/*************************************************************************
** GFReader.cpp                                                         **
**                                                                      **
** This file is part of dvisvgm -- a fast DVI to SVG converter          **
** Copyright (C) 2005-2016 Martin Gieseking <martin.gieseking@uos.de>   **
**                                                                      **
** 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, see <http://www.gnu.org/licenses/>. **
*************************************************************************/

#include <config.h>
#include <sstream>
#include "GFReader.h"
#include "SignalHandler.h"

using namespace std;

struct GFCommand
{
	void (GFReader::*method)(int);
	int numBytes;
};


/** Converts a fix point length to double (PS point units) */
static inline double fix2double (Int32 fix) {
	return double(fix)/(1 << 20)*72/72.27;
}


static inline double scaled2double (Int32 scaled) {
	return double(scaled)/(1 << 16);
}


GFReader::GFReader (istream &is) : _in(is), _insideCharDef(false), _penDown(false)
{
	_minX = _maxX = _minY = _maxY = _x = _y = 0;
	_currentChar = 0;
	_designSize = 0;
	_hppp = _vppp = 0;
	_checksum = 0;
}


UInt32 GFReader::readUnsigned (int bytes) {
	UInt32 ret = 0;
	for (int i=bytes-1; i >= 0 && !_in.eof(); i--) {
		UInt32 b = _in.get();
		ret |= b << (8*i);
	}
	return ret;
}


Int32 GFReader::readSigned (int bytes) {
	Int32 ret = _in.get();
	if (ret & 128)        // negative value?
		ret |= 0xffffff00;
	for (int i=bytes-2; i >= 0 && !_in.eof(); i--)
		ret = (ret << 8) | _in.get();
	return ret;
}


string GFReader::readString (int bytes) {
	vector<char> buf(bytes+1);
	if (bytes > 0)
		_in.get(&buf[0], bytes+1);  // reads 'bytes' bytes (pos. bytes+1 is set to 0)
	else
		buf[0] = 0;
	return &buf[0];
}


/** Reads a single GF command from the current position of the input stream and calls the
 *  corresponding cmdFOO method.
 *  @return opcode of the executed command */
int GFReader::executeCommand () {
	SignalHandler::instance().check();
	/* Each cmdFOO command reads the necessary number of bytes from the stream so executeCommand
	doesn't need to know the exact GF command format. Some cmdFOO methods are used for multiple
	GF commands because they only differ in the size of their parameters. */
	static const GFCommand commands[] = {
		{&GFReader::cmdPaint, 1}, {&GFReader::cmdPaint, 2}, {&GFReader::cmdPaint, 3},                        // 64-66
		{&GFReader::cmdBoc, 0},   {&GFReader::cmdBoc1, 0},                                                   // 67-68
		{&GFReader::cmdEoc, 0},                                                                              // 69
		{&GFReader::cmdSkip, 0},  {&GFReader::cmdSkip, 1},  {&GFReader::cmdSkip, 2},{&GFReader::cmdSkip, 3}, // 70-73
		{&GFReader::cmdXXX, 1},   {&GFReader::cmdXXX, 2},   {&GFReader::cmdXXX, 3}, {&GFReader::cmdXXX, 4},  // 239-242
		{&GFReader::cmdYYY, 0},                                                                              // 243
		{&GFReader::cmdNop, 0},                                                                              // 244
		{&GFReader::cmdCharLoc, 0}, {&GFReader::cmdCharLoc0, 0},                                             // 245-246
		{&GFReader::cmdPre, 0},     {&GFReader::cmdPost, 0}, {&GFReader::cmdPostPost, 0}                     // 247-249
	};

	int opcode = _in.get();
	if (opcode < 0)  // at end of file?
		throw GFException("unexpected end of file");

