thi-ng/umbrella

import type { IObjectOf } from "@thi.ng/api";

/**
 * Higher order helper function for {@link rename} transducer. Takes an object
 * of key mappings and returns function applying these mapping/renames.
 *
 * @remarks
 * Keys in `kmap` are the new/renamed keys, their values the original names. For
 * keys which simply should be kept, but not renamed, set their value to `true`.
 *
 * @param kmap -
 */
export const renamer = (kmap: IObjectOf<PropertyKey | boolean>) => {
    const ks = Object.keys(kmap);
    const [a2, b2, c2] = ks;
    const [a1, b1, c1] = ks.map((k) =>
        kmap[k] === true ? k : <PropertyKey>kmap[k]
    );
    switch (ks.length) {
        case 3:
            return (x: any) => {
                const res: any = {};
                let v;
                (v = x[c1]) !== undefined && (res[c2] = v);
                (v = x[b1]) !== undefined && (res[b2] = v);
                (v = x[a1]) !== undefined && (res[a2] = v);
                return res;
            };
        case 2:
            return (x: any) => {
                const res: any = {};
                let v;
                (v = x[b1]) !== undefined && (res[b2] = v);
                (v = x[a1]) !== undefined && (res[a2] = v);
                return res;
            };
        case 1:
            return (x: any) => {
                const res: any = {};
                let v;
                (v = x[a1]) !== undefined && (res[a2] = v);
                return res;
            };
        default:
            return (x: any) => {
                let k, kk, v;
                const res: any = {};
                for (let i = ks.length - 1; i >= 0; i--) {
                    k = ks[i];
                    kk = kmap[k];
                    (v = x[kk === true ? k : <PropertyKey>kk]) !== undefined &&
                        (res[k] = v);
                }
                return res;
            };
    }
};