import createSpy = jasmine.createSpy;
import createSpyObj = jasmine.createSpyObj;

/**
 * Spy on a field which has a getter defined.
 * A getter is required as spying on a field of an object without a getter is not supported in jasmine.
 * @param spy Object on which you wish to spy.
 * @param fieldToSpyOn Name of the field (getter) you want to spy on.
 * @param callback The new return value of the field (getter).
 */
export function spyOnField(spy: any, fieldToSpyOn: string, callback: any): void {
    let oldFieldDescriptor = Object.getOwnPropertyDescriptor(spy, fieldToSpyOn);
    Object.defineProperty(spy, fieldToSpyOn, {
        set: oldFieldDescriptor.set,
        get: callback
    });
}


/**
 * Creates a spy for a desired object on which we automatically add all functions present on the class to the spy.
 * @param spyName The name of the spy you are creating.
 * @param classToSpyOn The class of the spy you are creating.
 * @returns {any|T} Your newly created spy object.
 */
export function createSpyForObject(spyName: string, classToSpyOn: any): any {
    // Spy on all functions belonging to the specified class
    let functions = [];
    for (let i in classToSpyOn.prototype) {
        functions.push(i);
    }

    // Create the spy for the specified class
    return createSpyObj(spyName, functions);
}