// SPDX-License-Identifier: Apache-2.0
//
// Copyright 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.

//go:build windows

package iis

import (
	"errors"
	"fmt"
	"log/slog"
	"regexp"
	"slices"
	"strconv"
	"strings"
	"time"

	"github.com/alecthomas/kingpin/v2"
	"github.com/prometheus-community/windows_exporter/internal/mi"
	"github.com/prometheus-community/windows_exporter/internal/types"
	"github.com/prometheus/client_golang/prometheus"
	"golang.org/x/sys/windows/registry"
)

const Name = "iis"

type Config struct {
	SiteInclude *regexp.Regexp `yaml:"site-include"`
	SiteExclude *regexp.Regexp `yaml:"site-exclude"`
	AppInclude  *regexp.Regexp `yaml:"app-include"`
	AppExclude  *regexp.Regexp `yaml:"app-exclude"`
}

//nolint:gochecknoglobals
var ConfigDefaults = Config{
	SiteInclude: types.RegExpAny,
	SiteExclude: types.RegExpEmpty,
	AppInclude:  types.RegExpAny,
	AppExclude:  types.RegExpEmpty,
}

type Collector struct {
	collectorWebService
	collectorHttpServiceRequestQueues
	collectorAppPoolWAS
	collectorW3SVCW3WP
	collectorWebServiceCache

	config     Config
	iisVersion simpleVersion

	logger *slog.Logger

	info *prometheus.Desc
}

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

	if config.AppExclude == nil {
		config.AppExclude = ConfigDefaults.AppExclude
	}

	if config.AppInclude == nil {
		config.AppInclude = ConfigDefaults.AppInclude
	}

	if config.SiteExclude == nil {
		config.SiteExclude = ConfigDefaults.SiteExclude
	}

	if config.SiteInclude == nil {
		config.SiteInclude = ConfigDefaults.SiteInclude
	}

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

	return c
}

func NewWithFlags(app *kingpin.Application) *Collector {
	c := &Collector{
		config: ConfigDefaults,
	}

	var appExclude, appInclude, siteExclude, siteInclude string

	app.Flag(
		"collector.iis.app-exclude",
		"Regexp of apps to exclude. App name must both match include and not match exclude to be included.",
	).Default("").StringVar(&appExclude)

	app.Flag(
		"collector.iis.app-include",
		"Regexp of apps to include. App name must both match include and not match exclude to be included.",
	).Default(".+").StringVar(&appInclude)

	app.Flag(
		"collector.iis.site-exclude",
		"Regexp of sites to exclude. Site name must both match include and not match exclude to be included.",
	).Default("").StringVar(&siteExclude)

	app.Flag(
		"collector.iis.site-include",
		"Regexp of sites to include. Site name must both match include and not match exclude to be included.",
	).Default(".+").StringVar(&siteInclude)

	app.Action(func(*kingpin.ParseContext) error {
		var err error

		c.config.AppExclude, err = regexp.Compile(fmt.Sprintf("^(?:%s)$", appExclude))
		if err != nil {
			return fmt.Errorf("collector.iis.app-exclude: %w", err)
		}

		c.config.AppInclude, err = regexp.Compile(fmt.Sprintf("^(?:%s)$", appInclude))
		if err != nil {
			return fmt.Errorf("collector.iis.app-include: %w", err)
		}

		c.config.SiteExclude, err = regexp.Compile(fmt.Sprintf("^(?:%s)$", siteExclude))
		if err != nil {
			return fmt.Errorf("collector.iis.site-exclude: %w", err)
		}

		c.config.SiteInclude, err = regexp.Compile(fmt.Sprintf("^(?:%s)$", siteInclude))
		if err != nil {
			return fmt.Errorf("collector.iis.site-include: %w", err)
		}

		return nil
	})

	return c
}

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

func (c *Collector) Close() error {
	c.perfDataCollectorWebService.Close()
	c.perfDataCollectorHttpServiceRequestQueues.Close()
	c.perfDataCollectorAppPoolWAS.Close()

	if c.w3SVCW3WPPerfDataCollector != nil {
		c.w3SVCW3WPPerfDataCollector.Close()
	}

	c.w3SVCW3WPPerfDataCollectorV8.Close()

	if c.serviceCachePerfDataCollector != nil {
		c.serviceCachePerfDataCollector.Close()
	}

	return nil
}

func (c *Collector) Build(logger *slog.Logger, _ *mi.Session) error {
	c.logger = logger.With(slog.String("collector", Name))

	c.iisVersion = c.getIISVersion()

	c.info = prometheus.NewDesc(
		prometheus.BuildFQName(types.Namespace, Name, "info"),
		"ISS information",
		[]string{},
		prometheus.Labels{"version": fmt.Sprintf("%d.%d", c.iisVersion.major, c.iisVersion.minor)},
	)

	errs := make([]error, 0)

	if err := c.buildWebService(); err != nil {
		errs = append(errs, fmt.Errorf("failed to build Web Service collector: %w", err))
	}

	if err := c.buildHttpServiceRequestQueues(); err != nil {
		errs = append(errs, fmt.Errorf("failed to build Http Service collector: %w", err))
	}

	if err := c.buildAppPoolWAS(); err != nil {
		errs = append(errs, fmt.Errorf("failed to build APP_POOL_WAS collector: %w", err))
	}

	if err := c.buildW3SVCW3WP(); err != nil {
		errs = append(errs, fmt.Errorf("failed to build W3SVC_W3WP collector: %w", err))
	}

