// Copyright The OpenTelemetry 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.

package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"

import (
	"context"
	"time"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/metric/metricdata"
)

// Reservoir holds the sampled exemplar of measurements made.
type Reservoir[N int64 | float64] interface {
	// Offer accepts the parameters associated with a measurement. The
	// parameters will be stored as an exemplar if the Reservoir decides to
	// sample the measurement.
	//
	// The passed ctx needs to contain any baggage or span that were active
	// when the measurement was made. This information may be used by the
	// Reservoir in making a sampling decision.
	//
	// The time t is the time when the measurement was made. The val and attr
	// parameters are the value and dropped (filtered) attributes of the
	// measurement respectively.
	Offer(ctx context.Context, t time.Time, val N, attr []attribute.KeyValue)

	// Collect returns all the held exemplars.
	//
	// The Reservoir state is preserved after this call.
	Collect(dest *[]metricdata.Exemplar[N])
}