//---------------------------------------------------------
// Copyright 2015 Ontario Institute for Cancer Research
// Written by Matei David (matei@cs.toronto.edu)
//---------------------------------------------------------

// Reference:
// http://stackoverflow.com/questions/14086417/how-to-write-custom-input-stream-in-c

#pragma once

#include <cassert>
#include <cstdint>
#include <fstream>
#include <sstream>
#include <zlib.h>
#include <memory>
#include <iostream>
#include "strict_fstream.hpp"

#if defined(__GNUC__) && !defined(__clang__)
#if (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__>0)
#define CAN_MOVE_IOSTREAM
#endif
#else
#define CAN_MOVE_IOSTREAM
#endif

namespace zstr
{

static const std::size_t default_buff_size = static_cast<std::size_t>(1 << 20);

/// Exception class thrown by failed zlib operations.
class Exception
    : public std::ios_base::failure
{
public:
    static std::string error_to_message(z_stream * zstrm_p, int ret)
    {
        std::string msg = "zlib: ";
        switch (ret)
        {
        case Z_STREAM_ERROR:
            msg += "Z_STREAM_ERROR: ";
            break;
        case Z_DATA_ERROR:
            msg += "Z_DATA_ERROR: ";
            break;
        case Z_MEM_ERROR:
            msg += "Z_MEM_ERROR: ";
            break;
        case Z_VERSION_ERROR:
            msg += "Z_VERSION_ERROR: ";
            break;
        case Z_BUF_ERROR:
            msg += "Z_BUF_ERROR: ";
            break;
        default:
            std::ostringstream oss;
            oss << ret;
            msg += "[" + oss.str() + "]: ";
            break;
        }
        if (zstrm_p->msg) {
            msg += zstrm_p->msg;
        }
        msg += " ("
                "next_in: " +
                std::to_string(uintptr_t(zstrm_p->next_in)) +
                ", avail_in: " +
                std::to_string(uintptr_t(zstrm_p->avail_in)) +
                ", next_out: " +
                std::to_string(uintptr_t(zstrm_p->next_out)) +
                ", avail_out: " +
                std::to_string(uintptr_t(zstrm_p->avail_out)) +
                ")";
        return msg;
    }

    Exception(z_stream * zstrm_p, int ret)
        : std::ios_base::failure(error_to_message(zstrm_p, ret))
    {
    }
}; // class Exception

namespace detail
{

class z_stream_wrapper
    : public z_stream
{
public:
    z_stream_wrapper(bool _is_input, int _level, int _window_bits)
        : is_input(_is_input)
    {
        this->zalloc = nullptr;//Z_NULL
        this->zfree = nullptr;//Z_NULL
        this->opaque = nullptr;//Z_NULL
        int ret;
        if (is_input)
        {
            this->avail_in = 0;
            this->next_in = nullptr;//Z_NULL
            ret = inflateInit2(this, _window_bits ? _window_bits : 15+32);
        }
        else
        {
            ret = deflateInit2(this, _level, Z_DEFLATED, _window_bits ? _window_bits : 15+16, 8, Z_DEFAULT_STRATEGY);
        }
        if (ret != Z_OK) throw Exception(this, ret);
    }
    ~z_stream_wrapper()
    {
        if (is_input)
        {
            inflateEnd(this);
        }
        else
        {
            deflateEnd(this);
        }
    }
private:
    bool is_input;
}; // class z_stream_wrapper

} // namespace detail

class istreambuf
    : public std::streambuf
{
public:
    istreambuf(std::streambuf * _sbuf_p,
               std::size_t _buff_size = default_buff_size, bool _auto_detect = true, int _window_bits = 0)
        : sbuf_p(_sbuf_p),
          in_buff(),
          in_buff_start(nullptr),
          in_buff_end(nullptr),
          out_buff(),
          zstrm_p(nullptr),
          buff_size(_buff_size),
          auto_detect(_auto_detect),
          auto_detect_run(false),
          is_text(false),
          window_bits(_window_bits)
    {
        assert(sbuf_p);
        in_buff = std::unique_ptr<char[]>(new char[buff_size]);
        in_buff_start = in_buff.get();
        in_buff_end = in_buff.get();
        out_buff = std::unique_ptr<char[]>(new char[buff_size]);
        setg(out_buff.get(), out_buff.get(), out_buff.get());
    }

