using PaintDotNet.SystemLayer;
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Text;

namespace PaintDotNet
{
    public abstract class InternalFileType : FileType
    {
        /// <summary>
        /// The actual bit-depths we can save with.
        /// </summary>
        internal enum SavableBitDepths
        {
            Rgba32, // 2^24 colors, plus a full 8-bit alpha channel
            Rgb24,  // 2^24 colors
            Rgb8,   // 256 colors
            Rgba8   // 255 colors + 1 transparent
        }

        protected unsafe void SquishSurfaceTo24Bpp(Surface surface)
        {
            byte* dst = (byte*)surface.GetRowAddress(0);
            int byteWidth = surface.Width * 3;
            int stride24bpp = ((byteWidth + 3) / 4) * 4; // round up to multiple of 4
            int delta = stride24bpp - byteWidth;

            for (int y = 0; y < surface.Height; ++y)
            {
                ColorBgra* src = surface.GetRowAddress(y);
                ColorBgra* srcEnd = src + surface.Width;

                while (src < srcEnd)
                {
                    dst[0] = src->B;
                    dst[1] = src->G;
                    dst[2] = src->R;
                    ++src;
                    dst += 3;
                }

                dst += delta;
            }

            return;
        }

        private string PrintSet<T>(Set<T> set)
        {
            StringBuilder sb = new StringBuilder();

            bool first = true;

            foreach (T item in set)
            {
                if (!first)
                {
                    sb.Append(", ");
                }

                first = false;

                sb.Append(item.ToString());
            }

            string sbTS = sb.ToString();

            return sbTS;
        }

        internal SavableBitDepths ChooseBitDepth(
            Set<SavableBitDepths> allowedBitDepths,
            Set<SavableBitDepths> losslessBitDepths,
            bool allOpaque,
            bool all0Or255Alpha,
            int uniqueColorCount)
        {
            if (allowedBitDepths.Count == 0)
            {
                throw new ArgumentException("Count must be 1 or more", "allowedBitDepths");
            }

            Tracing.Ping("allowedBitDepths = " + PrintSet(allowedBitDepths));
            Tracing.Ping("losslessBitDepths = " + PrintSet(losslessBitDepths));

            if (allowedBitDepths.Count == 1)
            {
                return allowedBitDepths.ToArray()[0];
            }

            // allowedBitDepths.Count >= 2

            Set<SavableBitDepths> bestBitDepths = Set<SavableBitDepths>.Intersect(allowedBitDepths, losslessBitDepths);

            if (bestBitDepths.Count == 1)
            {
                return bestBitDepths.ToArray()[0];
            }

            Set<SavableBitDepths> candidates;

            if (bestBitDepths.Count == 0)
            {
                candidates = allowedBitDepths;
            }
            else
            {
                candidates = bestBitDepths;
            }

            // candidates.Count >= 2

            // lossless choices

            if (candidates.Contains(SavableBitDepths.Rgba8) && all0Or255Alpha && uniqueColorCount <= 255)
            {
                return SavableBitDepths.Rgba8;
            }

            if (candidates.Contains(SavableBitDepths.Rgb8) && allOpaque && uniqueColorCount <= 256)
            {
                return SavableBitDepths.Rgb8;
            }

            if (candidates.Contains(SavableBitDepths.Rgb24) && allOpaque)
            {
                return SavableBitDepths.Rgb24;
            }

            if (candidates.Contains(SavableBitDepths.Rgba32))
            {
                return SavableBitDepths.Rgba32;
            }

            // forced choices -- we wanted Rgba32 but it was not allowed

            if (candidates.IsEqualTo(Set.Create(SavableBitDepths.Rgb8, SavableBitDepths.Rgb24)))
            {
                return SavableBitDepths.Rgb24;
            }

            if (candidates.IsEqualTo(Set.Create(SavableBitDepths.Rgb8, SavableBitDepths.Rgba8)))
            {
                return SavableBitDepths.Rgba8;
            }

            if (candidates.IsEqualTo(Set.Create(SavableBitDepths.Rgba8, SavableBitDepths.Rgb24)))
            {
                return SavableBitDepths.Rgb24;
            }

            throw new ArgumentException("Could not accomodate input values -- internal error?");
        }

        protected unsafe Bitmap CreateAliased24BppBitmap(Surface surface)
        {
            int stride = surface.Width * 3;
            int realStride = ((stride + 3) / 4) * 4; // round up to multiple of 4
            return new Bitmap(surface.Width, surface.Height, realStride, PixelFormat.Format24bppRgb, new IntPtr(surface.Scan0.VoidStar));
        }

        private unsafe void Analyze(Surface scratchSurface, out bool allOpaque, out bool all0or255Alpha, out int uniqueColorCount)
        {
            allOpaque = true;
            all0or255Alpha = true;
            Set<ColorBgra> uniqueColors = new Set<ColorBgra>();

            for (int y = 0; y < scratchSurface.Height; ++y)
            {
                ColorBgra* srcPtr = scratchSurface.GetRowAddress(y);
                ColorBgra* endPtr = srcPtr + scratchSurface.Width;

                while (srcPtr < endPtr)
                {
                    ColorBgra p = *srcPtr;

                    if (p.A != 255)
                    {
                        allOpaque = false;
                    }

                    if (p.A > 0 && p.A < 255)
                    {
                        all0or255Alpha = false;
                    }

                    if (p.A == 255 && !uniqueColors.Contains(p) && uniqueColors.Count < 300)
                    {
                        uniqueColors.Add(*srcPtr);
                    }

                    ++srcPtr;
                }
            }

            uniqueColorCount = uniqueColors.Count;
        }

        internal InternalFileType(string name, FileTypeFlags flags, string[] extensions)
            : base(name, flags, extensions)
        {
        }
    }
}