fix styled string builder

src/main/java/com/reandroid/arsc/item/StyleItem.java

@@ -1,4 +1,4 @@
- /*
+/*
   *  Copyright (C) 2022 github.com/REAndroid
   *
   *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -17,6 +17,7 @@ package com.reandroid.arsc.item;
 
 import com.reandroid.arsc.io.BlockReader;
 import com.reandroid.arsc.model.StyleSpanInfo;
+import com.reandroid.arsc.model.StyledStringBuilder;
 import com.reandroid.arsc.pool.StringPool;
 import com.reandroid.json.JSONConvert;
 import com.reandroid.json.JSONArray;
@@ -268,84 +269,10 @@ public class StyleItem extends IntegerArray implements JSONConvert<JSONObject> {
     }
 
     public String applyHtml(String str, boolean xml){
-        if(str==null){
+        if(str == null){
             return null;
         }
-        List<StyleSpanInfo> spanInfoList = getSpanInfoList();
-        if(isEmpty(spanInfoList)){
-            return str;
-        }
-        StringBuilder builder=new StringBuilder();
-        char[] allChars=str.toCharArray();
-        int max=allChars.length;
-        for(int i=0;i<max;i++){
-            char ch=allChars[i];
-            boolean lastAppend=false;
-            for(StyleSpanInfo info:spanInfoList){
-                if(info==null){
-                    continue;
-                }
-                boolean isLast=(info.getLast()==i);
-                if(info.getFirst()==i || isLast){
-                    if(isLast){
-                        builder.append(info.getEndTag());
-                    }
-                    if(isLast && !lastAppend){
-                        builder.append(ch);
-                        lastAppend=true;
-                    }
-                    if(!isLast) {
-                        builder.append(info.getStartTag(xml));
-                    }
-                }
-            }
-            if(!lastAppend){
-                if(xml){
-                    if(isWildXml(ch) && !isEntity(allChars, i)){
-                        if(ch=='>'){
-                            builder.append("&gt;");
-                        }else if(ch=='<'){
-                            builder.append("&lt;");
-                        }else if(ch=='&'){
-                            builder.append("&amp;");
-                        }
-                        continue;
-                    }
-                }
-                builder.append(ch);
-            }
-        }
-        return builder.toString();
-    }
-    private boolean isWildXml(char ch){
-        switch (ch){
-            case '&':
-            case '<':
-            case '>':
-                return true;
-            default:
-                return false;
-        }
-    }
-    private boolean isEntity(char[] chars, int offset){
-        if((offset+4)>=chars.length){
-            return false;
-        }
-        return chars[offset]=='a'
-                && chars[offset+1]=='m'
-                && chars[offset+2]=='p'
-                && chars[offset+3]==';';
-    }
-    private boolean isEmpty(List<StyleSpanInfo> spanInfoList){
-        if(spanInfoList.size()==0){
-            return true;
-        }
-        for(StyleSpanInfo spanInfo:spanInfoList){
-            if(spanInfo!=null){
-                return false;
-            }
-        }
-        return true;
+        return StyledStringBuilder.build(str, getSpanInfoList(), xml);
     }
     @Override
     public void setNull(boolean is_null){

