package services

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"

	"lokistack/models"
	"lokistack/repository"
)

const (
	// maxAuditLogs 审计日志条数上限。JSON DB 是全量读进内存、全量写盘，
	// 不设上限的话审计表会把内存和落盘时间一起拖垮。
	maxAuditLogs = 20000
	// 保留期改由系统设置配置（见 services/retention.go）
)

// RecordAudit 写入一条审计日志。
//
// 并发安全：直接拿 db 锁追加，与其它业务写入同一把锁，避免 RequestSave 时丢更新。
// 裁剪：超过条数上限或保留期时从最早开始删。
func RecordAudit(entry models.AuditLog) {
	db := repository.GetDB()
	if db == nil {
		return
	}
	db.Lock()
	defer db.Unlock()

	if entry.CreatedAt.IsZero() {
		entry.CreatedAt = time.Now()
	}
	// 单字段长度保护：UA/Detail 可能来自客户端，不能无限制落盘
	entry.UserAgent = truncateRunes(entry.UserAgent, 200)
	entry.Detail = truncateRunes(entry.Detail, 500)
	entry.Before = truncateRunes(entry.Before, 1000)
	entry.After = truncateRunes(entry.After, 1000)
	entry.Error = truncateRunes(entry.Error, 500)
	entry.ResourceID = truncateRunes(entry.ResourceID, 128)

	nextID := uint(1)
	for _, a := range db.AuditLogs {
		if a.ID >= nextID {
			nextID = a.ID + 1
		}
	}
	entry.ID = nextID
	db.AuditLogs = append(db.AuditLogs, entry)

	pruneAuditLocked(db)
	db.RequestSave()
}

// pruneAuditLocked 裁剪审计日志（调用方必须已持锁）。
// 从头部（最早）开始丢，直到满足条数与保留期两条约束。
func pruneAuditLocked(db *repository.JsonDB) {
	logs := db.AuditLogs
	cut := 0
	// 保留期来自 系统设置->通用配置->日志保留时间，默认 90 天
	// 注意：调用方已持写锁，必须用无锁读取版本，否则 RWMutex 会死锁
	deadline := time.Now().Add(-auditLogRetentionLocked(db))

	// 1) 先按保留期裁
	for cut < len(logs) && logs[cut].CreatedAt.Before(deadline) {
		cut++
	}
	// 2) 再按条数上限裁（保留最新的 maxAuditLogs 条）
	if remain := len(logs) - cut; remain > maxAuditLogs {
		cut += remain - maxAuditLogs
	}
	if cut > 0 {
		db.AuditLogs = append([]models.AuditLog{}, logs[cut:]...)
	}
}

// PruneAuditLogs 按当前保留期裁剪一次审计日志（供保存设置后立即生效）。
func PruneAuditLogs() {
	db := repository.GetDB()
	if db == nil {
		return
	}
	db.Lock()
	defer db.Unlock()
	before := len(db.AuditLogs)
	pruneAuditLocked(db)
	if len(db.AuditLogs) != before {
		db.RequestSave()
	}
}

// ListAuditLogs 分页查询审计日志（按时间倒序）。
func ListAuditLogs(q models.AuditQuery) ([]models.AuditLog, int64) {
	db := repository.GetDB()
	if db == nil {
		return nil, 0
	}
	db.RLock()
	all := db.AuditLogs
	db.RUnlock()

	matched := make([]models.AuditLog, 0, len(all))
	for _, a := range all {
		if q.Username != "" && !strings.Contains(strings.ToLower(a.Username), strings.ToLower(q.Username)) {
			continue
		}
		if q.Module != "" && a.Module != q.Module {
			continue
		}
		if q.Action != "" && a.Action != q.Action {
			continue
		}
		if q.ResourceID != "" && !strings.Contains(a.ResourceID, q.ResourceID) {
			continue
		}
		switch q.Status {
		case 1:
			if a.Status < 200 || a.Status >= 300 {
				continue
			}
		case 2:
			if a.Status < 400 {
				continue
			}
		}
		if q.StartTime != nil && a.CreatedAt.Before(*q.StartTime) {
			continue
		}
		if q.EndTime != nil && a.CreatedAt.After(*q.EndTime) {
			continue
		}
		matched = append(matched, a)
	}

	// 时间倒序
	sort.Slice(matched, func(i, j int) bool { return matched[i].CreatedAt.After(matched[j].CreatedAt) })

	total := int64(len(matched))
	if q.PageSize <= 0 {
		q.PageSize = 20
	}
	if q.Page <= 0 {
		q.Page = 1
	}
	start := (q.Page - 1) * q.PageSize
	if start >= len(matched) {
		return []models.AuditLog{}, total
	}
	end := start + q.PageSize
	if end > len(matched) {
		end = len(matched)
	}
	return matched[start:end], total
}

