package com.randomnoun.common.jexl.eval.function;
   
   /* (c) 2013-2018 randomnoun. All Rights Reserved. This work is licensed under a
    * BSD Simplified License. (http://www.randomnoun.com/bsd-simplified.html)
    */
   
   import java.util.List;
   
   import com.randomnoun.common.jexl.eval.EvalContext;
  import com.randomnoun.common.jexl.eval.EvalException;
  import com.randomnoun.common.jexl.eval.EvalFunction;
  
  /** Defines a like() function.
   *
   * <p>like() takes a two parameters, the string being matched and the SQL LIKE pattern we
   * are matching on. The LIKE pattern uses the "%" character to represent any sequence of
   * characters, and "_" to indicate a single character. This class automatically deals
   * with conflicts with the Java regex parser, so the pattern may contain any other
   * Unicode or regular expression characters, which will be treated like any other
   * character.
   *
   * <p>The result of the function is of type Boolean.
   */
  public class LikeFunction
      implements EvalFunction
  {
      /** Implements the function as per the class description. */
      public Object evaluate(String functionName, EvalContext context, List<Object> arguments)
          throws EvalException
      {
          if (arguments.size() != 2) { throw new EvalException(functionName + "() must contain two parameters"); }
          if (!(arguments.get(0) instanceof String)) {
              throw new EvalException(functionName + "() parameter 1 must be a string type");
          }
          if (!(arguments.get(1) instanceof String)) {
              throw new EvalException(functionName + "() parameter 2 must be a string type");
          }
  
          String arg0 = (String)arguments.get(0);
          String arg1 = (String)arguments.get(1);
          if (arg0 == null) {
              throw new EvalException(functionName + "() first parameter cannot be null");
          }
          if (arg1 == null) {
              throw new EvalException(functionName + "() second parameter cannot be null");
          }
  
          // convert arg1 into a regex; first escape any chars that may confuse the
          // regex engine (see java.util.regex.Pattern class to see how this list was derived)
          String specialChars = "\\[]^$?*+{}|().";
          for (int i = 0; i < specialChars.length(); i++) {
              arg1 = arg1.replaceAll("\\" + specialChars.charAt(i),
                      "\\\\" + "\\" + specialChars.charAt(i));
          }
          arg1 = arg1.replaceAll("%", ".*");
          arg1 = arg1.replaceAll("_", ".");
          return Boolean.valueOf(arg0.matches(arg1));
      }
  }