#include <QtCore/QDebug>
#include <QtSql/QSqlError>

#include "global.h"
#include "board.h"
#include "xmlrpcinterface.h"
#include "fetchtopicsaction.h"
#include "forummodel.h"

ForumModel::ForumModel(QObject *parent) :
    QAbstractListModel(parent), _board(0), _forumId(-1),
    _numAnnouncements(0), _numSticky(0), _eof(false)
{
	QHash<int, QByteArray> roles = roleNames();
	roles[TitleRole] = QByteArray("title");
	roles[IconRole] = QByteArray("icon");
	roles[TopicIdRole] = QByteArray("topicId");
	roles[TopicTypeRole] = QByteArray("topicType");
	roles[LastReplyTimeRole] = QByteArray("lastReplyTime");
	roles[NumRepliesRole] = QByteArray("numReplies");
	roles[RelativeDateRole] = QByteArray("relativeDate");
	roles[UnreadRole] = QByteArray("unread");
	setRoleNames(roles);
}

Board * ForumModel::board() const
{
	return _board;
}

void ForumModel::setBoard(Board *board)
{
	if (_board != board) {
		disconnect(this, SLOT(handleForumTopicsChanged(int,Board::TopicType,int,int)));
		disconnect(this, SLOT(handleForumTopicChanged(int,int)));
		clearModel();

		_board = board;

		if (_board) {
			connect(_board, SIGNAL(forumTopicsChanged(int,Board::TopicType,int,int)),
			        SLOT(handleForumTopicsChanged(int,Board::TopicType,int,int)));
			connect(_board, SIGNAL(forumTopicChanged(int,int)),
			        SLOT(handleForumTopicChanged(int,int)));
			if (_forumId >= 0) {
				update();
				reload();
			}
		}
		emit boardChanged();
	}
}

int ForumModel::forumId() const
{
	return _forumId;
}

void ForumModel::setForumId(const int id)
{
	if (_forumId != id) {
		clearModel();

		_forumId = id;

		if (_forumId >= 0 && _board) {
			update();
			reload();
		}
		emit forumIdChanged();
	}
}

int ForumModel::rowCount(const QModelIndex &parent) const
{
	return parent.isValid() ? 0 : _data.size();
}

QVariant ForumModel::data(const QModelIndex &index, int role) const
{
	if (!index.isValid()) return QVariant();
	const int row = index.row();
	if (row >= _data.size()) {
		qWarning() << "Could not seek to" << row;
		return QVariant();
	}

	switch (role) {
	case TitleRole:
		if (_data[row].last_update_time.secsTo(QDateTime::currentDateTimeUtc()) > FORUM_TOPICS_TLL) {
			fetchTopic(row);
		}
		return _data[row].title;
	case TopicIdRole:
		return _data[row].topic_id;
	case TopicTypeRole:
		return _data[row].type;
	case LastReplyTimeRole:
		return _data[row].last_reply_time;
	case NumRepliesRole:
		return _data[row].num_replies;
	case RelativeDateRole:
		switch (_data[row].type) {
		case Board::Announcement:
			return tr("Announcement");
		case Board::Sticky:
			return tr("Sticky");
		default:
			return _board->formatDateTime(_data[row].last_reply_time,
			                              Board::RelativeDate);
		}
	case UnreadRole:
		return _data[row].unread;
	}

	return QVariant();
}

bool ForumModel::canFetchMore(const QModelIndex &parent) const
{
	if (parent.isValid() || !_board || _forumId < 0) return false; // Invalid state
	return !_eof;
}

void ForumModel::fetchMore(const QModelIndex &parent)
{
	if (parent.isValid()) return;
	if (!_board || _forumId < 0) return;
	if (_eof) return;

	const int normal_offset = _numAnnouncements + _numSticky;
	const int normal_start = _data.size() - normal_offset;
	QList<Topic> topics = loadTopics(Board::Normal,
	                                 normal_start, normal_start + FORUM_PAGE_SIZE - 1);
	const int normal_new_end = normal_start + topics.size() - 1;

