Rest: message encoding

[ricardopereira]

I am implementing RSL4a.

Payloads must be binary, strings, or objects capable of JSON representation, or can be empty (omitted). Any other data type should not be permitted and an exception should be raised

Well, I dig into it and I found two places to setup the encoding (one for the payload and one for the client messages):

ARTChannel.payloadEncoder //I don't understand this property. Isn't supposed to encode the payload from the data type?

ARTRest.defaultEncoder //Message encoder

There are 4 payload encoders:

• ARTBase64PayloadEncoder
• ARTUtf8PayloadEncoder
• ARTJsonPayloadEncoder
• ARTCipherPayloadEncoder

and one ARTPayloadEncoderChain that allows "multi-encoding".

ARTChannel

When a ARTChannel is created it uses a private payload encoder [ARTPayload defaultPayloadEncoder] and I my opinion it is supposed to use the ARTRest.defaultEncoder. The private payload encoder (ARTChannel.payloadEncoder) is used to encode/decode the messages.

The [ARTPayload defaultPayloadEncoder] is an [ARTJsonPayloadEncoder instance] when the cipherParams is empty. If it is not then it uses a ARTPayloadEncoderChain with ARTJsonPayloadEncoder, ARTUtf8PayloadEncoder and finally ARTCipherPayloadEncoder.

ARTMessage

The ARTMessage when it is created it initialises the payload with an empty one where the encoding is nothing ([ARTPayload payloadWithPayload:data encoding:@""]).

ARTRest

The defaultEncoder is always an ARTJsonEncoder and it is used to publish a message ([rest.defaultEncoder encodeMessage:message]).

[ricardopereira]

@mattheworiordan I need some orientation with this. I don't know what makes sense or not.

[ricardopereira]

Message encoding

• MessagePack (not implemented)
• JSON

Payload encoding

• Binary encoded as Base64
• String encoded as JSON string
• JSON encoded as JSON string (JSON Object or Array)
• Int ? encoded as JSON string
• Double ? encoded as JSON string
• Empty ? no payload field

Payload encryption (after encoding)

• AES 256
• 128 CBC

---

Test with presence fixtures jsonCommon["post_apps"]["channels"][0]["presence"]

Messages received:

encoding: empty
expected: Bool
data: Optional(true) //Boolean

encoding: empty
expected: NSNumber
data: Optional(24) //Number

encoding: empty
expected: NSString
data: Optional(This is a string clientData payload) //UTF8

encoding: json/utf-8
expected: JSONObject
data: Optional({"example":{"json":"Object"}}) //JSON Object

encoding: empty
expected: JSONObject
data: Optional({ "test": "This is a JSONObject clientData payload"}) //Decoded

encoding: json/utf-8/cipher+aes-128-cbc/base64
expected: NSData
data: Optional(<1cee1c61 23fc2f26 cf6013d9 3c740eb6 e0f9df2a c3dd8577 341a1311 8061e14d 0dd505c7 6ed91fb0 37d3b292 9e2d016d>) //AES-128

[mattheworiordan]

@ricardopereira lets chat tomorrow, probably easier to talk this through.

[tcard]

This has changed completely with #171. payloadEncoder and children are gone, now we have a single dataEncoder and the only state it has is the cipher params. Should I close?