    istreambuf(const istreambuf &) = delete;
    istreambuf & operator = (const istreambuf &) = delete;

    pos_type seekoff(off_type off, std::ios_base::seekdir dir,
                     std::ios_base::openmode which) override
    {
        if (off != 0 || dir != std::ios_base::cur) {
            return std::streambuf::seekoff(off, dir, which);
        }

        if (!zstrm_p) {
            return 0;
        }

        return static_cast<long int>(zstrm_p->total_out - static_cast<uLong>(in_avail()));
    }

    std::streambuf::int_type underflow() override
    {
        if (this->gptr() == this->egptr())
        {
            // pointers for free region in output buffer
            char * out_buff_free_start = out_buff.get();
            int tries = 0;
            do
            {
                if (++tries > 1000) {
                    throw std::ios_base::failure("Failed to fill buffer after 1000 tries");
                }

                // read more input if none available
                if (in_buff_start == in_buff_end)
                {
                    // empty input buffer: refill from the start
                    in_buff_start = in_buff.get();
                    std::streamsize sz = sbuf_p->sgetn(in_buff.get(), static_cast<std::streamsize>(buff_size));
                    in_buff_end = in_buff_start + sz;
                    if (in_buff_end == in_buff_start) break; // end of input
                }
                // auto detect if the stream contains text or deflate data
                if (auto_detect && ! auto_detect_run)
                {
                    auto_detect_run = true;
                    unsigned char b0 = *reinterpret_cast< unsigned char * >(in_buff_start);
                    unsigned char b1 = *reinterpret_cast< unsigned char * >(in_buff_start + 1);
                    // Ref:
                    // http://en.wikipedia.org/wiki/Gzip
                    // http://stackoverflow.com/questions/9050260/what-does-a-zlib-header-look-like
                    is_text = ! (in_buff_start + 2 <= in_buff_end
                                 && ((b0 == 0x1F && b1 == 0x8B)         // gzip header
                                     || (b0 == 0x78 && (b1 == 0x01      // zlib header
                                                        || b1 == 0x9C
                                                        || b1 == 0xDA))));
                }
                if (is_text)
                {
                    // simply swap in_buff and out_buff, and adjust pointers
                    assert(in_buff_start == in_buff.get());
                    std::swap(in_buff, out_buff);
                    out_buff_free_start = in_buff_end;
                    in_buff_start = in_buff.get();
                    in_buff_end = in_buff.get();
                }
                else
                {
                    // run inflate() on input
                    if (! zstrm_p) zstrm_p = std::unique_ptr<detail::z_stream_wrapper>(new detail::z_stream_wrapper(true, Z_DEFAULT_COMPRESSION, window_bits));
                    zstrm_p->next_in = reinterpret_cast< decltype(zstrm_p->next_in) >(in_buff_start);
                    zstrm_p->avail_in = uint32_t(in_buff_end - in_buff_start);
                    zstrm_p->next_out = reinterpret_cast< decltype(zstrm_p->next_out) >(out_buff_free_start);
                    zstrm_p->avail_out = uint32_t((out_buff.get() + buff_size) - out_buff_free_start);
                    int ret = inflate(zstrm_p.get(), Z_NO_FLUSH);
                    // process return code
                    if (ret != Z_OK && ret != Z_STREAM_END) throw Exception(zstrm_p.get(), ret);
                    // update in&out pointers following inflate()
                    in_buff_start = reinterpret_cast< decltype(in_buff_start) >(zstrm_p->next_in);
                    in_buff_end = in_buff_start + zstrm_p->avail_in;
                    out_buff_free_start = reinterpret_cast< decltype(out_buff_free_start) >(zstrm_p->next_out);
                    assert(out_buff_free_start + zstrm_p->avail_out == out_buff.get() + buff_size);

                    if (ret == Z_STREAM_END) {
                        // if stream ended, deallocate inflator
                        zstrm_p.reset();
                    }
                }
            } while (out_buff_free_start == out_buff.get());
            // 2 exit conditions:
            // - end of input: there might or might not be output available
            // - out_buff_free_start != out_buff: output available
            this->setg(out_buff.get(), out_buff.get(), out_buff_free_start);
        }
        return this->gptr() == this->egptr()
            ? traits_type::eof()
            : traits_type::to_int_type(*this->gptr());
    }
private:
    std::streambuf * sbuf_p;
    std::unique_ptr<char[]> in_buff;
    char * in_buff_start;
    char * in_buff_end;
    std::unique_ptr<char[]> out_buff;
    std::unique_ptr<detail::z_stream_wrapper> zstrm_p;
    std::size_t buff_size;
    bool auto_detect;
    bool auto_detect_run;
    bool is_text;
    int window_bits;

