using System;
using System.Diagnostics.CodeAnalysis;
using System.Drawing;
using System.Net.Http;
using System.Numerics;
using System.Text;
using Dashboard.Drawing;

namespace Dashboard.ImmediateUI
{
    public class DimUIConfig
    {
        public Vector2 Margin = new Vector2(8, 4);
        public Vector2 Padding = new Vector2(4);
        public required IFont Font { get; init; }

        public IBrush TextBrush = new SolidBrush(Color.Black);
        public IBrush DisabledText = new SolidBrush(Color.Gray);

        public float ButtonBorderSize = 2f;
        public IBrush ButtonBorderBrush = new SolidBrush(Color.SteelBlue);
        public IBrush ButtonFillBrush = new SolidBrush(Color.SlateGray);
        public IBrush? ButtonShadowBrush = new SolidBrush(Color.FromArgb(32, Color.LightSteelBlue));
        public float ButtonShadowOffset = 2f;

        public float InputBorderSize = 2f;
        public IBrush InputPlaceholderTextBrush = new SolidBrush(Color.SteelBlue);
        public IBrush InputBorderBrush = new SolidBrush(Color.SlateGray);
        public IBrush InputFillBrush = new SolidBrush(Color.LightGray);
        public IBrush? InputShadowBrush = new SolidBrush(Color.FromArgb(32, Color.LightSteelBlue));
        public float InputShadowOffset = -2f;

        public float MenuBorderSize = 2f;
        public IBrush MenuBorderBrush = new SolidBrush(Color.SteelBlue);
        public IBrush MenuFillBrush = new SolidBrush(Color.SlateGray);
        public IBrush? MenuShadowBrush = new SolidBrush(Color.FromArgb(32, Color.LightSteelBlue));
        public float MenuShadowOffset = 2f;
    }

    public class DimUI
    {
        private readonly DimUIConfig _config;
        private Vector2 _pen;
        private Box2d _bounds;
        private bool _firstLine = false;
        private bool _sameLine = false;
        private float _z = -1;
        private float _lineHeight;
        private DrawQueue _queue;

        public DimUI(DimUIConfig config)
        {
            _config = config;
        }

        [MemberNotNull(nameof(_queue))]
        public void Begin(Box2d bounds, DrawQueue queue)
        {
            _bounds = bounds;
            _pen = _bounds.Min;
            _queue = queue;
            _firstLine = true;
            _lineHeight = 0;
            _z = -1;
        }

        public void SameLine()
        {
            _sameLine = true;
        }

        private void Line()
        {
            if (!_firstLine && !_sameLine)
            {
                _pen = new Vector2(_bounds.Left, _pen.Y + _lineHeight);
            }
            else
            {
                _firstLine = false;
                _sameLine = false;
            }

            _pen.X += _config.Margin.X;
            _lineHeight = 0;
        }

        private float Z()
        {
            return _z += 0.001f;
        }

        public void Text(string text)
        {
            Line();

            SizeF sz = Typesetter.MeasureString(_config.Font, text);
            float z = Z();
            float h = _config.Margin.Y * 2 + sz.Height;
            _queue.Text(new Vector3(_pen + new Vector2(0, _config.Margin.X), z), _config.TextBrush, text, _config.Font);

            _lineHeight = Math.Max(_lineHeight, h);
            _pen.X += sz.Width;
        }

        public void DrawBox(
            Vector2 position,
            Vector2 size,
            IBrush fill,
            IBrush border, float borderWidth,
            IBrush? shadow, float offset)
        {
            float z = Z();

            if (shadow != null)
            {
                if (offset >= 0)
                {
                    _queue.Rect(position + new Vector2(offset), position + size + new Vector2(offset + borderWidth), z, shadow);
                }
                else
                {
                    // Inset shadows are draw a bit weirdly.
                    _queue.Rect(position, position + new Vector2(offset, size.Y), z, shadow);
                    _queue.Rect(position + new Vector2(offset, 0), position + new Vector2(size.X - offset, offset), z, shadow);
                }
            }

            _queue.Rect(position, position + size, z, fill, border, borderWidth, BorderKind.Outset);
        }

        public bool Button(string label)
        {
            Line();

            SizeF sz = Typesetter.MeasureString(_config.Font, label);

            float h = _config.Margin.Y * 2 + _config.Padding.Y * 2 + sz.Height;
            DrawBox(
                _pen + new Vector2(0, _config.Margin.Y),
                new Vector2(sz.Width + 2 * _config.Padding.X, sz.Height + 2 * _config.Padding.Y),
                _config.ButtonFillBrush,
                _config.ButtonBorderBrush,
                _config.ButtonBorderSize,
                _config.ButtonShadowBrush,
                _config.ButtonShadowOffset);

            float z = Z();

            _queue.Text(new Vector3(_pen + new Vector2(_config.Padding.X, _config.Margin.Y + _config.Padding.Y), z),
                _config.TextBrush, label, _config.Font);
            _lineHeight = Math.Max(_lineHeight, h);

            _pen.X += sz.Width + 2 * _config.Padding.X;
            return false;
        }

        public bool Input(string placeholder, StringBuilder value)
        {
            Line();

            IBrush textBrush;
            string str;
            if (value.Length == 0)
            {
                textBrush = _config.DisabledText;
                str = placeholder;
            }
            else
            {
                textBrush = _config.TextBrush;
                str = value.ToString();
            }

            SizeF sz = Typesetter.MeasureString(_config.Font, str);

            float h = _config.Margin.Y * 2 + _config.Padding.Y * 2 + sz.Height;
            DrawBox(
                _pen + new Vector2(0, _config.Margin.Y),
                new Vector2(sz.Width + 2 * _config.Padding.X, sz.Height + 2 * _config.Padding.Y),
                _config.InputFillBrush,
                _config.InputBorderBrush,
                _config.InputBorderSize,
                _config.InputShadowBrush,
                _config.InputShadowOffset);

            float z = Z();

            _queue.Text(new Vector3(_pen + new Vector2(_config.Padding.X, _config.Margin.Y + _config.Padding.Y), z),
                textBrush, str, _config.Font);
            _lineHeight = Math.Max(_lineHeight, h);

            _pen.X += sz.Width + 2 * _config.Padding.X;
            return false;
        }

        public void BeginMenu()
        {

        }

        public bool MenuItem(string name)
        {
            return false;
        }

        public void EndMenu()
        {

        }

        public int Id(ReadOnlySpan<char> str)
        {
            // Uses the FVN-1A algorithm in 32-bit mode.
            const int PRIME = 0x01000193;
            const int BASIS = unchecked((int)0x811c9dc5);

            int hash = BASIS;
            for (int i = 0; i < str.Length; i++)
            {
                hash ^= str[i] & 0xFF;
                hash *= PRIME;
                hash ^= str[i] >> 8;
                hash *= PRIME;
            }

            return hash;
        }

        public void Finish()
        {
            // TODO:
        }
    }
}