backend-service/internal/middleware/error.go

package middleware

import (
	"fmt"
	"net/http"
	"runtime/debug"

	"attune-heart-therapy/internal/errors"
	"attune-heart-therapy/internal/logger"

	"github.com/gin-gonic/gin"
)

// ErrorHandlerMiddleware handles errors and panics in a structured way
func ErrorHandlerMiddleware() gin.HandlerFunc {
	return gin.CustomRecovery(func(c *gin.Context, recovered interface{}) {
		log := logger.New("error_handler")

		if recovered != nil {
			// Handle panic
			err := fmt.Errorf("panic recovered: %v", recovered)
			log.Error("Panic recovered", err, map[string]interface{}{
				"method":     c.Request.Method,
				"path":       c.Request.URL.Path,
				"client_ip":  c.ClientIP(),
				"user_agent": c.Request.UserAgent(),
				"stack":      string(debug.Stack()),
			})

			// Return internal server error for panics
			appErr := errors.ErrInternalServer.WithDetails("An unexpected error occurred")
			c.JSON(appErr.HTTPStatus, appErr.ToErrorResponse())
			c.Abort()
			return
		}

		// Handle regular errors
		if len(c.Errors) > 0 {
			err := c.Errors.Last()
			handleError(c, err.Err, log)
		}
	})
}

// handleError processes different types of errors and returns appropriate responses
func handleError(c *gin.Context, err error, log *logger.Logger) {
	// Check if it's already an AppError
	if appErr := errors.GetAppError(err); appErr != nil {
		logError(log, c, appErr, appErr.Cause)
		c.JSON(appErr.HTTPStatus, appErr.ToErrorResponse())
		return
	}

	// Handle validation errors
	if validationErrs, ok := err.(errors.ValidationErrors); ok {
		appErr := validationErrs.ToAppError()
		logError(log, c, appErr, err)
		c.JSON(appErr.HTTPStatus, appErr.ToErrorResponse())
		return
	}

	// Handle other known error types
	appErr := classifyError(err)
	logError(log, c, appErr, err)
	c.JSON(appErr.HTTPStatus, appErr.ToErrorResponse())
}

// classifyError converts generic errors to AppErrors based on error content
func classifyError(err error) *errors.AppError {
	errMsg := err.Error()

	// Database errors
	if containsAny(errMsg, []string{"database", "sql", "connection", "timeout"}) {
		return errors.ErrDatabaseError.WithCause(err)
	}

	// Network/external API errors
	if containsAny(errMsg, []string{"network", "connection refused", "timeout", "dns"}) {
		return errors.ErrExternalAPI.WithCause(err)
	}

	// Validation errors
	if containsAny(errMsg, []string{"invalid", "validation", "required", "format"}) {
		return errors.ErrValidationFailed.WithCause(err)
	}

	// Not found errors
	if containsAny(errMsg, []string{"not found", "does not exist"}) {
		return errors.ErrNotFound.WithCause(err)
	}

	// Default to internal server error
	return errors.ErrInternalServer.WithCause(err)
}

// logError logs error information with context
func logError(log *logger.Logger, c *gin.Context, appErr *errors.AppError, cause error) {
	fields := map[string]interface{}{
		"error_code": appErr.Code,
		"method":     c.Request.Method,
		"path":       c.Request.URL.Path,
		"client_ip":  c.ClientIP(),
		"user_agent": c.Request.UserAgent(),
		"status":     appErr.HTTPStatus,
	}

	// Add user ID if available
	if userID, exists := c.Get("user_id"); exists {
		fields["user_id"] = userID
	}

	// Add trace ID if available
	if traceID, exists := c.Get("trace_id"); exists {
		fields["trace_id"] = traceID
	}

	// Add error fields if available
	if appErr.Fields != nil {
		for k, v := range appErr.Fields {
			fields["error_"+k] = v
		}
	}

	// Log based on severity
	if appErr.HTTPStatus >= 500 {
		log.Error("Server error occurred", cause, fields)
	} else if appErr.HTTPStatus >= 400 {
		log.Warn("Client error occurred", fields)
	} else {
		log.Info("Request completed with error", fields)
	}
}

// containsAny checks if a string contains any of the given substrings
func containsAny(s string, substrings []string) bool {
	for _, substr := range substrings {
		if len(s) >= len(substr) {
			for i := 0; i <= len(s)-len(substr); i++ {
				if s[i:i+len(substr)] == substr {
					return true
				}
			}
		}
	}
	return false
}

// NotFoundHandler handles 404 errors
func NotFoundHandler() gin.HandlerFunc {
	return func(c *gin.Context) {
		appErr := errors.ErrNotFound.WithDetails(fmt.Sprintf("Route %s %s not found", c.Request.Method, c.Request.URL.Path))
		c.JSON(appErr.HTTPStatus, appErr.ToErrorResponse())
	}
}

// MethodNotAllowedHandler handles 405 errors
func MethodNotAllowedHandler() gin.HandlerFunc {
	return func(c *gin.Context) {
		appErr := errors.New(errors.ErrCodeValidationFailed, "Method not allowed", http.StatusMethodNotAllowed).
			WithDetails(fmt.Sprintf("Method %s not allowed for route %s", c.Request.Method, c.Request.URL.Path))
		c.JSON(appErr.HTTPStatus, appErr.ToErrorResponse())
	}
}