// +build linux

package libpod

import (
	"strings"
	"syscall"
	"time"

	"github.com/containerd/cgroups"
	"github.com/pkg/errors"
)

// GetContainerStats gets the running stats for a given container
func (c *Container) GetContainerStats(previousStats *ContainerStats) (*ContainerStats, error) {
	stats := new(ContainerStats)
	stats.ContainerID = c.ID()
	stats.Name = c.Name()
	c.lock.Lock()
	defer c.lock.Unlock()
	if err := c.syncContainer(); err != nil {
		return stats, err
	}
	if c.state.State != ContainerStateRunning {
		return stats, nil
	}

	cgroupPath, err := c.CGroupPath()
	if err != nil {
		return nil, err
	}

	cgroup, err := cgroups.Load(cgroups.V1, cgroups.StaticPath(cgroupPath))
	if err != nil {
		return stats, errors.Wrapf(err, "unable to load cgroup at %s", cgroupPath)
	}

	cgroupStats, err := cgroup.Stat()
	if err != nil {
		return stats, errors.Wrapf(err, "unable to obtain cgroup stats")
	}
	conState := c.state.State
	if err != nil {
		return stats, errors.Wrapf(err, "unable to determine container state")
	}

	netStats, err := getContainerNetIO(c)
	if err != nil {
		return nil, err
	}

	previousCPU := previousStats.CPUNano
	previousSystem := previousStats.SystemNano
	stats.CPU = calculateCPUPercent(cgroupStats, previousCPU, previousSystem)
	stats.MemUsage = cgroupStats.Memory.Usage.Usage
	stats.MemLimit = getMemLimit(cgroupStats.Memory.Usage.Limit)
	stats.MemPerc = (float64(stats.MemUsage) / float64(stats.MemLimit)) * 100
	stats.PIDs = 0
	if conState == ContainerStateRunning {
		stats.PIDs = cgroupStats.Pids.Current
	}
	stats.BlockInput, stats.BlockOutput = calculateBlockIO(cgroupStats)
	stats.CPUNano = cgroupStats.CPU.Usage.Total
	stats.SystemNano = cgroupStats.CPU.Usage.Kernel
	stats.NetInput = netStats.TxBytes
	stats.NetOutput = netStats.RxBytes

	return stats, nil
}

// getMemory limit returns the memory limit for a given cgroup
// If the configured memory limit is larger than the total memory on the sys, the
// physical system memory size is returned
func getMemLimit(cgroupLimit uint64) uint64 {
	si := &syscall.Sysinfo_t{}
	err := syscall.Sysinfo(si)
	if err != nil {
		return cgroupLimit
	}

	physicalLimit := uint64(si.Totalram)
	if cgroupLimit > physicalLimit {
		return physicalLimit
	}
	return cgroupLimit
}

func calculateCPUPercent(stats *cgroups.Metrics, previousCPU, previousSystem uint64) float64 {
	var (
		cpuPercent  = 0.0
		cpuDelta    = float64(stats.CPU.Usage.Total - previousCPU)
		systemDelta = float64(uint64(time.Now().UnixNano()) - previousSystem)
	)
	if systemDelta > 0.0 && cpuDelta > 0.0 {
		// gets a ratio of container cpu usage total, multiplies it by the number of cores (4 cores running
		// at 100% utilization should be 400% utilization), and multiplies that by 100 to get a percentage
		cpuPercent = (cpuDelta / systemDelta) * float64(len(stats.CPU.Usage.PerCPU)) * 100
	}
	return cpuPercent
}

func calculateBlockIO(stats *cgroups.Metrics) (read uint64, write uint64) {
	for _, blkIOEntry := range stats.Blkio.IoServiceBytesRecursive {
		switch strings.ToLower(blkIOEntry.Op) {
		case "read":
			read += blkIOEntry.Value
		case "write":
			write += blkIOEntry.Value
		}
	}
	return
}
