using Misaki.HighPerformance.Image.Runtime;
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;

namespace Misaki.HighPerformance.Image
{
    internal class AnimatedGifEnumerator : IEnumerator<AnimatedFrameResult>
    {
        private readonly StbImage.stbi__context _context;
        private StbImage.stbi__gif _gif;
        private readonly ColorComponents _colorComponents;

        public AnimatedGifEnumerator(Stream input, ColorComponents colorComponents)
        {
            if (input == null)
                throw new ArgumentNullException("input");

            _context = new StbImage.stbi__context(input);

            if (StbImage.stbi__gif_test(_context) == 0)
                throw new Exception("Input stream is not GIF file.");

            _gif = new StbImage.stbi__gif();
            _colorComponents = colorComponents;
        }

        public ColorComponents ColorComponents
        {
            get
            {
                return _colorComponents;
            }
        }

        public AnimatedFrameResult Current
        {
            get; private set;
        }

        object IEnumerator.Current
        {
            get
            {
                return Current;
            }
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        public unsafe bool MoveNext()
        {
            // Read next frame
            int ccomp;
            byte two_back;
            var result = StbImage.stbi__gif_load_next(_context, _gif, &ccomp, (int)ColorComponents, &two_back);
            if (result == null)
                return false;

            if (Current == null)
            {
                Current = new AnimatedFrameResult
                {
                    Width = (uint)_gif.w,
                    Height = (uint)_gif.h,
                    SourceComponent = (ColorComponents)ccomp,
                    Component = ColorComponents == ColorComponents.Default ? (ColorComponents)ccomp : ColorComponents
                };

                Current.SetData(result);
            }

            Current.DelayInMs = _gif.delay;

            return true;
        }

        public void Reset()
        {
            throw new NotImplementedException();
        }

        ~AnimatedGifEnumerator()
        {
            Dispose(false);
        }

        protected unsafe virtual void Dispose(bool disposing)
        {
            if (_gif != null)
            {
                if (_gif._out_ != null)
                {
                    CRuntime.free(_gif._out_);
                    _gif._out_ = null;
                }

                if (_gif.history != null)
                {
                    CRuntime.free(_gif.history);
                    _gif.history = null;
                }

                if (_gif.background != null)
                {
                    CRuntime.free(_gif.background);
                    _gif.background = null;
                }

                _gif = null;
            }
        }
    }

    internal class AnimatedGifEnumerable : IEnumerable<AnimatedFrameResult>
    {
        private readonly Stream _input;
        private readonly ColorComponents _colorComponents;

        public AnimatedGifEnumerable(Stream input, ColorComponents colorComponents)
        {
            _input = input;
            _colorComponents = colorComponents;
        }

        public ColorComponents ColorComponents
        {
            get
            {
                return _colorComponents;
            }
        }

        public IEnumerator<AnimatedFrameResult> GetEnumerator()
        {
            return new AnimatedGifEnumerator(_input, ColorComponents);
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }
}