package auth

import (
	"fmt"
	"net/http"
	"strings"

	"github.com/M1ngdaXie/realtime-collab/internal/store"
	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
)

type contextKey string

const UserContextKey contextKey = "user"
const ContextUserIDKey = "user_id"

// AuthMiddleware provides auth middleware
type AuthMiddleware struct {
    store     store.Store
    jwtSecret string
}

// NewAuthMiddleware creates a new auth middleware
func NewAuthMiddleware(store store.Store, jwtSecret string) *AuthMiddleware {
    return &AuthMiddleware{
        store:     store,
        jwtSecret: jwtSecret,
    }
}

// RequireAuth middleware requires valid authentication
func (m *AuthMiddleware) RequireAuth() gin.HandlerFunc {
    return func(c *gin.Context) {
        fmt.Println("🔒 RequireAuth: Starting authentication check")

        user, claims, err := m.getUserFromToken(c)

        fmt.Printf("🔒 RequireAuth: user=%v, err=%v\n", user, err)
        if claims != nil {
            fmt.Printf("🔒 RequireAuth: claims.Name=%s, claims.Email=%s\n", claims.Name, claims.Email)
        }

        if err != nil || user == nil {
            fmt.Printf("❌ RequireAuth: FAILED - err=%v, user=%v\n", err, user)
            c.JSON(http.StatusUnauthorized, gin.H{"error": "Unauthorized"})
            c.Abort()
            return
        }

        // Note: Name and Email might be empty for old JWT tokens
        if claims.Name == "" || claims.Email == "" {
            fmt.Printf("⚠️  RequireAuth: WARNING - Token missing name/email (using old token format)\n")
        }

        fmt.Printf("✅ RequireAuth: SUCCESS - setting context for user %v\n", user)
        c.Set(ContextUserIDKey, user)
        c.Set("user_email", claims.Email)
        c.Set("user_name", claims.Name)
        if claims.AvatarURL != nil {
            c.Set("avatar_url", *claims.AvatarURL)
        }
        c.Next()
    }
}

// OptionalAuth middleware sets user if authenticated, but doesn't require it
func (m *AuthMiddleware) OptionalAuth() gin.HandlerFunc {
    return func(c *gin.Context) {
        user, claims, _ := m.getUserFromToken(c)
        if user != nil {
            c.Set(string(UserContextKey), user)
            c.Set(ContextUserIDKey, user)
            if claims != nil {
                c.Set("user_email", claims.Email)
                c.Set("user_name", claims.Name)
                if claims.AvatarURL != nil {
                    c.Set("avatar_url", *claims.AvatarURL)
                }
            }
        }
        c.Next()
    }
}

// getUserFromToken parses the JWT and returns the UserID and the full Claims (for name/email)
// 注意：返回值变了，现在返回 (*uuid.UUID, *UserClaims, error)
func (m *AuthMiddleware) getUserFromToken(c *gin.Context) (*uuid.UUID, *UserClaims, error) {
    authHeader := c.GetHeader("Authorization")
    fmt.Printf("🔍 getUserFromToken: Authorization header = '%s'\n", authHeader)

    if authHeader == "" {
        fmt.Println("⚠️  getUserFromToken: No Authorization header")
        return nil, nil, nil
    }

    parts := strings.Split(authHeader, " ")
    if len(parts) != 2 || parts[0] != "Bearer" {
        fmt.Printf("⚠️  getUserFromToken: Invalid header format (parts=%d, prefix=%s)\n", len(parts), parts[0])
        return nil, nil, nil
    }

    tokenString := parts[1]
    fmt.Printf("🔍 getUserFromToken: Token = %s...\n", tokenString[:min(20, len(tokenString))])

    token, err := jwt.ParseWithClaims(tokenString, &UserClaims{}, func(token *jwt.Token) (interface{}, error) {
        // 必须要验证签名算法是 HMAC (HS256)
        if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
            return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
        }
        return []byte(m.jwtSecret), nil
    })

    if err != nil {
        fmt.Printf("❌ getUserFromToken: JWT parse error: %v\n", err)
        return nil, nil, err
    }

    // 2. 验证 Token 有效性并提取 Claims
    if claims, ok := token.Claims.(*UserClaims); ok && token.Valid {
        // 3. 把 String 类型的 Subject 转回 UUID
        // 因为我们在 GenerateJWT 里存的是 claims.Subject = userID.String()
        userID, err := uuid.Parse(claims.Subject)
        if err != nil {
            fmt.Printf("❌ getUserFromToken: Invalid UUID in subject: %v\n", err)
            return nil, nil, fmt.Errorf("invalid user ID in token")
        }

        // 成功！直接返回 UUID 和 claims (里面包含 Name 和 Email)
        // 这一步完全没有查数据库，速度极快
        fmt.Printf("✅ getUserFromToken: SUCCESS - userID=%v, name=%s, email=%s\n", userID, claims.Name, claims.Email)
        return &userID, claims, nil
    }

    fmt.Println("❌ getUserFromToken: Invalid token claims or token not valid")
    return nil, nil, fmt.Errorf("invalid token claims")
}

// GetUserFromContext extracts user ID from context
func GetUserFromContext(c *gin.Context) *uuid.UUID {
    // 修正点：使用和存入时完全一样的 Key
    val, exists := c.Get(ContextUserIDKey)
    fmt.Println("within getFromContext the id is ... ")
    fmt.Println(val);
    if !exists {
        return nil
    }

    // 修正点：断言为 *uuid.UUID (因为我们在中间件里存的就是这个类型)
    uid, ok := val.(*uuid.UUID)
    if !ok {
        return nil
    }

    return uid
}

// ValidateToken validates a JWT token and returns user ID, name, and avatar URL from JWT claims
// STATELESS: No database lookup - relies entirely on JWT signature and expiration
func (m *AuthMiddleware) ValidateToken(tokenString string) (*uuid.UUID, string, string, error) {
	// Parse and validate JWT signature and expiration
	claims, err := ValidateJWT(tokenString, m.jwtSecret)
	if err != nil {
		return nil, "", "", fmt.Errorf("invalid token: %w", err)
	}

	// Parse user ID from claims
	userID, err := uuid.Parse(claims.Subject)
	if err != nil {
		return nil, "", "", fmt.Errorf("invalid user ID in token: %w", err)
	}

	// Extract avatar URL from claims (handle nil gracefully)
	avatarURL := ""
	if claims.AvatarURL != nil {
		avatarURL = *claims.AvatarURL
	}

	// Return user data from JWT claims - ZERO database queries!
	return &userID, claims.Name, avatarURL, nil
}