/*
 * Copyright (c) 2011, 2012 Roberto Tyley
 *
 * This file is part of 'Agit' - an Android Git client.
 *
 * Agit is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Agit 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, see http://www.gnu.org/licenses/ .
 */

package com.madgag.agit.guice;

import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Scope;

import java.util.Map;

public abstract class ScopeBase implements Scope {
    private static final Provider<Object> SEEDED_KEY_PROVIDER = new Provider<Object>() {
        public Object get() {
            throw new IllegalStateException(
                    "If you got here then it means that"
                            + " your code asked for scoped object which should have been"
                            + " explicitly seeded in this scope, but was not.");
        }
    };

    /**
     * Returns a provider that always throws exception complaining that the
     * object in question must be seeded before it can be injected.
     *
     * @return typed provider
     */
    @SuppressWarnings({ "unchecked" })
    public static <T> Provider<T> seededKeyProvider() {
        return (Provider<T>) SEEDED_KEY_PROVIDER;
    }

    public <T> Provider<T> scope(final Key<T> key, final Provider<T> unscoped) {
        return new Provider<T>() {
            public T get() {
                Map<Key<?>, Object> scopedObjects = getScopedObjectMap(key);

                @SuppressWarnings("unchecked")
                T current = (T) scopedObjects.get(key);
                if (current == null && !scopedObjects.containsKey(key)) {
                    current = unscoped.get();
                    scopedObjects.put(key, current);
                }
                return current;
            }
        };
    }

    protected abstract <T> Map<Key<?>, Object> getScopedObjectMap(Key<T> key);
}