// **********************************************************************
//
// Copyright (c) 2003-2017 ZeroC, Inc. All rights reserved.
//
// This copy of Ice is licensed to you under the terms described in the
// ICE_LICENSE file included in this distribution.
//
// **********************************************************************

namespace IceInternal
{

    using System;
    using System.Diagnostics;
    using System.Runtime.InteropServices;

#if !MANAGED
    internal static class NativeMethods
    {
        [DllImport("bzip2.dll")]
        internal static extern IntPtr BZ2_bzlibVersion();

        [DllImport("bzip2.dll")]
        internal static extern int BZ2_bzBuffToBuffCompress(byte[] dest,
                                                            ref int destLen,
                                                            byte[] source,
                                                            int sourceLen,
                                                            int blockSize100k,
                                                            int verbosity,
                                                            int workFactor);

        [DllImport("bzip2.dll")]
        internal static extern int BZ2_bzBuffToBuffDecompress(byte[] dest,
                                                              ref int destLen,
                                                              byte[] source,
                                                              int sourceLen,
                                                              int small,
                                                              int verbosity);
    }
#endif

    public class BZip2
    {
        static BZip2()
        {
#if MANAGED
            //
            // Protocol compression is not supported when using managed code.
            //
            _bzlibInstalled = false;
#else
            //
            // Simple trick to find out whether bzip2 is installed: Call the BZ2_bzlibVersion() function in the
            // library. If we get an exception, the library is not available.
            //
            _bzlibInstalled = false;

            //
            // We are setting the library name here because, under Mono, we don't know the exact library name.
            // In addition, the FileName member of the BadImageFormatException is the empty string, even though
            // it should provide the name of the library.
            //
            try
            {
                NativeMethods.BZ2_bzlibVersion();
                _bzlibInstalled = true;
            }
            catch(DllNotFoundException)
            {
                // Expected -- bzip2.dll not installed or not in PATH.
            }
            catch(EntryPointNotFoundException)
            {
                Console.Error.WriteLine("warning: found bzip2.dll but entry point BZ2_bzlibVersion is missing.");
            }
            catch(BadImageFormatException ex)
            {
                string lib = "bzip2.dll";
                if(!String.IsNullOrEmpty(ex.FileName))
                {
                    lib = ex.FileName; // Future-proof: we'll do the right thing if the FileName member is non-empty.
                }
                Console.Error.Write("warning: " + lib + " could not be loaded (likely due to 32/64-bit mismatch).");
                if(IntPtr.Size == 8)
                {
                    Console.Error.Write(" Make sure the directory containing the 64-bit " + lib + " is in your PATH.");
                }
                Console.Error.WriteLine();
            }
#endif
        }

#if !MANAGED
        static string getBZ2Error(int error)
        {
            string rc;

            switch(error)
            {
                case BZ_SEQUENCE_ERROR:
                {
                    rc = "BZ_SEQUENCE_ERROR";
                    break;
                }
                case BZ_PARAM_ERROR:
                {
                    rc = "BZ_PARAM_ERROR";
                    break;
                }
                case BZ_MEM_ERROR:
                {
                    rc = "BZ_MEM_ERROR";
                    break;
                }
                case BZ_DATA_ERROR:
                {
                    rc = "BZ_DATA_ERROR";
                    break;
                }
                case BZ_DATA_ERROR_MAGIC:
                {
                    rc = "BZ_DATA_ERROR_MAGIC";
                    break;
                }
                case BZ_IO_ERROR:
                {
                    rc = "BZ_IO_ERROR";
                    break;
                }
                case BZ_UNEXPECTED_EOF:
                {
                    rc = "BZ_UNEXPECTED_EOF";
                    break;
                }
                case BZ_OUTBUFF_FULL:
                {
                    rc = "BZ_OUTBUFF_FULL";
                    break;
                }
                case BZ_CONFIG_ERROR:
                {
                    rc = "BZ_CONFIG_ERROR";
                    break;
                }
                default:
                {
                    rc = "Unknown bzip2 error: " + error;
                    break;
                }
            }
            return rc;
        }
#endif

        public static bool supported()
        {
            return _bzlibInstalled;
        }

        public static Buffer compress(Buffer buf, int headerSize, int compressionLevel)
        {
            Debug.Assert(supported());

