/*************************************************************************
** Ghostscript.cpp                                                      **
**                                                                      **
** This file is part of dvisvgm -- a fast DVI to SVG converter          **
** Copyright (C) 2005-2019 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 "FilePath.hpp"
#include "Ghostscript.hpp"
#include "utility.hpp"
#if !defined(DISABLE_GS)
#include <cstring>
#include <iomanip>
#include <sstream>
#if defined(HAVE_LIBGS)
	#include <ghostscript/ierrors.h>
#else
	#include "ierrors.h"
	#include "FileFinder.hpp"
#endif

using namespace std;

// name of Ghostscript shared library set by the user
string Ghostscript::LIBGS_NAME;

#ifndef HAVE_LIBGS

#ifdef _WIN32
/** Looks up the path of the Ghostscript DLL in the Windows registry and returns it.
 *  If there is no proper registry entry, the returned string is empty. */
static string get_path_from_registry () {
#ifdef RRF_RT_REG_SZ   // RegGetValueA and RRF_RT_REG_SZ may not be defined for some oldish MinGW
	REGSAM mode = KEY_READ|KEY_QUERY_VALUE;
#ifdef KEY_WOW64_64KEY
#ifdef _WIN64
	mode |= KEY_WOW64_64KEY;
#else
	mode |= KEY_WOW64_32KEY;
#endif
#endif
	for (const char *gs_company : {"GPL", "GNU", "AFPL", "Aladdin"}) {
		const string reg_path = string("SOFTWARE\\") + gs_company + " Ghostscript";
		for (HKEY reg_root : {HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE}) {
			HKEY hkey;
			if (RegOpenKeyExA(reg_root, reg_path.c_str(), 0, mode, &hkey) == ERROR_SUCCESS) {
				char subkey[16];
				for (int k=0; RegEnumKeyA(hkey, k, subkey, 16) == ERROR_SUCCESS; k++) {
					istringstream iss(subkey);
					int major_version;
					iss >> major_version;
					if (major_version >= 7) {
						char dll_path[512];  // path to Ghostscript DLL stored in the registry
						DWORD length = 512;
						if (RegGetValueA(hkey, subkey, "GS_DLL", RRF_RT_REG_SZ, 0, dll_path, &length) == ERROR_SUCCESS) {
							RegCloseKey(hkey);
							return dll_path;
						}
					}
				}
				RegCloseKey(hkey);
			}
		}
	}
#endif  // RRF_RT_REG_SZ
	return "";
}
#endif // _WIN32

#if defined(_WIN32) && !defined(_WIN64)
static string get_gsdll32 () {
	string pathstr;
#if defined(TEXLIVEWIN32)
	char exepath[256];
	if (GetModuleFileNameA(NULL, exepath, 256)) {
		FilePath path(exepath);
		path.set(path.absolute(false)+"/../../tlpkg/tlgs");
		pathstr = util::replace(path.absolute(false)+"/", "/", "\\");
		string envvar = "GS_LIB=";
		for (string dirs : {"lib", "fonts", "Resource\\Init", "Resource", "kanji"})
			envvar += pathstr+dirs+";";
		_putenv(envvar.c_str());
		pathstr += "bin\\";
	}
#endif
	return pathstr+"gsdll32.dll";
}
#endif  // _WIN32  && !_WIN64


