waku-org/go-waku

package protocol

import (
    "errors"
    "fmt"
    "strconv"
    "strings"
)

var ErrInvalidFormat = errors.New("invalid content topic format")
var ErrMissingGeneration = errors.New("missing part: generation")
var ErrInvalidGeneration = errors.New("generation should be a number")

// ContentTopic is used for content based.
type ContentTopic struct {
    ContentTopicParams
    ApplicationName    string
    ApplicationVersion string
    ContentTopicName   string
    Encoding           string
}

// ContentTopicParams contains all the optional params for a content topic
type ContentTopicParams struct {
    Generation int
}

// Equal method used to compare 2 contentTopicParams
func (ctp ContentTopicParams) Equal(ctp2 ContentTopicParams) bool {
    return ctp.Generation == ctp2.Generation
}

// ContentTopicOption is following the options pattern to define optional params
type ContentTopicOption func(*ContentTopicParams)

// String formats a content topic in string format as per RFC 23.
func (ct ContentTopic) String() string {
    return fmt.Sprintf("/%s/%s/%s/%s", ct.ApplicationName, ct.ApplicationVersion, ct.ContentTopicName, ct.Encoding)
}

// NewContentTopic creates a new content topic based on params specified.
// Returns ErrInvalidGeneration if an unsupported generation is specified.
// Note that this is recommended to be used for autosharding where contentTopic format is enforced as per https://rfc.vac.dev/spec/51/#content-topics-format-for-autosharding
func NewContentTopic(applicationName string, applicationVersion string,
    contentTopicName string, encoding string, opts ...ContentTopicOption) (ContentTopic, error) {

    params := new(ContentTopicParams)
    optList := DefaultOptions()
    optList = append(optList, opts...)
    for _, opt := range optList {
        opt(params)
    }
    if params.Generation > 0 {
        return ContentTopic{}, ErrInvalidGeneration
    }
    return ContentTopic{
        ContentTopicParams: *params,
        ApplicationName:    applicationName,
        ApplicationVersion: applicationVersion,
        ContentTopicName:   contentTopicName,
        Encoding:           encoding,
    }, nil
}

// WithGeneration option can be used to specify explicitly a generation for contentTopic
func WithGeneration(generation int) ContentTopicOption {
    return func(params *ContentTopicParams) {
        params.Generation = generation
    }
}

// DefaultOptions sets default values for contentTopic optional params.
func DefaultOptions() []ContentTopicOption {
    return []ContentTopicOption{
        WithGeneration(0),
    }
}

// Equal to compare 2 content topics.
func (ct ContentTopic) Equal(ct2 ContentTopic) bool {
    return ct.ApplicationName == ct2.ApplicationName && ct.ApplicationVersion == ct2.ApplicationVersion &&
        ct.ContentTopicName == ct2.ContentTopicName && ct.Encoding == ct2.Encoding &&
        ct.ContentTopicParams.Equal(ct2.ContentTopicParams)
}

// StringToContentTopic can be used to create a ContentTopic object from a string
// Note that this has to be used only when following the rfc format of contentTopic, which is currently validated only for Autosharding.
// For static and named-sharding, contentTopic can be of any format and hence it is not recommended to use this function.
// This can be updated if required to handle such a case.
func StringToContentTopic(s string) (ContentTopic, error) {
    p := strings.Split(s, "/")
    switch len(p) {
    case 5:
        if len(p[1]) == 0 || len(p[2]) == 0 || len(p[3]) == 0 || len(p[4]) == 0 {
            return ContentTopic{}, ErrInvalidFormat
        }
        return ContentTopic{
            ApplicationName:    p[1],
            ApplicationVersion: p[2],
            ContentTopicName:   p[3],
            Encoding:           p[4],
        }, nil
    case 6:
        if len(p[1]) == 0 {
            return ContentTopic{}, ErrMissingGeneration
        }
        generation, err := strconv.Atoi(p[1])
        if err != nil || generation > 0 {
            return ContentTopic{}, ErrInvalidGeneration
        }
        if len(p[2]) == 0 || len(p[3]) == 0 || len(p[4]) == 0 || len(p[5]) == 0 {
            return ContentTopic{}, ErrInvalidFormat
        }
        return ContentTopic{
            ContentTopicParams: ContentTopicParams{Generation: generation},
            ApplicationName:    p[2],
            ApplicationVersion: p[3],
            ContentTopicName:   p[4],
            Encoding:           p[5],
        }, nil
    default:
        return ContentTopic{}, ErrInvalidFormat
    }
}