//
// VMime library (http://www.vmime.org)
// Copyright (C) 2002 Vincent Richard <vincent@vmime.org>
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 3 of
// the License, or (at your option) any later version.
//
// This program 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
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// Linking this library statically or dynamically with other modules is making
// a combined work based on this library.  Thus, the terms and conditions of
// the GNU General Public License cover the whole combination.
//

#ifndef VMIME_UTILITY_FILTEREDSTREAM_HPP_INCLUDED
#define VMIME_UTILITY_FILTEREDSTREAM_HPP_INCLUDED


#include <algorithm>

#include "vmime/utility/inputStream.hpp"
#include "vmime/utility/outputStream.hpp"


namespace vmime {
namespace utility {


/** A stream whose input is filtered.
  */
class VMIME_EXPORT filteredInputStream : public inputStream {
public:

	virtual size_t getBlockSize();

	/** Return a reference to the stream being filtered.
	  *
	  * @return stream being filtered
	  */
	virtual inputStream& getPreviousInputStream() = 0;
};


/** A stream whose output is filtered.
  */
class VMIME_EXPORT filteredOutputStream : public outputStream {

public:

	virtual size_t getBlockSize();

	/** Return a reference to the stream being filtered.
	  *
	  * @return destination stream for filtered data
	  */
	virtual outputStream& getNextOutputStream() = 0;
};


/** A filtered input stream which replaces "\n.."
  * sequences with "\n." sequences.
  */
class VMIME_EXPORT dotFilteredInputStream : public filteredInputStream {

public:

	/** Construct a new filter for the specified input stream.
	  *
	  * @param is stream from which to read data to be filtered
	  */
	dotFilteredInputStream(inputStream& is);

	inputStream& getPreviousInputStream();

	bool eof() const;

	void reset();

	size_t read(byte_t* const data, const size_t count);

	size_t skip(const size_t count);

private:

	inputStream& m_stream;

	byte_t m_previousChar2; // (N - 1)th character of previous buffer
	byte_t m_previousChar1; // (N)th (last) character of previous buffer
};


/** A filtered output stream which replaces "\n."
  * sequences with "\n.." sequences.
  */
class VMIME_EXPORT dotFilteredOutputStream : public filteredOutputStream {

public:

	/** Construct a new filter for the specified output stream.
	  *
	  * @param os stream into which write filtered data
	  */
	dotFilteredOutputStream(outputStream& os);

	outputStream& getNextOutputStream();

	void flush();

	size_t getBlockSize();

protected:

	void writeImpl(const byte_t* const data, const size_t count);

private:

	outputStream& m_stream;
	byte_t m_previousChar;
	bool m_start;
};


/** A filtered output stream which replaces CRLF sequences
  * with single LF characters.
  */
class VMIME_EXPORT CRLFToLFFilteredOutputStream : public filteredOutputStream {

public:

	/** Construct a new filter for the specified output stream.
	  *
	  * @param os stream into which write filtered data
	  */
	CRLFToLFFilteredOutputStream(outputStream& os);

	outputStream& getNextOutputStream();

	void flush();

	size_t getBlockSize();

protected:

	void writeImpl(const byte_t* const data, const size_t count);

private:

	outputStream& m_stream;
	byte_t m_previousChar;
};


/** A filtered output stream which replaces CR or LF characters
  * with CRLF sequences.
  */
class VMIME_EXPORT LFToCRLFFilteredOutputStream : public filteredOutputStream {

public:

	/** Construct a new filter for the specified output stream.
	  *
	  * @param os stream into which write filtered data
	  */
	LFToCRLFFilteredOutputStream(outputStream& os);

	outputStream& getNextOutputStream();

	void flush();

	size_t getBlockSize();

protected:

	void writeImpl(const byte_t* const data, const size_t count);

private:

	outputStream& m_stream;
	byte_t m_previousChar;
};


/** A filtered input stream which stops when a specified sequence
  * is found (eof() method will return 'true').
  */
template <int COUNT>
class VMIME_EXPORT stopSequenceFilteredInputStream : public filteredInputStream {

public:

