package middleware

import (
	"errors"
	"net/http"
	"reflect"
	"strconv"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"kefu-cloud/server/internal/model"
)

var jwtSecret []byte

func InitJWT(secret string) {
	jwtSecret = []byte(secret)
}

type Claims struct {
	UserID   uint   `json:"user_id"`
	TenantID uint   `json:"tenant_id"`
	Role     string `json:"role"`
	jwt.RegisteredClaims
}

func GenerateToken(userID, tenantID uint, role string) (string, error) {
	claims := Claims{
		UserID:   userID,
		TenantID: tenantID,
		Role:     role,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(24 * time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(jwtSecret)
}

func ParseToken(tokenStr string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (interface{}, error) {
		if t.Method.Alg() != jwt.SigningMethodHS256.Alg() {
			return nil, errors.New("不支持的签名算法")
		}
		return jwtSecret, nil
	})
	if err != nil || !token.Valid {
		if err == nil {
			err = errors.New("token无效")
		}
		return nil, err
	}

	claims, ok := token.Claims.(*Claims)
	if !ok {
		return nil, errors.New("token声明无效")
	}
	return claims, nil
}

// ValidateUserAccess 确保令牌对应的账号与租户当前仍可使用。
func ValidateUserAccess(userID, tenantID uint, role string) (int, string) {
	var user model.User
	if err := model.DB.Select("id", "tenant_id", "role", "status").First(&user, userID).Error; err != nil ||
		user.TenantID != tenantID || user.Role != role {
		return http.StatusUnauthorized, "账号状态已变化，请重新登录"
	}
	if user.Status == "disabled" {
		return http.StatusForbidden, "账号已被禁用"
	}

	if role == "platform_admin" {
		if tenantID != 0 {
			return http.StatusUnauthorized, "平台管理员租户无效"
		}
		return 0, ""
	}

	var tenant model.Tenant
	if err := model.DB.Select("id", "status").First(&tenant, tenantID).Error; err != nil {
		return http.StatusForbidden, "租户不存在或不可用"
	}
	if tenant.Status == "suspended" || tenant.Status == "expired" {
		return http.StatusForbidden, "租户已暂停或已过期"
	}
	return 0, ""
}

func tokenFromRequest(c *gin.Context) string {
	auth := c.GetHeader("Authorization")
	if strings.HasPrefix(auth, "Bearer ") {
		return strings.TrimPrefix(auth, "Bearer ")
	}

	// 浏览器 WebSocket 无法设置 Authorization；仅接受约定子协议中的令牌。
	protocols := strings.Split(c.GetHeader("Sec-WebSocket-Protocol"), ",")
	if len(protocols) == 2 && strings.TrimSpace(protocols[0]) == "kefu-v1" {
		return strings.TrimSpace(protocols[1])
	}
	return ""
}

func AuthRequired() gin.HandlerFunc {
	return func(c *gin.Context) {
		tokenStr := tokenFromRequest(c)
		if tokenStr == "" {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "未授权"})
			c.Abort()
			return
		}

		claims, err := ParseToken(tokenStr)
		if err != nil {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "token无效"})
			c.Abort()
			return
		}

		if status, message := ValidateUserAccess(claims.UserID, claims.TenantID, claims.Role); status != 0 {
			c.JSON(status, gin.H{"code": status, "message": message})
			c.Abort()
			return
		}

		c.Set("user_id", claims.UserID)
		c.Set("tenant_id", claims.TenantID)
		c.Set("role", claims.Role)
		permissionVersion := LoadPermissions(c, claims.UserID, claims.TenantID, claims.Role)
		if permissionVersion != "" {
			c.Header("X-Permission-Version", permissionVersion)
		}
		c.Next()
	}
}

func GetRole(c *gin.Context) string {
	role, _ := c.Get("role")
	value, _ := role.(string)
	return value
}

func HasAnyRole(c *gin.Context, roles ...string) bool {
	role := GetRole(c)
	for _, allowed := range roles {
		if role == allowed {
			return true
		}
	}
	return false
}

func AdminRequired() gin.HandlerFunc {
	return func(c *gin.Context) {
		if !HasAnyRole(c, "admin", "platform_admin") {
			c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权限"})
			c.Abort()
			return
		}
		c.Next()
	}
}

func PlatformRequired() gin.HandlerFunc {
	return func(c *gin.Context) {
		if !HasAnyRole(c, "platform_admin") {
			c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "仅平台管理员可操作"})
			c.Abort()
			return
		}
		c.Next()
	}
}

func GetTenantID(c *gin.Context) uint {
	id, _ := c.Get("tenant_id")
	return id.(uint)
}

func GetUserID(c *gin.Context) uint {
	id, _ := c.Get("user_id")
	return id.(uint)
}

func GetPageParams(c *gin.Context) (page, pageSize int) {
	page, _ = strconv.Atoi(c.DefaultQuery("page", "1"))
	pageSize, _ = strconv.Atoi(c.DefaultQuery("pageSize", "10"))
	if page < 1 {
		page = 1
	}
	if pageSize < 1 || pageSize > 100 {
		pageSize = 10
	}
	return
}

func JSON(c *gin.Context, data interface{}) {
	c.JSON(http.StatusOK, gin.H{"code": 0, "message": "ok", "data": nonNilSlice(data)})
}

func JSONList(c *gin.Context, list interface{}, total int64, page, pageSize int) {
	c.JSON(http.StatusOK, gin.H{
		"code":     0,
		"message":  "ok",
		"list":     nonNilSlice(list),
		"total":    total,
		"page":     page,
		"pageSize": pageSize,
	})
}

// nonNilSlice 统一将空切片序列化为 []，避免前端收到 null 后调用数组方法崩溃。
func nonNilSlice(data interface{}) interface{} {
	value := reflect.ValueOf(data)
	if value.IsValid() && value.Kind() == reflect.Slice && value.IsNil() {
		return reflect.MakeSlice(value.Type(), 0, 0).Interface()
	}
	return data
}