package org.apache.poi.ss.usermodel;

import java.math.BigDecimal;

import java.math.MathContext;

import java.math.RoundingMode;

import java.text.DecimalFormat;

import java.text.DecimalFormatSymbols;

import java.text.FieldPosition;

import java.text.Format;

import java.text.ParsePosition;

import java.util.Locale;

/** A format that formats a double as Excel would, ignoring FieldPosition. All other operations are unsupported. */

public class ExcelGeneralNumberFormat extends Format {

    private static final long serialVersionUID = 1L;

    private static final DecimalFormat SCIENTIFIC_FORMAT = new DecimalFormat("0.#####E0");

    static {

        SCIENTIFIC_FORMAT.setRoundingMode(RoundingMode.HALF_UP);

    }

    private static final MathContext TO_10_SF = new MathContext(10, RoundingMode.HALF_UP);

    private final DecimalFormatSymbols decimalSymbols;

    private final Format wholeNumFormat;

    private final Format decimalNumFormat;

    public ExcelGeneralNumberFormat(final Locale locale) {

        decimalSymbols = new DecimalFormatSymbols(locale);

        wholeNumFormat = new DecimalFormat("#", decimalSymbols);

        decimalNumFormat = new DecimalFormat("#.##########", decimalSymbols);

    }

    public StringBuffer format(Object number, StringBuffer toAppendTo, FieldPosition pos) {

        final double value;

        if (number instanceof Number) {

            value = ((Number)number).doubleValue();

            if (Double.isInfinite(value) || Double.isNaN(value)) {

                return wholeNumFormat.format(number, toAppendTo, pos);

            }

        } else {

            // testBug54786 gets here with a date, so retain previous behaviour

            return wholeNumFormat.format(number, toAppendTo, pos);

        }

        final double abs = Math.abs(value);

        if (abs >= 1E11 || (abs <= 1E-10 && abs > 0)) {

            return SCIENTIFIC_FORMAT.format(number, toAppendTo, pos);

        } else if (Math.floor(value) == value || abs >= 1E10) {

            // integer, or integer portion uses all 11 allowed digits

            return wholeNumFormat.format(number, toAppendTo, pos);

        }

        // Non-integers of non-scientific magnitude are formatted as "up to 11

        // numeric characters, with the decimal point counting as a numeric

        // character". We know there is a decimal point, so limit to 10 digits.

        // https://support.microsoft.com/en-us/kb/65903

        final double rounded = new BigDecimal(value).round(TO_10_SF).doubleValue();

        return decimalNumFormat.format(rounded, toAppendTo, pos);

    }

    public Object parseObject(String source, ParsePosition pos) {

        throw new UnsupportedOperationException();

    }

}

    public void testLargeNumbersAndENotation() throws IOException{

      assertFormatsTo("1E+86", 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999d);

      assertFormatsTo("1E-84", 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000001d);

      // Smallest double

      assertFormatsTo("1E-323", 0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001d);

      // "up to 11 numeric characters, with the decimal point counting as a numeric character"

      // https://support.microsoft.com/en-us/kb/65903

      assertFormatsTo( "12345678911",   12345678911d);

      assertFormatsTo( "1.23457E+11",   123456789112d);  // 12th digit of integer -> scientific

      assertFormatsTo( "-12345678911", -12345678911d);

      assertFormatsTo( "-1.23457E+11", -123456789112d);

      assertFormatsTo( "0.1",           0.1);

      assertFormatsTo( "0.000000001",   0.000000001);

      assertFormatsTo( "1E-10",         0.0000000001);  // 12th digit

      assertFormatsTo( "-0.000000001", -0.000000001);

      assertFormatsTo( "-1E-10",       -0.0000000001);

      assertFormatsTo( "123.4567892",   123.45678919);  // excess decimals are simply rounded away

      assertFormatsTo("-123.4567892",  -123.45678919);

      assertFormatsTo( "123.4567893",   123.45678925);  // rounding mode is half-up

      assertFormatsTo("-123.4567893",  -123.45678925);

      assertFormatsTo( "1.23457E+19",   12345650000000000000d);

      assertFormatsTo("-1.23457E+19",  -12345650000000000000d);

      assertFormatsTo( "1.23457E-19",   0.0000000000000000001234565d);

      assertFormatsTo("-1.23457E-19",  -0.0000000000000000001234565d);

      assertFormatsTo( "1.000000001",   1.000000001);

      assertFormatsTo( "1",             1.0000000001);

      assertFormatsTo( "1234.567891",   1234.567891123456789d);

      assertFormatsTo( "1234567.891",   1234567.891123456789d);

      assertFormatsTo( "12345678912",   12345678911.63456789d);  // integer portion uses all 11 digits

      assertFormatsTo( "12345678913",   12345678912.5d);  // half-up here too

      assertFormatsTo("-12345678913",  -12345678912.5d);

      assertFormatsTo( "1.23457E+11",   123456789112.3456789d);

    }

    private static void assertFormatsTo(String expected, double input) throws IOException {

        Workbook wb = new HSSFWorkbook();

        try {

            Sheet s1 = wb.createSheet();

            Row row = s1.createRow(0);

            Cell rawValue = row.createCell(0);

            rawValue.setCellValue(input);

            CellStyle newStyle = wb.createCellStyle();

            DataFormat dataFormat = wb.createDataFormat();

            newStyle.setDataFormat(dataFormat.getFormat("General"));

            String actual = new DataFormatter().formatCellValue(rawValue);

            assertEquals(expected, actual);

        }

        finally {

            wb.close();

        }

    }