realm-js/impl/transact_log_handler.cpp

////////////////////////////////////////////////////////////////////////////
//
// Copyright 2015 Realm Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////

#include "transact_log_handler.hpp"

#include "../binding_context.hpp"

#include <realm/commit_log.hpp>
#include <realm/group_shared.hpp>
#include <realm/lang_bind_helper.hpp>

namespace realm {
class TransactLogHandler {
    using ColumnInfo = BindingContext::ColumnInfo;
    using ObserverState = BindingContext::ObserverState;

    // Observed table rows which need change information
    std::vector<ObserverState> m_observers;
    // Userdata pointers for rows which have been deleted
    std::vector<void *> invalidated;
    // Delegate to send change information to
    BindingContext* m_binding_context;

    // Index of currently selected table
    size_t m_current_table = 0;
    // Change information for the currently selected LinkList, if any
    ColumnInfo* m_active_linklist = nullptr;

    // Get the change info for the given column, creating it if needed
    static ColumnInfo& get_change(ObserverState& state, size_t i)
    {
        if (state.changes.size() <= i) {
            state.changes.resize(std::max(state.changes.size() * 2, i + 1));
        }
        return state.changes[i];
    }

    // Loop over the columns which were changed in an observer state
    template<typename Func>
    static void for_each(ObserverState& state, Func&& f)
    {
        for (size_t i = 0; i < state.changes.size(); ++i) {
            auto const& change = state.changes[i];
            if (change.changed) {
                f(i, change);
            }
        }
    }

    // Mark the given row/col as needing notifications sent
    bool mark_dirty(size_t row_ndx, size_t col_ndx)
    {
        auto it = lower_bound(begin(m_observers), end(m_observers), ObserverState{m_current_table, row_ndx, nullptr});
        if (it != end(m_observers) && it->table_ndx == m_current_table && it->row_ndx == row_ndx) {
            get_change(*it, col_ndx).changed = true;
        }
        return true;
    }

    // Remove the given observer from the list of observed objects and add it
    // to the listed of invalidated objects
    void invalidate(ObserverState *o)
    {
        invalidated.push_back(o->info);
        m_observers.erase(m_observers.begin() + (o - &m_observers[0]));
    }

public:
    template<typename Func>
    TransactLogHandler(BindingContext* binding_context, SharedGroup& sg, Func&& func)
    : m_binding_context(binding_context)
    {
        if (!binding_context) {
            func();
            return;
        }

        m_observers = binding_context->get_observed_rows();
        if (m_observers.empty()) {
            auto old_version = sg.get_version_of_current_transaction();
            func();
            if (old_version != sg.get_version_of_current_transaction()) {
                binding_context->did_change({}, {});
            }
            return;
        }

        func(*this);
        binding_context->did_change(m_observers, invalidated);
    }

    // Called at the end of the transaction log immediately before the version
    // is advanced
    void parse_complete()
    {
        m_binding_context->will_change(m_observers, invalidated);
    }

    // These would require having an observer before schema init
    // Maybe do something here to throw an error when multiple processes have different schemas?
    bool insert_group_level_table(size_t, size_t, StringData) { return false; }
    bool erase_group_level_table(size_t, size_t) { return false; }
    bool rename_group_level_table(size_t, StringData) { return false; }
    bool insert_column(size_t, DataType, StringData, bool) { return false; }
    bool insert_link_column(size_t, DataType, StringData, size_t, size_t) { return false; }
    bool erase_column(size_t) { return false; }
    bool erase_link_column(size_t, size_t, size_t) { return false; }
    bool rename_column(size_t, StringData) { return false; }
    bool add_search_index(size_t) { return false; }
    bool remove_search_index(size_t) { return false; }
    bool add_primary_key(size_t) { return false; }
    bool remove_primary_key() { return false; }
    bool set_link_type(size_t, LinkType) { return false; }

    bool select_table(size_t group_level_ndx, int, const size_t*) noexcept
    {
        m_current_table = group_level_ndx;
        return true;
    }

    bool insert_empty_rows(size_t, size_t, size_t, bool)
    {
        // rows are only inserted at the end, so no need to do anything
        return true;
    }

    bool erase_rows(size_t row_ndx, size_t, size_t last_row_ndx, bool unordered)
    {
        for (size_t i = 0; i < m_observers.size(); ++i) {
            auto& o = m_observers[i];
            if (o.table_ndx == m_current_table) {
                if (o.row_ndx == row_ndx) {
                    invalidate(&o);
                    --i;
                }
                else if (unordered && o.row_ndx == last_row_ndx) {
                    o.row_ndx = row_ndx;
                }
                else if (!unordered && o.row_ndx > row_ndx) {
                    o.row_ndx -= 1;
                }
            }
        }
        return true;
    }

    bool clear_table()
    {
        for (size_t i = 0; i < m_observers.size(); ) {
            auto& o = m_observers[i];
            if (o.table_ndx == m_current_table) {
                invalidate(&o);
            }
            else {
                ++i;
            }
        }
        return true;
    }

    bool select_link_list(size_t col, size_t row, size_t)
    {
        m_active_linklist = nullptr;
        for (auto& o : m_observers) {
            if (o.table_ndx == m_current_table && o.row_ndx == row) {
                m_active_linklist = &get_change(o, col);
                break;
            }
        }
        return true;
    }

    void append_link_list_change(ColumnInfo::Kind kind, size_t index) {
        ColumnInfo *o = m_active_linklist;
        if (!o || o->kind == ColumnInfo::Kind::SetAll) {
            // Active LinkList isn't observed or already has multiple kinds of changes
            return;
        }

