//go:build windows

package os

import (
	"errors"
	"fmt"
	"log/slog"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/alecthomas/kingpin/v2"
	"github.com/prometheus-community/windows_exporter/pkg/headers/kernel32"
	"github.com/prometheus-community/windows_exporter/pkg/headers/netapi32"
	"github.com/prometheus-community/windows_exporter/pkg/headers/psapi"
	"github.com/prometheus-community/windows_exporter/pkg/headers/sysinfoapi"
	"github.com/prometheus-community/windows_exporter/pkg/perflib"
	"github.com/prometheus-community/windows_exporter/pkg/types"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/yusufpapurcu/wmi"
	"golang.org/x/sys/windows"
	"golang.org/x/sys/windows/registry"
)

const Name = "os"

type Config struct{}

var ConfigDefaults = Config{}

// A Collector is a Prometheus Collector for WMI metrics.
type Collector struct {
	config Config

	hostname         *prometheus.Desc
	osInformation    *prometheus.Desc
	pagingFreeBytes  *prometheus.Desc
	pagingLimitBytes *prometheus.Desc

	// users
	// Deprecated: Use windows_system_processes instead.
	processes *prometheus.Desc
	// users
	// Deprecated: Use windows_system_process_limit instead.
	processesLimit *prometheus.Desc

	// users
	// Deprecated: Use count(windows_logon_logon_type) instead.
	users *prometheus.Desc

	// physicalMemoryFreeBytes
	// Deprecated: Use windows_memory_physical_free_bytes instead.
	physicalMemoryFreeBytes *prometheus.Desc

	// processMemoryLimitBytes
	// Deprecated: Use windows_memory_process_memory_limit_bytes instead.
	processMemoryLimitBytes *prometheus.Desc

	// time
	// Deprecated: Use windows_time_current_timestamp_seconds instead.
	time *prometheus.Desc
	// timezone
	// Deprecated: Use windows_time_timezone instead.
	timezone *prometheus.Desc
	// virtualMemoryBytes
	// Deprecated: Use windows_memory_commit_limit instead.
	virtualMemoryBytes *prometheus.Desc
	// virtualMemoryFreeBytes
	// Deprecated: Use windows_memory_commit_limit instead.
	virtualMemoryFreeBytes *prometheus.Desc
	// visibleMemoryBytes
	// Deprecated: Use windows_memory_physical_total_bytes instead.
	visibleMemoryBytes *prometheus.Desc
}

type pagingFileCounter struct {
	Name      string
	Usage     float64 `perflib:"% Usage"`
	UsagePeak float64 `perflib:"% Usage Peak"`
}

func New(config *Config) *Collector {
	if config == nil {
		config = &ConfigDefaults
	}

	c := &Collector{
		config: *config,
	}

	return c
}

func NewWithFlags(_ *kingpin.Application) *Collector {
	return &Collector{}
}

func (c *Collector) GetName() string {
	return Name
}

func (c *Collector) GetPerfCounter(_ *slog.Logger) ([]string, error) {
	return []string{"Paging File"}, nil
}

func (c *Collector) Close(_ *slog.Logger) error {
	return nil
}

func (c *Collector) Build(logger *slog.Logger, _ *wmi.Client) error {
	logger.Warn("The os collect holds a number of deprecated metrics and will be removed mid 2025. " +
		"See https://github.com/prometheus-community/windows_exporter/pull/1596 for more information.")

	workstationInfo, err := netapi32.GetWorkstationInfo()
	if err != nil {
		return fmt.Errorf("failed to get workstation info: %w", err)
	}

	productName, buildNumber, revision, err := c.getWindowsVersion()
	if err != nil {
		return fmt.Errorf("failed to get Windows version: %w", err)
	}

	c.osInformation = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "info"),
		`Contains full product name & version in labels. Note that the "major_version" for Windows 11 is \"10\"; a build number greater than 22000 represents Windows 11.`,
		nil,
		prometheus.Labels{
			"product":       productName,
			"version":       fmt.Sprintf("%d.%d.%s", workstationInfo.VersionMajor, workstationInfo.VersionMinor, buildNumber),
			"major_version": strconv.FormatUint(uint64(workstationInfo.VersionMajor), 10),
			"minor_version": strconv.FormatUint(uint64(workstationInfo.VersionMinor), 10),
			"build_number":  buildNumber,
			"revision":      revision,
		},
	)

