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Groovy: A powerful, dynamic language for the JVM
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/*
 * Copyright 2003-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package groovy.util;

import groovy.lang.GroovyRuntimeException;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;

/**
 * A helper class for printing indented text. This can be used stand-alone or, more commonly, from Builders.
 *
 * By default, a PrintWriter to System.out is used as the Writer, but it is possible
 * to change the Writer by passing a new one as a constructor argument.
 *
 * Indention by default is 2 characters but can be changed by passing a
 * different value as a constructor argument.
 *
 * The following is an example usage. Note that within a "with" block you need to
 * specify a parameter name so that this.println is not called instead of IndentPrinter.println: 
 *  * new IndentPrinter(new PrintWriter(out)).with { p ->
 *     p.printIndent()
 *     p.println('parent1')
 *     p.incrementIndent()
 *     p.printIndent()
 *     p.println('child 1')
 *     p.printIndent()
 *     p.println('child 2')
 *     p.decrementIndent()
 *     p.printIndent()
 *     p.println('parent2')
 *     p.flush()
 * }
 * 
 * The above example prints this to standard output: 
 *  * parent1
 *   child 1
 *   child 2
 * parent2
 * 
 * @author James Strachan
 */
public class IndentPrinter {

    private int indentLevel;
    private String indent;
    private Writer out;
    private final boolean addNewlines;

    /**
     * Creates an IndentPrinter backed by a PrintWriter pointing to System.out, with an indent of two spaces.
     *
     * @see #IndentPrinter(Writer, String)
     */
    public IndentPrinter() {
        this(new PrintWriter(System.out), "  ");
    }

    /**
     * Creates an IndentPrinter backed by the supplied Writer, with an indent of two spaces.
     *
     * @param out Writer to output to
     * @see #IndentPrinter(Writer, String)
     */
    public IndentPrinter(Writer out) {
        this(out, "  ");
    }

    /**
     * Creates an IndentPrinter backed by the supplied Writer,
     * with a user-supplied String to be used for indenting.
     *
     * @param out Writer to output to
     * @param indent character(s) used to indent each line
     */
    public IndentPrinter(Writer out, String indent) {
        this(out, indent, true);
    }

    /**
     * Creates an IndentPrinter backed by the supplied Writer,
     * with a user-supplied String to be used for indenting
     * and the ability to override newline handling.
     *
     * @param out Writer to output to
     * @param indent character(s) used to indent each line
     * @param addNewlines set to false to gobble all new lines (default true)
     */
    public IndentPrinter(Writer out, String indent, boolean addNewlines) {
        this.addNewlines = addNewlines;
        if (out == null) {
            throw new IllegalArgumentException("Must specify a Writer");
        }
        this.out = out;
        this.indent = indent;
    }

    /**
     * Prints a string followed by an end of line character.
     *
     * @param  text String to be written
     */
    public void println(String text) {
        try {
            out.write(text);
            println();
        } catch(IOException ioe) {
            throw new GroovyRuntimeException(ioe);
        }
    }

    /**
     * Prints a string.
     *
     * @param  text String to be written
     */
    public void print(String text) {
        try {
            out.write(text);
        } catch(IOException ioe) {
            throw new GroovyRuntimeException(ioe);
        }
    }

    /**
     * Prints a character.
     *
     * @param  c char to be written
     */
    public void print(char c) {
        try {
            out.write(c);
        } catch(IOException ioe) {
            throw new GroovyRuntimeException(ioe);
        }
    }

    /**
     * Prints the current indent level.
     */
    public void printIndent() {
        for (int i = 0; i < indentLevel; i++) {
            try {
                out.write(indent);
            } catch(IOException ioe) {
                throw new GroovyRuntimeException(ioe);
            }
        }
    }

    /**
     * Prints an end-of-line character (if enabled via addNewLines property).
     * Defaults to outputting a single '\n' character but by using a custom
     * Writer, e.g. PlatformLineWriter, you can get platform-specific
     * end-of-line characters.
     *
     * @see #IndentPrinter(Writer, String, boolean)
     */
    public void println() {
        if (addNewlines) {
            try {
                out.write("\n");
            } catch(IOException ioe) {
                throw new GroovyRuntimeException(ioe);
            }
        }
    }

    public void incrementIndent() {
        ++indentLevel;
    }

    public void decrementIndent() {
        --indentLevel;
    }

    public int getIndentLevel() {
        return indentLevel;
    }

    public void setIndentLevel(int indentLevel) {
        this.indentLevel = indentLevel;
    }

    public void flush() {
        try {
            out.flush();
        } catch(IOException ioe) {
            throw new GroovyRuntimeException(ioe);
        }
    }
}