// Package autoban 提供 fail2ban 风格的自动临时封禁：检测批量扫描/探测特征后
// 临时封禁来源 IP，并可回调发送告警。纯标准库实现，便于独立测试与复用。
package autoban

import (
	"strings"
	"sync"
	"time"
)

// 探测事件类型
const (
	KindNone      = 0 // 无探测特征
	KindSensitive = 1 // 命中敏感路径
	KindNotFound  = 2 // 404 响应（未命中敏感路径）
)

// 默认阈值/窗口（Options 未配置或为 0 时兜底）。
const (
	DefaultWindowSeconds      = 60
	DefaultDurationMinutes    = 15
	DefaultThresholdSensitive = 10
	DefaultThreshold404       = 20
	pathSampleMax             = 6
)

// Options 自动封禁配置。
type Options struct {
	Enabled bool
	// TrackNotFound 是否把 KindNotFound（未注册路径的 404）计入封禁统计。
	// 默认 false：正常业务路径一律放行，仅敏感扫描特征路径参与计数封禁，
	// 避免共享出口下正常访问被 404 探测连坐误伤（详见 conf.Security.BanTrackNotFound）。
	TrackNotFound      bool
	ThresholdSensitive int                                                        // 窗口内敏感路径命中次数
	Threshold404       int                                                        // 窗口内 404 次数
	Window             time.Duration                                              // 统计窗口
	Duration           time.Duration                                              // 封禁时长
	AlertEmail         string                                                     // 告警收件人（留空不发送）
	SendAlert          func(ip string, paths []string, durationMinutes int) error // 告警发送函数（nil 则不发送）
}

// sensitivePaths 常见后台/配置/漏洞探测路径特征（忽略大小写，完整段前缀匹配）。
// 注意：前缀匹配抓不到 //xxx/wp-includes/wlwmanifest.xml 这类"目录枚举变体"（敏感段
// 出现在路径中部），需要与 sensitiveFragments（任意位置子串）配合使用。
var sensitivePaths = []string{
	"/admin", "/wp-admin", "/wp-login.php", "/wp-content", "/wordpress",
	"/administrator", "/manager", "/cpanel", "/plesk",
	"/.env", "/.git", "/.aws", "/.ssh", "/.svn", "/.hg", "/.htaccess",
	"/config", "/configuration", "/backup", "/database", "/db",
	"/actuator", "/swagger", "/api-docs", "/openapi", "/v2/api-docs",
	"/phpmyadmin", "/pma", "/mysql", "/server-status", "/server-info",
	"/shell", "/webshell", "/cmd", "/eval", "/hack", "/shell.php",
	"/login.php", "/admin.php", "/index.php", "/console", "/vendor",
}

// sensitiveFragments 任意位置命中即算敏感的"强指纹"（忽略大小写，子串匹配）。
// 与 sensitivePaths 互补：捕获 /<枚举前缀>/wp-includes/wlwmanifest.xml、//wp/xmlrpc.php
// 等前缀匹配失效的变体。仅收录业务 URL 空间（/、/_/、/user、/api/v1、/vote、/explore、
// /i18n、/static…）绝不可能出现的 WordPress 特征，确保不误伤正常路径。
var sensitiveFragments = []string{
	"/wp-includes/", "/wp-json/", "/wp-cron.php", "/wp-trackback.php",
	"/wp-admin", "/wp-content", "/wp-login.php", "/wlwmanifest.xml",
	"/xmlrpc.php", "/wordpress",
}

type probeEvent struct {
	at   time.Time
	kind int
}

type probeStat struct {
	events    []probeEvent
	sensitive int
	notFound  int
	paths     []string // 命中路径样本（告警用）
}

// Banner 自动封禁器。方法并发安全。
type Banner struct {
	mu sync.Mutex

	probes  map[string]*probeStat
	banned  map[string]time.Time
	alerted map[string]bool

	thresholdSensitive int
	threshold404       int
	trackNotFound      bool
	window             time.Duration
	duration           time.Duration
	alertEmail         string
	sendAlert          func(ip string, paths []string, durationMinutes int) error
	enabled            bool
}

// New 按配置创建封禁器并注册全局清理。
func New(opts Options) *Banner {
	window := opts.Window
	if window <= 0 {
		window = DefaultWindowSeconds * time.Second
	}
	duration := opts.Duration
	if duration <= 0 {
		duration = DefaultDurationMinutes * time.Minute
	}
	sensitive := opts.ThresholdSensitive
	if sensitive <= 0 {
		sensitive = DefaultThresholdSensitive
	}
	notFound := opts.Threshold404
	if notFound <= 0 {
		notFound = DefaultThreshold404
	}
	b := &Banner{
		probes:             make(map[string]*probeStat),
		banned:             make(map[string]time.Time),
		alerted:            make(map[string]bool),
		thresholdSensitive: sensitive,
		threshold404:       notFound,
		trackNotFound:      opts.TrackNotFound,
		window:             window,
		duration:           duration,
		alertEmail:         strings.TrimSpace(opts.AlertEmail),
		sendAlert:          opts.SendAlert,
		enabled:            opts.Enabled,
	}
	register(b)
	return b
}