	if (topics.empty()) {
		// We could not load anything more from DB!
		_eof = true;
	} else {
		qDebug() << "Insert rows" << normal_offset + normal_start << normal_offset + normal_new_end;
		beginInsertRows(QModelIndex(),
		                normal_offset + normal_start, normal_offset + normal_new_end);
		_data.append(topics);
		_eof = topics.size() < FORUM_PAGE_SIZE; // If short read, we reached EOF.
		endInsertRows();
	}

	if (_board->service()->isAccessible() && _eof) {
		// Try to fetch more topics if board is online and we reached the end of DB
		qDebug() << "Fetching topics because of EOF";
		const int normal_cur_end = _data.size() - 1 - normal_offset;
		_board->enqueueAction(new FetchTopicsAction(_forumId,
													Board::Normal,
													normal_cur_end + 1,
													normal_cur_end + FORUM_PAGE_SIZE,
													_board));
	}
}

void ForumModel::refresh()
{
	// Forcefully refresh all topics on this forum
	_board->enqueueAction(new FetchTopicsAction(_forumId,
	                                            Board::Announcement,
	                                            0,
	                                            FetchTopicsAction::FetchAllTopics,
	                                            _board));
	_board->enqueueAction(new FetchTopicsAction(_forumId,
	                                            Board::Sticky,
	                                            0,
	                                            FetchTopicsAction::FetchAllTopics,
	                                            _board));
	_board->enqueueAction(new FetchTopicsAction(_forumId,
	                                            Board::Normal,
	                                            0,
	                                            FetchTopicsAction::FetchAllTopics,
	                                            _board));
}

QDateTime ForumModel::parseDateTime(const QVariant &v)
{
	QString s = v.toString();
	QDateTime dt = QDateTime::fromString(s, Qt::ISODate);
	dt.setTimeSpec(Qt::UTC);
	return dt;
}

QDateTime ForumModel::oldestPostUpdate(const QList<Topic> &topics)
{
	if (topics.empty()) return QDateTime::currentDateTimeUtc();
	QDateTime min = topics.first().last_update_time;
	foreach (const Topic& topic, topics) {
		if (min < topic.last_update_time) min = topic.last_update_time;
	}
	return min;
}

QDateTime ForumModel::lastTopPostUpdate()
{
	if (!_board) return QDateTime();
	QSqlDatabase db = _board->database();
	QSqlQuery query(db);
	query.prepare("SELECT MIN(last_update_time) FROM topics "
	              "WHERE forum_id = :forum_id AND position = 0");
	query.bindValue(":forum_id", _forumId);
	if (query.exec()) {
		if (query.next()) {
			return parseDateTime(query.value(0));
		}
	} else {
		qWarning() << "Could not fetch posts:" << query.lastError().text();
	}
	return QDateTime();
}

QList<ForumModel::Topic> ForumModel::loadTopics(Board::TopicType type, int start, int end)
{
	Q_ASSERT(_board);
	QList<Topic> topics;
	QSqlQuery query(_board->database());
	query.prepare("SELECT topic_id, topic_type, topic_title, reply_number, new_post, last_reply_time, last_update_time FROM topics "
	              "WHERE forum_id = :forum_id AND topic_type = :topic_type AND position BETWEEN :start AND :end "
	              "ORDER by position ASC ");
	query.bindValue(":forum_id", _forumId);
	query.bindValue(":topic_type", type);
	query.bindValue(":start", start);
	query.bindValue(":end", end);
	if (query.exec()) {
		topics.reserve(end - start + 1);
		while (query.next()) {
			Topic topic;
			topic.topic_id = query.value(0).toInt();
			topic.type = type;
			topic.title = query.value(2).toString();
			topic.num_replies = query.value(3).toInt();
			topic.unread = query.value(4).toBool();
			topic.last_reply_time = parseDateTime(query.value(5));
			topic.last_update_time = parseDateTime(query.value(6));
			topics.append(topic);
		}
	} else {
		qWarning() << "Could not load topics:" << query.lastError().text();
	}
	return topics;
}

