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A light but powerful object mapper and SQL generator for Java/Android
There is a newer version: 1.6.0
/*
 * Copyright 2016 requery.io
 *
 * 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 io.requery.sql;

import io.requery.meta.Attribute;

import java.util.Arrays;
import java.util.Iterator;
import java.util.Locale;
import java.util.Set;

/**
 * String Builder for creating SQL statements.
 *
 * @author Nikhil Purushe
 */
public class QueryBuilder implements CharSequence {

    public interface Appender {
        void append(QueryBuilder qb, T value);
    }

    public static class Options {
        private final String quotedIdentifier;
        private final boolean lowercaseKeywords;
        private final boolean quoteTableNames;
        private final boolean quoteColumnNames;

        public Options(String quotedIdentifier,
                       boolean lowercaseKeywords,
                       boolean quoteTableNames,
                       boolean quoteColumnNames) {

            if (quotedIdentifier.equals(" ")) {
                quotedIdentifier = "\"";
            }
            this.quotedIdentifier = quotedIdentifier;
            this.lowercaseKeywords = lowercaseKeywords;
            this.quoteTableNames = quoteTableNames;
            this.quoteColumnNames = quoteColumnNames;
        }
    }

    private final StringBuilder sb;
    private final Options options;

    public QueryBuilder(Options options) {
        this.options = options;
        this.sb = new StringBuilder(32);
    }

    @SuppressWarnings("NullableProblems")
    @Override
    public String toString() {
        return sb.toString();
    }

    @Override
    public int length() {
        return sb.length();
    }

    @Override
    public char charAt(int index) {
        return sb.charAt(index);
    }

    @Override
    public CharSequence subSequence(int start, int end) {
        return sb.subSequence(start, end);
    }

    public QueryBuilder keyword(Keyword... keywords) {
        for (Keyword keyword : keywords) {
            sb.append(options.lowercaseKeywords ? keyword.toString().toLowerCase(Locale.US) : keyword);
            sb.append(" ");
        }
        return this;
    }

    public QueryBuilder appendIdentifier(String value, String identifier) {
        return append(identifier, false).append(value, false).append(identifier);
    }

    public QueryBuilder appendQuoted(String value) {
        return appendIdentifier(value, "\'");
    }

    public QueryBuilder tableName(Object value) {
        if(options.quoteTableNames) {
            appendIdentifier(value.toString(), options.quotedIdentifier);
        } else {
            append(value);
        }
        return space();
    }

    public QueryBuilder attribute(Attribute value) {
        if(options.quoteColumnNames) {
            appendIdentifier(value.name(), options.quotedIdentifier);
        } else {
            append(value.name());
        }
        return space();
    }

    public QueryBuilder aliasAttribute(String alias, Attribute value) {
        append(alias);
        append(".");
        return attribute(value);
    }

    public QueryBuilder append(Object value) {
        return append(value, false);
    }

    public QueryBuilder value(Object value) {
        return append(value, true);
    }

    public QueryBuilder append(Object value, boolean space) {
        if (value == null) {
            sb.append(Keyword.NULL);
        } else if (value instanceof String[]) {
            commaSeparated(Arrays.asList((String[]) value));
        } else {
            if (value instanceof Keyword) {
                sb.append(options.lowercaseKeywords ?
                        value.toString().toLowerCase(Locale.US) : value.toString());
            } else {
                sb.append(value.toString());
            }
        }
        if (space) {
            sb.append(" ");
        }
        return this;
    }

    public  QueryBuilder appendWhereConditions(Set> attributes) {
        int index = 0;
        for (Attribute attribute : attributes) {
            if (index > 0) {
                sb.append(Keyword.AND);
            }
            attribute(attribute);
            space();
            append("=?");
            space();
            index++;
        }
        return this;
    }

    public  QueryBuilder commaSeparatedAttributes(Iterable> values) {
        return commaSeparated(values, new QueryBuilder.Appender>() {
            @Override
            public void append(QueryBuilder qb, Attribute value) {
                qb.attribute(value);
            }
        });
    }

    public  QueryBuilder commaSeparated(Iterable values) {
        return commaSeparated(values, null);
    }

    public  QueryBuilder commaSeparated(Iterable values, Appender appender) {
        return commaSeparated(values.iterator(), appender);
    }

    public  QueryBuilder commaSeparated(Iterator values, Appender appender) {
        int i = 0;
        while (values.hasNext()) {
            T value = values.next();
            if (i > 0) {
                comma();
            }
            if (appender == null) {
                append(value);
            } else {
                appender.append(this, value);
            }
            i++;
        }
        return this;
    }

    public QueryBuilder openParenthesis() {
        sb.append("(");
        return this;
    }

    public QueryBuilder closeParenthesis() {
        if (sb.charAt(sb.length() - 1) == ' ') {
            sb.setCharAt(sb.length() - 1, ')');
        } else {
            sb.append(')');
        }
        return this;
    }

    public QueryBuilder space() {
        if (sb.charAt(sb.length() - 1) != ' ') {
            sb.append(" ");
        }
        return this;
    }

    public QueryBuilder comma() {
        if (sb.charAt(sb.length() - 1) == ' ') {
            sb.setCharAt(sb.length() - 1, ',');
        } else {
            sb.append(',');
        }
        space();
        return this;
    }
}