Sync pins back from Matrix to Discord

src/m2d/converters/diff-pins.js

@@ -0,0 +1,17 @@
+// @ts-check
+
+/**
+ * @param {string[]} pins
+ * @param {string[]} prev
+ * @returns {[string, boolean][]}
+ */
+function diffPins(pins, prev) {
+	/** @type {[string, boolean][]} */
+	const result = []
+	return result.concat(
+		prev.filter(id => !pins.includes(id)).map(id => [id, false]), // removed
+		pins.filter(id => !prev.includes(id)).map(id => [id, true]) // added
+	)
+}
+
+module.exports.diffPins = diffPins

src/m2d/converters/diff-pins.test.js

@@ -0,0 +1,11 @@
+// @ts-check
+
+const {test} = require("supertape")
+const diffPins = require("./diff-pins")
+
+test("diff pins: diff is as expected", t => {
+	t.deepEqual(
+		diffPins.diffPins(["same", "new"], ["same", "old"]),
+		[["old", false], ["new", true]]
+	)
+})