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Cypher Shell
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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.
 *
 * This program 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 .
 */
package org.neo4j.shell.commands;

import java.util.Arrays;
import java.util.List;

import org.neo4j.shell.exception.CommandException;
import org.neo4j.shell.log.AnsiFormattedText;
import org.neo4j.shell.log.Logger;

import static org.neo4j.shell.commands.CommandHelper.simpleArgParse;

/**
 * Help command, which prints help documentation.
 */
public class Help implements Command
{
    public static final String COMMAND_NAME = ":help";
    public static final String CYPHER_MANUAL_LINK = "https://neo4j.com/docs/cypher-manual/current/";
    private final Logger logger;
    private final CommandHelper commandHelper;

    public Help( final Logger shell, final CommandHelper commandHelper )
    {
        this.logger = shell;
        this.commandHelper = commandHelper;
    }

    @Override
    public String getName()
    {
        return COMMAND_NAME;
    }

    @Override
    public String getDescription()
    {
        return "Show this help message";
    }

    @Override
    public String getUsage()
    {
        return "[command]";
    }

    @Override
    public String getHelp()
    {
        return "Show the list of available commands or help for a specific command.";
    }

    @Override
    public List getAliases()
    {
        return Arrays.asList( ":man" );
    }

    @Override
    public void execute( final String argString ) throws CommandException
    {
        String[] args = simpleArgParse( argString, 0, 1, COMMAND_NAME, getUsage() );
        if ( args.length == 0 )
        {
            printGeneralHelp();
        }
        else
        {
            printHelpFor( args[0] );
        }
    }

    private void printHelpFor( final String name ) throws CommandException
    {
        Command cmd = commandHelper.getCommand( name );
        if ( cmd == null && !name.startsWith( ":" ) )
        {
            // Be friendly to users and don't force them to type colons for help if possible
            cmd = commandHelper.getCommand( ":" + name );
        }

        if ( cmd == null )
        {
            throw new CommandException( AnsiFormattedText.from( "No such command: " ).bold( name ) );
        }

        logger.printOut( AnsiFormattedText.from( "\nusage: " )
                                          .bold( cmd.getName() )
                                          .append( " " )
                                          .append( cmd.getUsage() )
                                          .append( "\n\n" )
                                          .append( cmd.getHelp() )
                                          .append( "\n" )
                                          .formattedString() );
    }

    private void printGeneralHelp()
    {
        logger.printOut( "\nAvailable commands:" );

        // Get longest command so we can align them nicely
        List allCommands = commandHelper.getAllCommands();

        int leftColWidth = longestCmdLength( allCommands );

        allCommands.stream().forEach( cmd -> logger.printOut(
                AnsiFormattedText.from( "  " )
                                 .bold( String.format( "%-" + leftColWidth + "s", cmd.getName() ) )
                                 .append( " " + cmd.getDescription() )
                                 .formattedString() ) );

        logger.printOut( "\nFor help on a specific command type:" );
        logger.printOut( AnsiFormattedText.from( "    " )
                                          .append( COMMAND_NAME )
                                          .bold( " command" )
                                          .append( "\n" ).formattedString() );

        logger.printOut( "Use up and down arrows to access statement history." );

        logger.printOut( "\nFor help on cypher please visit:" );
        logger.printOut( AnsiFormattedText.from( "    " )
                                          .append( CYPHER_MANUAL_LINK )
                                          .append( "\n" ).formattedString() );
    }

    private static int longestCmdLength( List allCommands )
    {
        String longestCommand = allCommands.stream()
                                           .map( Command::getName )
                                           .reduce( "", ( s1, s2 ) -> s1.length() > s2.length() ? s1 : s2 );
        return longestCommand.length();
    }
}