syntax = "proto3";
import "google/protobuf/descriptor.proto";

package NUnifiedAgentProto;

option java_package = "com.yandex.unified_agent";
option go_package = "a.yandex-team.ru/library/cpp/unified_agent_client/proto;unifiedagent";

extend google.protobuf.FileOptions {
    bool GenerateYaStyle = 66777;
}

message Request {
    message SessionMetaItem {
        string name = 1;
        string value = 2;
    }

    message Initialize {
        // Session_id provided by server, use it in case of reconnects.
        string session_id = 1;

        // Session metadata
        repeated SessionMetaItem meta = 2;

        string shared_secret_key = 3;
    }

    message MessageMetaItem {
        // Arbitrary key-value pairs. Can be used by agent filters to modify/filter messages
        // or to route them to target outputs.

        // Meta items of all messages should be grouped by meta key, it's expected in the 'key' field.
        // Meta values should be passed in the 'value' sequence, it corresponds to the payload
        // sequence from DataBatch. If some messages don't have a meta with this key, the range of such messages
        // can be passed via skip_start/skip_length sequences.
        // For example, [{m:v1}, {}, {}, {m: v2}, {}, {m: v3}, {}, {}] can be represented as follows:
        //   key: 'm'
        //   value: ['v1', 'v2', 'v3']
        //   skip_start: [1, 4]
        //   skip_length: [2, 1]

        string key = 1;
        repeated string value = 2;
        repeated uint32 skip_start = 3;
        repeated uint32 skip_length = 4;
    }

    message DataBatch {
        repeated uint64 seq_no = 1;
        repeated uint64 timestamp = 2; //microseconds
        repeated bytes payload = 100;
        repeated MessageMetaItem meta = 101;
    }

    oneof request {
        Initialize initialize = 1;
        DataBatch data_batch = 2;
    }
}

message Response {
    message Initialized {
        // Session identifier for log and deduplication purposes.
        string session_id = 1;

        // Application can skip all formed messages by seq_no upto last_seq_no - they are consumed by server.
        uint64 last_seq_no = 2;
    }

    message Ack {
        uint64 seq_no = 1;
    }

    oneof response {
        Initialized initialized = 1;
        Ack ack = 2;
    }
}

service UnifiedAgentService {
    rpc Session(stream Request) returns (stream Response);
}


// dataflow:
// Request.initialize -> UnifiedAgent;
//      specify session_id when this is a retry. Сlient can already have sesison_id from previous init response,
//      or it can use some pregenerated sessionId for each session.
// Response.initializeded -> client;
// Request.entry -> UnifiedAgent;
// ....
// Response.ack -> client;
//      when this record is consumed by UnifiedAgent with choosen garanties UnifiedAgent will send ack to client;
//      client can forget about this log record now
//
// grpc finish session -> client;
//      something went wrong; client must reconnect and retry all not acknowleged records
//
// Exactly once retries - when reconnect, client must provide previous session_id and same seq_no`s
// for records - only in this case UnifiedAgent can dedup.