using System;
using System.Runtime.InteropServices;
using Vav1Player.Native;

namespace Vav1Player.Decoder
{
    public class Dav1dDecoder : IDisposable
    {
        private IntPtr _context = IntPtr.Zero;
        private bool _disposed = false;

        public bool Initialize(int threads = 0)
        {
            if (_context != IntPtr.Zero)
                return false;

            try
            {
                // Initialize all fields to zero before calling dav1d_default_settings
                var settings = new Dav1dSettings();

                // Now call dav1d_default_settings to populate with library defaults
                Dav1dNative.dav1d_default_settings(ref settings);

                // Override with user-specified values
                if (threads > 0)
                {
                    settings.n_threads = Math.Min(threads, 256); // Cap at library maximum
                }
                else if (settings.n_threads <= 0)
                {
                    settings.n_threads = Math.Min(Environment.ProcessorCount, 8); // Conservative default
                }

                settings.max_frame_delay = 1; // Low latency

                System.Diagnostics.Debug.WriteLine($"Final settings - Threads: {settings.n_threads}, Frame Delay: {settings.max_frame_delay}");
                System.Diagnostics.Debug.WriteLine(Dav1dSettingsValidator.GetSettingsSummary(settings));

                int result = Dav1dNative.dav1d_open(out _context, ref settings);

                if (result != 0)
                {
                    string errorMsg = $"dav1d_open failed with error code: {result}\n" +
                                    $"Description: {Dav1dErrorCodes.GetOpenErrorDescription(result)}\n" +
                                    $"Suggestion: {Dav1dErrorCodes.GetTroubleshootingSuggestion(result)}\n" +
                                    $"Recoverable: {Dav1dErrorCodes.IsRecoverable(result)}";

                    System.Diagnostics.Debug.WriteLine(errorMsg);
                    Console.WriteLine($"[DAV1D ERROR] {errorMsg}");
                    return false;
                }

                return true;
            }
            catch (DllNotFoundException ex)
            {
                System.Diagnostics.Debug.WriteLine($"dav1d.dll not found: {ex.Message}");
                return false;
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine($"Decoder initialization failed: {ex.Message}");
                return false;
            }
        }

        public unsafe bool DecodeFrame(byte[] data, out DecodedFrame? frame)
        {
            frame = null;

            if (_context == IntPtr.Zero || data == null || data.Length == 0)
                return false;

            fixed (byte* dataPtr = data)
            {
                var dav1dData = new Dav1dData();
                int result = Dav1dNative.dav1d_data_wrap(out dav1dData, (IntPtr)dataPtr, (nuint)data.Length, IntPtr.Zero, IntPtr.Zero);
                if (result != 0)
                    return false;

                result = Dav1dNative.dav1d_send_data(_context, ref dav1dData);
                if (result != 0 && result != -11) // -11 is EAGAIN (need more data)
                {
                    string errorMsg = $"[Dav1dDecoder] dav1d_send_data failed with error: {result}";
                    errorMsg += $"\n[Dav1dDecoder] Data size: {data.Length} bytes";
                    var hexData = string.Join(" ", data.Take(Math.Min(32, data.Length)).Select(b => b.ToString("X2")));
                    errorMsg += $"\n[Dav1dDecoder] Data prefix: {hexData}";
                    errorMsg += $"\n[Dav1dDecoder] Error details: {Dav1dErrorCodes.GetErrorDescription(result)}";

                    System.Diagnostics.Debug.WriteLine(errorMsg);
                    Console.WriteLine(errorMsg); // Also print to console so it shows in test output

                    Dav1dNative.dav1d_data_unref(ref dav1dData);
                    return false;
                }

                var picture = new Dav1dPicture();
                result = Dav1dNative.dav1d_get_picture(_context, out picture);
                if (result == 0)
                {
                    frame = new DecodedFrame
                    {
                        Picture = picture,
                        Width = picture.p.w,
                        Height = picture.p.h,
                        PixelLayout = picture.p.layout,
                        BitDepth = picture.p.bpc
                    };
                    return true;
                }
                else
                {
                    System.Diagnostics.Debug.WriteLine($"[Dav1dDecoder] dav1d_get_picture failed with error: {result}");
                }
            }

            return false;
        }

        public void Dispose()
        {
            if (!_disposed && _context != IntPtr.Zero)
            {
                Dav1dNative.dav1d_close(ref _context);
                _context = IntPtr.Zero;
                _disposed = true;
            }
        }
    }

    public struct DecodedFrame
    {
        public Dav1dPicture Picture;
        public int Width;
        public int Height;
        public Dav1dPixelLayout PixelLayout;
        public int BitDepth;

        public void Release()
        {
            Dav1dNative.dav1d_picture_unref(ref Picture);
        }
    }
}