	if (opcode >= 0 && opcode <= 63)
		cmdPaint0(opcode);
	else if (opcode >= 74 && opcode <= 238)
		cmdNewRow(opcode-74);
	else if (opcode >= 250) {
		ostringstream oss;
		oss << "undefined GF command (opcode " << opcode << ")";
		throw GFException(oss.str());
	}
	else {
		int offset = opcode <= 73 ? 64 : 239-(73-64+1);
		const GFCommand &cmd = commands[opcode-offset];
		if (cmd.method)
			(this->*cmd.method)(cmd.numBytes);
	}
	return opcode;
}


bool GFReader::executeChar (UInt8 c) {
	_in.clear();
	if (_charInfoMap.empty())
		executePostamble();          // read character info
	_in.clear();
	Iterator it = _charInfoMap.find(c);
	if (_in && it != _charInfoMap.end()) {
		_in.seekg(it->second.location);
		while (executeCommand() != 69);  // execute all commands until eoc is reached
		return true;
	}
	return false;
}


bool GFReader::executeAllChars () {
	_in.clear();
	if (_charInfoMap.empty())
		executePostamble();   // read character info
	_in.clear();
	if (_in) {
		_in.seekg(0);
		while (executeCommand() != 248); // execute all commands until postamble is reached
		return true;
	}
	return false;
}


bool GFReader::executePreamble () {
	_in.clear();
	if (!_in)
		return false;
	_in.seekg(0);
	executeCommand();
	return true;
}


bool GFReader::executePostamble () {
	_in.clear();
	if (!_in)
		return false;
	_in.seekg(-1, ios::end);
	while (_in.peek() == 223)        // skip fill bytes
		_in.seekg(-1, ios::cur);
	_in.seekg(-4, ios::cur);
	UInt32 q = readUnsigned(4);      // pointer to begin of postamble
	_in.seekg(q);                    // now on begin of postamble
	while (executeCommand() != 249); // execute all commands until postpost is reached
	return true;
}


/** Returns the design size of this font in PS point units. */
double GFReader::getDesignSize () const {
	return fix2double(_designSize);
}

/** Returns the number of horizontal pixels per point. */
double GFReader::getHPixelsPerPoint () const {
	return scaled2double(_hppp)*72/72.27;
}

/** Returns the number of vertical pixels per point. */
double GFReader::getVPixelsPerPoint () const {
	return scaled2double(_vppp)*72/72.27;
}

/** Returns the width of character c in PS point units */
double GFReader::getCharWidth (UInt32 c) const {
	ConstIterator it = _charInfoMap.find(c%256);
	return it == _charInfoMap.end() ? 0 : it->second.width*getDesignSize()/(1<<24);
}

///////////////////////


/** Reads the preamble. */
void GFReader::cmdPre (int) {
	UInt32 i = readUnsigned(1);
	if (i != 131)
		throw GFException("invalid identification number in GF preamble");
	else {
		UInt32 k = readUnsigned(1);
		string s = readString(k);
		preamble(s);
	}
}


/** Reads the postamble. */
void GFReader::cmdPost (int) {
	readUnsigned(4);                // pointer to byte after final eoc
	_designSize = readUnsigned(4);  // design size of font in points
	_checksum   = readUnsigned(4);  // checksum
	_hppp       = readUnsigned(4);  // horizontal pixels per point (scaled int)
	_vppp       = readUnsigned(4);  // vertical pixels per point (scaled int)
	_in.seekg(16, ios::cur);        // skip x and y bounds
	postamble();
}


/** Reads trailing bytes at end of stream. */
void GFReader::cmdPostPost (int) {
	readUnsigned(4);   // pointer to begin of postamble
	UInt32 i = readUnsigned(1);
	if (i != 131)
		throw GFException("invalid identification number in GF preamble");
	while (readUnsigned(1) == 223); // skip fill bytes
}


/** Inverts "paint color" (black to white or vice versa) of n pixels
 *  and advances the cursor by n.
 *  @param[in] n number of pixels to be inverted */
void GFReader::cmdPaint0 (int n) {
	if (!_insideCharDef)
		throw GFException("character-related command outside BOC and EOC");
	if (_penDown)                    // set pixels?
		_bitmap.setBits(_y, _x, n);
	_x += n;
	_penDown = !_penDown;             // inverse pen state
}


