Redefine artifact plugin node and edge semantics (#111)

Summary:
This commit revises our implementations of node and edge types, and
specifies the semantics for artifact plugin IDs: we create IDs by
slugifying an artifact name and then resolving collisions

Test Plan:
Unit tests added. Run `yarn flow` and `yarn test`.

wchargin-branch: artifact-plugin-node-edge-semantics

src/plugins/artifact/artifactPlugin.js

@@ -1,18 +1,45 @@
 // @flow
 
-export type ArtifactNodeID = string;
+import type {Address} from "../../core/address";
+import type {Graph} from "../../core/graph";
+
+export const ARTIFACT_PLUGIN_NAME = "sourcecred/artifact-beta";
+
+export const ARTIFACT_NODE_TYPE = "ARTIFACT";
 export type ArtifactNodePayload = {|
   +name: string,
+  +description: string,
 |};
 
 export type NodePayload = ArtifactNodePayload;
 
-export type ArtifactEdgeID = {|
-  +src: string,
-  +dst: string,
-|};
-export type ArtifactEdgePayload = {|
+export const INCLUDES_EDGE_TYPE = "INCLUDES";
+export type IncludesEdgePayload = {|
   +weight: number, // non-negative
 |};
 
-export type EdgePayload = ArtifactEdgePayload;
+export type EdgePayload = IncludesEdgePayload;
+
+const NON_SLUG_CHARACTER: RegExp = /[^a-z]/g;
+
+export function artifactAddress(
+  graph: Graph<NodePayload, EdgePayload>,
+  repoOwner: string,
+  repoName: string,
+  artifactName: string
+): Address {
+  const baseId = artifactName.toLowerCase().replace(NON_SLUG_CHARACTER, "-");
+  function address(id) {
+    return {
+      repositoryName: `${repoOwner}/${repoName}`,
+      pluginName: ARTIFACT_PLUGIN_NAME,
+      id,
+      type: ARTIFACT_NODE_TYPE,
+    };
+  }
+  let id = baseId;
+  for (let i = 0; graph.getNode(address(id)) != null; i++) {
+    id = baseId + "-" + i;
+  }
+  return address(id);
+}

src/plugins/artifact/artifactPlugin.test.js

@@ -0,0 +1,51 @@
+// @flow
+
+import {Graph} from "../../core/graph";
+import {artifactAddress} from "./artifactPlugin";
+
+describe("artifactPlugin", () => {
+  describe("artifactAddress", () => {
+    it("formats the repository name", () => {
+      const a = artifactAddress(
+        new Graph(),
+        "not-sourcecred",
+        "not-artifact-plugin",
+        "Sample artifact!"
+      );
+      expect(a.repositoryName).toEqual("not-sourcecred/not-artifact-plugin");
+    });
+
+    it("slugifies the artifact name", () => {
+      const a = artifactAddress(
+        new Graph(),
+        "not-sourcecred",
+        "not-artifact-plugin",
+        "Sample artifact!"
+      );
+      expect(a.id).toEqual("sample-artifact-");
+    });
+
+    it("resolves collisions", () => {
+      const g = new Graph();
+      const ids = [];
+      for (let i = 0; i < 3; i++) {
+        const a = artifactAddress(
+          g,
+          "not-sourcecred",
+          "not-artifact-plugin",
+          "Sample artifact!"
+        );
+        ids.push(a.id);
+        g.addNode({
+          address: a,
+          payload: {name: "Sample artifact!", description: ""},
+        });
+      }
+      expect(ids).toEqual([
+        "sample-artifact-",
+        "sample-artifact--0",
+        "sample-artifact--1",
+      ]);
+    });
+  });
+});

src/plugins/artifact/editor/App.js

@@ -34,7 +34,7 @@ function createSampleArtifact(name) {
       id,
       type: "artifact",
     },
-    payload: {name},
+    payload: {name, description: ""},
   };
 }