syntax = "proto3";

// Interface exported by the server.
service etcd {
  // Range gets the keys in the range from the store.
  rpc Range(RangeRequest) returns (RangeResponse) {}

  // Put puts the given key into the store.
  // A put request increases the index of the store,
  // and generates one event in the event history.
  rpc Put(PutRequest) returns (PutResponse) {}

  // Delete deletes the given range from the store.
  // A delete request increase the index of the store,
  // and generates one event in the event history.
  rpc DeleteRange(DeleteRangeRequest) returns (DeleteRangeResponse) {}

  // Tnx processes all the requests in one transaction.
  // A tnx request increases the index of the store,
  // and generates events with the same index in the event history.
  rpc Tnx(TnxRequest) returns (TnxResponse) {}

  // Watch watches the events happening or happened in etcd. Both input and output
  // are stream. One watch rpc can watch for multiple ranges and get a stream of
  // events. The whole events history can be watched unless compacted.
  rpc WatchRange(stream WatchRangeRequest) returns (stream WatchRangeResponse) {}

  // Compact compacts the event history in etcd. User should compact the
  // event history periodically, or it will grow infinitely.
  rpc Compact(CompactionRequest) returns (CompactionResponse) {}

  // LeaseCreate creates a lease. A lease has a TTL. The lease will expire if the
  // server does not receive a keepAlive within TTL from the lease holder.
  // All keys attached to the lease will be expired and deleted if the lease expires.
  // The key expiration generates an event in event history.
  rpc LeaseCreate(LeaseCreateRequest) returns (LeaseCreateResponse) {}

  // LeaseRevoke revokes a lease. All the key attached to the lease will be expired and deleted.
  rpc LeaseRevoke(LeaseRevokeRequest) returns (LeaseRevokeResponse) {}

  // LeaseAttach attaches keys with a lease.
  rpc LeaseAttach(LeaseAttachRequest) returns (LeaseAttachResponse) {}

  // LeaseTnx likes Tnx. It has two addition success and failure LeaseAttachRequest list.
  // If the Tnx is successful, then the success list will be executed. Or the failure list
  // will be executed.
  rpc LeaseTnx(LeaseTnxRequest) returns (LeaseTnxResponse) {}

  // KeepAlive keeps the lease alive.
  rpc LeaseKeepAlive(stream LeaseKeepAliveRequest) returns (stream LeaseKeepAliveResponse) {}
}

message ResponseHeader {
  // an error type message?
  optional string error = 1;
  optional uint64 cluster_id = 2;
  optional uint64 member_id = 3;
  // index of the store when the request was applied.
  optional int64 index = 4;
  // term of raft when the request was applied.
  optional uint64 raft_term = 5;
}

message RangeRequest {
  // if the range_end is not given, the request returns the key.
  optional bytes key = 1;
  // if the range_end is given, it gets the keys in range [key, range_end).
  optional bytes range_end = 2;
  // limit the number of keys returned.
  optional int64 limit = 3;
  // the response will be consistent with previous request with same token if the token is 
  // given and is vaild.
  optional bytes consistent_token = 4;
}

message RangeResponse {
  optional ResponseHeader header = 1;
  repeated KeyValue kvs = 2;
  optional bytes consistent_token = 3;
}

message PutRequest {
  optional bytes key = 1;
  optional bytes value = 2;
}

message PutResponse {
  optional ResponseHeader header = 1;
}

message DeleteRangeRequest {
  // if the range_end is not given, the request deletes the key.
  optional bytes key = 1;
  // if the range_end is given, it deletes the keys in range [key, range_end).
  optional bytes range_end = 2;
}

message DeleteRangeResponse {
  optional ResponseHeader header = 1;
}

message RequestUnion {
  oneof request {
    RangeRequest request_range = 1;
    PutRequest request_put = 2;
    DeleteRangeRequest request_delete_range = 3;
  }
}

message ResponseUnion {
  oneof response {
    RangeResponse reponse_range = 1;
    PutResponse response_put = 2;
    DeleteRangeResponse response_delete_range = 3;
  }
}

message Compare {
  enum CompareType {
    EQUAL = 0;
    GREATER = 1;
    LESS = 2;
  }
  optional CompareType type = 1;
  // key path
  optional bytes key = 2;
  oneof target {
    // version of the given key
    int64 version = 3;
    // create index of the given key
    int64 create_index = 4;
    // last modified index of the given key
    int64 mod_index = 5;
    // value of the given key
    bytes value = 6;
  }
}

// First all the compare requests are processed.
// If all the compare succeed, all the success
// requests will be processed.
// Or all the failure requests will be processed and
// all the errors in the comparison will be returned.

