Re-wrote scanning and parsing to handle problems from issues #3 and #4

src/main/java/me/legrange/mikrotik/impl/Scanner.java

@@ -0,0 +1,145 @@
+/*
+ * Copyright 2014 GideonLeGrange.
+ *
+ * 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 me.legrange.mikrotik.impl;
+
+/**
+ * A simple scanner.
+ * @author gideon
+ */
+class Scanner {
+    
+    enum Token {
+        SLASH("/"), COMMA(","), EOL(), WS, TEXT, 
+        LESS("<"), MORE(">"), EQUALS("="),
+        WHERE, NOT, AND, OR, RETURN;
+
+        @Override
+        public String toString() {
+            return (symb == null) ? name() : symb;
+        }
+
+        private Token(String symb) {
+            this.symb = symb;
+        }
+        
+        private Token() {
+            symb = null;
+        }
+        
+        
+        private final String symb;
+     }
+    
+    Scanner(String line) {
+        this.line = line;
+        nextChar();
+    }
+    
+    Token next() throws ScanException {
+        text = null;
+        switch (c) {
+            case '\n' : return Token.EOL;
+            case ' '  : 
+            case '\t' : 
+                return whiteSpace();
+            case ',' :
+                nextChar();
+                return Token.COMMA;
+            case '/' : 
+                nextChar(); 
+                return Token.SLASH;
+            case '<' : 
+                nextChar(); 
+                return Token.LESS;
+            case '>' : 
+                nextChar(); 
+                return Token.MORE;
+            case '=' : 
+                nextChar(); 
+                return Token.EQUALS;
+            case '"' : 
+                return quotedText();
+            default :
+                return name();
+        }
+        
+    }
+    
+    String text()  {
+        if (text != null) return text.toString(); 
+        return "";
+    }
+    
+    private Token name() throws ScanException {
+        text = new StringBuilder();
+        while (in(c,"[A-Za-z0-9-\\.]")) {
+            text.append(c);
+            nextChar();
+        }
+        String val = text.toString();
+        switch  (val) {
+            case "where" : return Token.WHERE;
+            case "not" : return Token.NOT;
+            case "and" : return Token.AND;
+            case "or" : return Token.OR;
+            case "return" : return Token.RETURN;
+        }
+        return Token.TEXT;
+    }
+    
+    /** process quoted text */
+    private Token quotedText() throws ScanException {
+        nextChar(); // eat the '"'
+        text = new StringBuilder();
+        while (c != '"') {
+            if (c == '\n') {
+                throw new ScanException("Unclosed quoted text");
+            }
+            text.append(c);
+            nextChar();
+        }
+        nextChar(); // eat the '"'
+        return Token.TEXT;
+    }
+    
+    /** process white space */
+    private Token whiteSpace() {
+        while ((c == ' ') || (c == '\t')) {
+            nextChar();
+        }
+        return Token.WS;
+    }
+    
+    private void nextChar() {
+        if (pos < line.length()) {
+           c = line.charAt(pos);
+            pos ++;
+        }
+        else {
+            c = '\n';
+        }
+    }
+    
+    private boolean in(char c, String cs) {
+        return ("" + c).matches(cs);
+    }
+    
+    private final String line;
+    private int pos = 0;
+    private char c;
+    private StringBuilder text;
+}