/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.logging.log4j.core.pattern;
  
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.config.Configuration;
  import org.apache.logging.log4j.core.config.plugins.PluginManager;
  import org.apache.logging.log4j.core.config.plugins.PluginType;
  import org.apache.logging.log4j.core.helpers.Strings;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * Most of the work of the {@link org.apache.logging.log4j.core.layout.PatternLayout} class
   * is delegated to the PatternParser class.
   * <p>It is this class that parses conversion patterns and creates
   * a chained list of {@link PatternConverter PatternConverters}.
   */
  public final class PatternParser {
      /**
       * Escape character for format specifier.
       */
      private static final char ESCAPE_CHAR = '%';
  
      /**
       * The states the parser can be in while parsing the pattern.
       */
      private enum ParserState {
          /**
           * Literal state.
           */
          LITERAL_STATE,
  
          /**
           * In converter name state.
           */
          CONVERTER_STATE,
  
          /**
           * Dot state.
           */
          DOT_STATE,
  
          /**
           * Min state.
           */
          MIN_STATE,
  
          /**
           * Max state.
           */
          MAX_STATE;
      }
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      private static final int BUF_SIZE = 32;
  
      private static final int DECIMAL = 10;
  
      private final Configuration config;
  
      private final Map<String, Class<PatternConverter>> converterRules;
  
  
      /**
       * Constructor.
       * @param converterKey The type of converters that will be used.
       */
      public PatternParser(final String converterKey) {
          this(null, converterKey, null, null);
      }
  
      /**
       * Constructor.
       * @param config The current Configuration.
       * @param converterKey The key to lookup the converters.
       * @param expected The expected base Class of each Converter.
      */
     public PatternParser(final Configuration config, final String converterKey, final Class<?> expected) {
         this(config, converterKey, expected, null);
     }
 
     /**
      * Constructor.
      * @param config The current Configuration.
      * @param converterKey The key to lookup the converters.
      * @param expectedClass The expected base Class of each Converter.
      * @param filterClass Filter the returned plugins after calling the plugin manager.
      */
     public PatternParser(final Configuration config, final String converterKey, final Class<?> expectedClass,
                          final Class<?> filterClass) {
         this.config = config;
         final PluginManager manager = new PluginManager(converterKey, expectedClass);
         manager.collectPlugins();
         final Map<String, PluginType<?>> plugins = manager.getPlugins();
         final Map<String, Class<PatternConverter>> converters = new HashMap<String, Class<PatternConverter>>();
 
         for (final PluginType<?> type : plugins.values()) {
             try {
                 @SuppressWarnings("unchecked")
                 final Class<PatternConverter> clazz = (Class<PatternConverter>)type.getPluginClass();
                 if (filterClass != null && !filterClass.isAssignableFrom(clazz)) {
                     continue;
                 }
                 final ConverterKeys keys = clazz.getAnnotation(ConverterKeys.class);
                 if (keys != null) {
                     for (final String key : keys.value()) {
                         converters.put(key, clazz);
                     }
                 }
             } catch (final Exception ex) {
                 LOGGER.error("Error processing plugin " + type.getElementName(), ex);
             }
         }
         converterRules = converters;
     }
 
     public List<PatternFormatter> parse(final String pattern) {
         return parse(pattern, false);
     }
 
     public List<PatternFormatter> parse(final String pattern, final boolean alwaysWriteExceptions) {
         final List<PatternFormatter> list = new ArrayList<PatternFormatter>();
         final List<PatternConverter> converters = new ArrayList<PatternConverter>();
         final List<FormattingInfo> fields = new ArrayList<FormattingInfo>();
 
         parse(pattern, converters, fields);
 
         final Iterator<FormattingInfo> fieldIter = fields.iterator();
         boolean handlesThrowable = false;
 
         for (final PatternConverter converter : converters) {
             LogEventPatternConverter pc;
             if (converter instanceof LogEventPatternConverter) {
                 pc = (LogEventPatternConverter) converter;
                 handlesThrowable |= pc.handlesThrowable();
             } else {
                 pc = new LiteralPatternConverter(config, "");
             }
 