}; // class istreambuf

class ostreambuf
    : public std::streambuf
{
public:
    ostreambuf(std::streambuf * _sbuf_p,
               std::size_t _buff_size = default_buff_size, int _level = Z_DEFAULT_COMPRESSION, int _window_bits = 0)
        : sbuf_p(_sbuf_p),
          in_buff(),
          out_buff(),
          zstrm_p(new detail::z_stream_wrapper(false, _level, _window_bits)),
          buff_size(_buff_size)
    {
        assert(sbuf_p);
        in_buff = std::unique_ptr<char[]>(new char[buff_size]);
        out_buff = std::unique_ptr<char[]>(new char[buff_size]);
        setp(in_buff.get(), in_buff.get() + buff_size);
    }

    ostreambuf(const ostreambuf &) = delete;
    ostreambuf & operator = (const ostreambuf &) = delete;

    int deflate_loop(int flush)
    {
        while (true)
        {
            zstrm_p->next_out = reinterpret_cast< decltype(zstrm_p->next_out) >(out_buff.get());
            zstrm_p->avail_out = uint32_t(buff_size);
            int ret = deflate(zstrm_p.get(), flush);
            if (ret != Z_OK && ret != Z_STREAM_END && ret != Z_BUF_ERROR) {
                failed = true;
                throw Exception(zstrm_p.get(), ret);
            }
            std::streamsize sz = sbuf_p->sputn(out_buff.get(), reinterpret_cast< decltype(out_buff.get()) >(zstrm_p->next_out) - out_buff.get());
            if (sz != reinterpret_cast< decltype(out_buff.get()) >(zstrm_p->next_out) - out_buff.get())
            {
                // there was an error in the sink stream
                return -1;
            }
            if (ret == Z_STREAM_END || ret == Z_BUF_ERROR || sz == 0)
            {
                break;
            }
        }
        return 0;
    }

    virtual ~ostreambuf()
    {
        // flush the zlib stream
        //
        // NOTE: Errors here (sync() return value not 0) are ignored, because we
        // cannot throw in a destructor. This mirrors the behaviour of
        // std::basic_filebuf::~basic_filebuf(). To see an exception on error,
        // close the ofstream with an explicit call to close(), and do not rely
        // on the implicit call in the destructor.
        //
        if (!failed) try {
            sync();
        } catch (...) {}
    }
    std::streambuf::int_type overflow(std::streambuf::int_type c = traits_type::eof()) override
    {
        zstrm_p->next_in = reinterpret_cast< decltype(zstrm_p->next_in) >(pbase());
        zstrm_p->avail_in = uint32_t(pptr() - pbase());
        while (zstrm_p->avail_in > 0)
        {
            int r = deflate_loop(Z_NO_FLUSH);
            if (r != 0)
            {
                setp(nullptr, nullptr);
                return traits_type::eof();
            }
        }
        setp(in_buff.get(), in_buff.get() + buff_size);
        return traits_type::eq_int_type(c, traits_type::eof()) ? traits_type::eof() : sputc(char_type(c));
    }
    int sync() override
    {
        // first, call overflow to clear in_buff
        overflow();
        if (! pptr()) return -1;
        // then, call deflate asking to finish the zlib stream
        zstrm_p->next_in = nullptr;
        zstrm_p->avail_in = 0;
        if (deflate_loop(Z_FINISH) != 0) return -1;
        deflateReset(zstrm_p.get());
        return 0;
    }
private:
    std::streambuf * sbuf_p = nullptr;
    std::unique_ptr<char[]> in_buff;
    std::unique_ptr<char[]> out_buff;
    std::unique_ptr<detail::z_stream_wrapper> zstrm_p;
    std::size_t buff_size;
    bool failed = false;

