// Copyright 2015 The Prometheus 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.

// +build !nocpu

package collector

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/common/log"
	"github.com/prometheus/procfs"
)

var (
	digitRegexp = regexp.MustCompile("[0-9]+")
)

type cpuCollector struct {
	cpu                *prometheus.Desc
	cpuGuest           *prometheus.Desc
	cpuFreq            *prometheus.Desc
	cpuFreqMin         *prometheus.Desc
	cpuFreqMax         *prometheus.Desc
	cpuCoreThrottle    *prometheus.Desc
	cpuPackageThrottle *prometheus.Desc
}

func init() {
	registerCollector("cpu", defaultEnabled, NewCPUCollector)
}

// NewCPUCollector returns a new Collector exposing kernel/system statistics.
func NewCPUCollector() (Collector, error) {
	return &cpuCollector{
		cpu: nodeCpuSecondsDesc,
		cpuGuest: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "guest_seconds_total"),
			"Seconds the cpus spent in guests (VMs) for each mode.",
			[]string{"cpu", "mode"}, nil,
		),
		cpuFreq: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "frequency_hertz"),
			"Current cpu thread frequency in hertz.",
			[]string{"cpu"}, nil,
		),
		cpuFreqMin: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "frequency_min_hertz"),
			"Minimum cpu thread frequency in hertz.",
			[]string{"cpu"}, nil,
		),
		cpuFreqMax: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "frequency_max_hertz"),
			"Maximum cpu thread frequency in hertz.",
			[]string{"cpu"}, nil,
		),
		cpuCoreThrottle: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "core_throttles_total"),
			"Number of times this cpu core has been throttled.",
			[]string{"package", "core"}, nil,
		),
		cpuPackageThrottle: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "package_throttles_total"),
			"Number of times this cpu package has been throttled.",
			[]string{"package"}, nil,
		),
	}, nil
}

// Update implements Collector and exposes cpu related metrics from /proc/stat and /sys/.../cpu/.
func (c *cpuCollector) Update(ch chan<- prometheus.Metric) error {
	if err := c.updateStat(ch); err != nil {
		return err
	}
	if err := c.updateCPUfreq(ch); err != nil {
		return err
	}
	return nil
}

// updateCPUfreq reads /sys/devices/system/cpu/cpu* and expose cpu frequency statistics.
func (c *cpuCollector) updateCPUfreq(ch chan<- prometheus.Metric) error {
	cpus, err := filepath.Glob(sysFilePath("devices/system/cpu/cpu[0-9]*"))
	if err != nil {
		return err
	}

	var value uint64
	packageThrottles := make(map[uint64]uint64)
	packageCoreThrottles := make(map[uint64]map[uint64]uint64)

	// cpu loop
	for _, cpu := range cpus {
		_, cpuName := filepath.Split(cpu)
		cpuNum := strings.TrimPrefix(cpuName, "cpu")

		if _, err := os.Stat(filepath.Join(cpu, "cpufreq")); os.IsNotExist(err) {
			log.Debugf("CPU %v is missing cpufreq", cpu)
		} else {
			// sysfs cpufreq values are kHz, thus multiply by 1000 to export base units (hz).
			// See https://www.kernel.org/doc/Documentation/cpu-freq/user-guide.txt
			if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq", "scaling_cur_freq")); err != nil {
				return err
			}
			ch <- prometheus.MustNewConstMetric(c.cpuFreq, prometheus.GaugeValue, float64(value)*1000.0, cpuNum)

			if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq", "scaling_min_freq")); err != nil {
				return err
			}
			ch <- prometheus.MustNewConstMetric(c.cpuFreqMin, prometheus.GaugeValue, float64(value)*1000.0, cpuNum)

			if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq", "scaling_max_freq")); err != nil {
				return err
			}
			ch <- prometheus.MustNewConstMetric(c.cpuFreqMax, prometheus.GaugeValue, float64(value)*1000.0, cpuNum)
		}

