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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.jdisc.application;

import com.google.common.collect.ImmutableList;

import java.net.URI;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 * This is an immutable set of ordered bindings from {@link UriPattern}s to some target type T. To create an instance
 * of this class, you must 1) create a {@link BindingRepository}, 2) configure it using the {@link
 * BindingRepository#bind(String, Object)} method, and finally 3) call {@link BindingRepository#activate()}.
 *
 * @author Simon Thoresen
 */
public class BindingSet implements Iterable>  {

    public static final String DEFAULT = "default";
    private final Collection> bindings;

    BindingSet(Collection> bindings) {
        this.bindings = sort(bindings);
    }

    /**
     * Resolves the binding that best matches (see commentary on {@link BindingRepository#bind(String, Object)}) the
     * given {@link URI}, and returns a {@link BindingMatch} object that describes the match and contains the
     * matched target. If there is no binding that matches the given URI, this method returns null.
     *
     * @param uri The URI to match against the bindings in this set.
     * @return A {@link BindingMatch} object describing the match found, or null if not found.
     */
    public BindingMatch match(URI uri) {
        for (Map.Entry entry : bindings) {
            UriPattern pattern = entry.getKey();
            UriPattern.Match match = pattern.match(uri);
            if (match != null) {
                return new BindingMatch<>(match, entry.getValue(), pattern);
            }
        }
        return null;
    }

    /**
     * Resolves the binding that best matches (see commentary on {@link BindingRepository#bind(String, Object)}) the
     * given {@link URI}, and returns that target. If there is no binding that matches the given URI, this method
     * returns null.
     *
     * Apart from a null-guard, this is equal to return match(uri).target().
     *
     * @param uri The URI to match against the bindings in this set.
     * @return The best matched target, or null.
     * @see #match(URI)
     */
    public T resolve(URI uri) {
        BindingMatch match = match(uri);
        if (match == null) {
            return null;
        }
        return match.target();
    }

    @Override
    public Iterator> iterator() {
        return bindings.iterator();
    }

    private static  Collection> sort(Collection> unsorted) {
        List> ret = new LinkedList<>(unsorted);
        Collections.sort(ret, new Comparator>() {

            @Override
            public int compare(Map.Entry lhs, Map.Entry rhs) {
                return lhs.getKey().compareTo(rhs.getKey());
            }
        });
        return ImmutableList.copyOf(ret);
    }
}