// -*- mode: c++; c-basic-offset:4 -*-

// This file is part of libdap, A C++ implementation of the OPeNDAP Data
// Access Protocol.

// Copyright (c) 2013 OPeNDAP, Inc.
// Author: James Gallagher <jgallagher@opendap.org>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.
//
// Portions of this code were taken verbatim from  Josuttis,
// "The C++ Standard Library," p.672

#ifndef _chunkedostream_h
#define _chunkedostream_h

#include "chunked_stream.h"

#include <ostream>
#include <stdexcept> // std::out_of_range
#include <streambuf>

#include "util.h"

namespace libdap {

class chunked_ostream;

/**
 * @brief output buffer for a chunked stream
 * This performs buffered output encoding the data in the stream using
 * the simple chunking protocol defined for DAP4's binary data transmission.
 * Each block of data is prefixed by four bytes: A CHUNK TYPE byte followed
 * by three bytes that are the CHUNK SIZE. There are three CHUNK TYPES:
 * data, end and error, indicated by the code values 0x00, 0x01 and 0x02.
 * The size of a chunk is limited to 2^24 data bytes + 4 bytes for the
 * chunk header.
 */
class chunked_outbuf : public std::streambuf {
    friend class chunked_ostream;

protected:
    std::ostream &d_os;      // Write stuff here
    unsigned int d_buf_size; // Size of the data buffer
    char *d_buffer;          // Data buffer
    bool d_big_endian;

public:
    chunked_outbuf(std::ostream &os, unsigned int buf_size) : d_os(os), d_buf_size(buf_size), d_buffer(0) {
        if (d_buf_size & CHUNK_TYPE_MASK)
            throw std::out_of_range(
                "A chunked_outbuf (or chunked_ostream) was built using a buffer larger than 0x00ffffff");

        d_big_endian = is_host_big_endian();
        d_buffer = new char[buf_size];
        // Trick: making the pointers think the buffer is one char smaller than it
        // really is ensures that overflow() will be called when there's space for
        // one more character.
        setp(d_buffer, d_buffer + (buf_size - 1));
    }

    virtual ~chunked_outbuf() {
        // call end_chunk() and not sync()
        end_chunk();

        delete[] d_buffer;
    }

protected:
    // data_chunk and end_chunk might not be needed because they
    // are called via flush() and ~chunked_outbuf(), resp. jhrg 9/13/13
    int_type data_chunk(); // sync() and overflow() call this
    int_type end_chunk();

    int_type err_chunk(const std::string &msg);

    virtual std::streamsize xsputn(const char *s, std::streamsize num);
    // Manipulate the buffer pointers using pbump() after filling the buffer
    // and then call data_chunk(). Leave remainder in buffer. Or copy logic
    // for data_chunk() into loop in this code.

    virtual int_type overflow(int c);
    virtual int_type sync();
};

/**
 * @brief A C++ stream class for chunked data.
 * This class uses the chunked_outbuf class to provide for chunked
 * binary serialization of data as specified by DAP4. Information
 * to be serialized is broken into 'chunks' that are no more than
 * 2^24 bytes in length. Each chunk is prefixed by a 4 byte header
 * that indicates the type of chunk and size (number of bytes in the
 * chunk body). There are three types of chunk: Data; End; and Error.
 * In normal operation, a DAP4 data document/response is serialized as
 * a sequence of DATA chunks followed by one END chunk (which may be
 * zero bytes in length). If, during serialization, an error is detected,
 * the currently buffered (but not sent) data are discarded and an
 * ERROR chunk is sent with an error message.
 *
 * This class sends the END chunk when its destructor is called.
 *
 * Calling flush() on the ostream object will force a DATA chunk to be
 * sent with the currently buffered data. Normal operation is to wait
 * for the buffer to fill before sending a DATA chunk.
 *
 * @see chunked_outbuf
 */
class chunked_ostream : public std::ostream {
protected:
    chunked_outbuf d_cbuf;

public:
    /**
     * Get a chunked_ostream with a buffer.
     * @note The buffer size must not be more than 2^24 bytes (0x00ffffff)
     * @param buf_size The size of the buffer in bytes.
     */
    chunked_ostream(std::ostream &os, unsigned int buf_size) : std::ostream(&d_cbuf), d_cbuf(os, buf_size) {}

    /**
     * @brief Send an end chunk.
     * Normally, an end chunk is sent by closing the chunked_ostream, but this
     * method can be used to force sending it without closing the stream. Subsequent
     * calls to send data will send data chunks.
     * @note An end chunk is sent when the stream is closed.
     * @return EOF on error or the number of bytes sent in the chunk body.
     */
    int_type write_end_chunk() { return d_cbuf.end_chunk(); }

    /**
     * @brief Send the current contents of the buffer as a data chunk.
     * Normally, the chunked_ostream object waits until the buffer is full before sending
     * the next data chunk. This will force a send with whatever is in the buffer (e.g.,
     * the DMR text). Data added after this call will be sent in subsequent chunks.
     * @note Calling flush() on the stream forces a data chunk to be sent.
     * @return EOF on error, otherwise the number of bytes sent in the chunk body.
     */
    int_type write_data_chunk() { return d_cbuf.data_chunk(); }

    /**
     * @brief Send an error message down the stream.
     * When called, this method dumps all the data currently in the buffer and
     * sends the error message text instead, using a chunk type of CHUNK_ERR. The
     * write buffer is maintained, however, so the stream ibject can still be used.
     * @param msg The error message text
     * @return The number of bytes 'dumped' from the write buffer.
     */
    int_type write_err_chunk(const std::string &msg) { return d_cbuf.err_chunk(msg); }
};

} // namespace libdap

#endif // _chunkedostream_h
