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68 lines
2.5 KiB
68 lines
2.5 KiB
/*
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* Copyright (C) 2019 The Dagger Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dagger.example.atm;
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import dagger.example.atm.Command.Result;
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import dagger.example.atm.Command.Status;
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import java.util.ArrayDeque;
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import java.util.Deque;
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import javax.inject.Inject;
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import javax.inject.Singleton;
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/**
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* Processes successive commands by delegating to a {@link CommandRouter}.
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*
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* <p>Whereas {@link CommandRouter} routes an input string to a particular {@link Command}, this
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* class maintains inter-command state to determine which {@link CommandRouter} should route
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* successive commands.
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*
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* <p>This class is {@link Singleton} scoped because it has mutable state ({@code
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* commandRouterStack}), and all users of {@link CommandProcessor} must use the same instance.
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*/
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@Singleton
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final class CommandProcessor {
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private final Deque<CommandRouter> commandRouterStack = new ArrayDeque<>();
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@Inject
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CommandProcessor(CommandRouter firstCommandRouter) {
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commandRouterStack.push(firstCommandRouter);
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}
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Status process(String input) {
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if (commandRouterStack.isEmpty()) {
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throw new IllegalStateException("No command router is available!");
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}
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Result result = commandRouterStack.peek().route(input);
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switch (result.status()) {
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case INPUT_COMPLETED:
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commandRouterStack.pop();
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return commandRouterStack.isEmpty() ? Status.INPUT_COMPLETED : Status.HANDLED;
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case HANDLED:
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// TODO(ronshapiro): We currently have a case of using a subcomponent for nested commands,
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// which requires maintaining a binding indicating whether we are in the subcomponent are
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// not. We can include another example where there's a CommandRouter that is created from an
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// entirely different component, that way there are no inherited commands.
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result.nestedCommandRouter().ifPresent(commandRouterStack::push);
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// fall through
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case INVALID:
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return result.status();
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}
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throw new AssertionError(result.status());
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}
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}
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