// Copyright 2019 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.

package collector

import (
	"fmt"
	"runtime"

	perf "github.com/hodgesds/perf-utils"
	"github.com/prometheus/client_golang/prometheus"
)

const (
	perfSubsystem = "perf"
)

func init() {
	registerCollector(perfSubsystem, defaultDisabled, NewPerfCollector)
}

// perfCollector is a Collecter that uses the perf subsystem to collect
// metrics. It uses perf_event_open an ioctls for profiling. Due to the fact
// that the perf subsystem is highly dependent on kernel configuration and
// settings not all profiler values may be exposed on the target system at any
// given time.
type perfCollector struct {
	perfHwProfilers    map[int]perf.HardwareProfiler
	perfSwProfilers    map[int]perf.SoftwareProfiler
	perfCacheProfilers map[int]perf.CacheProfiler
	desc               map[string]*prometheus.Desc
}

// NewPerfCollector returns a new perf based collector, it creates a profiler
// per CPU.
func NewPerfCollector() (Collector, error) {
	collector := &perfCollector{
		perfHwProfilers:    map[int]perf.HardwareProfiler{},
		perfSwProfilers:    map[int]perf.SoftwareProfiler{},
		perfCacheProfilers: map[int]perf.CacheProfiler{},
	}
	ncpus := runtime.NumCPU()
	for i := 0; i < ncpus; i++ {
		// Use -1 to profile all processes on the CPU, see:
		// man perf_event_open
		collector.perfHwProfilers[i] = perf.NewHardwareProfiler(-1, i)
		if err := collector.perfHwProfilers[i].Start(); err != nil {
			return collector, err
		}
		collector.perfSwProfilers[i] = perf.NewSoftwareProfiler(-1, i)
		if err := collector.perfSwProfilers[i].Start(); err != nil {
			return collector, err
		}
		collector.perfCacheProfilers[i] = perf.NewCacheProfiler(-1, i)
		if err := collector.perfCacheProfilers[i].Start(); err != nil {
			return collector, err
		}
	}
	collector.desc = map[string]*prometheus.Desc{
		"cpucycles_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cpucycles_total",
			),
			"Number of CPU cycles (frequency scaled)",
			[]string{"cpu"},
			nil,
		),
		"instructions_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"instructions_total",
			),
			"Number of CPU instructions",
			[]string{"cpu"},
			nil,
		),
		"branch_instructions_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"branch_instructions_total",
			),
			"Number of CPU branch instructions",
			[]string{"cpu"},
			nil,
		),
		"branch_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"branch_misses_total",
			),
			"Number of CPU branch misses",
			[]string{"cpu"},
			nil,
		),
		"cache_refs_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_refs_total",
			),
			"Number of cache references (non frequency scaled)",
			[]string{"cpu"},
			nil,
		),
		"cache_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_misses_total",
			),
			"Number of cache misses",
			[]string{"cpu"},
			nil,
		),
		"ref_cpucycles_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"ref_cpucycles_total",
			),
			"Number of CPU cycles",
			[]string{"cpu"},
			nil,
		),
		"page_faults_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"page_faults_total",
			),
			"Number of page faults",
			[]string{"cpu"},
			nil,
		),
		"context_switches_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"context_switches_total",
			),
			"Number of context switches",
			[]string{"cpu"},
			nil,
		),
		"cpu_migrations_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cpu_migrations_total",
			),
			"Number of CPU process migrations",
			[]string{"cpu"},
			nil,
		),
		"minor_faults_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"minor_faults_total",
			),
			"Number of minor page faults",
			[]string{"cpu"},
			nil,
		),
		"major_faults_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"major_faults_total",
			),
			"Number of major page faults",
			[]string{"cpu"},
			nil,
		),
		"cache_l1d_read_hits_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_l1d_read_hits_total",
			),
			"Number L1 data cache read hits",
			[]string{"cpu"},
			nil,
		),
		"cache_l1d_read_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_l1d_read_misses_total",
			),
			"Number L1 data cache read misses",
			[]string{"cpu"},
			nil,
		),
		"cache_l1d_write_hits_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_l1d_write_hits_total",
			),
			"Number L1 data cache write hits",
			[]string{"cpu"},
			nil,
		),
		"cache_l1_instr_read_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_l1_instr_read_misses_total",
			),
			"Number instruction L1 instruction read misses",
			[]string{"cpu"},
			nil,
		),
		"cache_tlb_instr_read_hits_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_tlb_instr_read_hits_total",
			),
			"Number instruction TLB read hits",
			[]string{"cpu"},
			nil,
		),
		"cache_tlb_instr_read_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_tlb_instr_read_misses_total",
			),
			"Number instruction TLB read misses",
			[]string{"cpu"},
			nil,
		),
		"cache_ll_read_hits_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_ll_read_hits_total",
			),
			"Number last level read hits",
			[]string{"cpu"},
			nil,
		),
		"cache_ll_read_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_ll_read_misses_total",
			),
			"Number last level read misses",
			[]string{"cpu"},
			nil,
		),
		"cache_ll_write_hits_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_ll_write_hits_total",
			),
			"Number last level write hits",
			[]string{"cpu"},
			nil,
		),
		"cache_ll_write_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_ll_write_misses_total",
			),
			"Number last level write misses",
			[]string{"cpu"},
			nil,
		),
		"cache_bpu_read_hits_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_bpu_read_hits_total",
			),
			"Number BPU read hits",
			[]string{"cpu"},
			nil,
		),
		"cache_bpu_read_misses_total": prometheus.NewDesc(
			prometheus.BuildFQName(
				namespace,
				perfSubsystem,
				"cache_bpu_read_misses_total",
			),
			"Number BPU read misses",
			[]string{"cpu"},
			nil,
		),
	}