/** Try to detect name of the Ghostscript shared library depending on the user settings.
 *  @param[in] fname path/filename given by the user
 *  @return name of Ghostscript shared library */
static string get_libgs (const string &fname) {
	if (!fname.empty())
		return fname;
#ifdef MIKTEX
#if defined(_WIN64)
	const char *gsdll = "mgsdll64.dll";
#else
	const char *gsdll = "mgsdll32.dll";
#endif
	// try to look up the Ghostscript DLL coming with MiKTeX
	if (const char *gsdll_path = FileFinder::instance().lookup(gsdll))
		return gsdll_path;
#endif // MIKTEX
#if defined(_WIN32)
	// try to look up the path of the Ghostscript DLL in the Windows registry
	string gsdll_path = get_path_from_registry();
	if (!gsdll_path.empty())
		return gsdll_path;
#endif //_WIN32
#if defined(_WIN64)
	return "gsdll64.dll";
#elif defined(_WIN32)
	return get_gsdll32();
#else
	// try to find libgs.so.X on the user's system
	const int abi_min=7, abi_max=9; // supported libgs ABI versions
	for (int i=abi_max; i >= abi_min; i--) {
#if defined(__CYGWIN__)
		string dlname = "cyggs-" + to_string(i) + ".dll";
#else
		string dlname = "libgs.so." + to_string(i);
#endif
		DLLoader loader(dlname);
		if (loader.loaded())
			return dlname;
#if defined(__APPLE__)
		dlname = "libgs." + to_string(i) + ".dylib";
		if (loader.loadLibrary(dlname))
			return dlname;
#endif
	}
#endif
	// no appropriate library found
	return "";
}
#endif // !HAVE_LIBGS


/** Loads the Ghostscript library but does not create an instance. This
 *  constructor should only be used to call available() and revision(). */
Ghostscript::Ghostscript ()
#if !defined(HAVE_LIBGS)
	: DLLoader(get_libgs(LIBGS_NAME))
#endif
{
	_inst = 0;
}


/** Tries to load the shared library and to initialize Ghostscript.
 * @param[in] argc number of parameters in array argv
 * @param[in] argv parameters passed to Ghostscript
 * @param[in] caller this parameter is passed to all callback functions */
Ghostscript::Ghostscript (int argc, const char **argv, void *caller)
#if !defined(HAVE_LIBGS)
	: DLLoader(get_libgs(LIBGS_NAME))
#endif
{
	_inst = 0;
	init(argc, argv, caller);
}


/** Exits Ghostscript and unloads the dynamic library. */
Ghostscript::~Ghostscript () {
	if (_inst) {
		this->exit();
		delete_instance();
	}
}


bool Ghostscript::init (int argc, const char **argv, void *caller) {
	if (!_inst) {
		int status = new_instance(&_inst, caller);
		if (status < 0)
			_inst = 0;
		else {
			init_with_args(argc, const_cast<char**>(argv));
		}
	}
	return _inst != 0;
}


/** Returns true if Ghostscript library was found and can be loaded. */
bool Ghostscript::available () {
#if defined(HAVE_LIBGS)
	return true;
#else
	gsapi_revision_t rev;
	return loaded() && revision(&rev);
#endif
}


/** Retrieves version information about Ghostscript.
 * @param[out] r takes the revision information (see GS API documentation for further details)
 * @return true on success  */
bool Ghostscript::revision (gsapi_revision_t *r) {
#if defined(HAVE_LIBGS)
	return (gsapi_revision(r, sizeof(gsapi_revision_t)) == 0);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_revision))
		return (fn(r, sizeof(gsapi_revision_t)) == 0);
	return false;
#endif
}


/** Returns the revision number of the GS library. */
int Ghostscript::revision () {
	gsapi_revision_t r;
	if (revision(&r))
		return static_cast<int>(r.revision);
	return 0;
}


/** Returns the revision of the GS library as a string of the form "MAJOR.MINOR". */
string Ghostscript::revisionstr () {
	string revstr;
	if (int rev = revision()) {
		revstr = to_string(rev/100) + ".";
		if (rev % 100 < 10)
			revstr += "0";
	  	revstr += to_string(rev%100);
	}
	return revstr;
}


/** Creates a new instance of Ghostscript. This method is called by the constructor and
 *  should not be used elsewhere.
 *  @param[out] psinst handle of newly created instance (or 0 on error)
 *  @param[in] caller pointer forwarded to callback functions */
int Ghostscript::new_instance (void **psinst, void *caller) {
#if defined(HAVE_LIBGS)
	return gsapi_new_instance(psinst, caller);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_new_instance))
		return fn(psinst, caller);
	*psinst = 0;
	return 0;
#endif
}


