#include "CodeEditor.h"
#include "EditorGutter.h"
#include <QPainter>
#include <QTextBlock>
#include <QDebug>
//
// Adapted from codeeditor example
// http://doc.qt.io/qt-5/qtwidgets-widgets-codeeditor-example.html
//
// Used term gutter as I want to expand it to do other things to like error
// position marking.
//

CodeEditor::CodeEditor(QWidget *parent)
	: QPlainTextEdit(parent)
	, gutterArea(new EditorGutter(this))
{
	connect(this, SIGNAL(blockCountChanged(int)), this, SLOT(updateGutterAreaWidth(int)));
	connect(this, SIGNAL(updateRequest(QRect,int)), this, SLOT(updateGutterArea(QRect,int)));
	connect(this, SIGNAL(cursorPositionChanged()), this, SLOT(highlightCurrentLine()));
	connect(this, SIGNAL(textChanged()), this, SLOT(onTextChanged()));

	setWordWrapMode(QTextOption::NoWrap);

	updateGutterAreaWidth(0);
	setTabSize(4);
	highlightCurrentLine();
}

int CodeEditor::gutterAreaWidth()
{
	int digits = 1;
	int max = qMax(1, blockCount());
	while (max >= 10) {
		max /= 10;
		++digits;
	}

	int space = 3 + fontMetrics().horizontalAdvance(QLatin1Char('9')) * (digits + 2);

	return space;
}

void CodeEditor::updateGutterAreaWidth(int /* newBlockCount */)
{
	setViewportMargins(gutterAreaWidth(), 0, 0, 0);
}

void CodeEditor::updateGutterArea(const QRect &rect, int dy)
{
	if (dy)
		gutterArea->scroll(0, dy);
	else
		gutterArea->update(0, rect.y(), gutterArea->width(), rect.height());

	if (rect.contains(viewport()->rect()))
		updateGutterAreaWidth(0);
}

void CodeEditor::resizeEvent(QResizeEvent *e)
{
	QPlainTextEdit::resizeEvent(e);

	QRect cr = contentsRect();
	gutterArea->setGeometry(QRect(cr.left(), cr.top(), gutterAreaWidth(), cr.height()));
}

void CodeEditor::highlightCurrentLine()
{
	QTextEdit::ExtraSelection selection;
	QColor lineColor = QColor(Qt::yellow).lighter(160);
	selection.format.setBackground(lineColor);
	selection.format.setProperty(QTextFormat::FullWidthSelection, true);
	selection.cursor = textCursor();
	selection.cursor.clearSelection();
	currentLine = selection;

	updateExtraSelections();
}

void CodeEditor::onTextChanged()
{
	clearErrorMarkers();
}

void CodeEditor::addErrorMarker(int position, int length)
{
	QTextEdit::ExtraSelection selection;
	QColor lineColor = QColor(Qt::red).lighter(160);
	selection.format.setBackground(lineColor);
	selection.format.setFontItalic(true);
	selection.cursor = textCursor();
	selection.cursor.setPosition(position);
	int lineno = selection.cursor.blockNumber();
	errorLines.insert(lineno);
	selection.cursor.movePosition(QTextCursor::Right, QTextCursor::KeepAnchor, length);
	errorMarkers.append(selection);

	update();

	updateExtraSelections();
}

void CodeEditor::clearErrorMarkers()
{
	errorMarkers.clear();
	errorLines.clear();
	update();
	updateExtraSelections();
}

void CodeEditor::updateExtraSelections()
{
	QList<QTextEdit::ExtraSelection> extraSelections;
	extraSelections.append(currentLine);
	for (auto&& e : errorMarkers)
		extraSelections.append(e);

	setExtraSelections(extraSelections);
}

void CodeEditor::gutterAreaPaintEvent(QPaintEvent *event)
{
	QPainter painter(gutterArea);
	painter.fillRect(event->rect(), Qt::lightGray);

	QTextBlock block = firstVisibleBlock();
	int blockNumber = block.blockNumber();
	int top = (int) blockBoundingGeometry(block).translated(contentOffset()).top();
	int bottom = top + (int) blockBoundingRect(block).height();

