//
// TextValidateField.cs: single-line text editor with validation through providers.
//
// Authors:
//	José Miguel Perricone (jmperricone@hotmail.com)
//

using System.ComponentModel;
using System.Text.RegularExpressions;
using Terminal.Gui.TextValidateProviders;

namespace Terminal.Gui
{
    namespace TextValidateProviders
    {
        /// <summary>TextValidateField Providers Interface. All TextValidateField are created with a ITextValidateProvider.</summary>
        public interface ITextValidateProvider
        {
            /// <summary>Gets the formatted string for display.</summary>
            string DisplayText { get; }

            /// <summary>Set that this provider uses a fixed width. e.g. Masked ones are fixed.</summary>
            bool Fixed { get; }

            /// <summary>True if the input is valid, otherwise false.</summary>
            bool IsValid { get; }

            /// <summary>Set the input text and get the current value.</summary>
            string Text { get; set; }

            /// <summary>Set Cursor position to <paramref name="pos"/>.</summary>
            /// <param name="pos"></param>
            /// <returns>Return first valid position.</returns>
            int Cursor (int pos);

            /// <summary>Find the last valid character position.</summary>
            /// <returns>New cursor position.</returns>
            int CursorEnd ();

            /// <summary>First valid position before <paramref name="pos"/>.</summary>
            /// <param name="pos"></param>
            /// <returns>New cursor position if any, otherwise returns <paramref name="pos"/></returns>
            int CursorLeft (int pos);

            /// <summary>First valid position after <paramref name="pos"/>.</summary>
            /// <param name="pos">Current position.</param>
            /// <returns>New cursor position if any, otherwise returns <paramref name="pos"/></returns>
            int CursorRight (int pos);

            /// <summary>Find the first valid character position.</summary>
            /// <returns>New cursor position.</returns>
            int CursorStart ();

            /// <summary>Deletes the current character in <paramref name="pos"/>.</summary>
            /// <param name="pos"></param>
            /// <returns>true if the character was successfully removed, otherwise false.</returns>
            bool Delete (int pos);

            /// <summary>Insert character <paramref name="ch"/> in position <paramref name="pos"/>.</summary>
            /// <param name="ch"></param>
            /// <param name="pos"></param>
            /// <returns>true if the character was successfully inserted, otherwise false.</returns>
            bool InsertAt (char ch, int pos);

            /// <summary>Method that invoke the <see cref="TextChanged"/> event if it's defined.</summary>
            /// <param name="oldValue">The previous text before replaced.</param>
            /// <returns>Returns the <see cref="EventArgs{T}"/></returns>
            void OnTextChanged (EventArgs<string> oldValue);

            /// <summary>
            ///     Changed event, raised when the text has changed.
            ///     <remarks>
            ///         This event is raised when the <see cref="Text"/> changes. The passed <see cref="EventArgs"/> is a
            ///         <see cref="string"/> containing the old value.
            ///     </remarks>
            /// </summary>
            event EventHandler<EventArgs<string>> TextChanged;
        }

        //////////////////////////////////////////////////////////////////////////////
        // PROVIDERS
        //////////////////////////////////////////////////////////////////////////////

        #region NetMaskedTextProvider

        /// <summary>
        ///     .Net MaskedTextProvider Provider for TextValidateField.
        ///     <para></para>
        ///     <para>
        ///         <a
        ///             href="https://docs.microsoft.com/en-us/dotnet/api/system.componentmodel.maskedtextprovider?view=net-5.0">
        ///             Wrapper around MaskedTextProvider
        ///         </a>
        ///     </para>
        ///     <para>
        ///         <a
        ///             href="https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.maskedtextbox.mask?view=net-5.0">
        ///             Masking elements
        ///         </a>
        ///     </para>
        /// </summary>
        public class NetMaskedTextProvider : ITextValidateProvider
        {
            private MaskedTextProvider _provider;

            /// <summary>Empty Constructor</summary>
            public NetMaskedTextProvider (string mask) { Mask = mask; }

            /// <summary>Mask property</summary>
            public string Mask
            {
                get => _provider?.Mask;
                set
                {
                    string current = _provider != null
                                         ? _provider.ToString (false, false)
                                         : string.Empty;
                    _provider = new MaskedTextProvider (value == string.Empty ? "&&&&&&" : value);

                    if (!string.IsNullOrEmpty (current))
                    {
                        _provider.Set (current);
                    }
                }
            }

            /// <inheritdoc/>
            public event EventHandler<EventArgs<string>> TextChanged;

            /// <inheritdoc/>
            public string Text
            {
                get => _provider.ToString ();
                set => _provider.Set (value);
            }

