001/*
002 * Units of Measurement Reference Implementation
003 * Copyright (c) 2005-2020, Units of Measurement project.
004 *
005 * All rights reserved.
006 *
007 * Redistribution and use in source and binary forms, with or without modification,
008 * are permitted provided that the following conditions are met:
009 *
010 * 1. Redistributions of source code must retain the above copyright notice,
011 *    this list of conditions and the following disclaimer.
012 *
013 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
014 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
015 *
016 * 3. Neither the name of JSR-385, Indriya nor the names of their contributors may be used to endorse or promote products
017 *    derived from this software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
020 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
021 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
022 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
023 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
026 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
028 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package tech.units.indriya.internal.format;
031
032import java.math.BigDecimal;
033import java.math.BigInteger;
034import java.text.NumberFormat;
035import java.text.ParseException;
036import java.text.ParsePosition;
037import java.util.Stack;
038
039import javax.measure.format.MeasurementParseException;
040
041import tech.units.indriya.format.SimpleQuantityFormat;
042import tech.units.indriya.function.RationalNumber;
043import tech.units.indriya.internal.function.calc.Calculator;
044
045/**
046 * Support class for {@link SimpleQuantityFormat} and {@link RationalNumberFormat}.
047 * <p>
048 * In addition to decimal formats this also parses rational number format {@code 5÷3} or  {@code -5÷3}.
049 * 
050 * @author Andi Huber
051 *
052 */
053public class RationalNumberScanner {
054
055    private final CharSequence csq; 
056    private final ParsePosition cursor;
057    private final NumberFormat numberFormat;
058    
059    private boolean divisionCharacterDetected = false;
060    
061    public RationalNumberScanner(CharSequence csq, ParsePosition cursor, NumberFormat numberFormat) {
062        this.csq = csq;
063        this.cursor = cursor;
064        this.numberFormat = numberFormat;
065    }
066    
067    private int scanForStart(int pos) {
068        while (pos < csq.length()) {
069            char c = csq.charAt(pos);
070            if(!Character.isWhitespace(c)) {
071                return pos;
072            }
073            pos++;
074        }
075        return pos;       
076    }
077    
078    private int scanForEnd(int pos) {
079        divisionCharacterDetected = false;
080        while (pos < csq.length()) {
081            char c = csq.charAt(pos);
082            if(c == RationalNumber.DIVISION_CHARACTER) {
083                divisionCharacterDetected = true;
084                break;
085            }
086            if(Character.isWhitespace(c)) {
087                break;
088            } 
089            pos++;
090        }
091        cursor.setIndex(pos + 1);
092        return pos;        
093    }
094
095    public Number getNumber() {
096        
097        Stack<String> numberLiterals = new Stack<>();
098                
099        do {
100            int startDecimal = scanForStart(cursor.getIndex());
101            int endDecimal = scanForEnd(startDecimal+1);
102            
103            String numberLiteral = csq.subSequence(startDecimal, endDecimal).toString();
104            
105            numberLiterals.push(numberLiteral);
106            
107        } while (divisionCharacterDetected);
108        
109        if(numberLiterals.size()==2) {
110            // parsing RationalNumber
111            
112            BigInteger divisor = new BigInteger(numberLiterals.pop());
113            BigInteger dividend = new BigInteger(numberLiterals.pop());
114            return RationalNumber.of(dividend, divisor);
115        }
116
117        if(numberLiterals.size()==1) {
118            // parsing decimal number
119            
120            String numberLiteral = numberLiterals.pop();
121            
122            if(numberFormat==null) {
123                try {
124                    Number bigDecimal = new BigDecimal(numberLiteral);
125                    return Calculator.of(bigDecimal).peek();
126                } catch (Exception e) {
127                    throw new MeasurementParseException("Failed to parse number-literal '"+numberLiteral+"'.");
128                }
129            } 
130            
131            try {
132                return numberFormat.parse(numberLiteral);
133            } catch (ParseException e) {
134                throw new MeasurementParseException(e);
135            }
136            
137        }
138        
139        throw new MeasurementParseException("Unexpected number of number-literals in '" + csq + "'");
140        
141    }
142    
143}