104 lines
2.7 KiB
Go
104 lines
2.7 KiB
Go
/*
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Package format formats structured events.
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The "application/cloudevents+json" format is built-in and always
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available. Other formats may be added.
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*/
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package format
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import (
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"encoding/json"
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"fmt"
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"strings"
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ce "github.com/cloudevents/sdk-go/v1/cloudevents"
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)
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// Format marshals and unmarshals structured events to bytes.
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type Format interface {
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// MediaType identifies the format
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MediaType() string
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// Marshal event to bytes
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Marshal(ce.Event) ([]byte, error)
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// Unmarshal bytes to event
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Unmarshal([]byte, *ce.Event) error
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}
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// UnknownFormat allows an event with an unknown format string to be forwarded,
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// but Marshal() and Unmarshal will always fail.
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type UnknownFormat string
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func (uf UnknownFormat) MediaType() string { return string(uf) }
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func (uf UnknownFormat) Marshal(ce.Event) ([]byte, error) { return nil, unknown(uf.MediaType()) }
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func (uf UnknownFormat) Unmarshal([]byte, *ce.Event) error { return unknown(uf.MediaType()) }
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// Prefix for event-format media types.
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const Prefix = "application/cloudevents"
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// IsFormat returns true if mediaType begins with "application/cloudevents"
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func IsFormat(mediaType string) bool { return strings.HasPrefix(mediaType, Prefix) }
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// JSON is the built-in "application/cloudevents+json" format.
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var JSON = jsonFmt{}
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type jsonFmt struct{}
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func (jsonFmt) MediaType() string { return ce.ApplicationCloudEventsJSON }
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func (jsonFmt) Marshal(e ce.Event) ([]byte, error) { return json.Marshal(e) }
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func (jsonFmt) Unmarshal(b []byte, e *ce.Event) error {
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err := json.Unmarshal(b, e)
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if err != nil {
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return err
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}
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// Extensions to go types when unparsed
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for k, v := range e.Extensions() {
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var vParsed interface{}
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switch v.(type) {
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case json.RawMessage:
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err = json.Unmarshal(v.(json.RawMessage), &vParsed)
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if err != nil {
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return err
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}
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e.SetExtension(k, vParsed)
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}
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}
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return nil
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}
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// built-in formats
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var formats map[string]Format
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func init() {
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formats = map[string]Format{}
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Add(JSON)
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}
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// Lookup returns the format for mediaType, or nil if not found.
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func Lookup(mediaType string) Format { return formats[mediaType] }
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func unknown(mediaType string) error {
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return fmt.Errorf("unknown event format media-type %#v", mediaType)
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}
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// Add a new Format. It can be retrieved by Lookup(f.MediaType())
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func Add(f Format) { formats[f.MediaType()] = f }
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// Marshal an event to bytes using the mediaType event format.
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func Marshal(mediaType string, e ce.Event) ([]byte, error) {
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if f := formats[mediaType]; f != nil {
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return f.Marshal(e)
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}
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return nil, unknown(mediaType)
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}
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// Unmarshal bytes to an event using the mediaType event format.
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func Unmarshal(mediaType string, b []byte, e *ce.Event) error {
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if f := formats[mediaType]; f != nil {
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return f.Unmarshal(b, e)
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}
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return unknown(mediaType)
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}
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