Initiatives: create and parse InitiativeFile InitiativeId (#1643)

The private function `_initiativeFileId` will be used as a helper to
load a directory. The public function `initiativeFileURL` will be used
to add links to the remote file in the node description.

src/plugins/initiatives/initiativesDirectory.js

@@ -1,8 +1,17 @@
 // @flow
 
 import {type ReferenceDetector} from "../../core/references";
+import {type NodeAddressT, NodeAddress} from "../../core/graph";
 import {type Compatible, fromCompat, toCompat} from "../../util/compat";
-import {type InitiativeRepository, type URL} from "./initiative";
+import {initiativeNodeType} from "./declaration";
+import {
+  type InitiativeId,
+  type InitiativeRepository,
+  type URL,
+  createId,
+} from "./initiative";
+
+export const INITIATIVE_FILE_SUBTYPE = "INITIATIVE_FILE";
 
 /**
  * Represents an Initiatives directory.
@@ -61,3 +70,31 @@ export function fromJSON(j: Compatible<any>): InitiativeFile {
 export function toJSON(m: InitiativeFile): Compatible<InitiativeFile> {
   return toCompat(COMPAT_INFO, m);
 }
+
+/**
+ * When provided with the initiative NodeAddressT of an InitiativeFile this extracts
+ * the URL from it. Or null when the address is not for an InitiativeFile.
+ */
+export function initiativeFileURL(address: NodeAddressT): string | null {
+  const initiativeFilePrefix = NodeAddress.append(
+    initiativeNodeType.prefix,
+    INITIATIVE_FILE_SUBTYPE
+  );
+
+  if (!NodeAddress.hasPrefix(address, initiativeFilePrefix)) {
+    return null;
+  }
+
+  const parts = NodeAddress.toParts(address);
+  const remoteUrl = parts[4];
+  const fileName = parts[5];
+  return `${remoteUrl}/${fileName}`;
+}
+
+// Creates the InitiativeId for an InitiativeFile.
+export function _initiativeFileId(
+  {remoteUrl}: InitiativesDirectory,
+  fileName: string
+): InitiativeId {
+  return createId(INITIATIVE_FILE_SUBTYPE, remoteUrl, fileName);
+}

src/plugins/initiatives/initiativesDirectory.test.js

@@ -1,6 +1,15 @@
 // @flow
 
-import {type InitiativeFile, fromJSON, toJSON} from "./initiativesDirectory";
+import {NodeAddress} from "../../core/graph";
+import {createId, addressFromId} from "./initiative";
+import {
+  type InitiativeFile,
+  type InitiativesDirectory,
+  fromJSON,
+  toJSON,
+  initiativeFileURL,
+  _initiativeFileId,
+} from "./initiativesDirectory";
 
 const exampleInitiativeFile = (): InitiativeFile => ({
   title: "Sample initiative",
@@ -25,4 +34,49 @@ describe("plugins/initiatives/initiativesDirectory", () => {
       expect(actual).toEqual(initiativeFile);
     });
   });
+
+  describe("initiativeFileURL", () => {
+    it("should return null for a different prefix", () => {
+      // Given
+      const address = NodeAddress.fromParts(["foobar"]);
+
+      // When
+      const url = initiativeFileURL(address);
+
+      // Then
+      expect(url).toEqual(null);
+    });
+
+    it("should detect the correct prefix and create a URL", () => {
+      // Given
+      const remoteUrl = "http://foo.bar/dir";
+      const fileName = "sample.json";
+      const address = addressFromId(
+        createId("INITIATIVE_FILE", remoteUrl, fileName)
+      );
+
+      // When
+      const url = initiativeFileURL(address);
+
+      // Then
+      expect(url).toEqual(`${remoteUrl}/${fileName}`);
+    });
+  });
+
+  describe("_initiativeFileId", () => {
+    it("should add the correct prefix to a remoteUrl and fileName", () => {
+      // Given
+      const dir: InitiativesDirectory = {
+        localPath: "should-not-be-used",
+        remoteUrl: "http://foo.bar/dir",
+      };
+      const fileName = "sample.json";
+
+      // When
+      const id = _initiativeFileId(dir, fileName);
+
+      // Then
+      expect(id).toEqual(createId("INITIATIVE_FILE", dir.remoteUrl, fileName));
+    });
+  });
 });