		// See
		// https://www.kernel.org/doc/Documentation/x86/topology.txt
		// https://www.kernel.org/doc/Documentation/cputopology.txt
		// https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-devices-system-cpu
		var err error
		var physicalPackageID, coreID uint64

		// topology/physical_package_id
		if physicalPackageID, err = readUintFromFile(filepath.Join(cpu, "topology", "physical_package_id")); err != nil {
			log.Debugf("CPU %v is missing physical_package_id", cpu)
			continue
		}
		// topology/core_id
		if coreID, err = readUintFromFile(filepath.Join(cpu, "topology", "core_id")); err != nil {
			log.Debugf("CPU %v is missing core_id", cpu)
			continue
		}

		// metric node_cpu_core_throttles_total
		//
		// We process this metric before the package throttles as there
		// are cpu+kernel combinations that only present core throttles
		// but no package throttles.
		// Seen e.g. on an Intel Xeon E5472 system with RHEL 6.9 kernel.
		if _, present := packageCoreThrottles[physicalPackageID]; !present {
			packageCoreThrottles[physicalPackageID] = make(map[uint64]uint64)
		}
		if _, present := packageCoreThrottles[physicalPackageID][coreID]; !present {
			// Read thermal_throttle/core_throttle_count only once
			if coreThrottleCount, err := readUintFromFile(filepath.Join(cpu, "thermal_throttle", "core_throttle_count")); err == nil {
				packageCoreThrottles[physicalPackageID][coreID] = coreThrottleCount
			} else {
				log.Debugf("CPU %v is missing core_throttle_count", cpu)
			}
		}

		// metric node_cpu_package_throttles_total
		if _, present := packageThrottles[physicalPackageID]; !present {
			// Read thermal_throttle/package_throttle_count only once
			if packageThrottleCount, err := readUintFromFile(filepath.Join(cpu, "thermal_throttle", "package_throttle_count")); err == nil {
				packageThrottles[physicalPackageID] = packageThrottleCount
			} else {
				log.Debugf("CPU %v is missing package_throttle_count", cpu)
			}
		}
	}

	for physicalPackageID, packageThrottleCount := range packageThrottles {
		ch <- prometheus.MustNewConstMetric(c.cpuPackageThrottle,
			prometheus.CounterValue,
			float64(packageThrottleCount),
			strconv.FormatUint(physicalPackageID, 10))
	}

	for physicalPackageID, core_map := range packageCoreThrottles {
		for coreID, coreThrottleCount := range core_map {
			ch <- prometheus.MustNewConstMetric(c.cpuCoreThrottle,
				prometheus.CounterValue,
				float64(coreThrottleCount),
				strconv.FormatUint(physicalPackageID, 10),
				strconv.FormatUint(coreID, 10))
		}
	}
	return nil
}

// updateStat reads /proc/stat through procfs and exports cpu related metrics.
func (c *cpuCollector) updateStat(ch chan<- prometheus.Metric) error {
	fs, err := procfs.NewFS(*procPath)
	if err != nil {
		return fmt.Errorf("failed to open procfs: %v", err)
	}
	stats, err := fs.NewStat()
	if err != nil {
		return err
	}

	for cpuID, cpuStat := range stats.CPU {
		cpuNum := fmt.Sprintf("%d", cpuID)
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.User, cpuNum, "user")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.Nice, cpuNum, "nice")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.System, cpuNum, "system")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.Idle, cpuNum, "idle")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.Iowait, cpuNum, "iowait")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.IRQ, cpuNum, "irq")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.SoftIRQ, cpuNum, "softirq")
		ch <- prometheus.MustNewConstMetric(c.cpu, prometheus.CounterValue, cpuStat.Steal, cpuNum, "steal")

		// Guest CPU is also accounted for in cpuStat.User and cpuStat.Nice, expose these as separate metrics.
		ch <- prometheus.MustNewConstMetric(c.cpuGuest, prometheus.CounterValue, cpuStat.Guest, cpuNum, "user")
		ch <- prometheus.MustNewConstMetric(c.cpuGuest, prometheus.CounterValue, cpuStat.GuestNice, cpuNum, "nice")
	}

	return nil
}