#include "namereplace.h"
#include <QString>
#include <QRegularExpression>
#include <QFile>
#include <QTextStream>
#include <QDebug>
#include <QProcess>

#define SOURCE_FILE "/opt/openslx/lightdm/login-regexp"
#define LOOKUP_PROCESS "/opt/openslx/pam/get_username"

static QList< QPair< QRegularExpression, QString > > list;

static inline int find(QChar c, int start, const QString& line)
{
	do {
		int next = line.indexOf(c, start);
		if (next == -1)
			return -1;
		if (line.at(next - 1) != '\\')
			return next;
		start = next + 1;
	} while (true);
}

void NameReplace::loadSubs()
{
	int idx = 0;
	QFile inputFile(SOURCE_FILE);
	if (!inputFile.open(QIODevice::ReadOnly))
		return;
	QTextStream in(&inputFile);
	in.setCodec("UTF-8");
	while (!in.atEnd()) {
		QString line = in.readLine();
		idx++;
		if (line.isEmpty())
			continue;
		QChar delim = line.at(0);
		int first = find(delim, 1, line);
		if (first == -1)
			continue;
		int second = find(delim, first + 1, line);
		if (second == -1)
			continue;
		QString regex = line.mid(1, first - 1).replace(QString("\\") + delim, QString(delim));
		QString replace = line.mid(first + 1, second - first - 1).replace(QString("\\") + delim, QString(delim));
		QString flags = line.mid(second + 1);
		// ...
		QRegularExpression::PatternOptions opts = QRegularExpression::NoPatternOption;
		if (flags.contains("i")) {
			opts |= QRegularExpression::CaseInsensitiveOption;
		}
		QRegularExpression re(regex, opts);
		if (!re.isValid()) {
			qWarning() << "Invalid regex:" << regex << "on line" << idx;
			continue;
		}
		list.append(QPair<QRegularExpression, QString>(re, replace));
	}
	inputFile.close();
}

void NameReplace::replace(QString& input)
{
	if (!list.isEmpty()) {
		// First, apply user defined replacement
		for (auto &brumm : list) {
			input = input.replace(brumm.first, brumm.second);
		}
	}
	// Now, prefix names that start with a digit, since systemd/logind refuses
	// to work with those in more recent versions. It was never a good idea to
	// do this anyways, but now we don't have a choice, since sessions without
	// a proper systemd user instance will become more and more broken in the
	// future.
	if (*input.constData() >= '0' && *input.constData() <= '9') {
		input = QLatin1String("_x_") + input;
	}
	// Finally, look up the proper casing of the desired username, as some
	// servers (AD) are case insensitive, which can lead to problems if what the
	// user entered doesn't exactly match what it's actually spelled like
	// server-side.
	QProcess getCaps;
	getCaps.start(LOOKUP_PROCESS, QStringList(input));
	getCaps.waitForFinished(8000);
	QString output = QString::fromLocal8Bit(getCaps.readAllStandardOutput());
	int idx = output.indexOf('\n');
	if (idx != -1) {
		output = output.left(idx);
	}
	if (output.length() == input.length()) {
		input = output;
	} else {
		qDebug() << "Not replacing" << input << "by" << output;
	}
}