discourse: add likes edges to the graph (#1299)

A very simple commit; we add a type for likes edges, and add them to the
graph.

Test plan: Unit tests added; yarn test passes.

src/plugins/discourse/createGraph.js

@@ -8,7 +8,13 @@ import {
   type Edge,
   type NodeAddressT,
 } from "../../core/graph";
-import {type PostId, type TopicId, type Post, type Topic} from "./fetch";
+import {
+  type PostId,
+  type TopicId,
+  type Post,
+  type Topic,
+  type LikeAction,
+} from "./fetch";
 import {type DiscourseData} from "./mirror";
 import {
   topicNodeType,
@@ -18,6 +24,7 @@ import {
   authorsTopicEdgeType,
   postRepliesEdgeType,
   topicContainsPostEdgeType,
+  likesEdgeType,
 } from "./declaration";
 
 export function topicAddress(serverUrl: string, id: TopicId): NodeAddressT {
@@ -114,7 +121,6 @@ export function postRepliesEdge(
     String(post.id),
     String(basePostId)
   );
-
   return {
     address,
     timestampMs: post.timestampMs,
@@ -123,6 +129,21 @@ export function postRepliesEdge(
   };
 }
 
+export function likesEdge(serverUrl: string, like: LikeAction): Edge {
+  const address = EdgeAddress.append(
+    likesEdgeType.prefix,
+    serverUrl,
+    like.username,
+    String(like.postId)
+  );
+  return {
+    address,
+    timestampMs: like.timestampMs,
+    src: userAddress(serverUrl, like.username),
+    dst: postAddress(serverUrl, like.postId),
+  };
+}
+
 export function createGraph(serverUrl: string, data: DiscourseData): Graph {
   if (serverUrl.endsWith("/")) {
     throw new Error(`by convention, serverUrl should not end with /`);
@@ -161,5 +182,9 @@ export function createGraph(serverUrl: string, data: DiscourseData): Graph {
     }
   }
 
+  for (const like of data.likes()) {
+    g.addEdge(likesEdge(serverUrl, like));
+  }
+
   return g;
 }

src/plugins/discourse/createGraph.test.js

@@ -13,6 +13,9 @@ import {
   authorsPostEdge,
   topicContainsPostEdge,
   postRepliesEdge,
+  likesEdge,
+  userAddress,
+  postAddress,
 } from "./createGraph";
 import {
   userNodeType,
@@ -22,6 +25,7 @@ import {
   authorsPostEdgeType,
   topicContainsPostEdgeType,
   postRepliesEdgeType,
+  likesEdgeType,
 } from "./declaration";
 import type {EdgeType, NodeType} from "../../analysis/types";
 
@@ -98,7 +102,7 @@ describe("plugins/discourse/createGraph", () => {
       authorUsername: "mzargham",
     };
     const likes: $ReadOnlyArray<LikeAction> = [
-      {timestampMs: 3, username: "mzargam", postId: 2},
+      {timestampMs: 3, username: "mzargham", postId: 2},
       {timestampMs: 4, username: "decentralion", postId: 3},
     ];
     const posts = [post1, post2, post3];
@@ -260,6 +264,26 @@ describe("plugins/discourse/createGraph", () => {
                         ]
                   `);
     });
+    it("for likes", () => {
+      const {url, likes} = example();
+      const like = likes[0];
+      const expectedSrc = userAddress(url, like.username);
+      const expectedDst = postAddress(url, like.postId);
+      const edge = likesEdge(url, like);
+      expect(edge.src).toEqual(expectedSrc);
+      expect(edge.dst).toEqual(expectedDst);
+      expect(edge.timestampMs).toEqual(like.timestampMs);
+      expect(EdgeAddress.toParts(edge.address)).toMatchInlineSnapshot(`
+        Array [
+          "sourcecred",
+          "discourse",
+          "likes",
+          "https://url.com",
+          "mzargham",
+          "2",
+        ]
+      `);
+    });
   });
 
   describe("has the right nodes", () => {
@@ -322,5 +346,10 @@ describe("plugins/discourse/createGraph", () => {
       ];
       expectEdgesOfType(edges, postRepliesEdgeType);
     });
+    it("likes edges", () => {
+      const {url, likes} = example();
+      const edges = likes.map((l) => likesEdge(url, l));
+      expectEdgesOfType(edges, likesEdgeType);
+    });
   });
 });

src/plugins/discourse/declaration.js

@@ -71,6 +71,14 @@ export const authorsPostEdgeType: EdgeType = deepFreeze({
   description: "Connects an author to a post they've created.",
 });
 
+export const likesEdgeType: EdgeType = deepFreeze({
+  forwardName: "likes",
+  backwardName: "is liked by",
+  prefix: EdgeAddress.fromParts(["sourcecred", "discourse", "likes"]),
+  defaultWeight: {forwards: 1, backwards: 0},
+  description: "Connects a Discourse user to a post they liked.",
+});
+
 export const declaration: PluginDeclaration = deepFreeze({
   name: "discourse",
   nodeTypes: [userNodeType, topicNodeType, postNodeType],
@@ -79,5 +87,6 @@ export const declaration: PluginDeclaration = deepFreeze({
     authorsTopicEdgeType,
     authorsPostEdgeType,
     topicContainsPostEdgeType,
+    likesEdgeType,
   ],
 });