Make foreign keys clickable using tag2link

lib/featureDiff/DiffColumn.js

@@ -2,15 +2,17 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import { config } from '../config';
 
-export const DiffColumn = function({ diff, prop, type, propClass }) {
-  return (
-    <td className={propClass}>
-      <DiffColumnContent diff={diff} prop={prop} type={type} />
-    </td>
-  );
-};
+export class DiffColumn extends React.Component {
+  render() {
+    return (
+      <td className={this.props.propClass}>
+        <DiffColumnContent {...this.props} {...this.context} />
+      </td>
+    );
+  }
+}
 
-const DiffColumnContent = function({ diff, prop, type }) {
+const DiffColumnContent = function({ diff, prop, type, tag2link }) {
   let renderOutput;
   const value = diff[prop][type],
     propIsWikidata = typeof prop == 'string' && /wikidata$/.test(prop);
@@ -54,6 +56,21 @@ const DiffColumnContent = function({ diff, prop, type }) {
       }
     });
     renderOutput = <span>{renderArray}</span>;
+  } else if (tag2link[prop] && typeof value === 'string') {
+    // This is a foreign key which is defined in the tag2link DB.
+    // So, we render a clickable link.
+    renderOutput = (
+      <span>
+        <a
+          target="_blank"
+          rel="noopener noreferrer"
+          className="cmap-wikidata-link"
+          href={tag2link[prop].replace(/\$1/g, value)}
+        >
+          {value}
+        </a>
+      </span>
+    );
   } else {
     // Standard tag, no processing needed
     renderOutput = <span>{value}</span>;
@@ -67,3 +84,7 @@ DiffColumn.propTypes = {
   type: PropTypes.string.isRequired,
   propClass: PropTypes.string
 };
+
+DiffColumn.contextTypes = {
+  tag2link: PropTypes.objectOf(PropTypes.string)
+};

lib/featureDiff/DiffTable.js

@@ -1,6 +1,7 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 import { DiffRows } from './DiffRows';
+import { Tag2LinkContext } from '../tag2link';
 
 //Renders the markup for a table
 
@@ -30,13 +31,15 @@ export const DiffTable = function({ diff, ignoreList, header }) {
           </tr>
         </thead>
       )}
-      <DiffRows
-        diff={diff}
-        sortedProps={sortedProps}
-        types={types}
-        isAddedFeature={isAddedFeature}
-        ignoreList={ignoreList}
-      />
+      <Tag2LinkContext>
+        <DiffRows
+          diff={diff}
+          sortedProps={sortedProps}
+          types={types}
+          isAddedFeature={isAddedFeature}
+          ignoreList={ignoreList}
+        />
+      </Tag2LinkContext>
     </table>
   );
 };

lib/tag2link.js

@@ -0,0 +1,81 @@
+// @ts-check
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const URL = 'https://cdn.jsdelivr.net/gh/JOSM/tag2link@master/index.json';
+
+const RANKS = ['deprecated', 'normal', 'preferred'];
+
+/** @type {Promise<State> | undefined} */
+let promise;
+
+/**
+ * @param {Tag2LinkItem[]} input
+ * @returns {State}
+ */
+function convertSourceData(input) {
+  /** @type {Record<string, string>} */
+  const output = {};
+
+  const allKeys = new Set(input.map(item => item.key));
+
+  for (const key of allKeys) {
+    // find the item with the best rank
+    const bestDefinition = input
+      .filter(item => item.key === key)
+      .sort((a, b) => RANKS.indexOf(b.rank) - RANKS.indexOf(a.rank))[0];
+
+    output[key.replace('Key:', '')] = bestDefinition.url;
+  }
+
+  return { tag2link: output };
+}
+
+/**
+ * @typedef {{
+ *  key: `Key:${string}`;
+ *  url: string;
+ *  source: string;
+ *  rank: "normal" | "preferred";
+ * }} Tag2LinkItem
+ *
+ * @typedef {{
+ *   tag2link: Record<string, string>;
+ * }} State
+ *
+ * @typedef {React.PropsWithChildren} Props
+ */
+
+/** @type {React.Component<Props, State>} */
+export class Tag2LinkContext extends React.Component {
+  /** @param {Props} props */
+  constructor(props) {
+    super(props);
+    this.state = { tag2link: {} };
+  }
+
+  componentDidMount() {
+    if (!promise) {
+      promise = fetch(URL)
+        .then(r => r.json())
+        .then(convertSourceData);
+    }
+    promise.then(state => this.setState(state));
+  }
+
+  getChildContext() {
+    return this.state;
+  }
+
+  render() {
+    return this.props.children;
+  }
+}
+
+Tag2LinkContext.propTypes = {
+  children: PropTypes.node
+};
+
+Tag2LinkContext.childContextTypes = {
+  tag2link: PropTypes.objectOf(PropTypes.string)
+};