src/main/java/com/reandroid/arsc/model/StyledStringBuilder.java

@@ -0,0 +1,196 @@
+/*
+ *  Copyright (C) 2022 github.com/REAndroid
+ *
+ *  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 com.reandroid.arsc.model;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+public class StyledStringBuilder {
+
+    public static String build(String text, Collection<StyleSpanInfo> spanInfoList, boolean xml){
+        if(isEmpty(spanInfoList)){
+            return text;
+        }
+        CharPiece[] charPieceArray = toCharPieceArray(text);
+        boolean spansOk = initializeTags(charPieceArray, spanInfoList, xml);
+        if(!spansOk){
+            // TODO: should throw here ?
+            return text;
+        }
+        if(xml){
+            escapeXmlChars(charPieceArray);
+        }
+        StringBuilder builder = new StringBuilder();
+        int length = charPieceArray.length;
+        for(int i = 0; i < length; i++){
+            CharPiece charPiece = charPieceArray[i];
+            charPiece.append(builder);
+        }
+        return builder.toString();
+    }
+
+    private static boolean isEmpty(Collection<StyleSpanInfo> spanInfoList){
+        if(spanInfoList == null || spanInfoList.size()==0){
+            return true;
+        }
+        for(StyleSpanInfo spanInfo:spanInfoList){
+            if(spanInfo != null){
+                return false;
+            }
+        }
+        return true;
+    }
+    private static boolean initializeTags(CharPiece[] charPieceArray, Collection<StyleSpanInfo> spanInfoList, boolean xml){
+        for(StyleSpanInfo spanInfo : spanInfoList){
+            if(spanInfo == null){
+                continue;
+            }
+            boolean spanOk = initializeTag(charPieceArray, spanInfo, xml);
+            if(!spanOk){
+                return false;
+            }
+        }
+        return true;
+    }
+    private static boolean initializeTag(CharPiece[] charPieceArray, StyleSpanInfo spanInfo, boolean xml){
+        int length = charPieceArray.length;
+        int pos = spanInfo.getFirst();
+        if(pos < 0 || pos >= length){
+            return false;
+        }
+        CharPiece charPiece = charPieceArray[pos];
+        charPiece.addFirstTag(spanInfo.getStartTag(xml));
+
+        pos = spanInfo.getLast();
+        if(pos < 0 || pos >= length){
+            return false;
+        }
+        charPiece = charPieceArray[pos];
+        charPiece.addLastTag(spanInfo.getEndTag());
+        return true;
+    }
+
+    private static void escapeXmlChars(CharPiece[] charPieceArray){
+        int length = charPieceArray.length;
+        for(int i = 0; i < length; i++){
+            CharPiece charPiece = charPieceArray[i];
+            if(isSpecialXmlChar(charPiece.mChar) && !isAlreadyEscaped(charPieceArray, i)){
+                charPiece.escapedXml = escapeXmlChar(charPiece.mChar);
+            }
+        }
+    }
+    private static boolean isAlreadyEscaped(CharPiece[] charPieceArray, int position){
+        if(charPieceArray[position].mChar != '&'){
+            return false;
+        }
+        if((position + 3) >= charPieceArray.length){
+            return false;
+        }
+        if(charPieceArray[position + 3].mChar == ';'){
+            char ch = charPieceArray[position + 1].mChar;
+            return charPieceArray[position + 2].mChar == 't'
+                    && (ch == 'l' || ch == 'g') ;
+        }
+        if((position + 4) >= charPieceArray.length){
+            return false;
+        }
+        if(charPieceArray[position + 4].mChar == ';'){
+            return charPieceArray[position + 1].mChar == 'a'
+                    && charPieceArray[position + 2].mChar == 'm'
+                    && charPieceArray[position + 3].mChar == 'p';
+        }
+        return false;
+    }
+    private static String escapeXmlChar(char ch){
+        switch (ch){
+            case '&':
+                return "&amp;";
+            case '<':
+                return "&lt;";
+            case '>':
+                return "&gt;";
+            default:
+                throw new IllegalArgumentException("Not special xml char: '" + ch + "'");
+        }
+    }
+    private static boolean isSpecialXmlChar(char ch){
+        switch (ch){
+            case '&':
+            case '<':
+            case '>':
+                return true;
+            default:
+                return false;
+        }
+    }
+    private static CharPiece[] toCharPieceArray(String text){
+        char[] chars = text.toCharArray();
+        int length = chars.length;
+        CharPiece[] results = new CharPiece[length];
+        for(int i = 0; i < length; i++){
+            results[i] = new CharPiece(i, chars[i]);
+        }
+        return results;
+    }
+
+    static class CharPiece{
+        final int position;
+        private List<String> firstTagList;
+        final char mChar;
+        private List<String> lastTagList;
+        String escapedXml;
+        CharPiece(int position, char ch){
+            this.position = position;
+            this.mChar = ch;
+        }
+        void append(StringBuilder builder){
+            if(firstTagList != null){
+                for(String tag : firstTagList){
+                    builder.append(tag);
+                }
+            }
+            if(escapedXml != null){
+                builder.append(escapedXml);
+            }else {
+                builder.append(mChar);
+            }
+            if(lastTagList != null){
+                for(String tag : lastTagList){
+                    builder.append(tag);
+                }
+            }
+        }
+        void addFirstTag(String tag){
+            if(tag == null){
+                return;
+            }
+            if(this.firstTagList == null){
+                this.firstTagList = new ArrayList<>(2);
+            }
+            this.firstTagList.add(tag);
+        }
+        void addLastTag(String tag){
+            if(tag == null){
+                return;
+            }
+            if(this.lastTagList == null){
+                this.lastTagList = new ArrayList<>(2);
+            }
+            this.lastTagList.add(0, tag);
+        }
+    }
+}