java/src/com/android/textclassifier/utils/IndentingPrintWriter.java

/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * 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 com.android.textclassifier.utils;

import androidx.core.util.Preconditions;

import java.io.PrintWriter;

/**
 * A print writer that supports indentation.
 *
 * @see PrintWriter
 */
public final class IndentingPrintWriter {
    private static final String SINGLE_INDENT = "  ";

    private final PrintWriter mWriter;
    private StringBuilder mIndentBuilder = new StringBuilder();
    private String mCurrentIndent = "";

    public IndentingPrintWriter(PrintWriter writer) {
        mWriter = Preconditions.checkNotNull(writer);
    }

    /** Prints a string. */
    public IndentingPrintWriter println(String string) {
        mWriter.print(mCurrentIndent);
        mWriter.print(string);
        mWriter.println();
        return this;
    }

    /** Prints a empty line */
    public IndentingPrintWriter println() {
        mWriter.println();
        return this;
    }

    /** Increases indents for subsequent texts. */
    public IndentingPrintWriter increaseIndent() {
        mIndentBuilder.append(SINGLE_INDENT);
        mCurrentIndent = mIndentBuilder.toString();
        return this;
    }

    /** Decreases indents for subsequent texts. */
    public IndentingPrintWriter decreaseIndent() {
        mIndentBuilder.delete(0, SINGLE_INDENT.length());
        mCurrentIndent = mIndentBuilder.toString();
        return this;
    }

    /** Prints a key-valued pair. */
    public IndentingPrintWriter printPair(String key, Object value) {
        println(String.format("%s=%s", key, String.valueOf(value)));
        return this;
    }

    /** Flushes the stream. */
    public void flush() {
        mWriter.flush();
    }
}