import 'reflect-metadata'

export interface Constructor<T> {
    new(...args: any[]): T
}

type ClassDecorator<T extends Function> = (Target: Constructor<T>) => T | void

export const Injectable = (): ClassDecorator<any> => {
    return target => {}
}

export const Injector = new class {
    resolve<T>(Target: Constructor<T>) : T {
        const requiredParams = Reflect.getMetadata('design:paramtypes', Target) || []
        const resolvedParams = requiredParams.map((param: any) => Injector.resolve(param))
        const instance = new Target(...resolvedParams)
        return instance
    }
}()

/////////////////

@Injectable()
class NoDeps {
    doSth() {
        console.log(`I'm NoDeps!`);
    }
}

@Injectable()
class OneDep {
    constructor(public noDeps: NoDeps) {}
    doSth() {
        console.log(`I'm OneDep!`);
    }
}

@Injectable()
class MoarDeps {
    constructor(public noDeps: NoDeps, public oneDep: OneDep) {}
    doSth() {
        console.log(`I'm MoarDeps!`);
    }
}

const moarDeps = Injector.resolve(MoarDeps)
moarDeps.noDeps.doSth();
moarDeps.oneDep.doSth();
moarDeps.oneDep.noDeps.doSth();