            /// <inheritdoc/>
            public bool IsValid => _provider.MaskCompleted;

            /// <inheritdoc/>
            public bool Fixed => true;

            /// <inheritdoc/>
            public string DisplayText => _provider.ToDisplayString ();

            /// <inheritdoc/>
            public int Cursor (int pos)
            {
                if (pos < 0)
                {
                    return CursorStart ();
                }

                if (pos > _provider.Length)
                {
                    return CursorEnd ();
                }

                int p = _provider.FindEditPositionFrom (pos, false);

                if (p == -1)
                {
                    p = _provider.FindEditPositionFrom (pos, true);
                }

                return p;
            }

            /// <inheritdoc/>
            public int CursorStart ()
            {
                return _provider.IsEditPosition (0)
                           ? 0
                           : _provider.FindEditPositionFrom (0, true);
            }

            /// <inheritdoc/>
            public int CursorEnd ()
            {
                return _provider.IsEditPosition (_provider.Length - 1)
                           ? _provider.Length - 1
                           : _provider.FindEditPositionFrom (_provider.Length, false);
            }

            /// <inheritdoc/>
            public int CursorLeft (int pos)
            {
                int c = _provider.FindEditPositionFrom (pos - 1, false);

                return c == -1 ? pos : c;
            }

            /// <inheritdoc/>
            public int CursorRight (int pos)
            {
                int c = _provider.FindEditPositionFrom (pos + 1, true);

                return c == -1 ? pos : c;
            }

            /// <inheritdoc/>
            public bool Delete (int pos)
            {
                string oldValue = Text;
                bool result = _provider.Replace (' ', pos); // .RemoveAt (pos);

                if (result)
                {
                    OnTextChanged (new EventArgs<string> (in oldValue));
                }

                return result;
            }

            /// <inheritdoc/>
            public bool InsertAt (char ch, int pos)
            {
                string oldValue = Text;
                bool result = _provider.Replace (ch, pos);

                if (result)
                {
                    OnTextChanged (new EventArgs<string> (in oldValue));
                }

                return result;
            }

            /// <inheritdoc/>
            public void OnTextChanged (EventArgs<string> args) { TextChanged?.Invoke (this, args); }
        }

        #endregion

        #region TextRegexProvider

        /// <summary>Regex Provider for TextValidateField.</summary>
        public class TextRegexProvider : ITextValidateProvider
        {
            private List<Rune> _pattern;
            private Regex _regex;
            private List<Rune> _text;

            /// <summary>Empty Constructor.</summary>
            public TextRegexProvider (string pattern) { Pattern = pattern; }

            /// <summary>Regex pattern property.</summary>
            public string Pattern
            {
                get => StringExtensions.ToString (_pattern);
                set
                {
                    _pattern = value.ToRuneList ();
                    CompileMask ();
                    SetupText ();
                }
            }

            /// <summary>When true, validates with the regex pattern on each input, preventing the input if it's not valid.</summary>
            public bool ValidateOnInput { get; set; } = true;

            /// <inheritdoc/>
            public event EventHandler<EventArgs<string>> TextChanged;

            /// <inheritdoc/>
            public string Text
            {
                get => StringExtensions.ToString (_text);
                set
                {
                    _text = value != string.Empty ? value.ToRuneList () : null;
                    SetupText ();
                }
            }

            /// <inheritdoc/>
            public string DisplayText => Text;

            /// <inheritdoc/>
            public bool IsValid => Validate (_text);

            /// <inheritdoc/>
            public bool Fixed => false;

            /// <inheritdoc/>
            public int Cursor (int pos)
            {
                if (pos < 0)
                {
                    return CursorStart ();
                }

                if (pos >= _text.Count)
                {
                    return CursorEnd ();
                }

                return pos;
            }

            /// <inheritdoc/>
            public int CursorStart () { return 0; }

            /// <inheritdoc/>
            public int CursorEnd () { return _text.Count; }

            /// <inheritdoc/>
            public int CursorLeft (int pos)
            {
                if (pos > 0)
                {
                    return pos - 1;
                }

                return pos;
            }

            /// <inheritdoc/>
            public int CursorRight (int pos)
            {
                if (pos < _text.Count)
                {
                    return pos + 1;
                }

                return pos;
            }

            /// <inheritdoc/>
            public bool Delete (int pos)
            {
                if (_text.Count > 0 && pos < _text.Count)
                {
                    string oldValue = Text;
                    _text.RemoveAt (pos);
                    OnTextChanged (new EventArgs<string> (in oldValue));
                }

                return true;
            }

            /// <inheritdoc/>
            public bool InsertAt (char ch, int pos)
            {
                List<Rune> aux = _text.ToList ();
                aux.Insert (pos, (Rune)ch);

                if (Validate (aux) || ValidateOnInput == false)
                {
                    string oldValue = Text;
                    _text.Insert (pos, (Rune)ch);
                    OnTextChanged (new EventArgs<string> (in oldValue));

                    return true;
                }

                return false;
            }

            /// <inheritdoc/>
            public void OnTextChanged (EventArgs<string> args) { TextChanged?.Invoke (this, args); }

