// Copyright 2016-18, OpenCensus Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package opencensus.proto.stats.v1;

import "google/protobuf/timestamp.proto";

option go_package = "github.com/census-instrumentation/opencensus-proto/gen-go/stats/v1";

option java_multiple_files = true;
option java_package = "io.opencensus.proto.stats.v1";
option java_outer_classname = "StatsProto";

// TODO(bdrutu): Consider if this should be moved to a "tags" directory to match the API structure.
message Tag {
  string key = 1;
  string value = 2;
}

// Measure .
message Measure {
  // A string by which the measure will be referred to, e.g. "rpc_server_latency". Names MUST be
  // unique within the library.
  string name = 1;

  // Describes the measure, e.g. "RPC latency in seconds".
  string description = 2;

  // Describes the unit used for the Measure. Follows the format described by
  // http://unitsofmeasure.org/ucum.html.
  string unit = 3;

  enum Type {
    // Unknown type.
    TYPE_UNSPECIFIED = 0;
    // Indicates an int64 Measure.
    INT64 = 1;
    // Indicates a double Measure.
    DOUBLE = 2;
  }

  // The type used for this Measure.
  Type type = 4;
}

message View {
  // A string by which the View will be referred to, e.g. "rpc_latency". Names MUST be unique
  // within the library.
  string name = 1;

  // Describes the view, e.g. "RPC latency distribution"
  string description = 2;

  // The Measure to which this view is applied.
  Measure measure = 3;

  // An array of tag keys. These values associated with tags of this name form the basis by which
  // individual stats will be aggregated (one aggregation per unique tag value). If none are
  // provided, then all data is recorded in a single aggregation.
  repeated string columns = 4;

  // The description of the aggregation used for this view which describes how data collected are
  // aggregated.
  oneof aggregation {
    // Counts the number of measurements recorded.
    CountAggregation count_aggregation = 5;
    // Indicates that data collected and aggregated with this Aggregation will be summed up.
    SumAggregation sum_aggregation = 6;
    // Indicates that data collected and aggregated with this Aggregation will represent the last
    // recorded value. This is useful to support Gauges.
    LastValueAggregation last_value_aggregation = 7;
    // Indicates that the desired Aggregation is a histogram distribution. A distribution
    // Aggregation may contain a histogram of the values in the population. User should define the
    // bucket boundaries for that histogram (see DistributionAggregation).
    DistributionAggregation distribution_aggregation = 8;
  }
}

message CountAggregation {}

message SumAggregation {}

message LastValueAggregation {}

message DistributionAggregation {
  // A Distribution may optionally contain a histogram of the values in the
  // population. The bucket boundaries for that histogram are described by
  // `bucket_bounds`. This defines `size(bucket_bounds) + 1` (= N)
  // buckets. The boundaries for bucket index i are:
  //
  // (-infinity, bucket_bounds[i]) for i == 0
  // [bucket_bounds[i-1], bucket_bounds[i]) for 0 < i < N-2
  // [bucket_bounds[i-1], +infinity) for i == N-1
  //
  // i.e. an underflow bucket (number 0), zero or more finite buckets (1
  // through N - 2, and an overflow bucket (N - 1), with inclusive lower
  // bounds and exclusive upper bounds.
  //
  // If `bucket_bounds` has no elements (zero size), then there is no
  // histogram associated with the Distribution. If `bucket_bounds` has only
  // one element, there are no finite buckets, and that single element is the
  // common boundary of the overflow and underflow buckets. The values must
  // be monotonically increasing.
  repeated double bucket_bounds = 1;
}

// Describes a data point to be collected for a Measure.
message Measurement {
  repeated Tag tags = 1;

  // The name of the measure to which the value is applied.
  string measure_name = 2;

  // The recorded value, MUST have the appropriate type to match the Measure.
  oneof value {
    double double_value = 3;
    int64 int_value = 4;
  }

  // The time when this measurement was recorded. If the implementation uses a async buffer to
  // record measurements this may be the time when the measurement was read from the buffer.
  google.protobuf.Timestamp time = 5;
}
