using NTwain.Data;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace NTwain.Internals
{
    /// <summary>
    /// Contains the actual data transfer logic since TwainSession is getting too large.
    /// </summary>
    static class TransferLogic
    {
        /// <summary>
        /// Performs the TWAIN transfer routine at state 6. 
        /// </summary>
        public static void DoTransferRoutine(ITwainSessionInternal session)
        {
            var pending = new TWPendingXfers();
            var rc = ReturnCode.Success;

            do
            {
                #region build and raise xfer ready

                TWAudioInfo audInfo;
                if (session.DGAudio.AudioInfo.Get(out audInfo) != ReturnCode.Success)
                {
                    audInfo = null;
                }

                TWImageInfo imgInfo;
                if (session.DGImage.ImageInfo.Get(out imgInfo) != ReturnCode.Success)
                {
                    imgInfo = null;
                }

                // ask consumer for xfer details
                var preXferArgs = new TransferReadyEventArgs
                {
                    AudioInfo = audInfo,
                    PendingImageInfo = imgInfo,
                    PendingTransferCount = pending.Count,
                    EndOfJob = pending.EndOfJob == 0
                };

                session.SafeSyncableRaiseEvent(preXferArgs);

                #endregion

                #region actually handle xfer

                if (preXferArgs.CancelAll)
                {
                    rc = session.DGControl.PendingXfers.Reset(pending);
                }
                else if (!preXferArgs.CancelCurrent)
                {
                    DataGroups xferGroup = DataGroups.None;

                    if (session.DGControl.XferGroup.Get(ref xferGroup) != ReturnCode.Success)
                    {
                        xferGroup = DataGroups.None;
                    }

                    // some DS end up getting none but we will assume it's image
                    if (xferGroup == DataGroups.None ||
                        (xferGroup & DataGroups.Image) == DataGroups.Image)
                    {
                        var mech = session.GetCurrentCap(CapabilityId.ICapXferMech).ConvertToEnum<XferMech>();
                        switch (mech)
                        {
                            case XferMech.Memory:
                                DoImageMemoryXfer(session);
                                break;
                            case XferMech.File:
                                DoImageFileXfer(session);
                                break;
                            case XferMech.MemFile:
                                DoImageMemoryFileXfer(session);
                                break;
                            case XferMech.Native:
                            default: // always assume native
                                DoImageNativeXfer(session);
                                break;

                        }
                    }
                    if ((xferGroup & DataGroups.Audio) == DataGroups.Audio)
                    {
                        var mech = session.GetCurrentCap(CapabilityId.ACapXferMech).ConvertToEnum<XferMech>();
                        switch (mech)
                        {
                            case XferMech.File:
                                DoAudioFileXfer(session);
                                break;
                            case XferMech.Native:
                            default: // always assume native
                                DoAudioNativeXfer(session);
                                break;
                        }
                    }
                }
                rc = session.DGControl.PendingXfers.EndXfer(pending);

                #endregion

            } while (rc == ReturnCode.Success && pending.Count != 0);

            session.ChangeState(5, true);
            session.DisableSource();

        }

        #region audio xfers

        static void DoAudioNativeXfer(ITwainSessionInternal session)
        {
            IntPtr dataPtr = IntPtr.Zero;
            IntPtr lockedPtr = IntPtr.Zero;
            try
            {
                var xrc = session.DGAudio.AudioNativeXfer.Get(ref dataPtr);
                if (xrc == ReturnCode.XferDone)
                {
                    session.ChangeState(7, true);
                    if (dataPtr != IntPtr.Zero)
                    {
                        lockedPtr = Platform.MemoryManager.Lock(dataPtr);
                    }

                    session.SafeSyncableRaiseEvent(new DataTransferredEventArgs { NativeData = lockedPtr });
                }
                else
                {
                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.GetSourceStatus() });
                }
            }
            catch (Exception ex)
            {
                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
            }
            finally
            {
                session.ChangeState(6, true);
                // data here is allocated by source so needs to use shared mem calls
                if (lockedPtr != IntPtr.Zero)
                {
                    Platform.MemoryManager.Unlock(lockedPtr);
                    lockedPtr = IntPtr.Zero;
                }
                if (dataPtr != IntPtr.Zero)
                {
                    Platform.MemoryManager.Free(dataPtr);
                    dataPtr = IntPtr.Zero;
                }
            }
        }

        static void DoAudioFileXfer(ITwainSessionInternal session)
        {
            string filePath = null;
            TWSetupFileXfer setupInfo;
            if (session.DGControl.SetupFileXfer.Get(out setupInfo) == ReturnCode.Success)
            {
                filePath = setupInfo.FileName;
            }

            var xrc = session.DGAudio.AudioFileXfer.Get();
            if (xrc == ReturnCode.XferDone)
            {
                session.SafeSyncableRaiseEvent(new DataTransferredEventArgs { FileDataPath = filePath });
            }
            else
            {
                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.GetSourceStatus() });
            }
        }

