panosoft/services-common

Set of Common Definitions for Backend Services

Set of Common Definitions for Backend Services

Common definitions for writing backend services for Panoramic's websocket-based server architecture.

Install

Elm

Since the Elm Package Manager doesn't allow for Native code and most everything we write at Panoramic Software has some native code in it, you have to install this library directly from GitHub, e.g. via elm-github-install or some equivalent mechanism. It's just not worth the hassle of putting libraries into the Elm package manager until it allows native code.

Taggers

Taggers is a term that is used in Elm's codebase (in Effects Managers). It's effectively a Msg Constructor function.

Imagine the following:

type Msg =
	Message1
	Message2 String
	Message3 String Int

Here Message1 is a Msg, i.e. it's not a tagger/constructor, since it has NO parameters.

Message2, however, is a tagger since it has the following signature:

String -> Msg

Message "abc" is a Msg since the constructor has all of its parameters.

Message3 is also a tagger since it has the following signature:

String -> Int -> Msg

Message3 "abc" is still a tagger but with the following signature:

Int -> Msg

Message3 "abc" 13 is a Msg since the constructor has all of its parameters.

ErrorTagger

Used to convey an error to the Parent (usually the Service is the Child and the Server is the Parent).

type alias ErrorTagger payload msg =
    ( ErrorType, payload ) -> msg

• ErrorType - See elm-utils
• payload - This payload is Service Dependent. The key here is that a single parameter constructs a Msg.

LogTagger

Used to communicate to the Parent that the Child wants to Log a message with a specific LogLevel. Ultimately, the Server/App is the final destination and handler of Log Messages.

type alias LogTagger payload msg =
    ( LogLevel, payload ) -> msg

• LogLevel - See elm-utils
• payload - This payload is Service Dependent. The key here is that a single parameter constructs a Msg.