github.com/minhajuddin/prefixed_uuids

Prefixed UUIDs

A Go package that provides a type-safe way to work with prefixed UUIDs. This package allows you to create and parse UUIDs with entity-specific prefixes, making them more readable and ensuring type safety at runtime.

Features

• Create prefixed UUIDs for different entity types
• Parse prefixed UUIDs back to their original UUID form
• Type-safe entity handling
• URL-safe base64 encoding for compact representation
• Runtime validation of entity types and prefixes
• Support for versioned entities (e.g., UserV2, UserV3)
• Customizable separator character (defaults to ., can also use ~)

Installation

go get github.com/minhajuddin/prefixed_uuids

Usage

Basic Setup

First, define your entity types and create a registry:

const (
    User      Entity = 1
    Post      Entity = 2
    Comment   Entity = 3
    UserV2    Entity = 5
    UserV3    Entity = 6
    SessionID Entity = 7
)

registry, err := NewRegistry([]PrefixInfo{
    {User, "user"},
    {Post, "post"},
    {Comment, "comment"},
    {UserV2, "user_v2"},
    {UserV3, "user_v3"},
    {SessionID, "sid"},
})
if err != nil {
    // Handle error
}

Optional: Custom Separator

By default, the registry uses . as the separator. You can customize this using the fluent interface:

// Use '~' as a separator instead of the default '.'
registry, err = registry.WithSeparator("~")
if err != nil {
    // Handle error
}
// This will produce IDs like "user~AZXje_k_dRiprKK-aEY8fg"

Note: Only . and ~ are allowed as separators since they are not part of the base64url encoding alphabet and are not encoded in URLs.

Creating Prefixed UUIDs

uuid := uuid.MustParse("0195e37b-f93f-7518-a9ac-a2be68463c7e")
prefixedUUID := registry.Serialize(User, uuid)
// Result with default separator: "user.AZXje_k_dRiprKK-aEY8fg"
// Result with '~' separator: "user~AZXje_k_dRiprKK-aEY8fg"

// Versioned entities
prefixedUUIDV2 := registry.Serialize(UserV2, uuid)
// Result: "user_v2.AZXje_k_dRiprKK-aEY8fg"

Parsing Prefixed UUIDs

You can parse prefixed UUIDs in two ways:

• When you know the expected entity type:

uuid, err := registry.Deserialize(User, "user.AZXje_k_dRiprKK-aEY8fg")
if err != nil {
    // Handle error
}
// uuid.String() == "0195e37b-f93f-7518-a9ac-a2be68463c7e"

• When you want to determine the entity type from the prefix:

entity, uuid, err := registry.DeserializeWithEntity("post.AZXje_k_dRiprKK-aEY8fg")
if err != nil {
    // Handle error
}
// entity == Post
// uuid.String() == "0195e37b-f93f-7518-a9ac-a2be68463c7e"

Benefits

• Type Safety: The package ensures that UUIDs are used with their correct entity types at runtime.
• Readability: Prefixed UUIDs are more human-readable while maintaining their uniqueness.
• Compactness: The base64 encoding makes the prefixed UUIDs shorter than the original hex representation.
• URL Safety: The encoding is URL-safe, making it suitable for use in URLs and filenames.
• Versioning Support: Easy support for versioned entities with distinct prefixes.

Error Handling

The package returns errors in the following cases:

• ErrInvalidPrefixedUUIDFormat: When the input string doesn't match the expected format (e.g., empty string, no separator)
• ErrUnknownPrefix: When the prefix is not registered in the registry
• ErrInvalidUUIDBadBase64: When the base64 part is invalid
• ErrInvalidUUIDFormat: When the decoded bytes don't form a valid UUID
• ErrEntityMismatch: When the entity type doesn't match the prefix

Example error handling:

// Invalid format
_, err := registry.Deserialize(User, "userAZXje_k_dRiprKK-aEY8fg")
// err == ErrInvalidPrefixedUUIDFormat

// Unknown prefix
_, err = registry.Deserialize(User, "unknown.AZXje_k_dRiprKK-aEY8fg")
// err == ErrUnknownPrefix

// Entity mismatch
prefixedUUID := registry.Serialize(User, uuid)
_, err = registry.Deserialize(Post, prefixedUUID)
// err == ErrEntityMismatch

Prefix Rules

Prefixes must:

• Be lowercase
• Contain only alphanumeric characters, underscores, and hyphens
• Match the regex pattern: ^[a-z0-9_-]+$

Invalid prefixes will cause NewRegistry to return an error:

// These will all return errors:
registry, err := NewRegistry([]PrefixInfo{
    {Entity(1), "Test"},      // uppercase
    {Entity(1), "test prefix"}, // contains space
    {Entity(1), "test@prefix"}, // contains special char
})

Example Use Cases

The primary use case for this is to convert UUIDs to friendly external IDs when sending it to external systems. Whenever you show the ID to the outside world, you use a prefixed_uuid and once it gets past your edge code, it is parsed properly. This way, if you ask a customer for their id and they give you session.AZXje_k_dRiprKK-aEY8fg instead of user.AZXje_k_dRiprKK-aEY8fg, you'll know that they gave you the wrong ID. Also, looking at logs, whenever you see an id, you'll know exactly what it is referring to.

Example uses

• Session IDs: sid.AZXje_k_dRiprKK-aEY8fg
• User ID: user.AZXje_k_dRiprKK-aEY8fg
• JWT Token ID: jti.AZXje_k_dRiprKK-aEY8fg
• Secret Key (Production): sk_live.AZXje_k_dRiprKK-aEY8fg
• Secret Key (Test): sk_test.AZXje_k_dRiprKK-aEY8fg

FAQs

• Can I use this with integer IDs? No. However, feel free to fork this and change the code to serialize/deserialize ints. It is doable with just a few changes.
• Why use . for the separator instead of _ or -? _ and - are part of the alphabet for the base64url encoding scheme that we use to encode the UUID bytes. To make the code more robust, we use a separator that is not part of that alphabet. Also, we don't use : because it is encoded in urls which is a minor annoyance. The only other separator that can be used other than . which is not encoded is ~. You can now use either . or ~ as separators with the WithSeparator method.

Size Comparison

The prefixed UUID format is more compact than the standard UUID format:

uuid := uuid.MustParse("0195e37b-f93f-7518-a9ac-a2be68463c7e")
prefixedUUID := registry.Serialize(User, uuid)
// len(prefixedUUID) == 27  // "user.AZXje_k_dRiprKK-aEY8fg"
// len(uuid.String()) == 36 // "0195e37b-f93f-7518-a9ac-a2be68463c7e"

Inspiration

• Stripe's prefixed ids and the urn format https://datatracker.ietf.org/doc/html/rfc8141
• https://gist.github.com/fnky/76f533366f75cf75802c8052b577e2a5