinding (Key.End, Command.RightEnd);
			AddKeyBinding (Key.E | Key.CtrlMask, Command.RightEnd);

			AddKeyBinding (Key.CursorRight, Command.Right);
			AddKeyBinding (Key.F | Key.CtrlMask, Command.Right);
		}

		void TextField_TextChanged (object sender, TextChangedEventArgs e)
		{
			try {
				if (!TimeSpan.TryParseExact (Text.ToString ().Trim (), format.Trim (), CultureInfo.CurrentCulture, TimeSpanStyles.None, out TimeSpan result))
					Text = e.OldValue;
			} catch (Exception) {
				Text = e.OldValue;
			}
		}

		/// <summary>
		///   Gets or sets the time of the <see cref="TimeField"/>.
		/// </summary>
		/// <remarks>
		/// </remarks>
		public TimeSpan Time {
			get {
				return time;
			}
			set {
				if (ReadOnly)
					return;

				var oldTime = time;
				time = value;
				this.Text = " " + value.ToString (format.Trim ());
				var args = new DateTimeEventArgs<TimeSpan> (oldTime, value, format);
				if (oldTime != value) {
					OnTimeChanged (args);
				}
			}
		}

		/// <summary>
		/// Get or sets whether <see cref="TimeField"/> uses the short or long time format.
		/// </summary>
		public bool IsShortFormat {
			get => isShort;
			set {
				isShort = value;
				if (isShort)
					Width = 7;
				else
					Width = 10;
				var ro = ReadOnly;
				if (ro)
					ReadOnly = false;
				SetText (Text);
				ReadOnly = ro;
				SetNeedsDisplay ();
			}
		}

		/// <inheritdoc/>
		public override int CursorPosition {
			get => base.CursorPosition;
			set {
				base.CursorPosition = Math.Max (Math.Min (value, fieldLen), 1);
			}
		}

		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)
		{
			if (text.IsEmpty) {
				return false;
			}

			ustring [] vals = text.Split (ustring.Make (sepChar));
			bool isValidTime = true;
			int hour = Int32.Parse (vals [0].ToString ());
			int minute = Int32.Parse (vals [1].ToString ());
			int second = isShort ? 0 : vals.Length > 2 ? Int32.Parse (vals [2].ToString ()) : 0;
			if (hour < 0) {
				isValidTime = false;
				hour = 0;
				vals [0] = "0";
			} else if (hour > 23) {
				isValidTime = false;
				hour = 23;
				vals [0] = "23";
			}
			if (minute < 0) {
				isValidTime = false;
				minute = 0;
				vals [1] = "0";
			} else if (minute > 59) {
				isValidTime = false;
				minute = 59;
				vals [1] = "59";
			}
			if (second < 0) {
				isValidTime = false;
				second = 0;
				vals [2] = "0";
			} else if (second > 59) {
				isValidTime = false;
				second = 59;
				vals [2] = "59";
			}
			string t = isShort ? $" {hour,2:00}{sepChar}{minute,2:00}" : $" {hour,2:00}{sepChar}{minute,2:00}{sepChar}{second,2:00}";

			if (!TimeSpan.TryParseExact (t.Trim (), format.Trim (), CultureInfo.CurrentCulture, TimeSpanStyles.None, out TimeSpan result) ||
				!isValidTime)
				return false;
			Time = result;
			return true;
		}

		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++;
		}

		///<inheritdoc/>
		public override bool ProcessKey (KeyEvent kb)
		{
			var result = InvokeKeybindings (kb);
			if (result != null)
				return (bool)result;

			// Ignore non-numeric characters.
			if (kb.Key < (Key)((int)Key.D0) || kb.Key > (Key)((int)Key.D9))
				return false;

			if (ReadOnly)
				return true;

			if (SetText (TextModel.ToRunes (ustring.Make ((uint)kb.Key)).First ()))
				IncCursorPosition ();

			return true;
		}

		bool MoveRight ()
		{
			IncCursorPosition ();
			return true;
		}

		bool MoveEnd ()
		{
			CursorPosition = fieldLen;
			return true;
		}

		bool MoveLeft ()
		{
			DecCursorPosition ();
			return true;
		}

		bool MoveHome ()
		{
			// Home, C-A
			CursorPosition = 1;
			return true;
		}

		/// <inheritdoc/>
		public override void DeleteCharLeft (bool useOldCursorPos = true)
		{
			if (ReadOnly)
				return;

			SetText ('0');
			DecCursorPosition ();
			return;
		}

		/// <inheritdoc/>
		public override void DeleteCharRight ()
		{
			if (ReadOnly)
				return;

			SetText ('0');
			return;
		}

		///<inheritdoc/>
		public override bool MouseEvent (MouseEvent ev)
		{
			if (!ev.Flags.HasFlag (MouseFlags.Button1Clicked))
				return false;
			if (!HasFocus)
				SetFocus ();

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

		/// <summary>
		/// Event firing method that invokes the <see cref="TimeChanged"/> event.
		/// </summary>
		/// <param name="args">The event arguments</param>
		public virtual void OnTimeChanged (DateTimeEventArgs<TimeSpan> args)
		{
			TimeChanged?.Invoke (this,args);
		}
	}
}