/* ****************************************************************************
 * Copyright 2019 Open Systems Development BV                                 *
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#ifndef OSDEV_COMPONENTS_TIMELINE_H
#define OSDEV_COMPONENTS_TIMELINE_H

// boost
#include <boost/circular_buffer.hpp>

#include "ormbatchchange.h"

namespace osdev {
namespace components {

/**
 * @brief The timeline contains the changes that where made to a specific Batch/Merge update table.
 * Only a small number of changes is recorded. A change arrives that is older then the oldest recorded
 * change this change will not be considered.
 */
class Timeline
{
public:
    /**
     * @brief Creates an empty timeline.
     */
    Timeline();

    // Non copyable, non movable.
    Timeline(const Timeline&) = delete;
    Timeline& operator=(const Timeline&) = delete;
    Timeline(Timeline&&) = delete;
    Timeline& operator=(Timeline&&) = delete;

    /**
     * @brief Evaluate an incoming change against the already registered changes.
     * A previously evaluated change is discarded.
     * @param desiredChange The incoming change.
     * @param exclusiveUpdate Flag that indicates if this change should be evaluated in an exclusive manner.
     * @return The reshaped and possibly invalidated change that is left.
     * @note The evaluated change is cached so that it can be commited if the database update actually succeeds.
     */
    const OrmBatchChange& evaluate(const OrmBatchChange& desiredChange, bool exclusiveUpdate);

    /**
     * @brief Commit an evaluated change.
     * Only valid proposals are commited. This method should be called when the change
     * is sucessfuly written to the database.
     * @note To make this somewhat trustworthy the underlying database should support transactions.
     */
    void commit();

private:
    boost::circular_buffer<OrmBatchChange> m_timeline;  ///< Only a small number of changes are buffered.
    OrmBatchChange m_proposedChange;                    ///< Cache the evaluated proposed change for commiting.
};

}   /* End namespace components */
}   /* End namespace osdev */

#endif  /* OSDEV_COMPONENTS_TIMELINE_H */