        if (o->kind == ColumnInfo::Kind::None) {
            o->kind = kind;
            o->changed = true;
            o->indices.add(index);
        }
        else if (o->kind == kind) {
            if (kind == ColumnInfo::Kind::Remove) {
                o->indices.add_shifted(index);
            }
            else if (kind == ColumnInfo::Kind::Insert) {
                o->indices.insert_at(index);
            }
            else {
                o->indices.add(index);
            }
        }
        else {
            // Array KVO can only send a single kind of change at a time, so
            // if there's multiple just give up and send "Set"
            o->indices.set(0);
            o->kind = ColumnInfo::Kind::SetAll;
        }
    }

    bool link_list_set(size_t index, size_t)
    {
        append_link_list_change(ColumnInfo::Kind::Set, index);
        return true;
    }

    bool link_list_insert(size_t index, size_t)
    {
        append_link_list_change(ColumnInfo::Kind::Insert, index);
        return true;
    }

    bool link_list_erase(size_t index)
    {
        append_link_list_change(ColumnInfo::Kind::Remove, index);
        return true;
    }

    bool link_list_nullify(size_t index)
    {
        append_link_list_change(ColumnInfo::Kind::Remove, index);
        return true;
    }

    bool link_list_swap(size_t index1, size_t index2)
    {
        append_link_list_change(ColumnInfo::Kind::Set, index1);
        append_link_list_change(ColumnInfo::Kind::Set, index2);
        return true;
    }

    bool link_list_clear(size_t old_size)
    {
        ColumnInfo *o = m_active_linklist;
        if (!o || o->kind == ColumnInfo::Kind::SetAll) {
            return true;
        }

        if (o->kind == ColumnInfo::Kind::Remove)
            old_size += o->indices.size();
        else if (o->kind == ColumnInfo::Kind::Insert)
            old_size -= o->indices.size();

        o->indices.set(old_size);

        o->kind = ColumnInfo::Kind::Remove;
        o->changed = true;
        return true;
    }

    bool link_list_move(size_t from, size_t to)
    {
        ColumnInfo *o = m_active_linklist;
        if (!o || o->kind == ColumnInfo::Kind::SetAll) {
            return true;
        }
        if (from > to) {
            std::swap(from, to);
        }

        if (o->kind == ColumnInfo::Kind::None) {
            o->kind = ColumnInfo::Kind::Set;
            o->changed = true;
        }
        if (o->kind == ColumnInfo::Kind::Set) {
            for (size_t i = from; i <= to; ++i)
                o->indices.add(i);
        }
        else {
            o->indices.set(0);
            o->kind = ColumnInfo::Kind::SetAll;
        }
        return true;
    }

    // Things that just mark the field as modified
    bool set_int(size_t col, size_t row, int_fast64_t) { return mark_dirty(row, col); }
    bool set_bool(size_t col, size_t row, bool) { return mark_dirty(row, col); }
    bool set_float(size_t col, size_t row, float) { return mark_dirty(row, col); }
    bool set_double(size_t col, size_t row, double) { return mark_dirty(row, col); }
    bool set_string(size_t col, size_t row, StringData) { return mark_dirty(row, col); }
    bool set_binary(size_t col, size_t row, BinaryData) { return mark_dirty(row, col); }
    bool set_date_time(size_t col, size_t row, DateTime) { return mark_dirty(row, col); }
    bool set_table(size_t col, size_t row) { return mark_dirty(row, col); }
    bool set_mixed(size_t col, size_t row, const Mixed&) { return mark_dirty(row, col); }
    bool set_link(size_t col, size_t row, size_t, size_t) { return mark_dirty(row, col); }
    bool set_null(size_t col, size_t row) { return mark_dirty(row, col); }
    bool nullify_link(size_t col, size_t row, size_t) { return mark_dirty(row, col); }

    // Doesn't change any data
    bool optimize_table() { return true; }

    // Used for subtables, which we currently don't support
    bool select_descriptor(int, const size_t*) { return false; }

    // Not implemented
    bool insert_substring(size_t, size_t, size_t, StringData) { return false; }
    bool erase_substring(size_t, size_t, size_t, size_t) { return false; }
    bool swap_rows(size_t, size_t) { return false; }
    bool move_column(size_t, size_t) { return false; }
    bool move_group_level_table(size_t, size_t) { return false; }
};
} // anonymous namespace

namespace realm {
namespace _impl {
namespace transaction {
void advance(SharedGroup& sg, ClientHistory& history, BindingContext* binding_context) {
    TransactLogHandler(binding_context, sg, [&](auto&&... args) {
        LangBindHelper::advance_read(sg, history, std::move(args)...);
    });
}

void begin(SharedGroup& sg, ClientHistory& history, BindingContext* binding_context) {
    TransactLogHandler(binding_context, sg, [&](auto&&... args) {
        LangBindHelper::promote_to_write(sg, history, std::move(args)...);
    });
}

void commit(SharedGroup& sg, ClientHistory&, BindingContext* binding_context) {
    LangBindHelper::commit_and_continue_as_read(sg);

    if (binding_context) {
        binding_context->did_change({}, {});
    }
}

void cancel(SharedGroup& sg, ClientHistory& history, BindingContext* binding_context) {
    TransactLogHandler(binding_context, sg, [&](auto&&... args) {
        LangBindHelper::rollback_and_continue_as_read(sg, history, std::move(args)...);
    });
}

} // namespace transaction
} // namespace _impl
} // namespace realm