import {Type} from '@nestjs/common';

import {getColumnsMapper, getPropertiesMapper} from './decorator.utils';

function assignWithMapper(dst: any, src: any, mapper: Record<string, string>) {
    if (!mapper) {
        return Object.assign(dst, src);
    }
    for (const key of Object.keys(src)) {
        const dstKey = mapper[key] || key;
        dst[dstKey] = src[key];
    }
    return dst;
}

export function transformTo<T>(target: Type<T>, entity: any[]): T[];

export function transformTo<T>(target: Type<T>, entity: any): T;

export function transformTo<T>(target: Type<T>, entity: any): T | T[] {
    if (!target || !(target && typeof target === 'function') || !entity) {
        return entity;
    }
    const mapper = getColumnsMapper(new target());
    if (Array.isArray(entity)) {
        return entity.map((entity) => assignWithMapper(new target(), entity, mapper));
    }
    return assignWithMapper(new target(), entity, mapper);
}

export function transformFrom<T>(target: Type<T>, entity: any[]): T[];

export function transformFrom<T>(target: Type<T>, entity: any): T;

export function transformFrom<T>(target: Type<T>, entity: any): T | T[] {
    if (!target || !(target && typeof target === 'function') || !entity) {
        return entity;
    }
    const mapper = getPropertiesMapper(new target());
    if (Array.isArray(entity)) {
        return entity.map((entity) => assignWithMapper(new target(), entity, mapper));
    }
    return assignWithMapper(new target(), entity, mapper);
}