	/** Construct a new filter for the specified input stream.
	  *
	  * @param is stream from which to read data to be filtered
	  * @param sequence sequence on which to stop
	  */
	stopSequenceFilteredInputStream(inputStream& is, const byte_t* sequence)
		: m_stream(is),
		  m_sequence(sequence),
		  m_found(0),
		  m_eof(false) {

	}

	/** Construct a new filter for the specified input stream.
	  *
	  * @param is stream from which to read data to be filtered
	  * @param sequence sequence on which to stop
	  */
	stopSequenceFilteredInputStream(inputStream& is, const char* sequence)
		: m_stream(is),
		  m_sequence(reinterpret_cast <const byte_t*>(sequence)),
		  m_found(0),
		  m_eof(false) {

	}

	inputStream& getPreviousInputStream() {

		return m_stream;
	}

	bool eof() const {

		return m_found == COUNT || m_eof;
	}

	void reset() {

		m_found = 0;
		m_stream.reset();
	}

	size_t read(byte_t* const data, const size_t count) {

		// Read buffer must be at least 'COUNT' size + 1 byte
		if (eof() || count <= COUNT) {
			return 0;
		}

		if (m_stream.eof()) {

			if (m_found != 0) {

				const size_t found = m_found;

				for (size_t f = 0 ; f < found ; ++f) {
					data[f] = m_sequence[f];
				}

				m_found = 0;
				m_eof = true;

				return found;

			} else {

				m_eof = true;
				return 0;
			}
		}

		size_t read = m_stream.read(data, count - COUNT);

		byte_t* end = data + read;
		byte_t* pos = data;

		while (pos < end) {

			// Very simple case, search for the whole sequence
			if (m_found == 0) {

				while (pos < end) {

					pos = std::find(pos, end, m_sequence[0]);

					if (pos == end) {
						return read;
					}

					m_found = 1;
					++pos;

					while (pos < end && m_found < COUNT && m_sequence[m_found] == *pos) {
						++m_found;
						++pos;
					}

					// Didn't found whole sequence
					if (m_found != COUNT) {

						// We reached the end of the buffer
						if (pos == end) {

							return read - m_found;

						// Common prefix but not whole sequence
						} else {

							m_found = 0;
						}

					// Whole sequence found
					} else {

						// End of stream
						return pos - data - m_found;
					}
				}

			// More complex case: search for a sequence which has begun
			// in a previous buffer
			} else {

				// Search for the end of the previously started sequence
				while (pos < end && m_found < COUNT && m_sequence[m_found] == *pos) {
					++m_found;
					++pos;
				}

				if (m_found != COUNT) {

					// End of buffer
					if (pos == end) {

						// No data: this buffer is a sub-sequence of the
						// searched sequence
						return 0;

					// Common prefix
					} else {

						// We have to reinject the incomplete sequence into
						// the stream data

						// -- shift right data
						const size_t n = pos - data;

						byte_t* newEnd = data + read + m_found - n;
						byte_t* oldEnd = data + read;

						for (size_t i = 0 ; i < read - n ; ++i) {

							--newEnd;
							--oldEnd;

							*newEnd = *oldEnd;
						}

						// -- copy the prefix just before data
						for (size_t f = 0 ; f < m_found ; ++f) {
							data[f] = m_sequence[f];
						}

						read += m_found - n;
						end += m_found - n;

						m_found = 0;
					}

				} else {

					return 0;  // no more data
				}
			}
		}

		return read;
	}

	size_t skip(const size_t /* count */) {

		// Not supported
		return 0;
	}

private:

	inputStream& m_stream;

	const byte_t* m_sequence;
	size_t m_found;

	bool m_eof;
};


template <>
size_t stopSequenceFilteredInputStream <1>::read(byte_t* const data, const size_t count);


} // utility
} // vmime


#endif // VMIME_UTILITY_FILTEREDSTREAM_HPP_INCLUDED