             FormattingInfo field;
             if (fieldIter.hasNext()) {
                 field = fieldIter.next();
             } else {
                 field = FormattingInfo.getDefault();
             }
             list.add(new PatternFormatter(pc, field));
         }
         if (alwaysWriteExceptions && !handlesThrowable) {
             final LogEventPatternConverter pc = ExtendedThrowablePatternConverter.newInstance(null);
             list.add(new PatternFormatter(pc, FormattingInfo.getDefault()));
         }
         return list;
     }
 
     /**
      * Extract the converter identifier found at position i.
      * <p/>
      * After this function returns, the variable i will point to the
      * first char after the end of the converter identifier.
      * <p/>
      * If i points to a char which is not a character acceptable at the
      * start of a unicode identifier, the value null is returned.
      *
      * @param lastChar       last processed character.
      * @param pattern        format string.
      * @param i              current index into pattern format.
      * @param convBuf        buffer to receive conversion specifier.
      * @param currentLiteral literal to be output in case format specifier in unrecognized.
      * @return position in pattern after converter.
      */
     private static int extractConverter(
         final char lastChar, final String pattern, int i, final StringBuilder convBuf,
         final StringBuilder currentLiteral) {
         convBuf.setLength(0);
 
         // When this method is called, lastChar points to the first character of the
         // conversion word. For example:
         // For "%hello"     lastChar = 'h'
         // For "%-5hello"   lastChar = 'h'
         //System.out.println("lastchar is "+lastChar);
         if (!Character.isUnicodeIdentifierStart(lastChar)) {
             return i;
         }
 
         convBuf.append(lastChar);
 
         while (i < pattern.length() && Character.isUnicodeIdentifierPart(pattern.charAt(i))) {
             convBuf.append(pattern.charAt(i));
             currentLiteral.append(pattern.charAt(i));
             i++;
         }
 
         return i;
     }
 
     /**
      * Extract options.
      *
      * @param pattern conversion pattern.
      * @param i       start of options.
      * @param options array to receive extracted options
      * @return position in pattern after options.
      */
     private static int extractOptions(final String pattern, int i, final List<String> options) {
         while (i < pattern.length() && pattern.charAt(i) == '{') {
             final int begin = i++;
             int end;
             int depth = 0;
             do {
                 end = pattern.indexOf('}', i);
                 if (end != -1) {
                     final int next = pattern.indexOf("{", i);
                     if (next != -1 && next < end) {
                         i = end + 1;
                         ++depth;
                     } else if (depth > 0) {
                         --depth;
                     }
                 }
             } while (depth > 0);
 
             if (end == -1) {
                 break;
             }
 
             final String r = pattern.substring(begin + 1, end);
             options.add(r);
             i = end + 1;
         }
 
         return i;
     }
 
     /**
      * Parse a format specifier.
      *
      * @param pattern           pattern to parse.
      * @param patternConverters list to receive pattern converters.
      * @param formattingInfos   list to receive field specifiers corresponding to pattern converters.
      */
     public void parse(final String pattern, final List<PatternConverter> patternConverters,
             final List<FormattingInfo> formattingInfos) {
         if (pattern == null) {
             throw new NullPointerException("pattern");
         }
 
         final StringBuilder currentLiteral = new StringBuilder(BUF_SIZE);
 
         final int patternLength = pattern.length();
         ParserState state = ParserState.LITERAL_STATE;
         char c;
         int i = 0;
         FormattingInfo formattingInfo = FormattingInfo.getDefault();
 
         while (i < patternLength) {
             c = pattern.charAt(i++);
 
             switch (state) {
                 case LITERAL_STATE:
 
                     // In literal state, the last char is always a literal.
                     if (i == patternLength) {
                         currentLiteral.append(c);
 
                         continue;
                     }
 
                     if (c == ESCAPE_CHAR) {
                         // peek at the next char.
                         switch (pattern.charAt(i)) {
                             case ESCAPE_CHAR:
                                 currentLiteral.append(c);
                                 i++; // move pointer
 
                                 break;
 
                             default:
 
                                 if (currentLiteral.length() != 0) {
                                     patternConverters.add(new LiteralPatternConverter(config,
                                         currentLiteral.toString()));
                                     formattingInfos.add(FormattingInfo.getDefault());
                                 }
 
