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package com.bluecatcode.common.base;

import com.google.common.base.Supplier;

/**
 * Optional supplier for exceptions
 * 
 * The supplier is designed to be used for more DSL-like usage of the following pattern:
 * 
 * {@code}
 *  *  Optional<Something> optionalSomething = ...;
 *  if (!optional.isPresent()) {
 *      throw new SomeException();
 *  }
 *  Something something = optionalSomething.get();
 * 
 * {@code}
 * As shown here:
 *  *  Something something = optionalSomething.or(throwA(Something.class, new SomeException()));
 * 
 *
 * @see com.google.common.base.Optional#or(Supplier)
 */
public class ExceptionSupplier implements Supplier {

    private final E exception;

    private ExceptionSupplier(E exception) {
        this.exception = exception;
    }

    /**
     * Factory method for usage during variable or field initialisation.
     *
     * @param exception exception to throw
     * @param        Supplied object type
     * @param        RuntimeException subtype
     * @return the exception supplier
     * @throws E the provided exception
     */
    public static  ExceptionSupplier throwA(E exception) {
        return new ExceptionSupplier<>(exception);
    }

    /**
     * Factory method for usage inside a method call
     *
     * @param type      class type used only for type inference
     * @param exception exception to throw
     * @param        Supplied object type
     * @param        RuntimeException subtype
     * @return the exception supplier
     * @throws E the provided exception
     */
    public static  ExceptionSupplier throwA(
            @SuppressWarnings("UnusedParameters") Class type, E exception) {
        return new ExceptionSupplier<>(exception);
    }

    /**
     *{@inheritDoc}
     */
    @Override
    public T get() {
        throw exception;
    }
}