	// We will now loop through all visible lines and paint the line numbers in the
	// extra area for each line. Notice that in a plain text edit each line will
	// consist of one QTextBlock; though, if line wrapping is enabled, a line may span
	// several rows in the text edit's viewport.
	//
	// We get the top and bottom y-coordinate of the first text block, and adjust these
	// values by the height of the current text block in each iteration in the loop.
	while (block.isValid() && top <= event->rect().bottom()) {
		if (block.isVisible() && bottom >= event->rect().top()) {
			QString number = QString::number(blockNumber + 1);
			painter.setPen(Qt::black);
			painter.drawText(0, top, gutterArea->width(), fontMetrics().height(),
							 Qt::AlignRight, number);

			if (errorLines.count(blockNumber) > 0) {
				int s = fontMetrics().height() - 8;
				painter.setBrush(QBrush(Qt::red));
				painter.drawEllipse(4, top + 4, s, s);
			}
		}

		block = block.next();
		top = bottom;
		bottom = top + (int) blockBoundingRect(block).height();
		++blockNumber;
	}
}

void CodeEditor::keyPressEvent(QKeyEvent *e)
{
	auto k = e->key();
	qDebug() << QString("%1").arg(k, 0, 16);
	if (k == Qt::Key_Tab) {
		// Function returns false if there was no selection to indent
		if (indentSelection(true))
			return;
	}
	else if (k == Qt::Key_Backtab) {
		// Function returns false if there was no selection to indent
		if (indentSelection(false))
			return;
	}
	else if (k == Qt::Key_Equal || k == Qt::Key_Plus) {
		if (e->modifiers().testFlag(Qt::ControlModifier)) {
			auto f = font();
			f.setPointSize(f.pointSize() + 1);
			setFont(f);
		}
	}
	else if (k == Qt::Key_Minus) {
		if (e->modifiers().testFlag(Qt::ControlModifier)) {
			auto f = font();
			f.setPointSize(f.pointSize() - 1);
			setFont(f);
		}
	}
	QPlainTextEdit::keyPressEvent(e);
}

bool CodeEditor::indentSelection(bool indent)
{
	auto cursor = textCursor();

	if(!cursor.hasSelection())
		return false;

	auto first_pos = cursor.anchor();
	auto end_pos   = cursor.position();

	if(first_pos > end_pos)
		std::swap(first_pos, end_pos);

	cursor.setPosition(first_pos, QTextCursor::MoveAnchor);
	auto start_block = cursor.block().blockNumber();

	cursor.setPosition(end_pos, QTextCursor::MoveAnchor);
	auto end_block = cursor.block().blockNumber();
	if (end_block == start_block)
		return false;

	cursor.beginEditBlock();
	cursor.setPosition(first_pos, QTextCursor::MoveAnchor);
	const auto block_count = end_block - start_block;
	for(int block = 0; block <= block_count; ++block) {
		cursor.movePosition(QTextCursor::StartOfBlock, QTextCursor::MoveAnchor);
		if (indent) {
			if (m_useTab)
				cursor.insertText("\t");
			else
				cursor.insertText(QString(m_tabSize, ' '));
		}
		else {
			// remove tab if there is a tab
			cursor.movePosition(QTextCursor::EndOfLine, QTextCursor::KeepAnchor);
			const QString text = cursor.selectedText();
			int index = 0;
			int pos = 0;
			while (pos < m_tabSize && index < text.length()) {
				QChar c = text[index++];
				if (c == ' ')
					++pos;
				else if (c == '\t')
					pos = ((pos + m_tabSize) / m_tabSize) * m_tabSize;
				else {
					--index;
					break;
				}
			}
			cursor.movePosition(QTextCursor::StartOfBlock, QTextCursor::MoveAnchor);
			for (int i = 0; i < index; ++i)
				cursor.movePosition(QTextCursor::Right, QTextCursor::KeepAnchor);
			cursor.removeSelectedText();
		}
		cursor.movePosition(QTextCursor::NextBlock, QTextCursor::MoveAnchor);
	}
	cursor.endEditBlock();

	cursor.setPosition(first_pos, QTextCursor::MoveAnchor);
	cursor.movePosition(QTextCursor::StartOfBlock, QTextCursor::MoveAnchor);
	while(cursor.block().blockNumber() < end_block)
		cursor.movePosition(QTextCursor::NextBlock, QTextCursor::KeepAnchor);

	cursor.movePosition(QTextCursor::EndOfBlock, QTextCursor::KeepAnchor);

	setTextCursor(cursor);
	return true;
}

void CodeEditor::setFont(const QFont &f)
{
	QWidget::setFont(f);
	auto orig_tab = m_tabSize;
	m_tabSize = 0;
	setTabSize(orig_tab);
}

void CodeEditor::setTabSize(int chars)
{
	m_tabSize = chars;
	int pixels = fontMetrics().horizontalAdvance(QString(chars, '0'));
	this->setTabStopDistance(pixels);
}