Event Data Structure

[slinkydeveloper]

Data structures to represent CloudEvents that can be extended in future to support different cloudevents versions. Some examples:

• https://github.com/cloudevents/sdk-go/blob/master/pkg/cloudevents/event.go#L12
• https://github.com/kichristensen/rust-cloudevents/blob/master/cloudevents/src/event.rs#L8

We also need easy accessors to read cloudevents metadata, extensions and payload. An example to read and parse payload: https://github.com/slinkydeveloper/cloudevents-rust/blob/master/cloudevents-rust/src/event/payload.rs

Data structure could be immutable, so we builders to build them. For builders we can try to use https://docs.rs/crate/derive_builder/0.9.0

[slinkydeveloper]

Attributes should be represented as union type to support different spec versions.

The Event structure should have some simple accessors to read/write id, type, source & specversion. Event should look like:

struct Event {
    attribute: Attribute,
    data: Data
}

Extensions could be represented as https://github.com/kichristensen/rust-cloudevents/blob/master/cloudevents/src/v1_0/event.rs#L32

Accessors to read and write payload could be implemented like https://github.com/slinkydeveloper/cloudevents-rust/blob/master/cloudevents-rust/src/event/payload.rs#L56