	c.hostname = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "hostname"),
		"Labelled system hostname information as provided by ComputerSystem.DNSHostName and ComputerSystem.Domain",
		[]string{
			"hostname",
			"domain",
			"fqdn",
		},
		nil,
	)
	c.pagingLimitBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "paging_limit_bytes"),
		"OperatingSystem.SizeStoredInPagingFiles",
		nil,
		nil,
	)
	c.pagingFreeBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "paging_free_bytes"),
		"OperatingSystem.FreeSpaceInPagingFiles",
		nil,
		nil,
	)
	c.physicalMemoryFreeBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "physical_memory_free_bytes"),
		"Deprecated: Use `windows_memory_physical_free_bytes` instead.",
		nil,
		nil,
	)
	c.time = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "time"),
		"Deprecated: Use windows_time_current_timestamp_seconds instead.",
		nil,
		nil,
	)
	c.timezone = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "timezone"),
		"Deprecated: Use windows_time_timezone instead.",
		[]string{"timezone"},
		nil,
	)
	c.processes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "processes"),
		"Deprecated: Use `windows_system_processes` instead.",
		nil,
		nil,
	)
	c.processesLimit = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "processes_limit"),
		"Deprecated: Use `windows_system_process_limit` instead.",
		nil,
		nil,
	)
	c.processMemoryLimitBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "process_memory_limit_bytes"),
		"Deprecated: Use `windows_memory_process_memory_limit_bytes` instead.",
		nil,
		nil,
	)
	c.users = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "users"),
		"Deprecated: Use `count(windows_logon_logon_type)` instead.",
		nil,
		nil,
	)
	c.virtualMemoryBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "virtual_memory_bytes"),
		"Deprecated: Use `windows_memory_commit_limit` instead.",
		nil,
		nil,
	)
	c.visibleMemoryBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "visible_memory_bytes"),
		"Deprecated: Use `windows_memory_physical_total_bytes` instead.",
		nil,
		nil,
	)
	c.virtualMemoryFreeBytes = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "virtual_memory_free_bytes"),
		"Deprecated: Use `windows_memory_commit_limit - windows_memory_committed_bytes` instead.",
		nil,
		nil,
	)

	return nil
}

// Collect sends the metric values for each metric
// to the provided prometheus Metric channel.
func (c *Collector) Collect(ctx *types.ScrapeContext, logger *slog.Logger, ch chan<- prometheus.Metric) error {
	logger = logger.With(slog.String("collector", Name))

	errs := make([]error, 0, 5)

	c.collect(ch)

	if err := c.collectHostname(ch); err != nil {
		logger.Error("failed collecting os metrics",
			slog.Any("err", err),
		)

		errs = append(errs, err)
	}

	if err := c.collectLoggedInUserCount(ch); err != nil {
		logger.Error("failed collecting os user count metrics",
			slog.Any("err", err),
		)

		errs = append(errs, err)
	}

	if err := c.collectMemory(ch); err != nil {
		logger.Error("failed collecting os memory metrics",
			slog.Any("err", err),
		)

		errs = append(errs, err)
	}

	if err := c.collectTime(ch); err != nil {
		logger.Error("failed collecting os time metrics",
			slog.Any("err", err),
		)

		errs = append(errs, err)
	}

	if err := c.collectPaging(ctx, logger, ch); err != nil {
		logger.Error("failed collecting os paging metrics",
			slog.Any("err", err),
		)

		errs = append(errs, err)
	}

	return errors.Join(errs...)
}

func (c *Collector) collectLoggedInUserCount(ch chan<- prometheus.Metric) error {
	workstationInfo, err := netapi32.GetWorkstationInfo()
	if err != nil {
		return err
	}

	ch <- prometheus.MustNewConstMetric(
		c.users,
		prometheus.GaugeValue,
		float64(workstationInfo.LoggedOnUsers),
	)

	return nil
}

func (c *Collector) collectHostname(ch chan<- prometheus.Metric) error {
	hostname, err := sysinfoapi.GetComputerName(sysinfoapi.ComputerNameDNSHostname)
	if err != nil {
		return err
	}

	domain, err := sysinfoapi.GetComputerName(sysinfoapi.ComputerNameDNSDomain)
	if err != nil {
		return err
	}

	fqdn, err := sysinfoapi.GetComputerName(sysinfoapi.ComputerNameDNSFullyQualified)
	if err != nil {
		return err
	}

	ch <- prometheus.MustNewConstMetric(
		c.hostname,
		prometheus.GaugeValue,
		1.0,
		hostname,
		domain,
		fqdn,
	)

	return nil
}

func (c *Collector) collectTime(ch chan<- prometheus.Metric) error {
	timeZoneInfo, err := kernel32.GetDynamicTimeZoneInformation()
	if err != nil {
		return err
	}

