package middleware

import (
	"net/http"
	"strings"
	"time"

	"github.com/gin-gonic/gin"

	"lokistack/models"
	"lokistack/services"
)

// AuditInfo 由 controller 主动补充的业务语义。
//
// 中间件已经能自动记录 method/path/status/耗时/IP/用户，
// 但「改了哪个部署」「保留天数 7 → 3」这类信息只有 handler 自己知道，
// 所以提供 SetAudit 让 handler 补一刀，不补也能记全（只是 Detail 为空）。
type AuditInfo struct {
	Module     string
	Action     string
	Resource   string
	ResourceID string
	Detail     string
	Before     string
	After      string
	// Skip 置 true 表示这条请求不记（例如纯查询用了 POST 的场景）
	Skip bool
}

const auditInfoKey = "audit.info"

// SetAudit 由 controller 调用，补充审计语义。
func SetAudit(c *gin.Context, info AuditInfo) {
	c.Set(auditInfoKey, info)
}

// auditSkipPaths 这些路径不记审计：
//   - 健康检查 / metrics：高频噪音
//   - 日志查询：GET 本来就不记，但 /logs/query 之类用 POST 的也不记（只读）
var auditSkipPrefixes = []string{
	"/api/v1/health",
	"/api/v1/metrics",
	"/api/v1/logs/query",
	"/api/v1/logs/stats",
	"/api/v1/logs/histogram",
	"/api/v1/logs/labels",
	"/api/v1/logs/label",
	"/api/v1/logs/context",
	"/api/v1/logs/volume",
	"/api/v1/logs/my-scope",
	"/api/v1/deployments/", // 例外：其中 /deploy /stop /restart 要记，见下方白名单
}

// auditAlwaysRecord 匹配到的路径即使在上面的 skip 前缀里也要记。
var auditAlwaysRecordSuffixes = []string{
	"/deploy", "/stop", "/restart", "/install", "/uninstall", "/test", "/validate",
	"/preview", "/rollback", "/reset-password", "/backup", "/restore",
}

// AuditLog 审计中间件：自动记录所有写操作（POST / PUT / PATCH / DELETE）。
//
// 为什么用中间件而不是每个 controller 各写一段：
//   - LokiStack 有 60+ 个写接口，逐个埋点必然漏，漏掉的那个恰好最危险（删集群、改存储）
//   - 中间件能拿到统一的 status / 耗时 / IP / UA
//   - handler 需要更细的语义时再 SetAudit 补，不补也有基础记录
//
// 不含请求体（读 body 会影响后续 binding），敏感字段由 handler 通过 SetAudit
// 传入已脱敏的 Before/After。
func AuditLog() gin.HandlerFunc {
	return func(c *gin.Context) {
		method := c.Request.Method
		// 只读请求不记（GET/HEAD/OPTIONS）
		if method == http.MethodGet || method == http.MethodHead || method == http.MethodOptions {
			c.Next()
			return
		}

		path := c.Request.URL.Path
		if !shouldAudit(path) {
			c.Next()
			return
		}

		start := time.Now()
		c.Next()
		elapsed := time.Since(start).Milliseconds()

		info, _ := c.Get(auditInfoKey)
		ai, _ := info.(AuditInfo)
		if ai.Skip {
			return
		}

		status := c.Writer.Status()
		userID, _ := c.Get("userId")
		username, _ := c.Get("username")
		role, _ := c.Get("role")

		entry := models.AuditLog{
			IP:         c.ClientIP(),
			UserAgent:  c.Request.UserAgent(),
			Method:     method,
			Path:       path,
			Status:     status,
			DurationMs: elapsed,
			Detail:     ai.Detail,
			Before:     ai.Before,
			After:      ai.After,
			CreatedAt:  time.Now(),
		}
		if v, ok := userID.(uint); ok {
			entry.UserID = v
		}
		if v, ok := username.(string); ok {
			entry.Username = v
		}
		if v, ok := role.(string); ok {
			entry.Role = v
		}

		// 失败时把错误信息带上（gin 的 Error 里有 handler 写入的错误）
		if status >= 400 {
			if len(c.Errors) > 0 {
				entry.Error = c.Errors.String()
			}
		}

		// handler 没补语义时按路径推断，保证「谁删了什么」至少能看出模块
		module, action, resource, resourceID := inferAuditFields(method, path)
		if ai.Module != "" {
			module = ai.Module
		}
		if ai.Action != "" {
			action = ai.Action
		}
		if ai.Resource != "" {
			resource = ai.Resource
		}
		if ai.ResourceID != "" {
			resourceID = ai.ResourceID
		}
		entry.Module, entry.Action, entry.Resource, entry.ResourceID = module, action, resource, resourceID

		services.RecordAudit(entry)
	}
}

func shouldAudit(path string) bool {
	for _, suffix := range auditAlwaysRecordSuffixes {
		if strings.HasSuffix(path, suffix) {
			return true
		}
	}
	for _, p := range auditSkipPrefixes {
		if strings.HasPrefix(path, p) {
			return false
		}
	}
	return true
}

// inferAuditFields 从 method + path 推断模块与动作（handler 未补充时的兜底）。
func inferAuditFields(method, path string) (module, action, resource, resourceID string) {
	action = map[string]string{
		http.MethodPost:   "create",
		http.MethodPut:    "update",
		http.MethodPatch:  "update",
		http.MethodDelete: "delete",
	}[method]

	segments := strings.Split(strings.Trim(path, "/"), "/")
	// /api/v1/<module>/<resource>/<id>
	if len(segments) >= 3 {
		module = segments[2]
	}
	if len(segments) >= 4 {
		resource = segments[3]
		resourceID = segments[4]
	}

	// 语义化覆盖
	switch {
	case strings.HasSuffix(path, "/deploy"):
		action, resource = "deploy", "部署"
	case strings.HasSuffix(path, "/stop"):
		action, resource = "stop", "部署"
	case strings.HasSuffix(path, "/restart"):
		action, resource = "restart", "部署"
	case strings.HasSuffix(path, "/install"):
		action, resource = "install", "采集器"
	case strings.HasSuffix(path, "/uninstall"):
		action, resource = "uninstall", "采集器"
	case strings.HasSuffix(path, "/test"):
		action = "test"
	case strings.HasSuffix(path, "/validate"):
		action = "validate"
	case strings.HasSuffix(path, "/reset-password"):
		action, resource = "reset-password", "用户"
	case strings.HasSuffix(path, "/login"):
		module, action, resource = "auth", "login", "登录"
	case strings.HasSuffix(path, "/password"):
		module, action, resource = "auth", "change-password", "登录"
	}
	return module, action, resource, resourceID
}