// Record 记录一次探测事件，达到阈值时封禁 IP 并触发一次告警。
func (b *Banner) Record(ip, path string, kind int) {
	if !b.enabled || ip == "" || kind == KindNone {
		return
	}
	// 404 计数默认关闭（正常业务路径一律放行，仅敏感扫描特征参与封禁）：
	// 只有显式开启 TrackNotFound 时才把未注册路径的 404 计入统计。
	if kind == KindNotFound && !b.trackNotFound {
		return
	}
	b.mu.Lock()
	defer b.mu.Unlock()

	now := time.Now()
	cutoff := now.Add(-b.window)

	st := b.probes[ip]
	if st == nil {
		st = &probeStat{}
		b.probes[ip] = st
	}

	// 滚动清理过期事件并重算计数
	valid := st.events[:0]
	sensitive, notFound := 0, 0
	for _, e := range st.events {
		if e.at.After(cutoff) {
			valid = append(valid, e)
			if e.kind == KindSensitive {
				sensitive++
			} else if e.kind == KindNotFound {
				notFound++
			}
		}
	}
	valid = append(valid, probeEvent{at: now, kind: kind})
	if kind == KindSensitive {
		sensitive++
	} else {
		notFound++
	}
	st.events = valid
	st.sensitive = sensitive
	st.notFound = notFound
	if len(st.paths) < pathSampleMax && path != "" {
		st.paths = append(st.paths, path)
	}

	if sensitive < b.thresholdSensitive && notFound < b.threshold404 {
		return
	}

	// 已达阈值：封禁（已在封禁中则跳过）
	if until, ok := b.banned[ip]; ok && until.After(now) {
		return
	}
	until := now.Add(b.duration)
	b.banned[ip] = until

	// 告警（每 IP 仅一次）
	if b.alertEmail != "" && b.sendAlert != nil && !b.alerted[ip] {
		b.alerted[ip] = true
		sample := append([]string{}, st.paths...)
		dur := int(b.duration.Minutes())
		go func() {
			_ = b.sendAlert(ip, sample, dur)
		}()
	}
}

// IsBanned 判断 IP 是否处于封禁期；到期自动解除。
func (b *Banner) IsBanned(ip string) bool {
	if !b.enabled || ip == "" {
		return false
	}
	b.mu.Lock()
	defer b.mu.Unlock()
	if until, ok := b.banned[ip]; ok {
		if until.After(time.Now()) {
			return true
		}
		delete(b.banned, ip)
	}
	return false
}

// IsSensitivePath 判断路径是否命中敏感探测特征（忽略大小写）。
// 命中条件：① 与 sensitivePaths 完整段前缀匹配（/admin、/.env 等）；
// ② 包含 sensitiveFragments 强指纹子串（wp-includes/xmlrpc.php 等 WordPress 探测面，
//
//	覆盖 // 双斜杠与目录枚举变体）。
func IsSensitivePath(p string) bool {
	lower := strings.ToLower(p)
	for _, s := range sensitivePaths {
		if lower == s || strings.HasPrefix(lower, s+"/") {
			return true
		}
	}
	for _, f := range sensitiveFragments {
		if strings.Contains(lower, f) {
			return true
		}
	}
	return false
}

// ---------- 全局注册与清理 ----------

var (
	bannersMu   sync.Mutex
	banners     = make(map[*Banner]struct{})
	bannersOnce sync.Once
)

func register(b *Banner) {
	bannersMu.Lock()
	banners[b] = struct{}{}
	bannersMu.Unlock()

	bannersOnce.Do(func() {
		go func() {
			for {
				time.Sleep(2 * time.Minute)
				bannersMu.Lock()
				for b := range banners {
					b.cleanup()
				}
				bannersMu.Unlock()
			}
		}()
	})
}

// cleanup 定期清理过期探测记录与已到期封禁（防止内存膨胀）。
func (b *Banner) cleanup() {
	b.mu.Lock()
	defer b.mu.Unlock()

	now := time.Now()
	cutoff := now.Add(-b.window)

	for ip, st := range b.probes {
		if len(st.events) == 0 || st.events[len(st.events)-1].at.Before(cutoff) {
			delete(b.probes, ip)
			continue
		}
		valid := st.events[:0]
		sensitive, notFound := 0, 0
		for _, e := range st.events {
			if e.at.After(cutoff) {
				valid = append(valid, e)
				if e.kind == KindSensitive {
					sensitive++
				} else if e.kind == KindNotFound {
					notFound++
				}
			}
		}
		st.events = valid
		st.sensitive = sensitive
		st.notFound = notFound
	}
	for ip, until := range b.banned {
		if !until.After(now) {
			delete(b.banned, ip)
		}
	}
}