	// timeZoneKeyName contains the english name of the timezone.
	timezoneName := windows.UTF16ToString(timeZoneInfo.TimeZoneKeyName[:])

	ch <- prometheus.MustNewConstMetric(
		c.time,
		prometheus.GaugeValue,
		float64(time.Now().Unix()),
	)

	ch <- prometheus.MustNewConstMetric(
		c.timezone,
		prometheus.GaugeValue,
		1.0,
		timezoneName,
	)

	return nil
}

func (c *Collector) collectMemory(ch chan<- prometheus.Metric) error {
	memoryStatusEx, err := sysinfoapi.GlobalMemoryStatusEx()
	if err != nil {
		return err
	}

	ch <- prometheus.MustNewConstMetric(
		c.physicalMemoryFreeBytes,
		prometheus.GaugeValue,
		float64(memoryStatusEx.AvailPhys),
	)

	ch <- prometheus.MustNewConstMetric(
		c.virtualMemoryFreeBytes,
		prometheus.GaugeValue,
		float64(memoryStatusEx.AvailPageFile),
	)

	ch <- prometheus.MustNewConstMetric(
		c.virtualMemoryBytes,
		prometheus.GaugeValue,
		float64(memoryStatusEx.TotalPageFile),
	)

	ch <- prometheus.MustNewConstMetric(
		c.visibleMemoryBytes,
		prometheus.GaugeValue,
		float64(memoryStatusEx.TotalPhys),
	)

	ch <- prometheus.MustNewConstMetric(
		c.processMemoryLimitBytes,
		prometheus.GaugeValue,
		float64(memoryStatusEx.TotalVirtual),
	)

	return nil
}

func (c *Collector) collectPaging(ctx *types.ScrapeContext, logger *slog.Logger, ch chan<- prometheus.Metric) error {
	// Get total allocation of paging files across all disks.
	memManKey, err := registry.OpenKey(registry.LOCAL_MACHINE, `SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management`, registry.QUERY_VALUE)
	if err != nil {
		return err
	}

	defer memManKey.Close()

	pagingFiles, _, pagingErr := memManKey.GetStringsValue("ExistingPageFiles")

	var fsipf float64

	for _, pagingFile := range pagingFiles {
		fileString := strings.ReplaceAll(pagingFile, `\??\`, "")
		file, err := os.Stat(fileString)
		// For unknown reasons, Windows doesn't always create a page file. Continue collection rather than aborting.
		if err != nil {
			logger.Debug(fmt.Sprintf("Failed to read page file (reason: %s): %s\n", err, fileString))
		} else {
			fsipf += float64(file.Size())
		}
	}

	gpi, err := psapi.GetPerformanceInfo()
	if err != nil {
		return err
	}

	pfc := make([]pagingFileCounter, 0)
	if err = perflib.UnmarshalObject(ctx.PerfObjects["Paging File"], &pfc, logger); err != nil {
		return err
	}

	// Get current page file usage.
	var pfbRaw float64

	for _, pageFile := range pfc {
		if strings.Contains(strings.ToLower(pageFile.Name), "_total") {
			continue
		}

		pfbRaw += pageFile.Usage
	}

	if pagingErr == nil {
		// Subtract from total page file allocation on disk.
		pfb := fsipf - (pfbRaw * float64(gpi.PageSize))

		ch <- prometheus.MustNewConstMetric(
			c.pagingFreeBytes,
			prometheus.GaugeValue,
			pfb,
		)

		ch <- prometheus.MustNewConstMetric(
			c.pagingLimitBytes,
			prometheus.GaugeValue,
			fsipf,
		)
	} else {
		logger.Debug("Could not find HKLM:\\SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Memory Management key. windows_os_paging_free_bytes and windows_os_paging_limit_bytes will be omitted.")
	}

	ch <- prometheus.MustNewConstMetric(
		c.processes,
		prometheus.GaugeValue,
		float64(gpi.ProcessCount),
	)

	return nil
}

func (c *Collector) collect(ch chan<- prometheus.Metric) {
	ch <- prometheus.MustNewConstMetric(
		c.osInformation,
		prometheus.GaugeValue,
		1.0,
	)

	// Windows has no defined limit, and is based off available resources. This currently isn't calculated by WMI and is set to default value.
	// https://techcommunity.microsoft.com/t5/windows-blog-archive/pushing-the-limits-of-windows-processes-and-threads/ba-p/723824
	// https://docs.microsoft.com/en-us/windows/win32/cimwin32prov/win32-operatingsystem
	ch <- prometheus.MustNewConstMetric(
		c.processesLimit,
		prometheus.GaugeValue,
		float64(4294967295),
	)
}

func (c *Collector) getWindowsVersion() (string, string, string, error) {
	// Get build number and product name from registry
	ntKey, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion`, registry.QUERY_VALUE)
	if err != nil {
		return "", "", "", fmt.Errorf("failed to open registry key: %w", err)
	}

	defer ntKey.Close()

	productName, _, err := ntKey.GetStringValue("ProductName")
	if err != nil {
		return "", "", "", err
	}

	buildNumber, _, err := ntKey.GetStringValue("CurrentBuildNumber")
	if err != nil {
		return "", "", "", err
	}

	revision, _, err := ntKey.GetIntegerValue("UBR")
	if errors.Is(err, registry.ErrNotExist) {
		revision = 0
	} else if err != nil {
		return "", "", "", err
	}

	return productName, buildNumber, strconv.FormatUint(revision, 10), nil
}