// 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.

// +build !windows

package procfs

import (
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"github.com/prometheus/procfs/internal/util"
)

// The VM interface is described at
//   https://www.kernel.org/doc/Documentation/sysctl/vm.txt
// Each setting is exposed as a single file.
// Each file contains one line with a single numerical value, except lowmem_reserve_ratio which holds an array
// and numa_zonelist_order (deprecated) which is a string
type VM struct {
	AdminReserveKbytes        int64   // /proc/sys/vm/admin_reserve_kbytes
	BlockDump                 int64   // /proc/sys/vm/block_dump
	CompactUnevictableAllowed int64   // /proc/sys/vm/compact_unevictable_allowed
	DirtyBackgroundBytes      int64   // /proc/sys/vm/dirty_background_bytes
	DirtyBackgroundRatio      int64   // /proc/sys/vm/dirty_background_ratio
	DirtyBytes                int64   // /proc/sys/vm/dirty_bytes
	DirtyExpireCentisecs      int64   // /proc/sys/vm/dirty_expire_centisecs
	DirtyRatio                int64   // /proc/sys/vm/dirty_ratio
	DirtytimeExpireSeconds    int64   // /proc/sys/vm/dirtytime_expire_seconds
	DirtyWritebackCentisecs   int64   // /proc/sys/vm/dirty_writeback_centisecs
	DropCaches                int64   // /proc/sys/vm/drop_caches
	ExtfragThreshold          int64   // /proc/sys/vm/extfrag_threshold
	HugetlbShmGroup           int64   // /proc/sys/vm/hugetlb_shm_group
	LaptopMode                int64   // /proc/sys/vm/laptop_mode
	LegacyVaLayout            int64   // /proc/sys/vm/legacy_va_layout
	LowmemReserveRatio        []int64 // /proc/sys/vm/lowmem_reserve_ratio
	MaxMapCount               int64   // /proc/sys/vm/max_map_count
	MemoryFailureEarlyKill    int64   // /proc/sys/vm/memory_failure_early_kill
	MemoryFailureRecovery     int64   // /proc/sys/vm/memory_failure_recovery
	MinFreeKbytes             int64   // /proc/sys/vm/min_free_kbytes
	MinSlabRatio              int64   // /proc/sys/vm/min_slab_ratio
	MinUnmappedRatio          int64   // /proc/sys/vm/min_unmapped_ratio
	MmapMinAddr               int64   // /proc/sys/vm/mmap_min_addr
	NrHugepages               int64   // /proc/sys/vm/nr_hugepages
	NrHugepagesMempolicy      int64   // /proc/sys/vm/nr_hugepages_mempolicy
	NrOvercommitHugepages     int64   // /proc/sys/vm/nr_overcommit_hugepages
	NumaStat                  int64   // /proc/sys/vm/numa_stat
	NumaZonelistOrder         string  // /proc/sys/vm/numa_zonelist_order
	OomDumpTasks              int64   // /proc/sys/vm/oom_dump_tasks
	OomKillAllocatingTask     int64   // /proc/sys/vm/oom_kill_allocating_task
	OvercommitKbytes          int64   // /proc/sys/vm/overcommit_kbytes
	OvercommitMemory          int64   // /proc/sys/vm/overcommit_memory
	OvercommitRatio           int64   // /proc/sys/vm/overcommit_ratio
	PageCluster               int64   // /proc/sys/vm/page-cluster
	PanicOnOom                int64   // /proc/sys/vm/panic_on_oom
	PercpuPagelistFraction    int64   // /proc/sys/vm/percpu_pagelist_fraction
	StatInterval              int64   // /proc/sys/vm/stat_interval
	Swappiness                int64   // /proc/sys/vm/swappiness
	UserReserveKbytes         int64   // /proc/sys/vm/user_reserve_kbytes
	VfsCachePressure          int64   // /proc/sys/vm/vfs_cache_pressure
	WatermarkBoostFactor      int64   // /proc/sys/vm/watermark_boost_factor
	WatermarkScaleFactor      int64   // /proc/sys/vm/watermark_scale_factor
	ZoneReclaimMode           int64   // /proc/sys/vm/zone_reclaim_mode
}

