FIX: Quoting local dates bbcode regeneration (#17141)

This commit allows quoting of discourse-local-date elements
and converts the quoted tags back into bbcode so that the
rendered quote will also render the discourse-local-date HTML.
This works on single dates as well as date ranges, and supports
all of the options used by discourse-local-date.

This also necessitated adding addTextDecorateCallback to the
to-markdown core lib (similar to addBlockDecorateCallback and
addTagDecorateCallback) to transform the text nodes between
date ranges to remove the -> in the final quote.

c.f. https://meta.discourse.org/t/quotes-that-contain-date-time/101999

plugins/discourse-local-dates/assets/javascripts/initializers/discourse-local-dates.js

@@ -7,6 +7,11 @@ import { downloadCalendar } from "discourse/lib/download-calendar";
 import { renderIcon } from "discourse-common/lib/icon-library";
 import I18n from "I18n";
 import { hidePopover, showPopover } from "discourse/lib/d-popover";
+import {
+  addTagDecorateCallback,
+  addTextDecorateCallback,
+} from "discourse/lib/to-markdown";
+import generateDateMarkup from "discourse/plugins/discourse-local-dates/lib/local-date-markup-generator";
 
 // Import applyLocalDates from discourse/lib/local-dates instead
 export function applyLocalDates(dates, siteSettings) {
@@ -66,6 +71,24 @@ function buildOptionsFromElement(element, siteSettings) {
   return opts;
 }
 
+function buildOptionsFromMarkdownTag(element) {
+  const opts = {};
+
+  // siteSettings defaults as used by buildOptionsFromElement are purposefully
+  // ommitted to reproduce exactly what was on the original element
+  opts.time = element.attributes["data-time"];
+  opts.date = element.attributes["data-date"];
+  opts.recurring = element.attributes["data-recurring"];
+  opts.timezones = element.attributes["data-timezones"];
+  opts.timezone = element.attributes["data-timezone"];
+  opts.calendar = (element.attributes["data-calendar"] || "on") === "on";
+  opts.displayedTimezone = element.attributes["data-displayed-timezone"];
+  opts.format = element.attributes["data-format"];
+  opts.countdown = element.attributes["data-countdown"];
+
+  return opts;
+}
+
 function _rangeElements(element) {
   if (!element.parentElement) {
     return [];
@@ -128,6 +151,60 @@ function initializeDiscourseLocalDates(api) {
       },
     },
   });
+
+  addTextDecorateCallback(function (
+    text,
+    nextElement,
+    _previousElement,
+    metadata
+  ) {
+    if (
+      metadata.discourseLocalDateStartRangeOpts &&
+      nextElement?.attributes.class?.includes("discourse-local-date") &&
+      text === "→"
+    ) {
+      return "";
+    }
+  });
+  addTagDecorateCallback(function () {
+    if (this.element.attributes.class?.includes("discourse-local-date")) {
+      if (this.metadata.discourseLocalDateStartRangeOpts) {
+        const startRangeOpts = this.metadata.discourseLocalDateStartRangeOpts;
+        const endRangeOpts = buildOptionsFromMarkdownTag(this.element);
+        const markup = generateDateMarkup(
+          {
+            date: startRangeOpts.date,
+            time: startRangeOpts.time,
+            format: startRangeOpts.format,
+          },
+          endRangeOpts,
+          true,
+          {
+            date: endRangeOpts.date,
+            time: endRangeOpts.time,
+            format: endRangeOpts.format,
+          }
+        );
+        this.prefix = markup;
+        this.metadata.discourseLocalDateStartRangeOpts = null;
+        return "";
+      }
+      if (this.element.attributes["data-range"] === "true") {
+        this.metadata.discourseLocalDateStartRangeOpts = buildOptionsFromMarkdownTag(
+          this.element
+        );
+        return "";
+      }
+      const opts = buildOptionsFromMarkdownTag(this.element, siteSettings);
+      const markup = generateDateMarkup(
+        { date: opts.date, time: opts.time, format: opts.format },
+        opts,
+        false
+      );
+      this.prefix = markup;
+      return "";
+    }
+  });
 }
 
 function buildHtmlPreview(element, siteSettings) {