Sqlite: Add change set iterator

Task-number: QDS-2998
Change-Id: I7bfa8af51d9d7e6122902ee132ad51019e20afb5
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/libs/sqlite/sqlitesessionchangeset.h

@@ -27,17 +27,173 @@
 
 #include "sqliteblob.h"
 #include "sqliteglobal.h"
+#include "sqlitevalue.h"
+
+#include <utils/smallstring.h>
 
 #include <memory>
 #include <vector>
-
 #include <iosfwd>
 
+struct sqlite3_changeset_iter;
+
 namespace Sqlite {
 
 class Sessions;
 
-class SessionChangeSet
+namespace SessionChangeSetInternal {
+enum class Operation : char { Invalid, Insert, Update, Delete };
+
+class SentinelIterator
+{};
+
+class ValueViews
+{
+public:
+    ValueView newValue;
+    ValueView oldValue;
+};
+
+class ConstTupleIterator
+{
+public:
+    using difference_type = int;
+    using value_type = ValueView;
+    using pointer = const ValueView *;
+    using reference = const ValueView &;
+    using iterator_category = std::forward_iterator_tag;
+
+    ConstTupleIterator(sqlite3_changeset_iter *sessionIterator, int index, Operation operation)
+        : m_sessionIterator{sessionIterator}
+        , m_column{index}
+        , m_operation{operation}
+    {}
+
+    ConstTupleIterator operator++()
+    {
+        ++m_column;
+
+        return *this;
+    }
+
+    friend bool operator==(const ConstTupleIterator &first, const ConstTupleIterator &second)
+    {
+        return first.m_column == second.m_column;
+    }
+
+    friend bool operator!=(const ConstTupleIterator &first, const ConstTupleIterator &second)
+    {
+        return !(first == second);
+    }
+
+    ValueViews operator*() const;
+
+private:
+    sqlite3_changeset_iter *m_sessionIterator = {};
+    int m_column = 0;
+    Operation m_operation = Operation::Invalid;
+};
+
+class Tuple
+{
+public:
+    using difference_type = int;
+    using value_type = ValueView;
+    using reference = ValueView &;
+    using const_reference = const ValueView &;
+    using iterator = ConstTupleIterator;
+    using const_iterator = ConstTupleIterator;
+    using size_type = int;
+
+    Utils::SmallStringView table;
+    sqlite3_changeset_iter *sessionIterator = {};
+    int columnCount = 0;
+    Operation operation = Operation::Invalid;
+
+    ValueViews operator[](int column) const;
+    ConstTupleIterator begin() const { return {sessionIterator, 0, operation}; }
+    ConstTupleIterator end() const { return {sessionIterator, columnCount, operation}; }
+};
+
+enum class State : char { Invalid, Row, Done };
+
+class ConstIterator
+{
+public:
+    using difference_type = long;
+    using value_type = Tuple;
+    using pointer = const Tuple *;
+    using reference = const Tuple &;
+    using iterator_category = std::input_iterator_tag;
+
+    ConstIterator(sqlite3_changeset_iter *sessionIterator)
+        : m_sessionIterator(sessionIterator)
+    {}
+
+    ConstIterator(const ConstIterator &) = delete;
+    void operator=(const ConstIterator &) = delete;
+
+    ConstIterator(ConstIterator &&other)
+        : m_sessionIterator(other.m_sessionIterator)
+        , m_state(other.m_state)
+    {
+        other.m_sessionIterator = {};
+        other.m_state = State::Done;
+    }
+
+    ConstIterator &operator=(ConstIterator &&other)
+    {
+        auto tmp = std::move(other);
+        std::swap(tmp, *this);
+
+        return *this;
+    }
+
+    ~ConstIterator();
+
+    ConstIterator &operator++();
+
+    friend bool operator==(const ConstIterator &first, const ConstIterator &second)
+    {
+        return first.m_sessionIterator == second.m_sessionIterator;
+    }
+
+    friend bool operator!=(const ConstIterator &first, const ConstIterator &second)
+    {
+        return !(first == second);
+    }
+
+    friend bool operator==(const ConstIterator &first, SentinelIterator)
+    {
+        return first.m_state == State::Done;
+    }
+
+    friend bool operator!=(const ConstIterator &first, SentinelIterator)
+    {
+        return first.m_state == State::Row;
+    }
+
+    friend bool operator==(SentinelIterator first, const ConstIterator &second)
+    {
+        return second == first;
+    }
+
+    friend bool operator!=(SentinelIterator first, const ConstIterator &second)
+    {
+        return second != first;
+    }
+
+    Tuple operator*() const;
+
+    State state() const { return m_state; }
+
+private:
+    sqlite3_changeset_iter *m_sessionIterator = {};
+    State m_state = State::Invalid;
+};
+} // namespace SessionChangeSetInternal
+
+class SQLITE_EXPORT SessionChangeSet
 {
 public:
     SessionChangeSet(BlobView blob);
@@ -58,20 +214,27 @@ public:
     friend void swap(SessionChangeSet &first, SessionChangeSet &second) noexcept
     {
         SessionChangeSet temp;
-        std::swap(temp.data, first.data);
-        std::swap(temp.size, first.size);
-        std::swap(first.data, second.data);
-        std::swap(first.size, second.size);
-        std::swap(temp.data, second.data);
-        std::swap(temp.size, second.size);
+        std::swap(temp.m_data, first.m_data);
+        std::swap(temp.m_size, first.m_size);
+        std::swap(first.m_data, second.m_data);
+        std::swap(first.m_size, second.m_size);
+        std::swap(temp.m_data, second.m_data);
+        std::swap(temp.m_size, second.m_size);
     }
 
+    SessionChangeSetInternal::ConstIterator begin() const;
+    SessionChangeSetInternal::SentinelIterator end() const { return {}; }
+
+    void *data() const { return m_data; }
+
+    int size() const { return m_size; }
+
 private:
     SessionChangeSet() = default;
 
-public:
-    void *data = nullptr;
-    int size = {};
+private:
+    void *m_data = nullptr;
+    int m_size = {};
 };
 
 using SessionChangeSets = std::vector<SessionChangeSet>;