/** Inverts "paint color" (black to white or vice versa) of n pixels
 *  and advances the cursor by n. The number n of pixels is read from
 *  the input stream.
 *  @param[in] len size of n in bytes */
void GFReader::cmdPaint (int len) {
	UInt32 pixels = readUnsigned(len);
	cmdPaint0(pixels);
}


/** Beginning of character (generic format). */
void GFReader::cmdBoc (int) {
	_currentChar = readSigned(4);
	readSigned(4);  // pointer to previous boc with same c mod 256
	_minX = readSigned(4);
	_maxX = readSigned(4);
	_minY = readSigned(4);
	_maxY = readSigned(4);
	_x = _minX;
	_y = _maxY;
	_penDown = false;
	_bitmap.resize(_minX, _maxX, _minY, _maxY);
	_insideCharDef = true;
	beginChar(_currentChar);
}


/** Beginning of character (compact format). */
void GFReader::cmdBoc1 (int) {
	_currentChar = readUnsigned(1);
	UInt32 dx = readUnsigned(1);
	_maxX = readUnsigned(1);
	_minX = _maxX - dx;
	UInt32 dy = readUnsigned(1);
	_maxY = readUnsigned(1);
	_minY = _maxY - dy;
	_x = _minX;
	_y = _maxY;
	_penDown = false;
	_bitmap.resize(_minX, _maxX, _minY, _maxY);
	_insideCharDef = true;
	beginChar(_currentChar);
}


/** End of character. */
void GFReader::cmdEoc (int) {
	if (!_insideCharDef)
		throw GFException("misplaced EOC");
	_insideCharDef = false;
	endChar(_currentChar);
}


/** Moves cursor to the beginning of a following row and sets
 *  paint color to white.
 *  @param[in] len if 0: move to next row, otherwise: number of bytes to read.
 *                 The read value denotes the number of rows to be skipped.  */
void GFReader::cmdSkip (int len) {
	if (!_insideCharDef)
		throw GFException("character-related command outside BOC and EOC");
	if (len == 0)
		_y--;
	else
		_y -= readUnsigned(len)+1;
	_x = _minX;
	_penDown = false;
}


/** Moves cursor to pixel number 'col' in the next row and sets
 *  the paint color to black.
 *  @param[in] col pixel/column number */
void GFReader::cmdNewRow (int col) {
	if (!_insideCharDef)
		throw GFException("character-related command outside BOC and EOC");
	_x = _minX + col ;
	_y--;
	_penDown = true;
}


void GFReader::cmdXXX (int len) {
	UInt32 n = readUnsigned(len);
	string str = readString(n);
	special(str);
}


void GFReader::cmdYYY (int) {
	Int32 y = readSigned(4);
	numspecial(y);
}


/** Does nothing. */
void GFReader::cmdNop (int) {
}


/** Reads character locator (part of postamble) */
void GFReader::cmdCharLoc0 (int) {
	UInt8 c  = readUnsigned(1); // character code mod 256
	UInt8 dm = readUnsigned(1); //
	Int32 w  = readSigned(4);   // (1<<24)*characterWidth/designSize
	Int32 p   = readSigned(4);  // pointer to begin of (last) character data
	Int32 dx  = 65536*dm;
	Int32 dy  = 0;
	_charInfoMap[c] = CharInfo(dx, dy, w, p);
}


/** Reads character locator (part of postamble) */
void GFReader::cmdCharLoc (int) {
	UInt32 c = readUnsigned(1); // character code mod 256
	Int32 dx = readSigned(4);   // horizontal escapement (scaled pixel units)
	Int32 dy = readSigned(4);   // vertical escapement (scaled pixel units)
	Int32 w  = readSigned(4);   // (1<<24)*characterWidth/designSize
	Int32 p  = readSigned(4);   // pointer to begin of (last) character data
	_charInfoMap[c] = CharInfo(dx, dy, w, p);
}

