using System;
using Robust.Client.Graphics;
using Robust.Client.Graphics.Drawing;
using Robust.Shared.Maths;
using Robust.Shared.ViewVariables;

namespace Robust.Client.UserInterface.Controls
{
    /// <summary>
    ///     Most common button type that draws text in a fancy box.
    /// </summary>
    public class Button : BaseButton
    {
        public const string StylePropertyStyleBox = "stylebox";
        public const string StylePseudoClassNormal = "normal";
        public const string StylePseudoClassHover = "hover";
        public const string StylePseudoClassDisabled = "disabled";
        public const string StylePseudoClassPressed = "pressed";
        private int? _textWidthCache;
        private string _text;

        public Button()
        {
            DrawModeChanged();
        }

        /// <summary>
        ///     How to align the text inside the button.
        /// </summary>
        [ViewVariables]
        public AlignMode TextAlign { get; set; } = AlignMode.Center;

        /// <summary>
        ///     If true, the button will allow shrinking and clip text
        ///     to prevent the text from going outside the bounds of the button.
        ///     If false, the minimum size will always fit the contained text.
        /// </summary>
        [ViewVariables]
        public bool ClipText { get; set; }

        /// <summary>
        ///     The text displayed by the button.
        /// </summary>
        [ViewVariables]
        public string Text
        {
            get => _text;
            set
            {
                _text = value;
                _textWidthCache = null;
                MinimumSizeChanged();
            }
        }

        private StyleBox ActualStyleBox
        {
            get
            {
                if (TryGetStyleProperty(StylePropertyStyleBox, out StyleBox box))
                {
                    return box;
                }

                return UserInterfaceManager.ThemeDefaults.ButtonStyle;
            }
        }

        public Font ActualFont
        {
            get
            {
                if (TryGetStyleProperty("font", out Font font))
                {
                    return font;
                }

                return UserInterfaceManager.ThemeDefaults.DefaultFont;
            }
        }

        public Color ActualFontColor
        {
            get
            {
                if (TryGetStyleProperty("font-color", out Color fontColor))
                {
                    return fontColor;
                }

                return FontColorOverride ?? Color.White;
            }
        }

        public Color? FontColorOverride { get; set; }
        public Color? FontColorDisabledOverride { get; set; }
        public Color? FontColorHoverOverride { get; set; }
        public Color? FontColorPressedOverride { get; set; }

        public enum AlignMode
        {
            /// <summary>
            ///     Text is aligned to the left of the button.
            /// </summary>
            Left = 0,

            /// <summary>
            ///     Text is aligned to the center of the button.
            /// </summary>
            Center = 1,

            /// <summary>
            ///     Text is aligned to the right of the button.
            /// </summary>
            Right = 2
        }

        protected internal override void Draw(DrawingHandleScreen handle)
        {
            base.Draw(handle);

            var style = ActualStyleBox;
            var drawBox = PixelSizeBox;
            style.Draw(handle, drawBox);

            if (_text == null)
            {
                return;
            }

            var contentBox = style.GetContentBox(drawBox);
            DrawTextInternal(handle, contentBox);
        }

        protected void DrawTextInternal(DrawingHandleScreen handle, UIBox2 box)
        {
            var width = EnsureWidthCache();
            var font = ActualFont;
            int drawOffset;

            if (box.Width < width)
            {
                drawOffset = 0;
            }
            else
            {
                switch (TextAlign)
                {
                    case AlignMode.Left:
                        drawOffset = 0;
                        break;
                    case AlignMode.Center:
                        drawOffset = (int) (box.Width - width) / 2;
                        break;
                    case AlignMode.Right:
                        drawOffset = (int) (box.Width - width);
                        break;
                    default:
                        throw new ArgumentOutOfRangeException();
                }
            }

            var color = ActualFontColor;
            var offsetY = (int) (box.Height - font.GetHeight(UIScale)) / 2;
            var baseLine = new Vector2i(drawOffset, offsetY + font.GetAscent(UIScale)) + box.TopLeft;

            foreach (var chr in _text)
            {
                if (!font.TryGetCharMetrics(chr, UIScale, out var metrics))
                {
                    continue;
                }

                if (!(ClipText && (baseLine.X < box.Left || baseLine.X + metrics.Advance > box.Right)))
                {
                    font.DrawChar(handle, chr, baseLine, UIScale, color);
                }

                baseLine += (metrics.Advance, 0);
            }
        }

        protected override Vector2 CalculateMinimumSize()
        {
            var style = ActualStyleBox;
            var font = ActualFont;

            var fontHeight = font.GetHeight(UIScale) / UIScale;

            if (ClipText)
            {
                return (0, fontHeight) + style.MinimumSize / UIScale;
            }

            var width = EnsureWidthCache();

            return (width / UIScale, fontHeight) + style.MinimumSize / UIScale;
        }

        protected override void DrawModeChanged()
        {
            switch (DrawMode)
            {
                case DrawModeEnum.Normal:
                    SetOnlyStylePseudoClass(StylePseudoClassNormal);
                    break;
                case DrawModeEnum.Pressed:
                    SetOnlyStylePseudoClass(StylePseudoClassPressed);
                    break;
                case DrawModeEnum.Hover:
                    SetOnlyStylePseudoClass(StylePseudoClassHover);
                    break;
                case DrawModeEnum.Disabled:
                    SetOnlyStylePseudoClass(StylePseudoClassDisabled);
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }
        }

        protected int EnsureWidthCache()
        {
            if (_textWidthCache.HasValue)
            {
                return _textWidthCache.Value;
            }

            if (_text == null)
            {
                _textWidthCache = 0;
                return 0;
            }

            var font = ActualFont;

            var textWidth = 0;
            foreach (var chr in _text)
            {
                var metrics = font.GetCharMetrics(chr, UIScale);
                if (metrics == null)
                {
                    continue;
                }

                textWidth += metrics.Value.Advance;
            }

            _textWidthCache = textWidth;
            return textWidth;
        }

        protected override void StylePropertiesChanged()
        {
            _textWidthCache = null;

            base.StylePropertiesChanged();
        }

        protected internal override void UIScaleChanged()
        {
            _textWidthCache = null;

            base.UIScaleChanged();
        }
    }
}