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/*
 * Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
 */

package io.permazen.util;

import com.google.common.base.Preconditions;

import java.util.function.Function;

/**
 * A {@link Function} that casts objects to some type.
 */
public class CastFunction implements Function {

    protected final Class type;

    /**
     * Constructor.
     *
     * @param type desired type
     * @throws IllegalArgumentException if {@code type} is null
     */
     public CastFunction(Class type) {
        Preconditions.checkArgument(type != null, "null type");
        this.type = type;
    }

    @Override
    public T apply(Object obj) {
        if (obj == null)
            return null;
        try {
            return this.type.cast(obj);
        } catch (ClassCastException e) {
            throw this.handleFailure(obj, e);
        }
    }

    public com.google.common.base.Function toGuava() {
        return this::apply;
    }

    /**
     * Generate an exception to throw when a cast failure occurs.
     *
     * 
     * The implementation in {@link CastFunction} just throws {@code e}.
     *
     * @param obj object on which cast failed
     * @param e resulting exception
     * @return exception to throw
     */
    protected RuntimeException handleFailure(Object obj, ClassCastException e) {
        return e;
    }
}