// From google paxosdb paper:
// Our implementation hinges around a powerful primitive which we call MultiOp. All other database
// operations except for iteration are implemented as a single call to MultiOp. A MultiOp is applied atomically
// and consists of three components:
// 1. A list of tests called guard. Each test in guard checks a single entry in the database. It may check
// for the absence or presence of a value, or compare with a given value. Two different tests in the guard
// may apply to the same or different entries in the database. All tests in the guard are applied and
// MultiOp returns the results. If all tests are true, MultiOp executes t op (see item 2 below), otherwise
// it executes f op (see item 3 below).
// 2. A list of database operations called t op. Each operation in the list is either an insert, delete, or
// lookup operation, and applies to a single database entry. Two different operations in the list may apply
// to the same or different entries in the database. These operations are executed
// if guard evaluates to
// true.
// 3. A list of database operations called f op. Like t op, but executed if guard evaluates to false.
message TnxRequest {
  repeated Compare compare = 1;
  repeated RequestUnion success = 2;
  repeated RequestUnion failure = 3;
}

message TnxResponse {
  optional ResponseHeader header = 1;
  optional bool succeeded = 2;
  repeated ResponseUnion responses = 3;
}

message KeyValue {
  optional bytes key = 1;
  // mod_index is the last modified index of the key.
  optional int64 create_index = 2;
  optional int64 mod_index = 3;
  // version is the version of the key. A deletion resets
  // the version to zero and any modification of the key
  // increases its version.
  optional int64 version = 4;
  optional bytes value = 5;
}

message WatchRangeRequest {
  // if the range_end is not given, the request returns the key.
  optional bytes key = 1;
  // if the range_end is given, it gets the keys in range [key, range_end).
  optional bytes range_end = 2;
  // start_index is an optional index (including) to watch from. No start_index is "now".
  optional int64 start_index = 3;
  // end_index is an optional index (excluding) to end watch. No end_index is "forever".
  optional int64 end_index = 4;
  optional bool progress_notification = 5;
}

message WatchRangeResponse {
  optional ResponseHeader header = 1;
  repeated Event events = 2;
}

message Event {
  enum EventType {
    PUT = 0;
    DELETE = 1;
    EXPIRE = 2;
  }
  optional EventType event_type = 1;
  // a put event contains the current key-value
  // a delete/expire event contains the previous
  // key-value
  optional KeyValue kv = 2;
}

message CompactionRequest {
  optional int64 index = 1;
}

message CompactionResponse {
  optional ResponseHeader header = 1;
}

message LeaseCreateRequest {
  // advisory ttl in seconds
  optional int64 ttl = 1;
}

message LeaseCreateResponse {
  optional ResponseHeader header = 1;
  optional int64 lease_id = 2;
  // server decided ttl in second
  optional int64 ttl = 3;
  optional string error = 4;
}

message LeaseRevokeRequest {
  optional int64 lease_id = 1;
}

message LeaseRevokeResponse {
  optional ResponseHeader header = 1;
}

message LeaseTnxRequest {
  optional TnxRequest request = 1;
  repeated LeaseAttachRequest success = 2;
  repeated LeaseAttachRequest failure = 3;
}

message LeaseTnxResponse {
  optional ResponseHeader header = 1;
  optional TnxResponse response = 2;
  repeated LeaseAttachResponse attach_responses = 3;
}

message LeaseAttachRequest {
  optional int64 lease_id = 1;
  optional bytes key = 2;
}

message LeaseAttachResponse {
  optional ResponseHeader header = 1;
}

message LeaseKeepAliveRequest {
  optional int64 lease_id = 1;
}

message LeaseKeepAliveResponse {
  optional ResponseHeader header = 1;
  optional int64 lease_id = 2;
  optional int64 ttl = 3;
}