void ForumModel::fetchTopic(int position) const
{
	if (_board->service()->isAccessible()) {
		// There are less posts on the DB than we wanted
		qDebug() << "Fetching topic" << position << "because of unfetched/old";
		// Figure out the topic type
		Board::TopicType type;
		if (position < _numAnnouncements) {
			type = Board::Announcement;
		} else if (position < _numAnnouncements + _numSticky) {
			type = Board::Sticky;
			position -= _numAnnouncements;
		} else {
			type = Board::Normal;
			position -= _numAnnouncements + _numSticky;
		}
		// Always fetch one page at least.
		int start = (position / FORUM_PAGE_SIZE) * FORUM_PAGE_SIZE;
		int end = (start + FORUM_PAGE_SIZE) - 1;
		qDebug() << "From" << start << "to" << end;
		_board->enqueueAction(new FetchTopicsAction(_forumId, type,
		                                            start, end, _board));
	}
}

void ForumModel::clearModel()
{
	beginResetModel();
	_eof = false;
	_data.clear();
	endResetModel();
}

void ForumModel::handleForumTopicsChanged(int forumId, Board::TopicType type,
                                          int start, int end)
{
	if (forumId != _forumId) {
		return; // Not our topics
	}
	// TODO This probably can be simplified quite a lot.
	if (type == Board::Normal) {
		// Yep, our normal topics list changed.
		const int normal_offset = _numAnnouncements + _numSticky;
		int current_normal_end = _data.size() - 1 - normal_offset;

		if (end >= current_normal_end) {
			// If for any reason we have more topics now, it means we might
			// no longer be EOF...
			_eof = false;
		}
		if (start > current_normal_end + 1) {
			// On the other hand, if the topics are too far away,
			// do not load them until we fetchMore().
			qDebug() << "Topics too far";
			return;
		}

		const int requested = end - start + 1;
		QList<Topic> topics = loadTopics(Board::Normal, start, end);

		end = start + topics.size() - 1;

		// Less topics than the number of topics we requested?
		if (topics.size() < requested) {
			_eof = true; // Short read

			if (current_normal_end > end) {
				const int current_full_end = _data.size() - 1;
				const int new_full_end = end + normal_offset;

				Q_ASSERT(new_full_end < current_full_end);
				qDebug() << "Remove rows" << new_full_end << current_full_end;
				beginRemoveRows(QModelIndex(),
				                new_full_end, current_full_end);
				while (_data.size() > new_full_end) {
					_data.removeLast();
				}
				current_normal_end = _data.size() - 1 - normal_offset;
				Q_ASSERT(current_normal_end == end);
				endRemoveRows();
			}
		}

		Q_ASSERT(end == start + topics.size() - 1);

		if (end > current_normal_end) {
			// More topics than we currently have in the model
			const int current_full_end = _data.size() - 1;
			const int new_full_end = end + normal_offset;
			qDebug() << "Insert rows" << current_full_end + 1 << new_full_end;
			beginInsertRows(QModelIndex(), current_full_end + 1, new_full_end);
			_data.reserve(new_full_end + 1);
			const int full_start = normal_offset + start;
			Q_ASSERT(current_full_end + 1 >= full_start);
			for (int i = current_full_end + 1; i <= new_full_end; i++) {
				_data.append(topics[i - full_start]);
			}
			endInsertRows();
			Q_ASSERT(new_full_end == _data.size() - 1);
			end = current_normal_end;
		}

		Q_ASSERT(end <= start + topics.size() - 1);

		const int full_start = normal_offset + start;
		const int full_end = normal_offset + end;
		for (int i = full_start; i < full_end; i++) {
			_data[i] = topics[i - full_start];
		}
		qDebug() << "Changed rows" << full_start << full_end;
		emit dataChanged(createIndex(full_start, 0), createIndex(full_end, 0));
	} else if (type == Board::Sticky || type == Board::Announcement) {
		// We just reload these fully
		QList<Topic> topics = loadTopics(type, 0, MAX_FORUM_PAGE_SIZE - 1);
		const int offset = type == Board::Sticky ? _numAnnouncements : 0;
		int * const cur_number_p = type == Board::Sticky ? &_numSticky : &_numAnnouncements;
		const int cur_number = *cur_number_p;

