[feature-request] Allow usage of a response body as URI templates

[deedubs]

I would like to be able to use a response body as template parameters further down the chain.

An example api could be

Where `self' returns:

{
  id: 1,
  name: 'Agent 007'
}

and clients == 'http://host/agents/{agent_id}/clients'

  traverson
    .from('http://api.example.com')
    .follow({name: 'self', asTemplate:'agent'}, 'clients') 
    .getResource(function(error, document) {
      ...
    });

[basti1302]

As said in this thread on Twitter, I think this is a good idea. I'll probably won't get around to implement this soon, because I'm still working on the traversal continuation feature whenever I have time to work on Traverson. If somebody else wants to take a shot at this, a PR would be most welcome.

I don't fully understand the example given here, though - I think it's a bit incomplete? I'll try to make up a more complete example, just to make sure we are on the same page:

Server Side Responses

http://api.example.com

{
  "agent_1": "007",
  "agent_2": "008",
  "agent_details": "http://api.example.com/agents/{agent_id}"
}

https://api.example.com/agents/007

{
  "id": "007",
  "name": "James Bond"
}

https://api.example.com/agents/008

{
  "id": "008",
  "name": "Mata Hari"
}

Traverson API

What we would like to do now is to fetch the first resource and use one of its attributes (for example, the value of the attribute agent_1, that is, "007") and feed this into the URI template agent_details to get to the resource at https://api.example.com/agents/007.

We need a way to tell Traverson about this. I don't think the follow method is what needs to change, this just tells Traverson which links are to be traversed, so in the example above it would still simply be follow('agent_details'). The proper place to tell Traverson about this is withTemplateParameters. It could look like this:

var traverson = require('traverson');

traverson
.from('http://api.example.com')
.follow('agent_details')
withTemplateParameters({
  agent_id: { 
    lookupStrategy: 'FROM_LAST_HTTP_RESPONSE',
    key: 'agent_1'
  }
})
.getResource(function(error, document) { ... });

This is to be read as: "Whenever you resolve a URI template and it has a URI template parameter agent_id, don't use a fixed substitution value but look up the value in the last HTTP response and use the value of the attribute agent_1. It would be nice if key could also be a JSONPath expression. The reason for the lookupStrategy thing: In future, we might conceive other sources for template substitution values.

@deedubs Is that roughly what you had in mind?

[basti1302]

It's a pity that @deedubs never got back to me on this one... 😢 😏