zenno/lib: legacy and affinity stuff

zenno/src/lib/data/affinity.ts

@@ -0,0 +1,35 @@
+import globalJSON from '../../../../global/affinity.json';
+
+/**
+ * Precomputed character pair and trio affinity.
+ */
+export interface Affinity {
+	/**
+	 * First character in the relation.
+	 */
+	chara_a: number;
+	/**
+	 * Second character in the relation.
+	 * chara_a < chara_b is an invariant.
+	 */
+	chara_b: number;
+	/**
+	 * Third character in the relation, if it is a trio relation.
+	 * If defined, chara_b < chara_c is an invariant.
+	 */
+	chara_c?: number;
+	/**
+	 * Total base compatibility between characters in the relation.
+	 */
+	affinity: number;
+}
+
+export const affinity = {
+	global: globalJSON as Affinity[],
+} as const;
+
+export function lookup(aff: Affinity[], chara_a: number, chara_b: number, chara_c?: number): number {
+	const [a, b, c] = [chara_a, chara_b, chara_c ?? Infinity].sort((a, b) => a - b);
+	const r = aff.find((v) => v.chara_a === a && v.chara_b === b && (v.chara_c ?? Infinity) === c);
+	return r?.affinity ?? 0;
+}