package middleware

import (
	"net/http"
	"strings"

	"github.com/edu-cloud/api-gateway/internal/config"
	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
)

// AuthMiddleware 验证 JWT 并注入用户信息到请求头
// P1 用 HS256，P2 改 RS256（IAM 签发）
func AuthMiddleware(cfg *config.Config) gin.HandlerFunc {
	return func(c *gin.Context) {
		// 健康检查跳过鉴权
		if c.Request.URL.Path == "/healthz" {
			c.Next()
			return
		}

		authHeader := c.GetHeader("Authorization")
		if authHeader == "" {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"success": false,
				"error": gin.H{
					"code":    "UNAUTHORIZED",
					"message": "missing authorization header",
				},
			})
			return
		}

		tokenStr := strings.TrimPrefix(authHeader, "Bearer ")
		if tokenStr == authHeader {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"success": false,
				"error": gin.H{
					"code":    "UNAUTHORIZED",
					"message": "invalid authorization scheme, expected Bearer",
				},
			})
			return
		}

		token, err := jwt.Parse(tokenStr, func(t *jwt.Token) (interface{}, error) {
			if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
				return nil, jwt.ErrSignatureInvalid
			}
			return []byte(cfg.JWTSecret), nil
		})

		if err != nil || !token.Valid {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"success": false,
				"error": gin.H{
					"code":    "INVALID_TOKEN",
					"message": "token validation failed",
				},
			})
			return
		}

		claims, ok := token.Claims.(jwt.MapClaims)
		if !ok {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
				"success": false,
				"error": gin.H{
					"code":    "INVALID_CLAIMS",
					"message": "invalid token claims",
				},
			})
			return
		}

		// 注入用户信息到下游请求头
		if sub, ok := claims["sub"].(string); ok {
			c.Request.Header.Set("x-user-id", sub)
		}
		if roles, ok := claims["roles"].([]interface{}); ok {
			roleStrs := make([]string, 0, len(roles))
			for _, r := range roles {
				if s, ok := r.(string); ok {
					roleStrs = append(roleStrs, s)
				}
			}
			c.Request.Header.Set("x-user-roles", strings.Join(roleStrs, ","))
		}

		c.Next()
	}
}

// RequestIDMiddleware 注入请求 ID 用于全链路追踪
func RequestIDMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		requestID := c.GetHeader("X-Request-ID")
		if requestID == "" {
			requestID = generateUUID()
		}
		c.Set("request_id", requestID)
		c.Writer.Header().Set("X-Request-ID", requestID)
		c.Next()
	}
}

// generateUUID 生成带 req- 前缀的唯一请求 ID
// 使用 uuid.New() 基于 RFC 4122 v4 随机 UUID，避免 time.Now() 产生的冲突与可预测性
func generateUUID() string {
	return "req-" + uuid.New().String()
}