Problem: metadata links are not parsed and rendered

Solution: create parser and renderer for metadata links.

editor/src/markdown.js

@@ -1,6 +1,6 @@
 import MarkdownIt from "markdown-it";
-//import MarkdownItWikilinks from "./wikilinks";
 import MarkdownItWikilinks2 from "./wikilinks2";
+import MarkdownItMetadata from "./metadatalinks";
 import MarkdownItMark from "markdown-it-mark";
 import MarkdownItKatex from "markdown-it-katex";
 
@@ -21,6 +21,7 @@ MD.use(MarkdownItWikilinks2({
         class: 'wiki-link'
     },
 }))
+MD.use(MarkdownItMetadata())
 // MD.use(MarkdownItWikilinks({
 //     baseURL: document.querySelector('body').dataset.baseUrl,
 //     uriSuffix: '',

editor/src/metadatalinks.js

@@ -0,0 +1,54 @@
+'use strict'
+
+var util = require('util')
+
+function Plugin(options) {
+    var self = function (md) {
+        self.options = options
+        self.init(md)
+    }
+
+    self.__proto__ = Plugin.prototype
+    self.id = 'metadata'
+
+    return self
+}
+
+util.inherits(Plugin, Function)
+
+Plugin.prototype.init = function (md) {
+    md.inline.ruler.before('text', this.id, this.parse.bind(this), {})
+    md.renderer.rules[this.id] = this.render.bind(this)
+}
+
+export function metadataLinkParser(id, state, silent) {
+    let input = state.src;
+    if (state.pos === 0 && input.match(/^([A-Za-z0-9 ]+)::/)) {
+        let [key, sep, value] = input.split(/::( |$)/)
+        console.log(key, value)
+        if (key.length === 0) return false;
+        if (!silent) {
+            let token = state.push(id, '', 0)
+            token.meta = {key, value, tag: 'metadata'}
+        }
+        state.pos = key.length + 3;
+        return true
+    }
+    return false
+}
+
+Plugin.prototype.parse = function (state, silent) {
+    return metadataLinkParser(this.id, state, silent)
+}
+
+Plugin.prototype.render = function (tokens, id, options, env) {
+    let {match: link, tag} = tokens[id].meta
+    if (tag === 'metadata') {
+        let {key, value} = tokens[id].meta
+        return '<span class="metadata-key"><a href="/edit/'+key.replace(/ +/g, '_')+'">'+key+'</a></span>: ';
+    }
+}
+
+export default (options) => {
+    return Plugin(options);
+}

editor/src/wikilinks2.js

@@ -23,6 +23,7 @@ Plugin.prototype.init = function (md) {
 
 export function linkParser(id, state, silent) {
     let input = state.src.slice(state.pos);
+
     const match = /^#?\[\[/.exec(input)
     if (!match) {
         return false