/**
 * \file os.cpp
 * This file is part of LyX, the document processor.
 * Licence details can be found in the file COPYING.
 *
 * \author Ruurd A. Reitsma
 * \author Enrico Forestieri
 *
 * Full author contact details are available in file CREDITS.
 */

#include <config.h>

#include "support/convert.h"
#include "support/debug.h"
#include "support/filetools.h"
#include "support/qstring_helpers.h"
#include "support/regex.h"

#include <QDir>

#if defined(__CYGWIN__)
#include "support/os_cygwin.cpp"
#elif defined(_WIN32)
#include "support/os_win32.cpp"
#else
#include "support/os_unix.cpp"
#endif

// Static assert to break compilation on platforms where
// int/unsigned int is not 4 bytes. Added to make sure that
// e.g., the author hash is always 32-bit.
template<bool Condition> struct static_assert_helper;
template <> struct static_assert_helper<true> {};
enum {
	dummy = sizeof(static_assert_helper<sizeof(int) == 4>)
};

namespace lyx {
namespace support {
namespace os {

int timeout_min()
{
	return 3;
}


static string const python23_call(string const & binary, bool verbose = false)
{
	const string version_info = " -c 'from __future__ import print_function;import sys; print(sys.version_info[:2], end=\"\")'";
	// Default to "python" if no binary is given.
	if (binary.empty())
		return "python -tt";

	if (verbose)
		lyxerr << "Examining " << binary << "\n";
	// Check whether this is a python 2 or 3 binary.
	cmd_ret const out = runCommand(binary + version_info);

	smatch sm;
	try {
		static regex const python_reg("\\((\\d*), (\\d*)\\)");
		if (out.first < 0 || !regex_match(out.second, sm, python_reg))
			return string();
	} catch(regex_error const & /*e*/) {
		LYXERR0("Regex error! This should not happen.");
		return string();
	}

	int major = convert<int>(sm.str(1));
	int minor = convert<int>(sm.str(2));
	if((major == 2 && minor < 7) || (major == 3 && minor < 5))
		return string();

	if (verbose)
		lyxerr << "Found Python " << out.second << "\n";
	// Add the -tt switch so that mixed tab/whitespace
	// indentation is an error
	return binary + " -tt";
}


static string const find_python_binary()
{
	// This function takes inspiration from PEP 394 and PEP 397
	// PEP 394 -- The "python" Command on Unix-Like Systems
	// https://www.python.org/dev/peps/pep-0394/
	// PEP 397 -- Python launcher for Windows
	// https://www.python.org/dev/peps/pep-0397/

	// Check whether python3 in PATH is the right one.
	string command = python23_call("python3");
	if (!command.empty())
		return command;

	// python3 does not exists, let us try to find python3.x in PATH
	// the search is probably broader than required
	// but we are trying hard to find a valid python binary
	vector<string> const path = getEnvPath("PATH");
	lyxerr << "Looking for python 3.x ...\n";
	for (auto bin: path) {
		QString const dir = toqstr(bin);
		string const localdir = dir.toLocal8Bit().constData();
		QDir qdir(dir);
		qdir.setFilter(QDir::Files | QDir::Executable);
		QStringList list = qdir.entryList(QStringList("python3*"));
		for (auto bin: list) {
			string const binary = addName(localdir,
				bin.toLocal8Bit().constData());
			command = python23_call(binary, true);
			if (!command.empty())
				return command;
		}
	}

	// python 3 was not found let us look for python 2
	command = python23_call("python2");
	if (!command.empty())
		return command;

	// python2 does not exists, let us try to find python2.x in PATH
	// the search is probably broader than required
	// but we are trying hard to find a valid python binary
	lyxerr << "Looking for python 2.x ...\n";
	for (auto bin: path) {
		QString const dir = toqstr(bin);
		string const localdir = dir.toLocal8Bit().constData();
		QDir qdir(dir);
		qdir.setFilter(QDir::Files | QDir::Executable);
		QStringList list = qdir.entryList(QStringList("python2*"));
		for (auto bin: list) {
			string const binary = addName(localdir,
				bin.toLocal8Bit().constData());
			command = python23_call(binary, true);
			if (!command.empty())
				return command;
		}
	}

	// If this happens all hope is lost that this is a sane system
	lyxerr << "Warning: No python v2.x or 3.x binary found.\n";
	return python23_call("");
}


string const python(bool reset)
{
	static string command = find_python_binary();
	// FIXME THREAD
	if (reset) {
		command = find_python_binary();
	}
	return command;
}

} // namespace os
} // namespace support
} // namespace lyx