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Core package for Neo4j Procedures
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * 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 apoc.number;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.ParseException;
import java.util.Arrays;
import java.util.Locale;
import org.apache.commons.lang3.StringUtils;
import org.neo4j.procedure.Description;
import org.neo4j.procedure.Name;
import org.neo4j.procedure.UserFunction;

/**
 *
 * @since 25.8.2016
 * @author inserpio
 */
public class Numbers {

    @UserFunction("apoc.number.format")
    @Description("Formats the given `INTEGER` or `FLOAT` using the given pattern and language to produce a `STRING`.")
    public String format(
            final @Name("number") Object value,
            @Name(value = "pattern", defaultValue = "") String pattern,
            @Name(value = "language", defaultValue = "") String lang) {
        Number number = validateNumberParam(value);
        if (number == null) return null;
        DecimalFormat format = buildFormatter(pattern, lang);
        if (format == null) return null;
        return format.format(number);
    }

    @UserFunction("apoc.number.parseInt")
    @Description("Parses the given `STRING` using the given pattern and language to produce a `INTEGER`.")
    public Long parseInt(
            final @Name("text") String text,
            @Name(value = "pattern", defaultValue = "") String pattern,
            @Name(value = "language", defaultValue = "") String lang) {
        Number res = parseNumber(text, pattern, lang);
        return res == null ? null : res.longValue();
    }

    private Number parseNumber(
            @Name("text") String text,
            @Name(value = "pattern", defaultValue = "") String pattern,
            @Name(value = "lang", defaultValue = "") String lang) {
        if (StringUtils.isBlank(text)) {
            return null;
        }
        try {
            return buildFormatter(pattern, lang).parse(text);
        } catch (ParseException e) {
            return null;
        }
    }

    @UserFunction("apoc.number.parseFloat")
    @Description("Parses the given `STRING` using the given pattern and language to produce a `FLOAT`.")
    public Double parseFloat(
            final @Name("text") String text,
            @Name(value = "pattern", defaultValue = "") String pattern,
            @Name(value = "language", defaultValue = "") String lang) {
        Number res = parseNumber(text, pattern, lang);
        return res == null ? null : res.doubleValue();
    }

    private Number validateNumberParam(Object number) {
        return number instanceof Number ? (Number) number : null;
    }

    private DecimalFormat buildFormatter(String pattern, String language) {
        if ("".equals(pattern)) pattern = null;
        if ("".equals(language)) language = "en";

        Locale locale = null;
        if (language != null) {
            if (!Arrays.asList(Locale.getISOLanguages()).contains(language)) {
                return null; // throw new IllegalArgumentException("Unrecognized language value: '" + language + "'
                // isn't a valid ISO language");
            }
            locale = new Locale(language);
        }

        DecimalFormatSymbols symbols = null;
        if (locale != null) {
            symbols = new DecimalFormatSymbols(locale);
        }

        DecimalFormat format = null;
        if (pattern == null && symbols == null) {
            format = new DecimalFormat();
        } else if (pattern == null) {
            format = new DecimalFormat();
            format.setDecimalFormatSymbols(symbols);
        } else if (symbols == null) {
            format = new DecimalFormat(pattern);
        } else {
            format = new DecimalFormat(pattern, symbols);
        }

        return format;
    }
}