package middleware

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/labstack/echo/v4"
	"github.com/redis/go-redis/v9"
	"github.com/rs/zerolog/log"
	"gorm.io/gorm"

	"github.com/treytartt/casera-api/internal/apperrors"
	"github.com/treytartt/casera-api/internal/models"
	"github.com/treytartt/casera-api/internal/services"
)

const (
	// AuthUserKey is the key used to store the authenticated user in the context
	AuthUserKey = "auth_user"
	// AuthTokenKey is the key used to store the token in the context
	AuthTokenKey = "auth_token"
	// TokenCacheTTL is the duration to cache tokens in Redis
	TokenCacheTTL = 5 * time.Minute
	// TokenCachePrefix is the prefix for token cache keys
	TokenCachePrefix = "auth_token_"
)

// AuthMiddleware provides token authentication middleware
type AuthMiddleware struct {
	db    *gorm.DB
	cache *services.CacheService
}

// NewAuthMiddleware creates a new auth middleware instance
func NewAuthMiddleware(db *gorm.DB, cache *services.CacheService) *AuthMiddleware {
	return &AuthMiddleware{
		db:    db,
		cache: cache,
	}
}

// TokenAuth returns an Echo middleware that validates token authentication
func (m *AuthMiddleware) TokenAuth() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			// Extract token from Authorization header
			token, err := extractToken(c)
			if err != nil {
				return apperrors.Unauthorized("error.not_authenticated")
			}

			// Try to get user from cache first
			user, err := m.getUserFromCache(c.Request().Context(), token)
			if err == nil && user != nil {
				// Cache hit - set user in context and continue
				c.Set(AuthUserKey, user)
				c.Set(AuthTokenKey, token)
				return next(c)
			}

			// Cache miss - look up token in database
			user, err = m.getUserFromDatabase(token)
			if err != nil {
				log.Debug().Err(err).Str("token", truncateToken(token)).Msg("Token authentication failed")
				return apperrors.Unauthorized("error.invalid_token")
			}

			// Cache the user ID for future requests
			if cacheErr := m.cacheUserID(c.Request().Context(), token, user.ID); cacheErr != nil {
				log.Warn().Err(cacheErr).Msg("Failed to cache user ID")
			}

			// Set user in context
			c.Set(AuthUserKey, user)
			c.Set(AuthTokenKey, token)
			return next(c)
		}
	}
}

// OptionalTokenAuth returns middleware that authenticates if token is present but doesn't require it
func (m *AuthMiddleware) OptionalTokenAuth() echo.MiddlewareFunc {
	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			token, err := extractToken(c)
			if err != nil {
				// No token or invalid format - continue without user
				return next(c)
			}

			// Try cache first
			user, err := m.getUserFromCache(c.Request().Context(), token)
			if err == nil && user != nil {
				c.Set(AuthUserKey, user)
				c.Set(AuthTokenKey, token)
				return next(c)
			}

			// Try database
			user, err = m.getUserFromDatabase(token)
			if err == nil {
				m.cacheUserID(c.Request().Context(), token, user.ID)
				c.Set(AuthUserKey, user)
				c.Set(AuthTokenKey, token)
			}

			return next(c)
		}
	}
}

// extractToken extracts the token from the Authorization header
func extractToken(c echo.Context) (string, error) {
	authHeader := c.Request().Header.Get("Authorization")
	if authHeader == "" {
		return "", fmt.Errorf("authorization header required")
	}

	// Support both "Token xxx" (Django style) and "Bearer xxx" formats
	parts := strings.SplitN(authHeader, " ", 2)
	if len(parts) != 2 {
		return "", fmt.Errorf("invalid authorization header format")
	}

	scheme := parts[0]
	token := parts[1]

	if scheme != "Token" && scheme != "Bearer" {
		return "", fmt.Errorf("invalid authorization scheme: %s", scheme)
	}

	if token == "" {
		return "", fmt.Errorf("token is empty")
	}

	return token, nil
}

// getUserFromCache tries to get user from Redis cache
func (m *AuthMiddleware) getUserFromCache(ctx context.Context, token string) (*models.User, error) {
	if m.cache == nil {
		return nil, fmt.Errorf("cache not available")
	}

	userID, err := m.cache.GetCachedAuthToken(ctx, token)
	if err != nil {
		if err == redis.Nil {
			return nil, fmt.Errorf("token not in cache")
		}
		return nil, err
	}

	// Get user from database by ID
	var user models.User
	if err := m.db.First(&user, userID).Error; err != nil {
		// User was deleted - invalidate cache
		m.cache.InvalidateAuthToken(ctx, token)
		return nil, err
	}

	// Check if user is active
	if !user.IsActive {
		m.cache.InvalidateAuthToken(ctx, token)
		return nil, fmt.Errorf("user is inactive")
	}

	return &user, nil
}

// getUserFromDatabase looks up the token in the database
func (m *AuthMiddleware) getUserFromDatabase(token string) (*models.User, error) {
	var authToken models.AuthToken
	if err := m.db.Preload("User").Where("key = ?", token).First(&authToken).Error; err != nil {
		return nil, fmt.Errorf("token not found")
	}

	// Check if user is active
	if !authToken.User.IsActive {
		return nil, fmt.Errorf("user is inactive")
	}

	return &authToken.User, nil
}

// cacheUserID caches the user ID for a token
func (m *AuthMiddleware) cacheUserID(ctx context.Context, token string, userID uint) error {
	if m.cache == nil {
		return nil
	}
	return m.cache.CacheAuthToken(ctx, token, userID)
}

// InvalidateToken removes a token from the cache
func (m *AuthMiddleware) InvalidateToken(ctx context.Context, token string) error {
	if m.cache == nil {
		return nil
	}
	return m.cache.InvalidateAuthToken(ctx, token)
}

// GetAuthUser retrieves the authenticated user from the Echo context.
// Returns nil if the context value is missing or not of the expected type.
func GetAuthUser(c echo.Context) *models.User {
	val := c.Get(AuthUserKey)
	if val == nil {
		return nil
	}
	user, ok := val.(*models.User)
	if !ok {
		return nil
	}
	return user
}

// GetAuthToken retrieves the auth token from the Echo context
func GetAuthToken(c echo.Context) string {
	token := c.Get(AuthTokenKey)
	if token == nil {
		return ""
	}
	return token.(string)
}

// MustGetAuthUser retrieves the authenticated user or returns error with 401
func MustGetAuthUser(c echo.Context) (*models.User, error) {
	user := GetAuthUser(c)
	if user == nil {
		return nil, apperrors.Unauthorized("error.not_authenticated")
	}
	return user, nil
}

// truncateToken safely truncates a token string for logging.
// Returns at most the first 8 characters followed by "...".
func truncateToken(token string) string {
	if len(token) > 8 {
		return token[:8] + "..."
	}
	return token + "..."
}