/*
 * Copyright (C) 2001-2008 Justin Karneges, Martin Hostettler
 *
 * 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 (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/>.
 *
 */

 // Generic tab completion support code.

#include <QDebug>
#include "tabcompletion.h"

TabCompletion::TabCompletion(QObject *parent)
 : QObject(parent)
{
	typingStatus_ = Typing_Normal;
	textEdit_ = 0;
}


TabCompletion::~TabCompletion()
{
}

void TabCompletion::setTextEdit(QTextEdit* textEdit) {
	textEdit_ = textEdit;

	QColor mleBackground(textEdit_->palette().color(QPalette::Active, QPalette::Base));

	if (mleBackground.value() < 128) {
		highlight_ = mleBackground.lighter(125);
	} else {
		highlight_ = mleBackground.darker(125);
	}
}

QTextEdit* TabCompletion::getTextEdit() {
	return textEdit_;
}


void TabCompletion::highlight(bool set) {
	Q_UNUSED(set);
/*
	if (set) {
		QTextEdit::ExtraSelection es;
		es.cursor = replacementCursor_;
		es.format.setBackground(highlight_);
		textEdit_->setExtraSelections(QList<QTextEdit::ExtraSelection>() << es);
	} else {
		if (textEdit_) textEdit_->setExtraSelections(QList<QTextEdit::ExtraSelection>());
	}*/
}




void TabCompletion::moveCursorToOffset(QTextCursor &cur, int offset, QTextCursor::MoveMode mode) {
	cur.movePosition(QTextCursor::Start, mode);
	for (int i = 0; i < offset; i++) { // some sane limit on iterations
		if (cur.position() >= offset) break; // done our work
		if (!cur.movePosition(QTextCursor::NextCharacter, mode)) break; // failed?
	}
}



/** Find longest common (case insensitive) prefix of \a list.
	*/
QString TabCompletion::longestCommonPrefix(QStringList list) {
	QString candidate = list.first().toLower();
	int len = candidate.length();
	while (len > 0) {
		bool found = true;
		foreach(QString str, list) {
			if (str.left(len).toLower() != candidate) {
				found = false;
				break;
			}
		}

		if (found) {
			break;
		}

		--len;
		candidate = candidate.left(len);
	}
	return candidate;
}

void TabCompletion::setup(QString text, int pos, int &start, int &end) {
	if (text.isEmpty() || pos==0) {
		atStart_ = true;
		toComplete_ = "";
		start = 0;
		end = 0;
		return;
	}
	end = pos;
	int i;
	for (i = pos - 1; i > 0; --i) {
		if (text[i].isSpace()) {
			break;
		}
	}
	if (!text[i].isSpace()) {
		atStart_ = true;
		start = 0;
	} else {
		atStart_ = false;
		start = i+1;
	}
	toComplete_ = text.mid(start, end-start);
}




QString TabCompletion::suggestCompletion(bool *replaced) {

	suggestedCompletion_ = possibleCompletions();
	suggestedIndex_ = -1;

	QString newText;
	if (suggestedCompletion_.count() == 1) {
		*replaced = true;
		newText = suggestedCompletion_.first();
	} else if (suggestedCompletion_.count() > 1) {
		newText = longestCommonPrefix(suggestedCompletion_);
		if (newText.isEmpty()) {
			return toComplete_; // FIXME is this right?
		}

		typingStatus_ = Typing_MultipleSuggestions;
		// TODO: display a tooltip that will contain all suggestedCompletion
		*replaced = true;
	}


	return newText;
}



void TabCompletion::reset() {
	typingStatus_ = Typing_Normal;
	highlight(false);
}

/** Handle tab completion.
	* User interface uses a dual model, first tab completes upto the
	* longest common (case insensitiv) match, further tabbing cycles through all
	* possible completions. When doing a tab completion without something to complete
	* possibly offers a special guess first.
	*/
void TabCompletion::tryComplete() {
	switch (typingStatus_) {
		case Typing_Normal:
			typingStatus_ = Typing_TabPressed;
			break;
		case Typing_TabPressed:
			typingStatus_ = Typing_TabbingCompletions;
			break;
		default:
			break;
	}


	QString newText;
	bool replaced = false;

	if (typingStatus_ == Typing_MultipleSuggestions) {
		if (!suggestedCompletion_.isEmpty()) {
			suggestedIndex_++;
			if (suggestedIndex_ >= (int)suggestedCompletion_.count()) {
				suggestedIndex_ = 0;
			}
			newText = suggestedCompletion_[suggestedIndex_];
			replaced = true;
		}
	} else {
		QTextCursor cursor = textEdit_->textCursor();
		QString wholeText = textEdit_->toPlainText();

		int begin, end;
		setup(wholeText, cursor.position(), begin, end);
		replacementCursor_ = QTextCursor(textEdit_->document());
		moveCursorToOffset(replacementCursor_, begin);
		moveCursorToOffset(replacementCursor_, end, QTextCursor::KeepAnchor);

		if (toComplete_.isEmpty() && typingStatus_ == Typing_TabbingCompletions) {
			typingStatus_ = Typing_MultipleSuggestions;

			QString guess;
			suggestedCompletion_ = allChoices(guess);

			if ( !guess.isEmpty() ) {
				suggestedIndex_ = -1;
				newText = guess;
				replaced = true;
			} else if (!suggestedCompletion_.isEmpty()) {
				suggestedIndex_ = 0;
				newText = suggestedCompletion_.first();
				replaced = true;
			}
		} else {
			newText = suggestCompletion(&replaced);
		}
	}

	if (replaced) {
		textEdit_->setUpdatesEnabled(false);

		int start = qMin(replacementCursor_.anchor(), replacementCursor_.position());

		replacementCursor_.beginEditBlock();
		replacementCursor_.insertText(newText);
		replacementCursor_.endEditBlock();

		QTextCursor newPos(replacementCursor_);

		moveCursorToOffset(replacementCursor_, start, QTextCursor::KeepAnchor);


		newPos.clearSelection();

		textEdit_->setTextCursor(newPos);

		textEdit_->setUpdatesEnabled(true);
		textEdit_->viewport()->update();
	}
	highlight(typingStatus_ == Typing_MultipleSuggestions);
}