        #endregion

        #region image xfers

        static void DoImageNativeXfer(ITwainSessionInternal session)
        {
            IntPtr dataPtr = IntPtr.Zero;
            IntPtr lockedPtr = IntPtr.Zero;
            try
            {
                var xrc = session.DGImage.ImageNativeXfer.Get(ref dataPtr);
                if (xrc == ReturnCode.XferDone)
                {
                    session.ChangeState(7, true);
                    if (dataPtr != IntPtr.Zero)
                    {
                        lockedPtr = Platform.MemoryManager.Lock(dataPtr);
                    }
                    DoImageXferredEventRoutine(session, lockedPtr, null, null);
                }
                else
                {
                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.GetSourceStatus() });
                }
            }
            catch (Exception ex)
            {
                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
            }
            finally
            {
                session.ChangeState(6, true);
                // data here is allocated by source so needs to use shared mem calls
                if (lockedPtr != IntPtr.Zero)
                {
                    Platform.MemoryManager.Unlock(lockedPtr);
                    lockedPtr = IntPtr.Zero;
                }
                if (dataPtr != IntPtr.Zero)
                {
                    Platform.MemoryManager.Free(dataPtr);
                    dataPtr = IntPtr.Zero;
                }
            }
        }

        static void DoImageFileXfer(ITwainSessionInternal session)
        {
            string filePath = null;
            TWSetupFileXfer setupInfo;
            if (session.DGControl.SetupFileXfer.Get(out setupInfo) == ReturnCode.Success)
            {
                filePath = setupInfo.FileName;
            }

            var xrc = session.DGImage.ImageFileXfer.Get();
            if (xrc == ReturnCode.XferDone)
            {
                DoImageXferredEventRoutine(session, IntPtr.Zero, null, filePath);
            }
            else
            {
                session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.GetSourceStatus() });
            }
        }

        static void DoImageMemoryXfer(ITwainSessionInternal session)
        {
            TWSetupMemXfer memInfo;
            if (session.DGControl.SetupMemXfer.Get(out memInfo) == ReturnCode.Success)
            {
                TWImageMemXfer xferInfo = new TWImageMemXfer();
                try
                {
                    // how to tell if going to xfer in strip vs tile?
                    // if tile don't allocate memory in app?

                    xferInfo.Memory = new TWMemory
                    {
                        Flags = MemoryFlags.AppOwns | MemoryFlags.Pointer,
                        Length = memInfo.Preferred,
                        TheMem = Platform.MemoryManager.Allocate(memInfo.Preferred)
                    };

                    // do the unthinkable and keep all xferred batches in memory, 
                    // possibly defeating the purpose of mem xfer
                    // unless compression is used.
                    // todo: use array instead of memory stream?
                    using (MemoryStream xferredData = new MemoryStream())
                    {
                        var xrc = ReturnCode.Success;
                        do
                        {
                            xrc = session.DGImage.ImageMemFileXfer.Get(xferInfo);

                            if (xrc == ReturnCode.Success ||
                                xrc == ReturnCode.XferDone)
                            {
                                session.ChangeState(7, true);
                                // optimize and allocate buffer only once instead of inside the loop?
                                byte[] buffer = new byte[(int)xferInfo.BytesWritten];

                                IntPtr lockPtr = IntPtr.Zero;
                                try
                                {
                                    lockPtr = Platform.MemoryManager.Lock(xferInfo.Memory.TheMem);
                                    Marshal.Copy(lockPtr, buffer, 0, buffer.Length);
                                    xferredData.Write(buffer, 0, buffer.Length);
                                }
                                finally
                                {
                                    if (lockPtr != IntPtr.Zero)
                                    {
                                        Platform.MemoryManager.Unlock(lockPtr);
                                    }
                                }
                            }
                        } while (xrc == ReturnCode.Success);

