refactor kstate, add stub user syncing function

matrix/kstate.js

@@ -0,0 +1,65 @@
+// @ts-check
+
+const assert = require("assert")
+
+/** Mutates the input. */
+function kstateStripConditionals(kstate) {
+	for (const [k, content] of Object.entries(kstate)) {
+		// conditional for whether a key is even part of the kstate (doing this declaratively on json is hard, so represent it as a property instead.)
+		if ("$if" in content) {
+			if (content.$if) delete content.$if
+			else delete kstate[k]
+		}
+	}
+	return kstate
+}
+
+function kstateToState(kstate) {
+	const events = []
+	kstateStripConditionals(kstate)
+	for (const [k, content] of Object.entries(kstate)) {
+		const [type, state_key] = k.split("/")
+		assert.ok(typeof type === "string")
+		assert.ok(typeof state_key === "string")
+		events.push({type, state_key, content})
+	}
+	return events
+}
+
+/**
+ * @param {import("../types").Event.BaseStateEvent[]} events
+ * @returns {any}
+ */
+function stateToKState(events) {
+	const kstate = {}
+	for (const event of events) {
+		kstate[event.type + "/" + event.state_key] = event.content
+	}
+	return kstate
+}
+
+function diffKState(actual, target) {
+	const diff = {}
+	// go through each key that it should have
+	for (const key of Object.keys(target)) {
+		if (key in actual) {
+			// diff
+			try {
+				assert.deepEqual(actual[key], target[key])
+			} catch (e) {
+				// they differ. reassign the target
+				diff[key] = target[key]
+			}
+		} else {
+			// not present, needs to be added
+			diff[key] = target[key]
+		}
+		// keys that are missing in "actual" will not be deleted on "target" (no action)
+	}
+	return diff
+}
+
+module.exports.kstateStripConditionals = kstateStripConditionals
+module.exports.kstateToState = kstateToState
+module.exports.stateToKState = stateToKState
+module.exports.diffKState = diffKState