            /// <summary>Compiles the regex pattern for validation./></summary>
            private void CompileMask () { _regex = new Regex (StringExtensions.ToString (_pattern), RegexOptions.Compiled); }

            private void SetupText ()
            {
                if (_text is { } && IsValid)
                {
                    return;
                }

                _text = new List<Rune> ();
            }

            private bool Validate (List<Rune> text)
            {
                Match match = _regex.Match (StringExtensions.ToString (text));

                return match.Success;
            }
        }

        #endregion
    }

    /// <summary>Text field that validates input through a  <see cref="ITextValidateProvider"/></summary>
    public class TextValidateField : View
    {
        private readonly int _defaultLength = 10;
        private int _cursorPosition;
        private ITextValidateProvider _provider;

        /// <summary>
        ///     Initializes a new instance of the <see cref="TextValidateField"/> class.
        /// </summary>
        public TextValidateField ()
        {
            Height = Dim.Auto (minimumContentDim: 1);
            CanFocus = true;

            // Things this view knows how to do
            AddCommand (
                        Command.LeftStart,
                        () =>
                        {
                            HomeKeyHandler ();

                            return true;
                        }
                       );

            AddCommand (
                        Command.RightEnd,
                        () =>
                        {
                            EndKeyHandler ();

                            return true;
                        }
                       );

            AddCommand (
                        Command.DeleteCharRight,
                        () =>
                        {
                            DeleteKeyHandler ();

                            return true;
                        }
                       );

            AddCommand (
                        Command.DeleteCharLeft,
                        () =>
                        {
                            BackspaceKeyHandler ();

                            return true;
                        }
                       );

            AddCommand (
                        Command.Left,
                        () =>
                        {
                            CursorLeft ();

                            return true;
                        }
                       );

            AddCommand (
                        Command.Right,
                        () =>
                        {
                            CursorRight ();

                            return true;
                        }
                       );

            // Default keybindings for this view
            KeyBindings.Add (Key.Home, Command.LeftStart);
            KeyBindings.Add (Key.End, Command.RightEnd);

            KeyBindings.Add (Key.Delete, Command.DeleteCharRight);

            KeyBindings.Add (Key.Backspace, Command.DeleteCharLeft);
            KeyBindings.Add (Key.CursorLeft, Command.Left);
            KeyBindings.Add (Key.CursorRight, Command.Right);
        }

        /// <summary>This property returns true if the input is valid.</summary>
        public virtual bool IsValid
        {
            get
            {
                if (_provider is null)
                {
                    return false;
                }

                return _provider.IsValid;
            }
        }

        /// <summary>Provider</summary>
        public ITextValidateProvider Provider
        {
            get => _provider;
            set
            {
                _provider = value;

                if (_provider.Fixed)
                {
                    Width = _provider.DisplayText == string.Empty
                                ? _defaultLength
                                : _provider.DisplayText.Length;
                }

                // HomeKeyHandler already call SetNeedsDisplay
                HomeKeyHandler ();
            }
        }

        /// <summary>Text</summary>
        public new string Text
        {
            get
            {
                if (_provider is null)
                {
                    return string.Empty;
                }

                return _provider.Text;
            }
            set
            {
                if (_provider is null)
                {
                    return;
                }

                _provider.Text = value;

                SetNeedsDisplay ();
            }
        }

        /// <inheritdoc/>
        protected override bool OnMouseEvent (MouseEventArgs mouseEvent)
        {
            if (mouseEvent.Flags.HasFlag (MouseFlags.Button1Pressed))
            {
                int c = _provider.Cursor (mouseEvent.Position.X - GetMargins (Viewport.Width).left);

                if (_provider.Fixed == false && TextAlignment == Alignment.End && Text.Length > 0)
                {
                    c++;
                }

                _cursorPosition = c;
                SetFocus ();
                SetNeedsDisplay ();

                return true;
            }

            return false;
        }

        /// <inheritdoc/>
        protected override bool OnDrawingContent (Rectangle viewport)
        {
            if (_provider is null)
            {
                Move (0, 0);
                Driver?.AddStr ("Error: ITextValidateProvider not set!");

                return true;
            }

            Color bgcolor = !IsValid ? new Color (Color.BrightRed) : ColorScheme.Focus.Background;
            var textColor = new Attribute (ColorScheme.Focus.Foreground, bgcolor);

