/***************************************************************************
    File             : ExpressionTextEdit.cpp
    Project          : LabPlot
    --------------------------------------------------------------------
    Copyright        : (C) 2014-2015 Alexander Semke (alexander.semke@web.de)
    Description      : widget for defining mathematical expressions
					   modified version of
					   http://qt-project.org/doc/qt-4.8/tools-customcompleter.html
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *  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 2 of the License, or      *
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 *                                                                         *
 *  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                                           *
 *                                                                         *
 ***************************************************************************/

/****************************************************************************
 **
 ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
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 **
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#include "ExpressionTextEdit.h"
#include "backend/gsl/ExpressionParser.h"
#include "tools/EquationHighlighter.h"

#include <QCompleter>
#include <QKeyEvent>
#include <QAbstractItemView>
#include <QScrollBar>



/*!
  \class ExpressionTextEdit
  \brief  Provides a widget for for defining mathematical expressions
		  Supports syntax-highlighting and completion.

		  Modified version of http://qt-project.org/doc/qt-4.8/tools-customcompleter.html

  \ingroup kdefrontend
*/
ExpressionTextEdit::ExpressionTextEdit(QWidget *parent) : KTextEdit(parent),
	m_highlighter(new EquationHighlighter(this)),
	m_expressionType(XYEquationCurve::Neutral),
	m_isValid(false) {

	QStringList list = ExpressionParser::getInstance()->functions();
	list.append(ExpressionParser::getInstance()->constants());

	setTabChangesFocus(true);

	m_completer = new QCompleter(list);
	m_completer->setWidget(this);
	m_completer->setCompletionMode(QCompleter::PopupCompletion);
	m_completer->setCaseSensitivity(Qt::CaseInsensitive);

	connect(m_completer, SIGNAL(activated(QString)),this, SLOT(insertCompletion(QString)));
	connect(this, SIGNAL(textChanged()), this, SLOT(validateExpression()) );
	connect(this, SIGNAL(cursorPositionChanged()), m_highlighter, SLOT(rehighlight()) );
}

EquationHighlighter* ExpressionTextEdit::highlighter() {
	return m_highlighter;
}

bool ExpressionTextEdit::isValid() const {
	return (!document()->toPlainText().trimmed().isEmpty() && m_isValid);
}

void ExpressionTextEdit::setExpressionType(XYEquationCurve::EquationType type) {
	m_expressionType = type;
	m_variables.clear();
	if (type==XYEquationCurve::Cartesian)
		m_variables<<"x";
	else if (type==XYEquationCurve::Polar)
		m_variables<<"phi";
	else if (type==XYEquationCurve::Parametric)
		m_variables<<"t";
	else if (type==XYEquationCurve::Implicit)
		m_variables<<"x"<<"y";

	m_highlighter->setVariables(m_variables);
}

void ExpressionTextEdit::setVariables(const QStringList& vars) {
	m_variables = vars;
	m_highlighter->setVariables(m_variables);
	validateExpression(true);
}

void ExpressionTextEdit::insertCompletion(const QString& completion) {
	QTextCursor tc = textCursor();
	int extra = completion.length() - m_completer->completionPrefix().length();
	tc.movePosition(QTextCursor::Left);
	tc.movePosition(QTextCursor::EndOfWord);
	tc.insertText(completion.right(extra));
	setTextCursor(tc);
}

QString ExpressionTextEdit::textUnderCursor() const {
	QTextCursor tc = textCursor();
	tc.select(QTextCursor::WordUnderCursor);
	return tc.selectedText();
}

void ExpressionTextEdit::focusInEvent(QFocusEvent *e) {
	m_completer->setWidget(this);
	QTextEdit::focusInEvent(e);
}

void ExpressionTextEdit::keyPressEvent(QKeyEvent *e) {
	switch (e->key()) {
		case Qt::Key_Enter:
		case Qt::Key_Return:
			e->ignore();
			return;
		default:
			break;
	}

	bool isShortcut = ((e->modifiers() & Qt::ControlModifier) && e->key() == Qt::Key_E); // CTRL+E
	if (!isShortcut) // do not process the shortcut when we have a completer
		QTextEdit::keyPressEvent(e);

	const bool ctrlOrShift = e->modifiers() & (Qt::ControlModifier | Qt::ShiftModifier);
	if ((ctrlOrShift && e->text().isEmpty()))
		return;

	static QString eow("~!@#$%^&*()_+{}|:\"<>?,./;'[]\\-="); // end of word
	bool hasModifier = (e->modifiers() != Qt::NoModifier) && !ctrlOrShift;
	QString completionPrefix = textUnderCursor();

	if (!isShortcut && (hasModifier || e->text().isEmpty()|| completionPrefix.length() < 1
					|| eow.contains(e->text().right(1)))) {
		m_completer->popup()->hide();
		return;
	}

	if (completionPrefix != m_completer->completionPrefix()) {
		m_completer->setCompletionPrefix(completionPrefix);
		m_completer->popup()->setCurrentIndex(m_completer->completionModel()->index(0, 0));
	}
	QRect cr = cursorRect();
	cr.setWidth(m_completer->popup()->sizeHintForColumn(0)
				+ m_completer->popup()->verticalScrollBar()->sizeHint().width());
	m_completer->complete(cr); // popup it up!
}

/*!
 * \brief Validates the current expression if the text was changed and highlights the text field red if the expression is invalid.
 * \param force forces the validation and highlighting when no text changes were made, used when new parameters/variables were provided
 */
void ExpressionTextEdit::validateExpression(bool force) {
	//check whether the expression was changed or only the formating
	QString text = toPlainText();
	if (text != m_currentExpression || force) {
		m_isValid = ExpressionParser::getInstance()->isValid(text, m_variables);
		if (!m_isValid)
			setStyleSheet("QTextEdit{background: red;}");
		else
			setStyleSheet("QTextEdit{background: white;}"); //TODO: assign the default color for the current style/theme

		m_currentExpression = text;
		emit(expressionChanged());
	}
}