                        if (xrc == ReturnCode.XferDone)
                        {
                            DoImageXferredEventRoutine(session, IntPtr.Zero, xferredData.ToArray(), null);
                        }
                        else
                        {
                            session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.GetSourceStatus() });
                        }
                    }
                }
                catch (Exception ex)
                {
                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
                }
                finally
                {
                    session.ChangeState(6, true);
                    if (xferInfo.Memory.TheMem != IntPtr.Zero)
                    {
                        Platform.MemoryManager.Free(xferInfo.Memory.TheMem);
                    }
                }

            }
        }

        static void DoImageMemoryFileXfer(ITwainSessionInternal session)
        {
            // since it's memory-file xfer need info from both (maybe)
            TWSetupMemXfer memInfo;
            TWSetupFileXfer fileInfo;
            if (session.DGControl.SetupMemXfer.Get(out memInfo) == ReturnCode.Success &&
                session.DGControl.SetupFileXfer.Get(out fileInfo) == ReturnCode.Success)
            {
                TWImageMemXfer xferInfo = new TWImageMemXfer();
                var tempFile = Path.GetTempFileName();
                string finalFile = null;
                try
                {
                    // no strip or tile here, just chunks
                    xferInfo.Memory = new TWMemory
                    {
                        Flags = MemoryFlags.AppOwns | MemoryFlags.Pointer,
                        Length = memInfo.Preferred,
                        TheMem = Platform.MemoryManager.Allocate(memInfo.Preferred)
                    };

                    var xrc = ReturnCode.Success;
                    using (var outStream = File.OpenWrite(tempFile))
                    {
                        do
                        {
                            xrc = session.DGImage.ImageMemFileXfer.Get(xferInfo);

                            if (xrc == ReturnCode.Success ||
                                xrc == ReturnCode.XferDone)
                            {
                                session.ChangeState(7, true);
                                byte[] buffer = new byte[(int)xferInfo.BytesWritten];

                                IntPtr lockPtr = IntPtr.Zero;
                                try
                                {
                                    lockPtr = Platform.MemoryManager.Lock(xferInfo.Memory.TheMem);
                                    Marshal.Copy(lockPtr, buffer, 0, buffer.Length);
                                }
                                finally
                                {
                                    if (lockPtr != IntPtr.Zero)
                                    {
                                        Platform.MemoryManager.Unlock(lockPtr);
                                    }
                                }
                                outStream.Write(buffer, 0, buffer.Length);
                            }
                        } while (xrc == ReturnCode.Success);
                    }

                    if (xrc == ReturnCode.XferDone)
                    {
                        finalFile = fileInfo.ChangeExtensionByFormat(tempFile);
                        File.Move(tempFile, finalFile);
                    }
                    else
                    {
                        session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { ReturnCode = xrc, SourceStatus = session.GetSourceStatus() });
                    }
                }
                catch (Exception ex)
                {
                    session.SafeSyncableRaiseEvent(new TransferErrorEventArgs { Exception = ex });
                }
                finally
                {
                    session.ChangeState(6, true);
                    if (xferInfo.Memory.TheMem != IntPtr.Zero)
                    {
                        Platform.MemoryManager.Free(xferInfo.Memory.TheMem);
                    }
                    if (File.Exists(tempFile))
                    {
                        File.Delete(tempFile);
                    }
                }

                if (File.Exists(finalFile))
                {
                    DoImageXferredEventRoutine(session, IntPtr.Zero, null, finalFile);
                }
            }
        }

        static void DoImageXferredEventRoutine(ITwainSessionInternal session, IntPtr dataPtr, byte[] dataArray, string filePath)
        {
            TWImageInfo imgInfo;
            TWExtImageInfo extInfo = null;
            if (session.SupportedCaps.Contains(CapabilityId.ICapExtImageInfo))
            {
                if (session.DGImage.ExtImageInfo.Get(out extInfo) != ReturnCode.Success)
                {
                    extInfo = null;
                }
            }
            if (session.DGImage.ImageInfo.Get(out imgInfo) != ReturnCode.Success)
            {
                imgInfo = null;
            }
            session.SafeSyncableRaiseEvent(new DataTransferredEventArgs
            {
                NativeData = dataPtr,
                MemData = dataArray,
                FileDataPath = filePath,
                ImageInfo = imgInfo,
                ExImageInfo = extInfo
            });
            if (extInfo != null) { extInfo.Dispose(); }
        }

        #endregion
    }
}