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A plugin API for Minecraft: Java Edition
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/*
 * This file is part of SpongeAPI, licensed under the MIT License (MIT).
 *
 * Copyright (c) SpongePowered 
 * Copyright (c) contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.spongepowered.api.service.context;

import org.spongepowered.configurate.util.UnmodifiableCollections;

import java.util.AbstractMap;
import java.util.Map;
import java.util.Objects;

/**
 * Encapsulates a single attribute about the state or circumstances of a
 * {@link Contextual}.
 *
 * A {@link Contextual}'s overall "context" is made up multiple
 * {@link Context} instances, usually stored together in a
 * {@link java.util.Set}.
 *
 * Any single {@link Context} attribute is made up of a key and a
 * value. The key represents the type of context, and the value is just
 * that, the value associated with the key. Some common/shared keys are
 * expressed as static fields on this class for convenience.
 *
 * For example, a context encapsulating a {@link Contextual}s circumstance
 * within a given world would have key of "world" and a value equal to the name
 * of the world.
 *
 * {@link Context} is immutable. The {@link #setValue(String)} inherited from
 * {@link java.util.Map.Entry} is not supported.
 */
public final class Context implements Map.Entry {

    public static final String USER_KEY = "user";
    public static final String WORLD_KEY = "world";
    public static final String DIMENSION_KEY = "dimension";
    public static final String REMOTE_IP_KEY = "remoteip";
    public static final String LOCAL_HOST_KEY = "localhost";
    public static final String LOCAL_IP_KEY = "localip";
    public static final String LOCAL_PORT_KEY = "localport";

    private final Map.Entry wrapped;

    /**
     * Create a new context instance.
     *
     * @param key Context key. Must not be null.
     * @param value Context value. Must not be null.
     */
    public Context(final String key, final String value) {
        Objects.requireNonNull(key, "key");
        Objects.requireNonNull(value, "value");
        this.wrapped = UnmodifiableCollections.immutableMapEntry(key, value);
    }

    /**
     * Gets the context key.
     *
     * @return The key
     */
    @Override
    public String getKey() {
        return this.wrapped.getKey();
    }

    /**
     * Gets the context value.
     *
     * @return The value
     */
    @Override
    public String getValue() {
        return this.wrapped.getValue();
    }

    /**
     * @deprecated Context does not support changing the values
     * @param value The value
     * @return Nothing
     * @throws UnsupportedOperationException Contexts are immutable
     */
    @Deprecated
    @Override
    public String setValue(final String value) {
        throw new UnsupportedOperationException("Contexts are immutable");
    }

    @Override
    public boolean equals(final Object other) {
        if (this == other) {
            return true;
        }
        return other instanceof Map.Entry && this.wrapped.equals(other);
    }

    @Override
    public int hashCode() {
        return this.wrapped.hashCode();
    }

    @Override
    public String toString() {
        return this.getKey() + "=" + this.getValue();
    }
}