feat: OutcomeService method to prepare request

OutcomeService gains methods to prepare requests without sending them. `ims-lti` would define and sign the request but and user can sent it by some other way.

Adds:

- OutcomeService.prototype.replace_result_request(score) -> {body, options}
- OutcomeService.prototype.replace_result_with_text_request(score) -> {body, options}
- OutcomeService.prototype.replace_result_with_url_request(score) -> {body, options}
- OutcomeService.prototype.read_result_request(score) -> {body, options}
- OutcomeService.prototype.delete_result_request(score) -> {body, options}

src/extensions/outcomes.coffee

@@ -97,91 +97,120 @@ class OutcomeService
     parts = @service_url_parts = url.parse @service_url, true
     @service_url_oauth = parts.protocol + '//' + parts.host + parts.pathname
 
-
-  send_replace_result: (score, callback) ->
+  replace_result_request: (score) ->
     doc = new OutcomeDocument @REQUEST_REPLACE, @source_did, @
+    doc.add_score score, @language
+    @_request doc
 
+  send_replace_result: (score, callback) ->
     try
-      doc.add_score score, @language
-      @_send_request doc, callback
+      req = @replace_result_request(score)
+      @_send(req.body, req.options, callback)
     catch err
       callback err, false
 
-
-  send_replace_result_with_text: (score, text, callback) ->
+  replace_result_with_text_request: (score, text) ->
     doc = new OutcomeDocument @REQUEST_REPLACE, @source_did, @
+    doc.add_score score, @language,
+    doc.add_text text
+    @_request doc
 
+  send_replace_result_with_text: (score, text, callback) ->
     try
-      doc.add_score score, @language,
-      doc.add_text text
-      @_send_request doc, callback
+      req = @replace_result_with_text_request score, text
+      @_send(req.body, req.options, callback)
     catch err
       callback err, false
 
 
-  send_replace_result_with_url: (score, url, callback) ->
+  replace_result_with_url_request: (score, url) ->
     doc = new OutcomeDocument @REQUEST_REPLACE, @source_did, @
+    doc.add_score score, @language,
+    doc.add_url url
+    @_request doc
 
+  send_replace_result_with_url: (score, url, callback) ->
     try
-      doc.add_score score, @language,
-      doc.add_url url
-      @_send_request doc, callback
+      req = @replace_result_with_url_request(score, url)
+      @_send req.body, req.options, callback
     catch err
       callback err, false
 
 
-  send_read_result: (callback) ->
+  read_result_request: ->
     doc = new OutcomeDocument @REQUEST_READ, @source_did, @
-    @_send_request doc, (err, result, xml) =>
-      return callback(err, result) if err
+    @_request(doc)
 
-      score = parseFloat navigateXml(xml, 'imsx_POXBody.readResultResponse.result.resultScore.textString'), 10
+  send_read_result: (callback) ->
+    try
+      req = @read_result_request()
+      @_send req.body, req.options, (err, result, xml) =>
+        return callback(err, result) if err
 
-      if (isNaN(score))
-        callback new errors.OutcomeResponseError('Invalid score response'), false
-      else
-        callback null, score
+        score = parseFloat navigateXml(xml, 'imsx_POXBody.readResultResponse.result.resultScore.textString'), 10
 
+        if (isNaN(score))
+          callback new errors.OutcomeResponseError('Invalid score response'), false
+        else
+          callback null, score
+    catch err
+      callback err, null
 
-  send_delete_result: (callback) ->
+
+  delete_result_request: ->
     doc = new OutcomeDocument @REQUEST_DELETE, @source_did, @
-    @_send_request doc, callback
+    @_request doc
 
+  send_delete_result: (callback) ->
+    try
+      req = @delete_result_request()
+      @_send req.body, req.options, callback
+    catch err
+      callback err, false
 
   supports_result_data: (type) ->
     return @result_data_types.length and (!type or @result_data_types.indexOf(type) != -1)
 
-
   _send_request: (doc, callback) ->
+    # deprecated Since version 3.1.
+    req = @_request doc
+    @_send req.body, req.options, callback
+
+  _request: (doc) ->
     xml     = doc.finalize()
-    body    = ''
-    is_ssl  = @service_url_parts.protocol == 'https:'
 
     options =
+      protocol: @service_url_parts.protocol
       hostname:  @service_url_parts.hostname
       path:      @service_url_parts.path
       method:    'POST'
       headers:   @_build_headers xml
 
+    return body: xml, options: options
+
+  _send: (body, options, callback) ->
+    result  = ''
+    client  = if options.protocol == 'https:' then https else http
+
     if @cert_authority and is_ssl
       options.ca = @cert_authority
     else
-      options.agent = if is_ssl then https.globalAgent else http.globalAgent
+      options.agent = client.globalAgent
 
     if @service_url_parts.port
       options.port = @service_url_parts.port
 
     # Make the request to the TC, verifying that the status code is valid and fetching the entire response body.
-    req = (if is_ssl then https else http).request options, (res) =>
+    req = client.request options, (res) =>
       res.setEncoding 'utf8'
-      res.on 'data', (chunk) => body += chunk
+      res.on 'data', (chunk) => result += chunk
       res.on 'end', () =>
-        @_process_response body, callback
+        @_process_response result, callback
 
     req.on 'error', (err) =>
       callback err, false
 
-    req.write xml
+    req.write body
     req.end()