// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package dockerstatsreceiver // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/dockerstatsreceiver"

import (
	"fmt"
	"strconv"
	"strings"

	dtypes "github.com/docker/docker/api/types"
	ctypes "github.com/docker/docker/api/types/container"
)

const nanosInASecond = 1e9

// Following functions has been copied from: calculateCPUPercentUnix(), calculateMemUsageUnixNoCache(), calculateMemPercentUnixNoCache()
// https://github.com/docker/cli/blob/a2e9ed3b874fccc177b9349f3b0277612403934f/cli/command/container/stats_helpers.go

// Copyright 2012-2017 Docker, Inc.
// This product includes software developed at Docker, Inc. (https://www.docker.com).
// The following is courtesy of our legal counsel:
// Use and transfer of Docker may be subject to certain restrictions by the
// United States and other governments.
// It is your responsibility to ensure that your use and/or transfer does not
// violate applicable laws.
// For more information, please see https://www.bis.doc.gov
// See also https://www.apache.org/dev/crypto.html and/or seek legal counsel.

func calculateCPUPercent(previous *dtypes.CPUStats, v *dtypes.CPUStats) float64 {
	var (
		cpuPercent = 0.0
		// calculate the change for the cpu usage of the container in between readings
		cpuDelta = float64(v.CPUUsage.TotalUsage) - float64(previous.CPUUsage.TotalUsage)
		// calculate the change for the entire system between readings
		systemDelta = float64(v.SystemUsage) - float64(previous.SystemUsage)
		onlineCPUs  = float64(v.OnlineCPUs)
	)

	if onlineCPUs == 0.0 {
		onlineCPUs = float64(len(v.CPUUsage.PercpuUsage))
	}
	if systemDelta > 0.0 && cpuDelta > 0.0 {
		cpuPercent = (cpuDelta / systemDelta) * onlineCPUs * 100.0
	}
	return cpuPercent
}

// calculateMemUsageNoCache calculate memory usage of the container.
// Cache is intentionally excluded to avoid misinterpretation of the output.
//
// On cgroup v1 host, the result is `mem.Usage - mem.Stats["total_inactive_file"]` .
// On cgroup v2 host, the result is `mem.Usage - mem.Stats["inactive_file"] `.
//
// This definition is consistent with cadvisor and containerd/CRI.
// * https://github.com/google/cadvisor/commit/307d1b1cb320fef66fab02db749f07a459245451
// * https://github.com/containerd/cri/commit/6b8846cdf8b8c98c1d965313d66bc8489166059a
//
// On Docker 19.03 and older, the result was `mem.Usage - mem.Stats["cache"]`.
// See https://github.com/moby/moby/issues/40727 for the background.
func calculateMemUsageNoCache(memoryStats *dtypes.MemoryStats) uint64 {
	// cgroup v1
	if v, isCgroup1 := memoryStats.Stats["total_inactive_file"]; isCgroup1 && v < memoryStats.Usage {
		return memoryStats.Usage - v
	}
	// cgroup v2
	if v := memoryStats.Stats["inactive_file"]; v < memoryStats.Usage {
		return memoryStats.Usage - v
	}
	return memoryStats.Usage
}

func calculateMemoryPercent(limit uint64, usedNoCache uint64) float64 {
	// MemoryStats.Limit will never be 0 unless the container is not running and we haven't
	// got any data from cgroup
	if limit != 0 {
		return float64(usedNoCache) / float64(limit) * 100.0
	}
	return 0.0
}

// calculateCPULimit calculate the number of cpus assigned to a container.
//
// Calculation is based on 3 alternatives by the following order:
// - nanocpus:   if set by i.e docker run -cpus=2
// - cpusetCpus: if set by i.e docker run -docker run -cpuset-cpus="0,2"
// - cpuquota:   if set by i.e docker run -cpu-quota=50000
//
// See https://docs.docker.com/config/containers/resource_constraints/#configure-the-default-cfs-scheduler for background.
func calculateCPULimit(hostConfig *ctypes.HostConfig) (float64, error) {
	var cpuLimit float64
	var err error

	switch {
	case hostConfig.NanoCPUs > 0:
		cpuLimit = float64(hostConfig.NanoCPUs) / nanosInASecond
	case hostConfig.CpusetCpus != "":
		cpuLimit, err = parseCPUSet(hostConfig.CpusetCpus)
		if err != nil {
			return cpuLimit, err
		}
	case hostConfig.CPUQuota > 0:
		period := hostConfig.CPUPeriod
		if period == 0 {
			period = 100000 // Default CFS Period
		}
		cpuLimit = float64(hostConfig.CPUQuota) / float64(period)
	}
	return cpuLimit, nil
}

// parseCPUSet helper function to decompose -cpuset-cpus value into number os cpus.
func parseCPUSet(line string) (float64, error) {
	var numCPUs uint64

	lineSlice := strings.Split(line, ",")
	for _, l := range lineSlice {
		lineParts := strings.Split(l, "-")
		if len(lineParts) == 2 {
			p0, err0 := strconv.Atoi(lineParts[0])
			if err0 != nil {
				return 0, fmt.Errorf("invalid -cpuset-cpus value: %w", err0)
			}
			p1, err1 := strconv.Atoi(lineParts[1])
			if err1 != nil {
				return 0, fmt.Errorf("invalid -cpuset-cpus value: %w", err1)
			}
			numCPUs += uint64(p1 - p0 + 1)
		} else if len(lineParts) == 1 {
			numCPUs++
		}
	}
	return float64(numCPUs), nil
}