// GetAuditLog 取单条（详情弹窗用）。
func GetAuditLog(id uint) (*models.AuditLog, error) {
	db := repository.GetDB()
	if db == nil {
		return nil, fmt.Errorf("数据库未初始化")
	}
	db.RLock()
	defer db.RUnlock()
	for i := range db.AuditLogs {
		if db.AuditLogs[i].ID == id {
			entry := db.AuditLogs[i]
			return &entry, nil
		}
	}
	return nil, fmt.Errorf("审计记录不存在")
}

// AuditStatistics 统计卡片数据。
func AuditStatistics() models.AuditStats {
	db := repository.GetDB()
	stats := models.AuditStats{}
	if db == nil {
		return stats
	}
	db.RLock()
	logs := db.AuditLogs
	db.RUnlock()

	now := time.Now()
	todayStart := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	weekStart := todayStart.AddDate(0, 0, -6)

	moduleCount := map[string]int64{}
	userCount := map[string]int64{}
	for _, a := range logs {
		stats.TotalCount++
		if a.CreatedAt.After(todayStart) {
			stats.TodayCount++
		}
		if a.CreatedAt.After(weekStart) {
			stats.WeekCount++
		}
		if a.Status >= 400 {
			stats.FailCount++
		}
		moduleCount[a.Module]++
		if a.Username != "" {
			userCount[a.Username]++
		}
	}
	stats.TopModules = topN(moduleCount, 5)
	stats.TopUsers = topN(userCount, 5)
	return stats
}

func topN(m map[string]int64, n int) []models.AuditCount {
	out := make([]models.AuditCount, 0, len(m))
	for k, v := range m {
		out = append(out, models.AuditCount{Name: k, Count: v})
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Count == out[j].Count {
			return out[i].Name < out[j].Name
		}
		return out[i].Count > out[j].Count
	})
	if len(out) > n {
		out = out[:n]
	}
	return out
}

// ───────────────────────── 脱敏 / 摘要 ─────────────────────────

// auditSensitiveKeys 这些字段一律不进审计（只留「已修改」的痕迹）。
var auditSensitiveKeys = map[string]bool{
	"password": true, "oldpassword": true, "newpassword": true,
	"secretkey": true, "accesskey": true, "secretaccesskey": true,
	"privatekey": true, "token": true, "accesstoken": true, "refreshtoken": true,
	"encryptionkey": true, "jwtsecret": true,
}

// MaskAuditPayload 把请求体里的敏感值替换成 ***，返回脱敏后的 JSON 字符串。
// 解析失败时返回 "<非 JSON 请求体>"，避免把表单里的密码原样落盘。
func MaskAuditPayload(body []byte, maxLen int) string {
	if len(body) == 0 {
		return ""
	}
	var v interface{}
	if err := json.Unmarshal(body, &v); err != nil {
		return "<非 JSON 请求体，已省略>"
	}
	masked := maskValue(v)
	out, err := json.Marshal(masked)
	if err != nil {
		return ""
	}
	return truncateRunes(string(out), maxLen)
}

func maskValue(v interface{}) interface{} {
	switch t := v.(type) {
	case map[string]interface{}:
		out := make(map[string]interface{}, len(t))
		for k, val := range t {
			if auditSensitiveKeys[strings.ToLower(k)] {
				if s, ok := val.(string); ok && s == "" {
					out[k] = ""
				} else {
					out[k] = "***"
				}
				continue
			}
			out[k] = maskValue(val)
		}
		return out
	case []interface{}:
		out := make([]interface{}, len(t))
		for i, val := range t {
			out[i] = maskValue(val)
		}
		return out
	default:
		return v
	}
}

// AuditDiff 生成「变更前后」摘要，只保留真正变化的字段。
// prev/next 传脱敏后的 JSON 字符串；解析失败时返回空（不硬编码原文）。
func AuditDiff(prev, next string) (string, string) {
	var a, b map[string]interface{}
	if prev == "" || next == "" || json.Unmarshal([]byte(prev), &a) != nil || json.Unmarshal([]byte(next), &b) != nil {
		return "", ""
	}
	before := map[string]interface{}{}
	after := map[string]interface{}{}
	for k, nv := range b {
		ov, existed := a[k]
		if !existed || fmt.Sprint(ov) != fmt.Sprint(nv) {
			if existed {
				before[k] = ov
			}
			after[k] = nv
		}
	}
	for k, ov := range a {
		if _, ok := b[k]; !ok {
			before[k] = ov
		}
	}
	if len(after) == 0 && len(before) == 0 {
		return "", ""
	}
	bs, _ := json.Marshal(before)
	as, _ := json.Marshal(after)
	return truncateRunes(string(bs), 1000), truncateRunes(string(as), 1000)
}

func truncateRunes(s string, n int) string {
	if n <= 0 {
		return s
	}
	r := []rune(s)
	if len(r) <= n {
		return s
	}
	return string(r[:n]) + "…"
}