alsatian-test/alsatian

import { Matcher } from "./matcher";
import { stringify } from "../stringification";

/**
 * Compares types that can be empty e.g. string, object and Array
 */
export class EmptyMatcher<T> extends Matcher<T> {
    /**
     * Checks that an array is empty, a string is empty, or an object literal has no properties
     */
    public toBeEmpty() {
        const actualValue = this.actualValue;
        const length = this.getLength(actualValue);

        this.registerMatcher(
            (length === 0) === this.shouldMatch,
            `Expected "${
                typeof actualValue === "string"
                    ? actualValue
                    : stringify(actualValue)
            }" ` + `${this.shouldMatch ? "" : "not "}to be empty.`,
            "value to be empty",
            {
                actualLength: length,
                expectedLength: this.shouldMatch ? 0 : "> 0"
            }
        );
    }

    private getLength(value: any) {
        if (value instanceof Map) {
            return value.size;
        }

        if (value.length !== undefined) {
            return value.length;
        }

        return Object.keys(value).length;
    }
}