}; // class ostreambuf

class istream
    : public std::istream
{
public:
    istream(std::istream & is,
            std::size_t _buff_size = default_buff_size, bool _auto_detect = true, int _window_bits = 0)
        : std::istream(new istreambuf(is.rdbuf(), _buff_size, _auto_detect, _window_bits))
    {
        exceptions(std::ios_base::badbit);
    }
    explicit istream(std::streambuf * sbuf_p)
        : std::istream(new istreambuf(sbuf_p))
    {
        exceptions(std::ios_base::badbit);
    }
    virtual ~istream()
    {
        delete rdbuf();
    }
}; // class istream

class ostream
    : public std::ostream
{
public:
    ostream(std::ostream & os,
            std::size_t _buff_size = default_buff_size, int _level = Z_DEFAULT_COMPRESSION, int _window_bits = 0)
        : std::ostream(new ostreambuf(os.rdbuf(), _buff_size, _level, _window_bits))
    {
        exceptions(std::ios_base::badbit);
    }
    explicit ostream(std::streambuf * sbuf_p)
        : std::ostream(new ostreambuf(sbuf_p))
    {
        exceptions(std::ios_base::badbit);
    }
    virtual ~ostream()
    {
        delete rdbuf();
    }
}; // class ostream

namespace detail
{

template < typename FStream_Type >
struct strict_fstream_holder
{
    strict_fstream_holder(const std::string& filename, std::ios_base::openmode mode = std::ios_base::in)
        : _fs(filename, mode)
    {}
    strict_fstream_holder() = default;
    FStream_Type _fs {};
}; // class strict_fstream_holder

} // namespace detail

class ifstream
    : private detail::strict_fstream_holder< strict_fstream::ifstream >,
      public std::istream
{
public:
    explicit ifstream(const std::string filename, std::ios_base::openmode mode = std::ios_base::in, size_t buff_size = default_buff_size)
        : detail::strict_fstream_holder< strict_fstream::ifstream >(filename, mode),
          std::istream(new istreambuf(_fs.rdbuf(), buff_size))
    {
        exceptions(std::ios_base::badbit);
    }
    explicit ifstream(): detail::strict_fstream_holder< strict_fstream::ifstream >(), std::istream(new istreambuf(_fs.rdbuf())){}
    void close() {
        _fs.close();
    }
    #ifdef CAN_MOVE_IOSTREAM
    void open(const std::string filename, std::ios_base::openmode mode = std::ios_base::in) {
        _fs.open(filename, mode);
        std::istream::operator=(std::istream(new istreambuf(_fs.rdbuf())));
    }
    #endif
    bool is_open() const {
        return _fs.is_open();
    }
    virtual ~ifstream()
    {
        if (_fs.is_open()) close();
        if (rdbuf()) delete rdbuf();
    }

    /// Return the position within the compressed file (wrapped filestream)
    std::streampos compressed_tellg()
    {
        return _fs.tellg();
    }
}; // class ifstream

class ofstream
    : private detail::strict_fstream_holder< strict_fstream::ofstream >,
      public std::ostream
{
public:
    explicit ofstream(const std::string filename, std::ios_base::openmode mode = std::ios_base::out,
                      int level = Z_DEFAULT_COMPRESSION, size_t buff_size = default_buff_size)
        : detail::strict_fstream_holder< strict_fstream::ofstream >(filename, mode | std::ios_base::binary),
          std::ostream(new ostreambuf(_fs.rdbuf(), buff_size, level))
    {
        exceptions(std::ios_base::badbit);
    }
    explicit ofstream(): detail::strict_fstream_holder< strict_fstream::ofstream >(), std::ostream(new ostreambuf(_fs.rdbuf())){}
    void close() {
        std::ostream::flush();
        _fs.close();
    }
    #ifdef CAN_MOVE_IOSTREAM
    void open(const std::string filename, std::ios_base::openmode mode = std::ios_base::out, int level = Z_DEFAULT_COMPRESSION) {
        flush();
        _fs.open(filename, mode | std::ios_base::binary);
        std::ostream::operator=(std::ostream(new ostreambuf(_fs.rdbuf(), default_buff_size, level)));
    }
    #endif
    bool is_open() const {
        return _fs.is_open();
    }
    ofstream& flush() {
        std::ostream::flush();
        _fs.flush();
        return *this;
    }
    virtual ~ofstream()
    {
        if (_fs.is_open()) close();
        if (rdbuf()) delete rdbuf();
    }

    // Return the position within the compressed file (wrapped filestream)
    std::streampos compressed_tellp()
    {
        return _fs.tellp();
    }
}; // class ofstream

} // namespace zstr
