DependencySolverBuilder.java

/*
 * Grapht, an open source dependency injector.
 * Copyright 2014-2015 various contributors (see CONTRIBUTORS.txt)
 * Copyright 2010-2014 Regents of the University of Minnesota
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
package org.grouplens.grapht.solver;

import org.grouplens.grapht.CachePolicy;
import org.grouplens.grapht.util.Preconditions;

import javax.annotation.Nonnull;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

/**
 * A builder for {@link DependencySolver}s.
 *
 * @see org.grouplens.grapht.solver.DependencySolver#newBuilder()
 * @since 0.6
 * @author <a href="http://grouplens.org">GroupLens Research</a>
 */
public class DependencySolverBuilder {
    private List<BindingFunction> bindingFunctions = new LinkedList<BindingFunction>();
    private List<BindingFunction> triggerFunctions = new LinkedList<BindingFunction>();
    private CachePolicy defaultPolicy = CachePolicy.NO_PREFERENCE;
    private int maxDepth = 100;

    /**
     * Get the current list of binding functions.
     * @return The current list of binding functions.
     */
    public List<BindingFunction> getBindingFunctions() {
        return Collections.unmodifiableList(bindingFunctions);
    }

    /**
     * Get the current list of trigger binding functions.  These are the binding functions for which
     * {@code canTriggerRewrite} is {@code true} in {@link #addBindingFunction(BindingFunction,boolean)}.
     *
     * @return The current list of trigger binding functions.
     */
    public List<BindingFunction> getTriggerFunctions() {
        return Collections.unmodifiableList(triggerFunctions);
    }

    /**
     * Add a binding function to the dependency solver.
     * @param func The binding function.
     * @return The builder (for chaining).
     */
    public DependencySolverBuilder addBindingFunction(@Nonnull BindingFunction func) {
        return addBindingFunction(func, true);
    }

    /**
     * Add a binding function to the dependency solver.
     * @param func The binding function.
     * @param canTriggerRewrite Controls whether this binding function can activate re-resolution
     *                          when doing a graph rewrite.  If {@code true} (the value passed by
     *                          all other binding function adders), this binding function returning
     *                          a binding will cause a graph rewrite; if {@code false}, it will be
     *                          ignored during rewrites until the rewrite has been triggered by some
     *                          other binding function.  Register the default binding function with
     *                          {@code false} here to keep default bindings from triggering rewrites.
     * @return The builder (for chaining).
     */
    public DependencySolverBuilder addBindingFunction(@Nonnull BindingFunction func,
                                                      boolean canTriggerRewrite) {
        Preconditions.notNull("binding function", func);
        bindingFunctions.add(func);
        if (canTriggerRewrite) {
            triggerFunctions.add(func);
        }
        return this;
    }

    /**
     * Add multiple binding function to the dependency solver.
     * @param funcs The binding functions.
     * @return The builder (for chaining).
     */
    public DependencySolverBuilder addBindingFunctions(@Nonnull BindingFunction... funcs) {
        return addBindingFunctions(Arrays.asList(funcs));
    }

    /**
     * Add multiple binding function to the dependency solver.
     * @param funcs The binding functions.
     * @return The builder (for chaining).
     */
    public DependencySolverBuilder addBindingFunctions(@Nonnull Iterable<BindingFunction> funcs) {
        for (BindingFunction fn: funcs) {
            addBindingFunction(fn);
        }
        return this;
    }

    /**
     * Get the current default policy.
     * @return The builder's current default policy.
     */
    public CachePolicy getDefaultPolicy() {
        return defaultPolicy;
    }

    /**
     * Set the default policy for the solver.  This policy will be used when a satisfaction has a
     * policy of {@link CachePolicy#NO_PREFERENCE}.  The default is {@link CachePolicy#NO_PREFERENCE},
     * so the injector will make final caching decisions.
     * @param policy The default policy for the solver.
     * @return The builder (for chaining).
     */
    public DependencySolverBuilder setDefaultPolicy(CachePolicy policy) {
        defaultPolicy = policy;
        return this;
    }

    /**
     * Get the maximum depth.
     * @return The maximum object graph depth.
     */
    public int getMaxDepth() {
        return maxDepth;
    }

    /**
     * Set the maximum object graph depth, for cycle detection.
     * @param depth The maximum object graph depth that the solver is allowed to produce.
     * @return The builder (for chaining).
     */
    public DependencySolverBuilder setMaxDepth(int depth) {
        if (depth < 1) {
            throw new IllegalArgumentException("max depth must be at least 1");
        }
        maxDepth = depth;
        return this;
    }

    /**
     * Build a dependency solver.
     * @return The dependency solver.
     */
    public DependencySolver build() {
        return new DependencySolver(bindingFunctions, triggerFunctions, defaultPolicy, maxDepth);
    }
}