syntax = "proto3";
package wolf.raft;

service Raft {
    rpc Bootstrap (RaftBootstrapReq) returns (RaftBootstrapRes);
    rpc AppendEntries (RaftAppendEntriesReq) returns (RaftAppendEntriesRes);
    rpc InstallSnapshot (RaftInstallSnapshotReq) returns (RaftInstallSnapshotRes);
    rpc Vote (RaftVoteReq) returns (RaftVoteRes);
    rpc GetMetrics (RaftGetMetricsReq) returns (RaftGetMetricsRes);
}

/*
    Represents all error codes of services
*/
enum ErrorCode {
    RAFT_UNDEFINED_ERROR = 0;
    RAFT_BOOTSTRAP_FAILED = 1;
    RAFT_APPEND_ENTRIES_JSON_OF_REQ_IS_NOT_VALID = 2;
    RAFT_APPEND_ENTRIES_FAILED = 3;
    RAFT_INSTALL_SNAPSHOT_FAILED = 4;
    RAFT_VOTE_FAILED = 5;
    RAFT_GET_METRICS_FAILED = 6;
}

/*
    The structure of the error response which is shared
    between all rpc(s) of all services.
*/
message RaftErrorRes {
    string msg_id = 1;
    ErrorCode code = 2;
    string msg = 3;
}

/*
    messages for Bootstrap
*/
message RaftBootstrapReq {
    string msg_id = 1;
    uint64 number_of_nodes = 3;
}

message RaftBootstrapOkRes {
    string msg_id = 1;
}

message RaftBootstrapRes {
    oneof response {
        RaftBootstrapOkRes ok_res = 1;
        RaftErrorRes error_res = 2;
    }
}

/*
    messages for AppendEntries
*/
message RaftAppendEntriesReq {
    string msg_id = 1;
    string req = 2;
}

message ConflictOpt {
    /// The term of the most recent entry which does not conflict with the received request.
    uint64 term = 1;
    /// The index of the most recent entry which does not conflict with the received request.
    uint64 index =2;
}

message RaftAppendEntriesOkRes {
    /// The message id.
    string msg_id = 1;
    /// The responding node's current term, for leader to update itself.
    uint64 term = 2;
    /// Will be true if follower contained entry matching `prev_log_index` and `prev_log_term`.
    bool success = 3;
    /// A value used to implement the _conflicting term_ optimization outlined in §5.3.
    /// This value will only be present, and should only be considered, when `success` is `false`.
    optional ConflictOpt conflict_opt = 4;
}

message RaftAppendEntriesRes {
    oneof response {
        RaftAppendEntriesOkRes ok_res = 1;
        RaftErrorRes error_res = 2;
    }
}

/*
    messages for InstallSnapshot
*/
message RaftInstallSnapshotReq {

    /// message ID
    string msg_id = 1;

    /// The leader's current term.
    uint64 term = 2;

    /// The leader's ID. Useful in redirecting clients.
    uint64 leader_id = 3;

    /// The snapshot replaces all log entries up through and including this index.
    uint64 last_included_index = 4;

    /// The term of the `last_included_index`.
    uint64 last_included_term = 5;

    /// The byte offset where this chunk of data is positioned in the snapshot file.
    uint64 offset = 6;

    /// Will be `true` if this is the last chunk in the snapshot.
    bool done = 7;

    /// The raw bytes of the snapshot chunk, starting at `offset`.
    bytes data = 8;
}

message RaftInstallSnapshotOkRes {
    /// message ID
    string msg_id = 1;

    /// The receiving node's current term, for leader to update itself.
    uint64 term = 2;
}

message RaftInstallSnapshotRes {
    oneof response {
        RaftInstallSnapshotOkRes ok_res = 1;
        RaftErrorRes error_res = 2;
    }
}

/*
    messages for Vote
*/
message RaftVoteReq {

    /// message ID
    string msg_id = 1;

    /// The candidate's current term.
    uint64 term = 2;

    /// The candidate's ID.
    uint64 candidate_id = 3;

    /// The index of the candidate’s last log entry.
    uint64 last_log_index = 4;

    /// The term of the candidate’s last log entry.
    uint64 last_log_term = 5;

}

message RaftVoteOkRes {
    /// message ID
    string msg_id = 1;

    /// The current term of the responding node, for the candidate to update itself.
    uint64 term = 2;

    /// Will be true if the candidate received a vote from the responder.
    bool vote_granted = 3;
}

message RaftVoteRes {
    oneof response {
        RaftVoteOkRes ok_res = 1;
        RaftErrorRes error_res = 2;
    }
}

/*
    messages for GetMetrics
*/
message RaftGetMetricsReq {
    string msg_id = 1;
}

message RaftGetMetricsOkRes {
    string msg_id = 1;
    string metrics = 2;
}

message RaftGetMetricsRes {
    oneof response {
        RaftGetMetricsOkRes ok_res = 1;
        RaftErrorRes error_res = 2;
    }
}