	return collector, nil
}

// Update implements the Collector interface and will collect metrics per CPU.
func (c *perfCollector) Update(ch chan<- prometheus.Metric) error {
	if err := c.updateHardwareStats(ch); err != nil {
		return err
	}

	if err := c.updateSoftwareStats(ch); err != nil {
		return err
	}

	if err := c.updateCacheStats(ch); err != nil {
		return err
	}

	return nil
}

func (c *perfCollector) updateHardwareStats(ch chan<- prometheus.Metric) error {
	for cpu, profiler := range c.perfHwProfilers {
		cpuStr := fmt.Sprintf("%d", cpu)
		hwProfile, err := profiler.Profile()
		if err != nil {
			return err
		}
		if hwProfile == nil {
			continue
		}

		if hwProfile.CPUCycles != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cpucycles_total"],
				prometheus.CounterValue, float64(*hwProfile.CPUCycles),
				cpuStr,
			)
		}

		if hwProfile.Instructions != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["instructions_total"],
				prometheus.CounterValue, float64(*hwProfile.Instructions),
				cpuStr,
			)
		}

		if hwProfile.BranchInstr != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["branch_instructions_total"],
				prometheus.CounterValue, float64(*hwProfile.BranchInstr),
				cpuStr,
			)
		}

		if hwProfile.BranchMisses != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["branch_misses_total"],
				prometheus.CounterValue, float64(*hwProfile.BranchMisses),
				cpuStr,
			)
		}

		if hwProfile.CacheRefs != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_refs_total"],
				prometheus.CounterValue, float64(*hwProfile.CacheRefs),
				cpuStr,
			)
		}

		if hwProfile.CacheMisses != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_misses_total"],
				prometheus.CounterValue, float64(*hwProfile.CacheMisses),
				cpuStr,
			)
		}

		if hwProfile.RefCPUCycles != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["ref_cpucycles_total"],
				prometheus.CounterValue, float64(*hwProfile.RefCPUCycles),
				cpuStr,
			)
		}
	}

	return nil
}

func (c *perfCollector) updateSoftwareStats(ch chan<- prometheus.Metric) error {
	for cpu, profiler := range c.perfSwProfilers {
		cpuStr := fmt.Sprintf("%d", cpu)
		swProfile, err := profiler.Profile()
		if err != nil {
			return err
		}
		if swProfile == nil {
			continue
		}

