logging and diagnostic features added

internal/errors/errors.go

@@ -0,0 +1,114 @@
+package errors
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// ErrorCode represents a specific error type
+type ErrorCode string
+
+const (
+	ErrCodeInternal           ErrorCode = "INTERNAL_ERROR"
+	ErrCodeNotFound           ErrorCode = "NOT_FOUND"
+	ErrCodeBadRequest         ErrorCode = "BAD_REQUEST"
+	ErrCodeConflict           ErrorCode = "CONFLICT"
+	ErrCodeUnauthorized       ErrorCode = "UNAUTHORIZED"
+	ErrCodeForbidden          ErrorCode = "FORBIDDEN"
+	ErrCodeServiceUnavailable ErrorCode = "SERVICE_UNAVAILABLE"
+	ErrCodeValidation         ErrorCode = "VALIDATION_ERROR"
+)
+
+// APIError represents a structured API error
+type APIError struct {
+	Code       ErrorCode `json:"code"`
+	Message    string    `json:"message"`
+	Details    string    `json:"details,omitempty"`
+	HTTPStatus int       `json:"-"`
+}
+
+func (e *APIError) Error() string {
+	if e.Details != "" {
+		return fmt.Sprintf("%s: %s (%s)", e.Code, e.Message, e.Details)
+	}
+	return fmt.Sprintf("%s: %s", e.Code, e.Message)
+}
+
+// NewAPIError creates a new API error
+func NewAPIError(code ErrorCode, message string, httpStatus int) *APIError {
+	return &APIError{
+		Code:       code,
+		Message:    message,
+		HTTPStatus: httpStatus,
+	}
+}
+
+// WithDetails adds details to an error
+func (e *APIError) WithDetails(details string) *APIError {
+	e.Details = details
+	return e
+}
+
+// Common error constructors
+func ErrNotFound(resource string) *APIError {
+	return NewAPIError(ErrCodeNotFound, fmt.Sprintf("%s not found", resource), http.StatusNotFound)
+}
+
+func ErrBadRequest(message string) *APIError {
+	return NewAPIError(ErrCodeBadRequest, message, http.StatusBadRequest)
+}
+
+func ErrConflict(message string) *APIError {
+	return NewAPIError(ErrCodeConflict, message, http.StatusConflict)
+}
+
+func ErrInternal(message string) *APIError {
+	return NewAPIError(ErrCodeInternal, message, http.StatusInternalServerError)
+}
+
+func ErrServiceUnavailable(service string) *APIError {
+	return NewAPIError(ErrCodeServiceUnavailable, fmt.Sprintf("%s service is unavailable", service), http.StatusServiceUnavailable)
+}
+
+func ErrValidation(message string) *APIError {
+	return NewAPIError(ErrCodeValidation, message, http.StatusBadRequest)
+}
+
+// RetryConfig defines retry behavior
+type RetryConfig struct {
+	MaxAttempts int
+	Backoff     func(attempt int) error // Returns error if should stop retrying
+}
+
+// DefaultRetryConfig returns a default retry configuration
+func DefaultRetryConfig() RetryConfig {
+	return RetryConfig{
+		MaxAttempts: 3,
+		Backoff: func(attempt int) error {
+			// Simple exponential backoff: 100ms, 200ms, 400ms
+			if attempt >= 3 {
+				return fmt.Errorf("max attempts reached")
+			}
+			return nil
+		},
+	}
+}
+
+// Retry executes a function with retry logic
+func Retry(fn func() error, config RetryConfig) error {
+	var lastErr error
+	for attempt := 1; attempt <= config.MaxAttempts; attempt++ {
+		if err := fn(); err == nil {
+			return nil
+		} else {
+			lastErr = err
+		}
+
+		if attempt < config.MaxAttempts {
+			if err := config.Backoff(attempt); err != nil {
+				return fmt.Errorf("retry aborted: %w", err)
+			}
+		}
+	}
+	return fmt.Errorf("retry failed after %d attempts: %w", config.MaxAttempts, lastErr)
+}