Refactor endpoints for GETing a dataset/narrative to make room for ad…

…ditional media types

Only sends Auspice's entrypoint for text/html-accepting clients (i.e.
all browsers) and moves existence check into the endpoint itself.  Other
media types won't need the existence check as they don't need to prevent
Auspice from hitting a 404 when it tries to load the dataset/narrative.

src/app.js

@@ -20,8 +20,8 @@ const {
   setDataset,
   setNarrative,
   canonicalizeDataset,
-  ifDatasetExists,
-  ifNarrativeExists,
+  getDataset,
+  getNarrative,
 } = endpoints.sources;
 
 const esc = encodeURIComponent;
@@ -124,12 +124,12 @@ app.use([coreBuildRoutes, "/narratives/*"], setSource("core"));
 
 app.routeAsync(coreBuildRoutes)
   .all(setDataset(req => req.path), canonicalizeDataset(path => `/${path}`))
-  .getAsync(ifDatasetExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getDataset)
 ;
 
 app.routeAsync("/narratives/*")
   .all(setNarrative(req => req.params[0]))
-  .getAsync(ifNarrativeExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getNarrative)
 ;
 
 
@@ -146,12 +146,12 @@ app.routeAsync("/staging/narratives")
 
 app.routeAsync("/staging/narratives/*")
   .all(setNarrative(req => req.params[0]))
-  .getAsync(ifNarrativeExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getNarrative)
 ;
 
 app.routeAsync("/staging/*")
   .all(setDataset(req => req.params[0]), canonicalizeDataset(path => `/staging/${path}`))
-  .getAsync(ifDatasetExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getDataset)
 ;
 
 
@@ -174,12 +174,12 @@ app.use(["/community/narratives/:user/:repo", "/community/:user/:repo"],
  */
 app.routeAsync(["/community/narratives/:user/:repo", "/community/narratives/:user/:repo/*"])
   .all(setNarrative(req => req.params[0]))
-  .getAsync(ifNarrativeExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getNarrative)
 ;
 
 app.routeAsync(["/community/:user/:repo", "/community/:user/:repo/*"])
   .all(setDataset(req => req.params[0]))
-  .getAsync(ifDatasetExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getDataset)
 ;
 
 
@@ -192,14 +192,14 @@ app.routeAsync("/fetch/narratives/:authority/*")
   .all(setNarrative(req => req.params[0]))
 
   // Assume existence; little benefit to checking when we don't have a fallback page.
-  .getAsync(endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getNarrative)
 ;
 
 app.routeAsync("/fetch/:authority/*")
   .all(setDataset(req => req.params[0]))
 
   // Assume existence; little benefit to checking when we don't have a fallback page.
-  .getAsync(endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getDataset)
 ;
 
 
@@ -229,12 +229,12 @@ app.routeAsync("/groups/:groupName/narratives")
 
 app.routeAsync("/groups/:groupName/narratives/*")
   .all(setNarrative(req => req.params[0]))
-  .getAsync(ifNarrativeExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getNarrative)
 ;
 
 app.routeAsync("/groups/:groupName/*")
   .all(setDataset(req => req.params[0]))
-  .getAsync(ifDatasetExists, endpoints.static.sendAuspiceEntrypoint)
+  .getAsync(getDataset)
 ;
 
 

src/endpoints/sources.js

@@ -1,7 +1,9 @@
 const {Forbidden, NotFound} = require("http-errors");
 
+const {contentTypesProvided} = require("../negotiate");
 const sources = require("../sources");
 const utils = require("../utils");
+const {sendAuspiceEntrypoint} = require("./static");
 
 
 /**
@@ -110,10 +112,15 @@ const canonicalizeDataset = (pathBuilder) => (req, res, next) => {
  */
 const ifDatasetExists = async (req, res, next) => {
   if (!(await req.context.dataset.exists())) throw new NotFound();
-  next();
+  return next();
 };
 
 
+const getDataset = contentTypesProvided([
+  ["text/html", ifDatasetExists, sendAuspiceEntrypoint],
+]);
+
+
 /* Narratives
  */
 
@@ -138,10 +145,15 @@ const setNarrative = (pathExtractor) => (req, res, next) => {
  */
 const ifNarrativeExists = async (req, res, next) => {
   if (!(await req.context.narrative.exists())) throw new NotFound();
-  next();
+  return next();
 };
 
 
+const getNarrative = contentTypesProvided([
+  ["text/html", ifNarrativeExists, sendAuspiceEntrypoint],
+]);
+
+
 /**
  * Split a dataset or narrative `path` into an array of parts.
  *
@@ -212,7 +224,9 @@ module.exports = {
   setDataset,
   canonicalizeDataset,
   ifDatasetExists,
+  getDataset,
 
   setNarrative,
   ifNarrativeExists,
+  getNarrative,
 };