Fetch more data on demand

We skip values we've already seen and only retrieve the new ones.
This currently only properly works in a non-live query and we don't
give the model any feedback when we can't fetch more data anymore.

However, it generally works and we get the desired effect.

1 files changed, 134 insertions, 0 deletions

diff --git a/common/resultset.cpp b/common/resultset.cpp
new file mode 100644
index 0000000..6e1479a
--- /dev/null
+++ b/common/resultset.cpp
@@ -0,0 +1,134 @@
+/*
+ *   Copyright (C) 2016 Christian Mollekopf <chrigi_1@fastmail.fm>
+ *
+ *   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, write to the
+ *   Free Software Foundation, Inc.,
+ *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA.
+ */
+#include "resultset.h"
+
+#include "common/log.h"
+
+ResultSet::ResultSet()
+    : mIt(nullptr)
+{
+
+}
+
+ResultSet::ResultSet(const ValueGenerator &generator, const SkipValue &skip)
+    : mIt(nullptr),
+    mValueGenerator(generator),
+    mSkip(skip)
+{
+
+}
+
+ResultSet::ResultSet(const IdGenerator &generator)
+    : mIt(nullptr),
+    mGenerator(generator),
+    mSkip([this]() {
+        next();
+    })
+{
+
+}
+
+ResultSet::ResultSet(const QVector<QByteArray> &resultSet)
+    : mResultSet(resultSet),
+    mIt(mResultSet.constBegin()),
+    mSkip([this]() {
+        if (mIt != mResultSet.constEnd()) {
+            mIt++;
+        }
+    }),
+    mFirst(true)
+{
+
+}
+
+ResultSet::ResultSet(const ResultSet &other)
+    : mResultSet(other.mResultSet),
+    mIt(nullptr),
+    mFirst(true)
+{
+    if (other.mValueGenerator) {
+        mValueGenerator = other.mValueGenerator;
+        mSkip = other.mSkip;
+    } else if (other.mGenerator) {
+        mGenerator = other.mGenerator;
+        mSkip = [this]() {
+            next();
+        };
+    } else {
+        mResultSet = other.mResultSet;
+        mIt = mResultSet.constBegin();
+        mSkip = [this]() {
+            if (mIt != mResultSet.constEnd()) {
+                mIt++;
+            }
+        };
+    }
+}
+
+bool ResultSet::next()
+{
+    if (mIt) {
+        if (mIt != mResultSet.constEnd() && !mFirst) {
+            mIt++;
+        }
+        mFirst = false;
+        return mIt != mResultSet.constEnd();
+    } else if (mGenerator) {
+        Q_ASSERT(mGenerator);
+        mCurrentValue = mGenerator();
+        if (!mCurrentValue.isNull()) {
+            return true;
+        }
+    } else {
+        next([](const Sink::ApplicationDomain::ApplicationDomainType::Ptr &value, Sink::Operation){ return false; });
+    }
+    return false;
+}
+
+bool ResultSet::next(std::function<bool(const Sink::ApplicationDomain::ApplicationDomainType::Ptr &value, Sink::Operation)> callback)
+{
+    Q_ASSERT(mValueGenerator);
+    return mValueGenerator(callback);
+}
+
+void ResultSet::skip(int number)
+{
+    Q_ASSERT(mSkip);
+    for (int i = 0; i < number; i++) {
+        mSkip();
+    }
+}
+
+QByteArray ResultSet::id()
+{
+    if (mIt) {
+        if (mIt == mResultSet.constEnd()) {
+            return QByteArray();
+        }
+        Q_ASSERT(mIt != mResultSet.constEnd());
+        return *mIt;
+    } else {
+        return mCurrentValue;
+    }
+}
+
+bool ResultSet::isEmpty()
+{
+    return mResultSet.isEmpty();
+}