#if MANAGED
            return null;
#else
            //
            // Compress the message body, but not the header.
            //
            int uncompressedLen = buf.size() - headerSize;
            byte[] data = buf.b.rawBytes(headerSize, uncompressedLen);
            int compressedLen = (int)(uncompressedLen * 1.01 + 600);
            byte[] compressed = new byte[compressedLen];

            int rc = NativeMethods.BZ2_bzBuffToBuffCompress(compressed, ref compressedLen, data, uncompressedLen,
                                                            compressionLevel, 0, 0);
            if(rc == BZ_OUTBUFF_FULL)
            {
                return null;
            }
            else if(rc < 0)
            {
                Ice.CompressionException ex = new Ice.CompressionException("BZ2_bzBuffToBuffCompress failed");
                ex.reason = getBZ2Error(rc);
                throw ex;
            }

            //
            // Don't bother if the compressed data is larger than the
            // uncompressed data.
            //
            if(compressedLen >= uncompressedLen)
            {
                return null;
            }

            Buffer r = new Buffer();
            r.resize(headerSize + 4 + compressedLen, false);
            r.b.position(0);

            //
            // Copy the header from the uncompressed stream to the
            // compressed one.
            //
            r.b.put(buf.b.rawBytes(0, headerSize));

            //
            // Add the size of the uncompressed stream before the
            // message body.
            //
            r.b.putInt(buf.size());

            //
            // Add the compressed message body.
            //
            r.b.put(compressed, 0, compressedLen);

            return r;
#endif
        }

        public static Buffer uncompress(Buffer buf, int headerSize, int messageSizeMax)
        {
            Debug.Assert(supported());

#if MANAGED
            return null;
#else
            buf.b.position(headerSize);
            int uncompressedSize = buf.b.getInt();
            if(uncompressedSize <= headerSize)
            {
                throw new Ice.IllegalMessageSizeException("compressed size <= header size");
            }
            if(uncompressedSize > messageSizeMax)
            {
                IceInternal.Ex.throwMemoryLimitException(uncompressedSize, messageSizeMax);
            }

            int compressedLen = buf.size() - headerSize - 4;
            byte[] compressed = buf.b.rawBytes(headerSize + 4, compressedLen);
            int uncompressedLen = uncompressedSize - headerSize;

            byte[] uncompressed = new byte[uncompressedLen];
            int rc = NativeMethods.BZ2_bzBuffToBuffDecompress(uncompressed, ref uncompressedLen, compressed,
                                                              compressedLen, 0, 0);
            if(rc < 0)
            {
                Ice.CompressionException ex = new Ice.CompressionException("BZ2_bzBuffToBuffDecompress failed");
                ex.reason = getBZ2Error(rc);
                throw ex;
            }

            Buffer r = new Buffer();
            r.resize(uncompressedSize, false);

            //
            // Copy the header from the compressed buffer to the uncompressed one.
            //
            r.b.position(0);
            r.b.put(buf.b.rawBytes(), 0, headerSize);
            r.b.put(uncompressed);

            return r;
#endif
        }

        private static bool _bzlibInstalled;

        const int BZ_SEQUENCE_ERROR = -1;
        const int BZ_PARAM_ERROR = -2;
        const int BZ_MEM_ERROR = -3;
        const int BZ_DATA_ERROR = -4;
        const int BZ_DATA_ERROR_MAGIC = -5;
        const int BZ_IO_ERROR = -6;
        const int BZ_UNEXPECTED_EOF = -7;
        const int BZ_OUTBUFF_FULL = -8;
        const int BZ_CONFIG_ERROR = -9;
    }

}