	if err := c.buildWebServiceCache(); err != nil {
		errs = append(errs, fmt.Errorf("failed to build Web Service Cache collector: %w", err))
	}

	return errors.Join(errs...)
}

type simpleVersion struct {
	major uint64
	minor uint64
}

func (c *Collector) getIISVersion() simpleVersion {
	k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\InetStp\`, registry.QUERY_VALUE)
	if err != nil {
		c.logger.Warn("couldn't open registry to determine IIS version",
			slog.Any("err", err),
		)

		return simpleVersion{}
	}

	defer func() {
		err = k.Close()
		if err != nil {
			c.logger.Warn("Failed to close registry key",
				slog.Any("err", err),
			)
		}
	}()

	major, _, err := k.GetIntegerValue("MajorVersion")
	if err != nil {
		c.logger.Warn("Couldn't open registry to determine IIS version",
			slog.Any("err", err),
		)

		return simpleVersion{}
	}

	minor, _, err := k.GetIntegerValue("MinorVersion")
	if err != nil {
		c.logger.Warn("Couldn't open registry to determine IIS version",
			slog.Any("err", err),
		)

		return simpleVersion{}
	}

	c.logger.Debug(fmt.Sprintf("Detected IIS %d.%d\n", major, minor))

	return simpleVersion{
		major: major,
		minor: minor,
	}
}

// Collect sends the metric values for each metric
// to the provided prometheus Metric channel.
func (c *Collector) Collect(ch chan<- prometheus.Metric, _ time.Duration) error {
	ch <- prometheus.MustNewConstMetric(
		c.info,
		prometheus.GaugeValue,
		1,
	)

	errs := make([]error, 0)

	if err := c.collectWebService(ch); err != nil {
		errs = append(errs, fmt.Errorf("failed to collect Web Service metrics: %w", err))
	}

	if err := c.collectHttpServiceRequestQueues(ch); err != nil {
		errs = append(errs, fmt.Errorf("failed to collect Http Service Request Queues metrics: %w", err))
	}

	if err := c.collectAppPoolWAS(ch); err != nil {
		errs = append(errs, fmt.Errorf("failed to collect APP_POOL_WAS metrics: %w", err))
	}

	if err := c.collectW3SVCW3WP(ch); err != nil {
		errs = append(errs, fmt.Errorf("failed to collect W3SVC_W3WP metrics: %w", err))
	}

	if err := c.collectWebServiceCache(ch); err != nil {
		errs = append(errs, fmt.Errorf("failed to collect Web Service Cache metrics: %w", err))
	}

	return errors.Join(errs...)
}

type collectorName interface {
	GetName() string
}

// deduplicateIISNames deduplicate IIS site names from various IIS perflib objects.
//
// IIS perflib may report duplicate entries for the same site/app-pool when
// instances are recycled; the duplicate carries a numeric suffix separated by
// "#" (e.g. "Site_B#2"). In that case "Site_B" is discarded and "Site_B#2"
// is kept. Callers must use iisCounterBaseName to present it as "Site_B".
//
// Application Pool names may legitimately contain a "#" character, so only a
// trailing "#<digits>" pattern is treated as an IIS counter suffix.
//
// Example input:  [ "Site_A", "Site_B", "Site_C", "Site_B#2" ]
// Example output: [ "Site_A", "Site_B#2", "Site_C" ].
func deduplicateIISNames[T collectorName](counterValues []T) []T {
	type dedupeEntry struct {
		resultIdx     int // index into result slice
		numericSuffix int // -1 for base (no suffix), ≥0 for "#N" variants
	}

	// Sort by base name for a deterministic output order.
	slices.SortFunc(counterValues, func(a, b T) int {
		return strings.Compare(iisCounterBaseName(a.GetName()), iisCounterBaseName(b.GetName()))
	})

	seen := make(map[string]dedupeEntry, len(counterValues))
	result := make([]T, 0, len(counterValues))

	for _, counterValue := range counterValues {
		name := counterValue.GetName()
		baseName := iisCounterBaseName(name)

		// Determine the numeric suffix for this entry (-1 means "no suffix").
		suffix := -1

		if baseName != name {
			// iisCounterBaseName guarantees the remainder after '#' is all digits.
			if n, err := strconv.Atoi(name[len(baseName)+1:]); err == nil {
				suffix = n
			}
		}

		if e, ok := seen[baseName]; ok {
			// Keep whichever entry carries the higher numeric suffix.
			if suffix > e.numericSuffix {
				result[e.resultIdx] = counterValue
				seen[baseName] = dedupeEntry{e.resultIdx, suffix}
			}
		} else {
			seen[baseName] = dedupeEntry{len(result), suffix}
			result = append(result, counterValue)
		}
	}

	return result
}

// iisCounterBaseName strips a trailing IIS perflib numeric suffix ("#<digits>")
// from name and returns the base name. If no such suffix is present, name is
// returned unchanged.
//
// Only a trailing "#" followed exclusively by ASCII digits is treated as a
// counter suffix, so "#" characters that are part of a legitimate application
// name (e.g. "App#Pool") are left intact.
func iisCounterBaseName(name string) string {
	idx := strings.LastIndex(name, "#")
	if idx < 0 || idx == len(name)-1 {
		return name
	}

	for _, r := range name[idx+1:] {
		if r < '0' || r > '9' {
			return name
		}
	}

	return name[:idx]
}