/*
 * Copyright 2003-2007 the original author or authors.
 *
 * 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 org.codehaus.groovy.syntax;

import java.math.BigInteger;
import java.math.BigDecimal;

/**
 *  Helper class for processing Groovy numeric literals.
 *
 *  @author Brian Larson
 *  @author <a href="mailto:cpoirier@dreaming.org">Chris Poirier</a>
 *
 *  @version $Id$
 */

public class Numbers
{


  //---------------------------------------------------------------------------
  // LEXING SUPPORT


   /**
    *  Returns true if the specified character is a base-10 digit.
    */

    public static boolean isDigit( char c )
    {
        return c >= '0' && c <= '9';
    }


   /**
    *  Returns true if the specific character is a base-8 digit.
    */

    public static boolean isOctalDigit( char c )
    {
        return c >= '0' && c <= '7';
    }


   /**
    *  Returns true if the specified character is a base-16 digit.
    */

    public static boolean isHexDigit( char c )
    {
        return isDigit(c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
    }


   /**
    *  Returns true if the specified character is a valid type specifier
    *  for a numeric value.
    */

    public static boolean isNumericTypeSpecifier( char c, boolean isDecimal )
    {
        if( isDecimal )
        {
            switch( c )
            {
                case 'G':
                case 'g':
                case 'D':
                case 'd':
                case 'F':
                case 'f':
                    return true;
            }
        }
        else
        {
            switch( c )
            {
                case 'G':
                case 'g':
                case 'I':
                case 'i':
                case 'L':
                case 'l':
                    return true;
            }
        }

        return false;
    }


  //---------------------------------------------------------------------------
  // PARSING SUPPORT


    private static final BigInteger MAX_LONG    = BigInteger.valueOf(Long.MAX_VALUE);
    private static final BigInteger MIN_LONG    = BigInteger.valueOf(Long.MIN_VALUE);

    private static final BigInteger MAX_INTEGER = BigInteger.valueOf(Integer.MAX_VALUE);
    private static final BigInteger MIN_INTEGER = BigInteger.valueOf(Integer.MIN_VALUE);

    private static final BigDecimal MAX_DOUBLE  = new BigDecimal(String.valueOf(Double.MAX_VALUE));
    private static final BigDecimal MIN_DOUBLE  = MAX_DOUBLE.negate();

    private static final BigDecimal MAX_FLOAT   = new BigDecimal(String.valueOf(Float.MAX_VALUE));
    private static final BigDecimal MIN_FLOAT   = MAX_FLOAT.negate();


   /**
    *  Builds a Number from the given integer descriptor.  Creates the narrowest
    *  type possible, or a specific type, if specified.
    *
    *  @param  text literal text to parse
    *  @return instantiated Number object
    *  @throws NumberFormatException if the number does not fit within the type
    *          requested by the type specifier suffix (invalid numbers don't make
    *          it here)
    */

    public static Number parseInteger( String text )
    {
        char c = ' ';
        int length = text.length();


        //
        // Strip off the sign, if present

        boolean negative = false;
        if( (c = text.charAt(0)) == '-' || c == '+' )
        {
            negative = (c == '-');
            text = text.substring( 1, length );
            length -= 1;
        }


        //
        // Determine radix (default is 10).

        int radix = 10;
        if( text.charAt(0) == '0' && length > 1 )
        {
            if( (c = text.charAt(1)) == 'X' || c == 'x' )
            {
                radix = 16;
                text = text.substring( 2, length);
                length -= 2;
            }
            else
            {
                radix = 8;
            }
        }


        //
        // Strip off any type specifier and convert it to lower
        // case, if present.

        char type = 'x';  // pick best fit
        if( isNumericTypeSpecifier(text.charAt(length-1), false) )
        {
            type = Character.toLowerCase( text.charAt(length-1) );
            text = text.substring( 0, length-1);

            length -= 1;
        }


        //
        // Add the sign back, if necessary

        if( negative )
        {
            text = "-" + text;
        }


        //
        // Build the specified type or, if no type was specified, the
        // smallest type in which the number will fit.

        switch (type)
        {
            case 'i':
                return new Integer( Integer.parseInt(text, radix) );

            case 'l':
                return new Long( Long.parseLong(text, radix) );

            case 'g':
                return new BigInteger( text, radix );

            default:

                //
                // If not specified, we will return the narrowest possible
                // of Integer, Long, and BigInteger.

                BigInteger value = new BigInteger( text, radix );

                if( value.compareTo(MAX_INTEGER) <= 0 && value.compareTo(MIN_INTEGER) >= 0 )
                {
                    return new Integer(value.intValue());
                }
                else if( value.compareTo(MAX_LONG) <= 0 && value.compareTo(MIN_LONG) >= 0 )
                {
                    return new Long(value.longValue());
                }

                return value;
        }
    }


   /**
    *  Builds a Number from the given decimal descriptor.  Uses BigDecimal,
    *  unless, Double or Float is requested.
    *
    *  @param  text literal text to parse
    *  @return instantiated Number object
    *  @throws NumberFormatException if the number does not fit within the type
    *          requested by the type specifier suffix (invalid numbers don't make
    *          it here)
    */

    public static Number parseDecimal( String text )
    {
        int length = text.length();


        //
        // Strip off any type specifier and convert it to lower
        // case, if present.

        char type = 'x';
        if( isNumericTypeSpecifier(text.charAt(length-1), true) )
        {
            type = Character.toLowerCase( text.charAt(length-1) );
            text = text.substring( 0, length-1 );

            length -= 1;
        }


        //
        // Build the specified type or default to BigDecimal

        BigDecimal value = new BigDecimal( text );
        switch( type )
        {
            case 'f':
                if( value.compareTo(MAX_FLOAT) <= 0 && value.compareTo(MIN_FLOAT) >= 0)
                {
                    return new Float( text );
                }
                throw new NumberFormatException( "out of range" );

            case 'd':
                if( value.compareTo(MAX_DOUBLE) <= 0 && value.compareTo(MIN_DOUBLE) >= 0)
                {
                    return new Double( text );
                }
                throw new NumberFormatException( "out of range" );

            case 'g':
            default:
                return value;
        }
    }

}