#pragma once

#include <Common/Exception.h>
#include <Core/Types.h>
#include <IO/WriteHelpers.h>

#include <mutex>
#include <condition_variable>


struct Stat;


namespace DB
{

class ReadBuffer;
class WriteBuffer;
class ReplicatedMergeTreeQueue;

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
    extern const int UNKNOWN_FORMAT_VERSION;
    extern const int CANNOT_PARSE_TEXT;
}


/// Record about what needs to be done. Only data (you can copy them).
struct ReplicatedMergeTreeLogEntryData
{
    enum Type
    {
        EMPTY,          /// Not used.
        GET_PART,       /// Get the part from another replica.
        MERGE_PARTS,    /// Merge the parts.
        DROP_RANGE,     /// Delete the parts in the specified partition in the specified number range.
        ATTACH_PART,    /// Move a part from the `detached` directory. Obsolete. TODO: Remove after half year.
        CLEAR_COLUMN,   /// Drop specific column from specified partition.
    };

    String typeToString() const
    {
        switch (type)
        {
            case ReplicatedMergeTreeLogEntryData::GET_PART:     return "GET_PART";
            case ReplicatedMergeTreeLogEntryData::MERGE_PARTS:  return "MERGE_PARTS";
            case ReplicatedMergeTreeLogEntryData::DROP_RANGE:   return "DROP_RANGE";
            case ReplicatedMergeTreeLogEntryData::ATTACH_PART:  return "ATTACH_PART";
            case ReplicatedMergeTreeLogEntryData::CLEAR_COLUMN: return "CLEAR_COLUMN";
            default:
                throw Exception("Unknown log entry type: " + DB::toString<int>(type), ErrorCodes::LOGICAL_ERROR);
        }
    }

    void writeText(WriteBuffer & out) const;
    void readText(ReadBuffer & in);
    String toString() const;

    String znode_name;

    Type type = EMPTY;
    String source_replica; /// Empty string means that this entry was added to the queue immediately, and not copied from the log.

    /// The name of resulting part.
    /// For DROP_RANGE, the name of a non-existent part. You need to remove all the parts covered by it.
    String new_part_name;
    String block_id;                        /// For parts of level zero, the block identifier for deduplication (node name in /blocks/).
    mutable String actual_new_part_name;    /// GET_PART could actually fetch a part covering 'new_part_name'.

    Strings parts_to_merge;
    bool deduplicate = false; /// Do deduplicate on merge
    String column_name;

    /// For DROP_RANGE, true means that the parts need not be deleted, but moved to the `detached` directory.
    bool detach = false;

    /// Access under queue_mutex, see ReplicatedMergeTreeQueue.
    bool currently_executing = false;    /// Whether the action is executing now.
    /// These several fields are informational only (for viewing by the user using system tables).
    /// Access under queue_mutex, see ReplicatedMergeTreeQueue.
    size_t num_tries = 0;                 /// The number of attempts to perform the action (since the server started, including the running one).
    std::exception_ptr exception;         /// The last exception, in the case of an unsuccessful attempt to perform the action.
    time_t last_attempt_time = 0;         /// The time at which the last attempt was attempted to complete the action.
    size_t num_postponed = 0;             /// The number of times the action was postponed.
    String postpone_reason;               /// The reason why the action was postponed, if it was postponed.
    time_t last_postpone_time = 0;        /// The time of the last time the action was postponed.

    /// Creation time or the time to copy from the general log to the queue of a particular replica.
    time_t create_time = 0;

    /// The quorum value (for GET_PART) is a non-zero value when the quorum write is enabled.
    size_t quorum = 0;
};


struct ReplicatedMergeTreeLogEntry : ReplicatedMergeTreeLogEntryData
{
    using Ptr = std::shared_ptr<ReplicatedMergeTreeLogEntry>;

    std::condition_variable execution_complete; /// Awake when currently_executing becomes false.

    static Ptr parse(const String & s, const Stat & stat);
};


}