		if swProfile.PageFaults != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["page_faults_total"],
				prometheus.CounterValue, float64(*swProfile.PageFaults),
				cpuStr,
			)
		}

		if swProfile.ContextSwitches != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["context_switches_total"],
				prometheus.CounterValue, float64(*swProfile.ContextSwitches),
				cpuStr,
			)
		}

		if swProfile.CPUMigrations != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cpu_migrations_total"],
				prometheus.CounterValue, float64(*swProfile.CPUMigrations),
				cpuStr,
			)
		}

		if swProfile.MinorPageFaults != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["minor_faults_total"],
				prometheus.CounterValue, float64(*swProfile.MinorPageFaults),
				cpuStr,
			)
		}

		if swProfile.MajorPageFaults != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["major_faults_total"],
				prometheus.CounterValue, float64(*swProfile.MajorPageFaults),
				cpuStr,
			)
		}
	}

	return nil
}

func (c *perfCollector) updateCacheStats(ch chan<- prometheus.Metric) error {
	for cpu, profiler := range c.perfCacheProfilers {
		cpuStr := fmt.Sprintf("%d", cpu)
		cacheProfile, err := profiler.Profile()
		if err != nil {
			return err
		}
		if cacheProfile == nil {
			continue
		}

		if cacheProfile.L1DataReadHit != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_l1d_read_hits_total"],
				prometheus.CounterValue, float64(*cacheProfile.L1DataReadHit),
				cpuStr,
			)
		}

		if cacheProfile.L1DataReadMiss != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_l1d_read_misses_total"],
				prometheus.CounterValue, float64(*cacheProfile.L1DataReadMiss),
				cpuStr,
			)
		}

		if cacheProfile.L1DataWriteHit != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_l1d_write_hits_total"],
				prometheus.CounterValue, float64(*cacheProfile.L1DataWriteHit),
				cpuStr,
			)
		}

		if cacheProfile.L1InstrReadMiss != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_l1_instr_read_misses_total"],
				prometheus.CounterValue, float64(*cacheProfile.L1InstrReadMiss),
				cpuStr,
			)
		}

		if cacheProfile.InstrTLBReadHit != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_tlb_instr_read_hits_total"],
				prometheus.CounterValue, float64(*cacheProfile.InstrTLBReadHit),
				cpuStr,
			)
		}

		if cacheProfile.InstrTLBReadMiss != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_tlb_instr_read_misses_total"],
				prometheus.CounterValue, float64(*cacheProfile.InstrTLBReadMiss),
				cpuStr,
			)
		}

		if cacheProfile.LastLevelReadHit != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_ll_read_hits_total"],
				prometheus.CounterValue, float64(*cacheProfile.LastLevelReadHit),
				cpuStr,
			)
		}

		if cacheProfile.LastLevelReadMiss != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_ll_read_misses_total"],
				prometheus.CounterValue, float64(*cacheProfile.LastLevelReadMiss),
				cpuStr,
			)
		}

		if cacheProfile.LastLevelWriteHit != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_ll_write_hits_total"],
				prometheus.CounterValue, float64(*cacheProfile.LastLevelWriteHit),
				cpuStr,
			)
		}

		if cacheProfile.LastLevelWriteMiss != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_ll_write_misses_total"],
				prometheus.CounterValue, float64(*cacheProfile.LastLevelWriteMiss),
				cpuStr,
			)
		}

		if cacheProfile.BPUReadHit != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_bpu_read_hits_total"],
				prometheus.CounterValue, float64(*cacheProfile.BPUReadHit),
				cpuStr,
			)
		}

		if cacheProfile.BPUReadMiss != nil {
			ch <- prometheus.MustNewConstMetric(
				c.desc["cache_bpu_read_misses_total"],
				prometheus.CounterValue, float64(*cacheProfile.BPUReadMiss),
				cpuStr,
			)
		}
	}

	return nil
}