132 lines
4.3 KiB
Java
132 lines
4.3 KiB
Java
/*
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* Copyright 2021 The Android Open Source Project
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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 android.app.appsearch.util;
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import android.annotation.NonNull;
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import android.app.appsearch.annotation.CanIgnoreReturnValue;
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/**
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* Utility for building indented strings.
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*
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* <p>This is a wrapper for {@link StringBuilder} for appending strings with indentation. The
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* indentation level can be increased by calling {@link #increaseIndentLevel()} and decreased by
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* calling {@link #decreaseIndentLevel()}.
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*
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* <p>Indentation is applied after each newline character for the given indent level.
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*
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* @hide
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*/
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public class IndentingStringBuilder {
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private final StringBuilder mStringBuilder = new StringBuilder();
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// Indicates whether next non-newline character should have an indent applied before it.
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private boolean mIndentNext = false;
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private int mIndentLevel = 0;
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/** Increases the indent level by one for appended strings. */
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@CanIgnoreReturnValue
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@NonNull
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public IndentingStringBuilder increaseIndentLevel() {
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mIndentLevel++;
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return this;
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}
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/** Decreases the indent level by one for appended strings. */
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@CanIgnoreReturnValue
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@NonNull
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public IndentingStringBuilder decreaseIndentLevel() throws IllegalStateException {
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if (mIndentLevel == 0) {
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throw new IllegalStateException("Cannot set indent level below 0.");
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}
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mIndentLevel--;
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return this;
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}
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/**
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* Appends provided {@code String} at the current indentation level.
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*
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* <p>Indentation is applied after each newline character.
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*/
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@CanIgnoreReturnValue
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@NonNull
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public IndentingStringBuilder append(@NonNull String str) {
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applyIndentToString(str);
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return this;
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}
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/**
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* Appends provided {@code Object}, represented as a {@code String}, at the current indentation
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* level.
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*
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* <p>Indentation is applied after each newline character.
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*/
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@CanIgnoreReturnValue
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@NonNull
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public IndentingStringBuilder append(@NonNull Object obj) {
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applyIndentToString(obj.toString());
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return this;
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}
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@Override
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@NonNull
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public String toString() {
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return mStringBuilder.toString();
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}
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/** Adds indent string to the {@link StringBuilder} instance for current indent level. */
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private void applyIndent() {
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for (int i = 0; i < mIndentLevel; i++) {
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mStringBuilder.append(" ");
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}
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}
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/**
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* Applies indent, for current indent level, after each newline character.
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*
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* <p>Consecutive newline characters are not indented.
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*/
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private void applyIndentToString(@NonNull String str) {
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int index = str.indexOf("\n");
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if (index == 0) {
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// String begins with new line character: append newline and slide past newline.
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mStringBuilder.append("\n");
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mIndentNext = true;
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if (str.length() > 1) {
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applyIndentToString(str.substring(index + 1));
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}
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} else if (index >= 1) {
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// String contains new line character: divide string between newline, append new line,
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// and recurse on each string.
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String beforeIndentString = str.substring(0, index);
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applyIndentToString(beforeIndentString);
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mStringBuilder.append("\n");
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mIndentNext = true;
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if (str.length() > index + 1) {
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String afterIndentString = str.substring(index + 1);
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applyIndentToString(afterIndentString);
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}
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} else {
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// String does not contain newline character: append string.
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if (mIndentNext) {
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applyIndent();
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mIndentNext = false;
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}
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mStringBuilder.append(str);
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}
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}
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}
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