de.lgblaumeiser.ptm.cli.engine.CommandInterpreter.java Source code

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Here is the source code for de.lgblaumeiser.ptm.cli.engine.CommandInterpreter.java

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/*
 * Copyright by Lars Geyer-Blaumeiser <lgblaumeiser@gmail.com>
 *
 * Licensed under MIT license
 */
package de.lgblaumeiser.ptm.cli.engine;

import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.Maps.newHashMap;
import static java.util.Collections.unmodifiableMap;
import static org.apache.commons.lang3.StringUtils.isAlpha;
import static org.apache.commons.lang3.StringUtils.isNotBlank;

import java.util.Collection;
import java.util.Map;
import java.util.StringTokenizer;

/**
 * The central parsing and distributing component of the command line client
 */
public class CommandInterpreter {
    private final Map<String, CommandHandler> commandToHandlerMap = newHashMap();

    public void addCommandHandler(final String command, final CommandHandler handler) {
        checkState(isNotBlank(command));
        String commandId = command.toUpperCase();
        checkState(!commandToHandlerMap.containsKey(commandId));
        commandToHandlerMap.put(commandId, handler);
    }

    public Map<String, CommandHandler> listHandler() {
        return unmodifiableMap(commandToHandlerMap);
    }

    public void handle(final String command) {
        StringTokenizer tokens = createTokens(command);
        String commandToken = getCommandToken(tokens);
        CommandHandler handler = getHandler(commandToken);
        Collection<String> parameters = extractParameters(handler, tokens);
        handler.handleCommand(parameters);
    }

    private Collection<String> extractParameters(final CommandHandler handler, final StringTokenizer tokens) {
        Collection<String> back = newArrayList();
        while (tokens.hasMoreTokens()) {
            back.add(tokens.nextToken());
        }
        return back;
    }

    private CommandHandler getHandler(final String commandToken) {
        CommandHandler handler = commandToHandlerMap.get(commandToken);
        checkState(handler != null);
        return handler;
    }

    private String getCommandToken(final StringTokenizer tokens) {
        checkState(tokens.hasMoreTokens());
        String commandToken = tokens.nextToken().toUpperCase();
        checkState(isNotBlank(commandToken));
        checkState(isAlpha(commandToken));
        return commandToken;
    }

    private StringTokenizer createTokens(final String command) {
        return new StringTokenizer(command);
    }
}