import { ValidationOptions } from "../ValidationOptions";
import { buildMessage, ValidateBy } from "../common/ValidateBy";

export const IS_INSTANCE = "isInstance";

/**
 * Checks if the value is an instance of the specified object.
 */
export function isInstance(object: unknown, targetTypeConstructor: new (...args: any[]) => any): boolean {
    return targetTypeConstructor
        && typeof targetTypeConstructor === "function"
        && object instanceof targetTypeConstructor;
}

/**
 * Checks if the value is an instance of the specified object.
 */
export function IsInstance(targetType: new (...args: any[]) => any, validationOptions?: ValidationOptions): PropertyDecorator {
    return ValidateBy(
        {
            name: IS_INSTANCE,
            constraints: [targetType],
            validator: {
                validate: (value, args): boolean => isInstance(value, args.constraints[0]),
                defaultMessage: buildMessage(
                    (eachPrefix, args) => {
                        if (args.constraints[0]) {
                            return eachPrefix + `$property must be an instance of ${args.constraints[0].name}`;
                        } else {
                            return eachPrefix + `${IS_INSTANCE} decorator expects and object as value, but got falsy value.`;
                        }
                    },
                    validationOptions
                )
            }
        },
        validationOptions
    );
}