// VM reads the VM statistics from the specified `proc` filesystem.
func (fs FS) VM() (*VM, error) {
	path := fs.proc.Path("sys/vm")
	file, err := os.Stat(path)
	if err != nil {
		return nil, err
	}
	if !file.Mode().IsDir() {
		return nil, fmt.Errorf("%s is not a directory", path)
	}

	files, err := ioutil.ReadDir(path)
	if err != nil {
		return nil, err
	}

	var vm VM
	for _, f := range files {
		if f.IsDir() {
			continue
		}

		name := filepath.Join(path, f.Name())
		// ignore errors on read, as there are some write only
		// in /proc/sys/vm
		value, err := util.SysReadFile(name)
		if err != nil {
			continue
		}
		vp := util.NewValueParser(value)

		switch f.Name() {
		case "admin_reserve_kbytes":
			vm.AdminReserveKbytes = *vp.PInt64()
		case "block_dump":
			vm.BlockDump = *vp.PInt64()
		case "compact_unevictable_allowed":
			vm.CompactUnevictableAllowed = *vp.PInt64()
		case "dirty_background_bytes":
			vm.DirtyBackgroundBytes = *vp.PInt64()
		case "dirty_background_ratio":
			vm.DirtyBackgroundRatio = *vp.PInt64()
		case "dirty_bytes":
			vm.DirtyBytes = *vp.PInt64()
		case "dirty_expire_centisecs":
			vm.DirtyExpireCentisecs = *vp.PInt64()
		case "dirty_ratio":
			vm.DirtyRatio = *vp.PInt64()
		case "dirtytime_expire_seconds":
			vm.DirtytimeExpireSeconds = *vp.PInt64()
		case "dirty_writeback_centisecs":
			vm.DirtyWritebackCentisecs = *vp.PInt64()
		case "drop_caches":
			vm.DropCaches = *vp.PInt64()
		case "extfrag_threshold":
			vm.ExtfragThreshold = *vp.PInt64()
		case "hugetlb_shm_group":
			vm.HugetlbShmGroup = *vp.PInt64()
		case "laptop_mode":
			vm.LaptopMode = *vp.PInt64()
		case "legacy_va_layout":
			vm.LegacyVaLayout = *vp.PInt64()
		case "lowmem_reserve_ratio":
			stringSlice := strings.Fields(value)
			int64Slice := make([]int64, 0, len(stringSlice))
			for _, value := range stringSlice {
				vp := util.NewValueParser(value)
				int64Slice = append(int64Slice, *vp.PInt64())
			}
			vm.LowmemReserveRatio = int64Slice
		case "max_map_count":
			vm.MaxMapCount = *vp.PInt64()
		case "memory_failure_early_kill":
			vm.MemoryFailureEarlyKill = *vp.PInt64()
		case "memory_failure_recovery":
			vm.MemoryFailureRecovery = *vp.PInt64()
		case "min_free_kbytes":
			vm.MinFreeKbytes = *vp.PInt64()
		case "min_slab_ratio":
			vm.MinSlabRatio = *vp.PInt64()
		case "min_unmapped_ratio":
			vm.MinUnmappedRatio = *vp.PInt64()
		case "mmap_min_addr":
			vm.MmapMinAddr = *vp.PInt64()
		case "nr_hugepages":
			vm.NrHugepages = *vp.PInt64()
		case "nr_hugepages_mempolicy":
			vm.NrHugepagesMempolicy = *vp.PInt64()
		case "nr_overcommit_hugepages":
			vm.NrOvercommitHugepages = *vp.PInt64()
		case "numa_stat":
			vm.NumaStat = *vp.PInt64()
		case "numa_zonelist_order":
			vm.NumaZonelistOrder = value
		case "oom_dump_tasks":
			vm.OomDumpTasks = *vp.PInt64()
		case "oom_kill_allocating_task":
			vm.OomKillAllocatingTask = *vp.PInt64()
		case "overcommit_kbytes":
			vm.OvercommitKbytes = *vp.PInt64()
		case "overcommit_memory":
			vm.OvercommitMemory = *vp.PInt64()
		case "overcommit_ratio":
			vm.OvercommitRatio = *vp.PInt64()
		case "page-cluster":
			vm.PageCluster = *vp.PInt64()
		case "panic_on_oom":
			vm.PanicOnOom = *vp.PInt64()
		case "percpu_pagelist_fraction":
			vm.PercpuPagelistFraction = *vp.PInt64()
		case "stat_interval":
			vm.StatInterval = *vp.PInt64()
		case "swappiness":
			vm.Swappiness = *vp.PInt64()
		case "user_reserve_kbytes":
			vm.UserReserveKbytes = *vp.PInt64()
		case "vfs_cache_pressure":
			vm.VfsCachePressure = *vp.PInt64()
		case "watermark_boost_factor":
			vm.WatermarkBoostFactor = *vp.PInt64()
		case "watermark_scale_factor":
			vm.WatermarkScaleFactor = *vp.PInt64()
		case "zone_reclaim_mode":
			vm.ZoneReclaimMode = *vp.PInt64()
		}
		if err := vp.Err(); err != nil {
			return nil, err
		}
	}

	return &vm, nil
}