		if (topics.size() < cur_number) {
			const int cur_end = offset + cur_number - 1;
			const int new_end = offset + topics.size() - 1;
			qDebug() << "Remove rows" << new_end + 1 << cur_end;
			beginRemoveRows(QModelIndex(), new_end + 1, cur_end);
			for (int i = new_end + 1; i <= cur_end; i++) {
				_data.removeAt(i);
				(*cur_number_p)--;
			}
			endRemoveRows();
		} else if (topics.size() > cur_number) {
			const int cur_end = offset + cur_number - 1;
			const int new_end = offset + topics.size() - 1;
			const int new_start = cur_end + 1;
			Q_ASSERT(new_end - offset == topics.size() - 1);
			qDebug() << "Insert rows" << new_start << new_end;
			beginInsertRows(QModelIndex(), new_start, new_end);
			for (int i = new_start; i <= new_end; i++) {
				_data.insert(i, topics.takeAt(new_start - offset));
				(*cur_number_p)++;
			}
			endInsertRows();
			Q_ASSERT(topics.size() == cur_number);
		}

		const int start = offset;
		const int end = offset + topics.size() - 1;
		if (end >= start) {
			for (int i = start; i <= end; i++) {
				_data.insert(i, topics.at(i - offset));
			}
			qDebug() << "Changed rows" << start << end;
			emit dataChanged(createIndex(start, 0), createIndex(end, 0));
		}
	}
}

void ForumModel::handleForumTopicChanged(int forumId, int topicId)
{
	if (forumId == _forumId) {
		Board::TopicType type = Board::Announcement;
		int pos = 0;
		for (int i = 0; i < _data.size(); i++) {
			Topic& topic = _data[i];
			if (topic.type != type) {
				type = topic.type;
				pos = 0;
			}
			if (topic.topic_id == topicId) {
				// Need to refresh this topic
				QList<Topic> topics = loadTopics(type, pos, pos);
				if (topics.size() == 1) {
					_data[i] = topics[0];
					emit dataChanged(createIndex(i, 0), createIndex(i, 0));
				} else {
					qWarning() << "Topic changed yet not in DB";
				}
			}
			pos++;
		}
	}
}

void ForumModel::update()
{
	if (!_board || _forumId < 0) return;
	// Start by requesting an update of the first 20 topics
	if (!_board->service()->isAccessible()) return;
	QDateTime last = lastTopPostUpdate();
	if (!last.isValid() ||
	        last.secsTo(QDateTime::currentDateTimeUtc()) > FORUM_TOP_TLL) {
		// Outdated or empty, refresh.
		qDebug() << "Fetching topics because the top are old";
		_board->enqueueAction(new FetchTopicsAction(_forumId, Board::Announcement,
		                                            0, FORUM_PAGE_SIZE - 1, _board));
		_board->enqueueAction(new FetchTopicsAction(_forumId, Board::Sticky,
		                                            0, FORUM_PAGE_SIZE - 1, _board));
		_board->enqueueAction(new FetchTopicsAction(_forumId, Board::Normal,
		                                            0, FORUM_PAGE_SIZE - 1, _board));
	} else {
		qDebug() << "Topics not outdated";
	}
}

void ForumModel::reload()
{
	Q_ASSERT(_data.empty());
	Q_ASSERT(!_eof);
	// Load announcements / sticky topics fully
	QList<Topic> topics;
	topics = loadTopics(Board::Announcement, 0, MAX_FORUM_PAGE_SIZE - 1);
	if (!topics.empty()) {
		qDebug() << "Insert rows" << 0 << topics.size() - 1;
		beginInsertRows(QModelIndex(), 0, topics.size() - 1);
		_data.append(topics);
		_numAnnouncements = topics.size();
		endInsertRows();
	} else {
		_numAnnouncements = 0;
	}

	topics = loadTopics(Board::Sticky, 0, MAX_FORUM_PAGE_SIZE - 1);
	if (!topics.empty()) {
		qDebug() << "Insert rows" << _numAnnouncements << _numAnnouncements + topics.size() - 1;
		beginInsertRows(QModelIndex(), _numAnnouncements, _numAnnouncements + topics.size() - 1);
		_data.append(topics);
		_numSticky = topics.size();
		endInsertRows();
	} else {
		_numSticky = 0;
	}

	// Fetch an initial bunch of normal topics
	fetchMore();
}