Go Enum

Go Enum

Generate type-safe Go enums following GO modular architecture conventions.

When to Use

• Create type-safe enumerations for a module
• Define domain constants with validation
• Add validated enum types (e.g., status, category, method)

Pattern

Place enums in internal/modules/<module>/enum/<name>_enum.go.

Each enum file contains: 1. String constants for each enum value 2. Validation map for O(1) lookups 3. Enum struct type 4. Constructor with validation (New<Type>Enum) 5. String() method 6. Private validation function (validate<Type>)

Note: When a file contains a struct with methods, do not add standalone functions. Use private methods on the struct instead. For enum files, the private validate<Type> function is acceptable because the enum struct is a simple value wrapper without complex methods.

Example — Enum File

For an enum named "ContactType" with values "email" and "webhook" in the monitor module:

package enum

import "github.com/cristiano-pacheco/pingo/internal/modules/monitor/errs"

const (
	ContactTypeEmail   = "email"
	ContactTypeWebhook = "webhook"
)

var validContactTypes = map[string]struct{}{
	ContactTypeEmail:   {},
	ContactTypeWebhook: {},
}

type ContactTypeEnum struct {
	value string
}

func NewContactTypeEnum(value string) (ContactTypeEnum, error) {
	if err := validateContactType(value); err != nil {
		return ContactTypeEnum{}, err
	}
	return ContactTypeEnum{value: value}, nil
}

func (e ContactTypeEnum) String() string {
	return e.value
}

func validateContactType(contactType string) error {
	if _, ok := validContactTypes[contactType]; !ok {
		return errs.ErrInvalidContactType
	}
	return nil
}

Example — Error Entry

Errors live in internal/modules/<module>/errs/errs.go and use errs.New from the bricks package:

package errs

import (
	"net/http"

	"github.com/cristiano-pacheco/bricks/pkg/errs"
)

var (
	ErrInvalidContactType = errs.New("MONITOR_01", "Invalid contact type", http.StatusBadRequest, nil)
)

errs.New signature: errs.New(code string, message string, httpStatus int, metadata any)

• code: <MODULE>_<NN> — uppercase module prefix, two-digit sequential number (e.g., MONITOR_01, IDENTITY_25). Read the existing errs.go to find the next available number.
• message: Sentence case, starting with uppercase (e.g., "Invalid contact type"). Keep it short and user-safe.
• httpStatus: Use http.StatusBadRequest for invalid enum values.
• metadata: Always nil for enum validation errors.

Generation Steps

1. Identify enum details:

• Enum name (e.g., ContactType, UserStatus, PKCEMethod)
• Possible values (e.g., ["email", "webhook"], ["active", "inactive"])
• Target module (e.g., monitor, identity)

2. Add error to `internal/modules/<module>/errs/errs.go`:

• Read the file to find the next available sequential error code number
• Add: ErrInvalid<EnumName> = errs.New("<MODULE>_<NN>", "Invalid <enum name>", http.StatusBadRequest, nil)
• Ensure net/http and github.com/cristiano-pacheco/bricks/pkg/errs are imported

3. Create the enum file at internal/modules/<module>/enum/<snake_case_name>_enum.go:

• Import: github.com/cristiano-pacheco/pingo/internal/modules/<module>/errs
• Follow the structure above with all six components

Naming Conventions

• File: <snake_case>_enum.go (e.g., contact_type_enum.go, user_status_enum.go)
• Constants: <EnumName><Value> (e.g., ContactTypeEmail, UserStatusActive)
• Validation map: valid<EnumName>s (unexported, plural, e.g., validContactTypes)
• Struct: <EnumName>Enum (e.g., ContactTypeEnum)
• Constructor: New<EnumName>Enum(value string) (<EnumName>Enum, error)
• Validator: validate<EnumName>(value string) error (unexported, singular)
• Error: ErrInvalid<EnumName> in internal/modules/<module>/errs/errs.go

Implementation Checklist

• [ ] Read internal/modules/<module>/errs/errs.go to find the next sequential error code
• [ ] Add ErrInvalid<EnumName> to internal/modules/<module>/errs/errs.go
• [ ] Create internal/modules/<module>/enum/<snake_case_name>_enum.go
• [ ] Define all string constants
• [ ] Create validation map (map[string]struct{}) with all constants
• [ ] Define enum struct with private value string field
• [ ] Implement constructor New<EnumName>Enum(value string) (<EnumName>Enum, error)
• [ ] Implement String() string method
• [ ] Implement validate<EnumName>(value string) error private function

Usage Pattern

// Validate and wrap an input value
contactType, err := enum.NewContactTypeEnum(input)
if err != nil {
    return err
}
fmt.Println(contactType.String()) // "email"

// Use constants directly when value is known at compile time
const defaultType = enum.ContactTypeEmail

When finished the enum implementation, ensure to test the constructor with valid and invalid values to confirm validation works as expected.

Run make lint and make nilaway to ensure code quality and no nil pointer issues.