/** Destroys the current instance of Ghostscript. This method is called by the destructor
 *  and should not be used elsewhere. */
void Ghostscript::delete_instance () {
#if defined(HAVE_LIBGS)
	gsapi_delete_instance(_inst);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_delete_instance))
		fn(_inst);
#endif
}


/** Exits the interpreter. Must be called before destroying the GS instance. */
int Ghostscript::exit () {
#if defined(HAVE_LIBGS)
	return gsapi_exit(_inst);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_exit))
		return fn(_inst);
	return 0;
#endif
}


/** Sets the I/O callback functions.
 * @param[in] in pointer to stdin handler
 * @param[in] out pointer to stdout handler
 * @param[in] err pointer to stderr handler */
int Ghostscript::set_stdio (Stdin in, Stdout out, Stderr err) {
#if defined(HAVE_LIBGS)
	return gsapi_set_stdio(_inst, in, out, err);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_set_stdio))
		return fn(_inst, in, out, err);
	return 0;
#endif
}


/** Initializes Ghostscript with a set of optional parameters. This
 *  method is called by the constructor and should not be used elsewhere.
 *  @param[in] argc number of paramters
 *  @param[in] argv parameters passed to Ghostscript */
int Ghostscript::init_with_args (int argc, char **argv) {
#if defined(HAVE_LIBGS)
	return gsapi_init_with_args(_inst, argc, argv);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_init_with_args))
		return fn(_inst, argc, argv);
	return 0;
#endif
}


/** Tells Ghostscript that several calls of run_string_continue will follow. */
int Ghostscript::run_string_begin (int user_errors, int *pexit_code) {
#if defined(HAVE_LIBGS)
	return gsapi_run_string_begin(_inst, user_errors, pexit_code);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_run_string_begin))
		return fn(_inst, user_errors, pexit_code);
	*pexit_code = 0;
	return 0;
#endif
}


/** Executes a chunk of PostScript commands given by a buffer of characters. The size of
 *  this buffer must not exceed 64KB. Longer programs can be split into arbitrary smaller chunks
 *  and passed to Ghostscript by successive calls of run_string_continue.
 *  @param[in] str buffer containing the PostScript code
 *  @param[in] length number of characters in buffer
 *  @param[in] user_errors if non-negative, the default PS error values will be generated, otherwise this value is returned
 *  @param[out] pexit_code takes the PS error code */
int Ghostscript::run_string_continue (const char *str, unsigned length, int user_errors, int *pexit_code) {
#if defined(HAVE_LIBGS)
	return gsapi_run_string_continue(_inst, str, length, user_errors, pexit_code);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_run_string_continue))
		return fn(_inst, str, length, user_errors, pexit_code);
	*pexit_code = 0;
	return 0;
#endif
}


/** Terminates the successive code feeding. Must be called after the last call of run_string_continue. */
int Ghostscript::run_string_end (int user_errors, int *pexit_code) {
#if defined(HAVE_LIBGS)
	return gsapi_run_string_end(_inst, user_errors, pexit_code);
#else
	if (auto fn = LOAD_SYMBOL(gsapi_run_string_end))
		return fn(_inst, user_errors, pexit_code);
	*pexit_code = 0;
	return 0;
#endif
}


const char* Ghostscript::error_name (int code) {
	if (code < 0)
		code = -code;
	const char *error_names[] = { ERROR_NAMES };
	if (code == 0 || (size_t)code > sizeof(error_names)/sizeof(error_names[0]))
		return nullptr;
#if defined(HAVE_LIBGS)
	// use array defined in libgs to avoid linking the error strings into the binary
	return gs_error_names[code-1];
#elif defined(_WIN32)
	// gs_error_names is private in the Ghostscript DLL so we can't access it here
	return error_names[code-1];
#else
	if (auto error_names = loadSymbol<const char**>("gs_error_names"))
		return error_names[code-1];
	return nullptr;
#endif
}

#endif  // !DISABLE_GS
