add guild settings helper

src/lib/guildSettings.js

@@ -0,0 +1,47 @@
+const {getGuildData, setGuildData} = require("./guildData.js");
+
+const flags = Object.freeze({
+  codePreviews: 1 << 0,
+  tweetUnrolling: 1 << 1,
+});
+
+async function getFlags(guildId) {
+  const value = await getGuildData(guildId, "settings_flags", 0);
+
+  const out = {};
+  for (const key in flags) {
+    out[key] = (value & flags[key]) !== 0;
+  }
+
+  return out;
+}
+
+async function hasFlag(guildId, key) {
+  return (
+    ((await getGuildData(guildId, "settings_flags", 0)) & flags[key]) !== 0
+  );
+}
+
+async function enableFlag(guildId, key) {
+  let value = await getGuildData(guildId, "settings_flags", 0);
+
+  value |= flags[key];
+
+  await setGuildData(guildId, "settings_flags", value);
+}
+
+async function disableFlag(guildId, key) {
+  let value = await getGuildData(guildId, "settings_flags", 0);
+
+  value ^= flags[key];
+
+  await setGuildData(guildId, "settings_flags", value);
+}
+
+module.exports = {
+  flags,
+  getFlags,
+  hasFlag,
+  enableFlag,
+  disableFlag,
+};