re #43

ismism.ts/src/eid/re.ts

@@ -0,0 +1,29 @@
+import type { Re, Usr } from "./typ.ts"
+import type { Update } from "./db.ts"
+import { is_id, is_lim } from "./is.ts"
+import { lim_re } from "./is.ts"
+
+export type UpdateRe = {
+	re: keyof Re,
+	op: "add" | "set" | "pull",
+	uid: Usr["_id"],
+}
+
+export function re_u(
+	re: Re,
+	u: UpdateRe,
+): Update<Re> | null {
+	if (!is_id(u.uid)) return null
+	const r = re[u.re]
+	switch (u.op) {
+		case "add": {
+			if (r && !is_lim(r.length + 1, lim_re)) return null
+			return { $addToSet: { [u.re]: u.uid } }
+		} case "set": {
+			return { $set: { [u.re]: [u.uid] } }
+		} case "pull": {
+			if (!r || !r.includes(u.uid)) return null
+			return r.length === 1 ? { $unset: { [u.re]: "" } } : { $pull: { [u.re]: u.uid } }
+		}
+	}
+}