/*
 * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
 *
 * 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 net

import (
	"github.com/montanaflynn/stats"
)

// Latency holds latency information for read/write operations to the drive
type Latency struct {
	Avg          float64 `json:"avg_secs,omitempty"`
	Percentile50 float64 `json:"percentile50_secs,omitempty"`
	Percentile90 float64 `json:"percentile90_secs,omitempty"`
	Percentile99 float64 `json:"percentile99_secs,omitempty"`
	Min          float64 `json:"min_secs,omitempty"`
	Max          float64 `json:"max_secs,omitempty"`
}

// Throughput holds throughput information for read/write operations to the drive
type Throughput struct {
	Avg          float64 `json:"avg_bytes_per_sec,omitempty"`
	Percentile50 float64 `json:"percentile50_bytes_per_sec,omitempty"`
	Percentile90 float64 `json:"percentile90_bytes_per_sec,omitempty"`
	Percentile99 float64 `json:"percentile99_bytes_per_sec,omitempty"`
	Min          float64 `json:"min_bytes_per_sec,omitempty"`
	Max          float64 `json:"max_bytes_per_sec,omitempty"`
}

// ComputeOBDStats takes arrays of Latency & Throughput to compute Statistics
func ComputeOBDStats(latencies, throughputs []float64) (Latency, Throughput, error) {
	var avgLatency float64
	var percentile50Latency float64
	var percentile90Latency float64
	var percentile99Latency float64
	var minLatency float64
	var maxLatency float64

	var avgThroughput float64
	var percentile50Throughput float64
	var percentile90Throughput float64
	var percentile99Throughput float64
	var minThroughput float64
	var maxThroughput float64
	var err error

	if avgLatency, err = stats.Mean(latencies); err != nil {
		return Latency{}, Throughput{}, err
	}
	if percentile50Latency, err = stats.Percentile(latencies, 50); err != nil {
		return Latency{}, Throughput{}, err
	}
	if percentile90Latency, err = stats.Percentile(latencies, 90); err != nil {
		return Latency{}, Throughput{}, err
	}
	if percentile99Latency, err = stats.Percentile(latencies, 99); err != nil {
		return Latency{}, Throughput{}, err
	}
	if maxLatency, err = stats.Max(latencies); err != nil {
		return Latency{}, Throughput{}, err
	}
	if minLatency, err = stats.Min(latencies); err != nil {
		return Latency{}, Throughput{}, err
	}
	l := Latency{
		Avg:          avgLatency,
		Percentile50: percentile50Latency,
		Percentile90: percentile90Latency,
		Percentile99: percentile99Latency,
		Min:          minLatency,
		Max:          maxLatency,
	}

	if avgThroughput, err = stats.Mean(throughputs); err != nil {
		return Latency{}, Throughput{}, err
	}
	if percentile50Throughput, err = stats.Percentile(throughputs, 50); err != nil {
		return Latency{}, Throughput{}, err
	}
	if percentile90Throughput, err = stats.Percentile(throughputs, 90); err != nil {
		return Latency{}, Throughput{}, err
	}
	if percentile99Throughput, err = stats.Percentile(throughputs, 99); err != nil {
		return Latency{}, Throughput{}, err
	}
	if maxThroughput, err = stats.Max(throughputs); err != nil {
		return Latency{}, Throughput{}, err
	}
	if minThroughput, err = stats.Min(throughputs); err != nil {
		return Latency{}, Throughput{}, err
	}
	t := Throughput{
		Avg:          avgThroughput,
		Percentile50: percentile50Throughput,
		Percentile90: percentile90Throughput,
		Percentile99: percentile99Throughput,
		Min:          minThroughput,
		Max:          maxThroughput,
	}

	return l, t, nil
}