            (int margin_left, int margin_right) = GetMargins (Viewport.Width);

            Move (0, 0);

            // Left Margin
            Driver?.SetAttribute (textColor);

            for (var i = 0; i < margin_left; i++)
            {
                Driver?.AddRune ((Rune)' ');
            }

            // Content
            Driver?.SetAttribute (textColor);

            // Content
            for (var i = 0; i < _provider.DisplayText.Length; i++)
            {
                Driver?.AddRune ((Rune)_provider.DisplayText [i]);
            }

            // Right Margin
            Driver?.SetAttribute (textColor);

            for (var i = 0; i < margin_right; i++)
            {
                Driver?.AddRune ((Rune)' ');
            }

            return true;
        }

        /// <inheritdoc/>
        protected override bool OnKeyDownNotHandled (Key a)
        {
            if (_provider is null)
            {
                return false;
            }

            if (a.AsRune == default (Rune))
            {
                return false;
            }

            Rune key = a.AsRune;

            bool inserted = _provider.InsertAt ((char)key.Value, _cursorPosition);

            if (inserted)
            {
                CursorRight ();
            }

            return false;
        }

        /// <inheritdoc/>
        public override Point? PositionCursor ()
        {
            (int left, _) = GetMargins (Viewport.Width);

            // Fixed = true, is for inputs that have fixed width, like masked ones.
            // Fixed = false, is for normal input.
            // When it's right-aligned and it's a normal input, the cursor behaves differently.
            int curPos;

            if (_provider?.Fixed == false && TextAlignment == Alignment.End)
            {
                curPos = _cursorPosition + left - 1;
            }
            else
            {
                curPos = _cursorPosition + left;
            }
            Move (curPos, 0);

            return new (curPos, 0);
        }

        /// <summary>Delete char at cursor position - 1, moving the cursor.</summary>
        /// <returns></returns>
        private bool BackspaceKeyHandler ()
        {
            if (_provider.Fixed == false && TextAlignment == Alignment.End && _cursorPosition <= 1)
            {
                return false;
            }

            _cursorPosition = _provider.CursorLeft (_cursorPosition);
            _provider.Delete (_cursorPosition);
            SetNeedsDisplay ();

            return true;
        }

        /// <summary>Try to move the cursor to the left.</summary>
        /// <returns>True if moved.</returns>
        private bool CursorLeft ()
        {
            if (_provider is null)
            {
                return false;
            }

            int current = _cursorPosition;
            _cursorPosition = _provider.CursorLeft (_cursorPosition);
            SetNeedsDisplay ();

            return current != _cursorPosition;
        }

        /// <summary>Try to move the cursor to the right.</summary>
        /// <returns>True if moved.</returns>
        private bool CursorRight ()
        {
            if (_provider is null)
            {
                return false;
            }

            int current = _cursorPosition;
            _cursorPosition = _provider.CursorRight (_cursorPosition);
            SetNeedsDisplay ();

            return current != _cursorPosition;
        }

        /// <summary>Deletes char at current position.</summary>
        /// <returns></returns>
        private bool DeleteKeyHandler ()
        {
            if (_provider.Fixed == false && TextAlignment == Alignment.End)
            {
                _cursorPosition = _provider.CursorLeft (_cursorPosition);
            }

            _provider.Delete (_cursorPosition);
            SetNeedsDisplay ();

            return true;
        }

        /// <summary>Moves the cursor to the last char.</summary>
        /// <returns></returns>
        private bool EndKeyHandler ()
        {
            _cursorPosition = _provider.CursorEnd ();
            SetNeedsDisplay ();

            return true;
        }

        /// <summary>Margins for text alignment.</summary>
        /// <param name="width">Total width</param>
        /// <returns>Left and right margins</returns>
        private (int left, int right) GetMargins (int width)
        {
            int count = Text.Length;
            int total = width - count;

            switch (TextAlignment)
            {
                case Alignment.Start:
                    return (0, total);
                case Alignment.Center:
                    return (total / 2, total / 2 + total % 2);
                case Alignment.End:
                    return (total, 0);
                default:
                    return (0, total);
            }
        }

        /// <summary>Moves the cursor to first char.</summary>
        /// <returns></returns>
        private bool HomeKeyHandler ()
        {
            _cursorPosition = _provider.CursorStart ();
            SetNeedsDisplay ();

            return true;
        }
    }
}