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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.calculator2;
     18 
     19 import android.text.SpannableStringBuilder;
     20 import android.text.Editable;
     21 
     22 class CalculatorEditable extends SpannableStringBuilder {
     23     private static final char[] ORIGINALS    = {'-',      '*',      '/'};
     24     private static final char[] REPLACEMENTS = {'\u2212', '\u00d7', '\u00f7'};
     25     private boolean isInsideReplace = false;
     26     private Logic mLogic;
     27 
     28     private CalculatorEditable(CharSequence source, Logic logic) {
     29         super(source);
     30         mLogic = logic;
     31     }
     32 
     33     @Override
     34     public SpannableStringBuilder
     35     replace(int start, int end, CharSequence tb, int tbstart, int tbend) {
     36         if (isInsideReplace) {
     37             return super.replace(start, end, tb, tbstart, tbend);
     38         } else {
     39             isInsideReplace = true;
     40             try {
     41                 String delta = tb.subSequence(tbstart, tbend).toString();
     42                 return internalReplace(start, end, delta);
     43             } finally {
     44                 isInsideReplace = false;
     45             }
     46         }
     47     }
     48 
     49     private SpannableStringBuilder internalReplace(int start, int end, String delta) {
     50         if (!mLogic.acceptInsert(delta)) {
     51             mLogic.cleared();
     52             start = 0;
     53             end = length();
     54         }
     55 
     56         for (int i = ORIGINALS.length - 1; i >= 0; --i) {
     57             delta = delta.replace(ORIGINALS[i], REPLACEMENTS[i]);
     58         }
     59 
     60         int length = delta.length();
     61         if (length == 1) {
     62             char text = delta.charAt(0);
     63 
     64             //don't allow two dots in the same number
     65             if (text == '.') {
     66                 int p = start - 1;
     67                 while (p >= 0 && Character.isDigit(charAt(p))) {
     68                     --p;
     69                 }
     70                 if (p >= 0 && charAt(p) == '.') {
     71                     return super.replace(start, end, "");
     72                 }
     73             }
     74 
     75             char prevChar = start > 0 ? charAt(start-1) : '\0';
     76 
     77             //don't allow 2 successive minuses
     78             if (text == Logic.MINUS && prevChar == Logic.MINUS) {
     79                 return super.replace(start, end, "");
     80             }
     81 
     82             //don't allow multiple successive operators
     83             if (Logic.isOperator(text)) {
     84                 while (Logic.isOperator(prevChar) &&
     85                        (text != Logic.MINUS || prevChar == '+')) {
     86                     --start;
     87                     prevChar = start > 0 ? charAt(start-1) : '\0';
     88                 }
     89             }
     90 
     91             //don't allow leading operator + * /
     92             if (start == 0 && Logic.isOperator(text) && text != Logic.MINUS) {
     93                 return super.replace(start, end, "");
     94             }
     95         }
     96         return super.replace(start, end, delta);
     97     }
     98 
     99     public static class Factory extends Editable.Factory {
    100         private Logic mLogic;
    101 
    102         public Factory(Logic logic) {
    103             mLogic = logic;
    104         }
    105 
    106         public Editable newEditable(CharSequence source) {
    107             return new CalculatorEditable(source, mLogic);
    108         }
    109     }
    110 }
    111