                                 currentLiteral.setLength(0);
                                 currentLiteral.append(c); // append %
                                 state = ParserState.CONVERTER_STATE;
                                 formattingInfo = FormattingInfo.getDefault();
                         }
                     } else {
                         currentLiteral.append(c);
                     }
 
                     break;
 
                 case CONVERTER_STATE:
                     currentLiteral.append(c);
 
                     switch (c) {
                         case '-':
                             formattingInfo =
                                 new FormattingInfo(true, formattingInfo.getMinLength(),
                                     formattingInfo.getMaxLength());
                             break;
 
                         case '.':
                             state = ParserState.DOT_STATE;
                             break;
 
                         default:
 
                             if (c >= '0' && c <= '9') {
                                 formattingInfo = new FormattingInfo(formattingInfo.isLeftAligned(), c - '0',
                                         formattingInfo.getMaxLength());
                                 state = ParserState.MIN_STATE;
                             } else {
                                 i = finalizeConverter(c, pattern, i, currentLiteral, formattingInfo,
                                         converterRules, patternConverters, formattingInfos);
 
                                 // Next pattern is assumed to be a literal.
                                 state = ParserState.LITERAL_STATE;
                                 formattingInfo = FormattingInfo.getDefault();
                                 currentLiteral.setLength(0);
                             }
                     } // switch
 
                     break;
 
                 case MIN_STATE:
                     currentLiteral.append(c);
 
                     if (c >= '0' && c <= '9') {
                         // Multiply the existing value and add the value of the number just encountered.
                         formattingInfo = new FormattingInfo(formattingInfo.isLeftAligned(),
                                 formattingInfo.getMinLength() * DECIMAL + c - '0',
                                 formattingInfo.getMaxLength());
                     } else if (c == '.') {
                         state = ParserState.DOT_STATE;
                     } else {
                         i = finalizeConverter(c, pattern, i, currentLiteral, formattingInfo,
                                 converterRules, patternConverters, formattingInfos);
                         state = ParserState.LITERAL_STATE;
                         formattingInfo = FormattingInfo.getDefault();
                         currentLiteral.setLength(0);
                     }
 
                     break;
 
                 case DOT_STATE:
                     currentLiteral.append(c);
 
                     if (c >= '0' && c <= '9') {
                         formattingInfo = new FormattingInfo(formattingInfo.isLeftAligned(),
                             formattingInfo.getMinLength(), c - '0');
                         state = ParserState.MAX_STATE;
                     } else {
                         LOGGER.error("Error occurred in position " + i
                                 + ".\n Was expecting digit, instead got char \"" + c + "\".");
 
                         state = ParserState.LITERAL_STATE;
                     }
 
                     break;
 
                 case MAX_STATE:
                     currentLiteral.append(c);
 
                     if (c >= '0' && c <= '9') {
                         // Multiply the existing value and add the value of the number just encountered.
                         formattingInfo = new FormattingInfo(
                                 formattingInfo.isLeftAligned(), formattingInfo.getMinLength(),
                                 formattingInfo.getMaxLength() * DECIMAL + c - '0');
                     } else {
                         i = finalizeConverter(c, pattern, i, currentLiteral, formattingInfo,
                                 converterRules, patternConverters, formattingInfos);
                         state = ParserState.LITERAL_STATE;
                         formattingInfo = FormattingInfo.getDefault();
                         currentLiteral.setLength(0);
                     }
 
                     break;
             } // switch
         }
 
         // while
         if (currentLiteral.length() != 0) {
             patternConverters.add(new LiteralPatternConverter(config, currentLiteral.toString()));
             formattingInfos.add(FormattingInfo.getDefault());
         }
     }
 
     /**
      * Creates a new PatternConverter.
      *
      * @param converterId       converterId.
      * @param currentLiteral    literal to be used if converter is unrecognized or following converter
      *                          if converterId contains extra characters.
      * @param rules             map of stock pattern converters keyed by format specifier.
      * @param options           converter options.
      * @return converter or null.
      */
     private PatternConverter createConverter(final String converterId, final StringBuilder currentLiteral,
             final Map<String, Class<PatternConverter>> rules,
             final List<String> options) {
         String converterName = converterId;
         Class<PatternConverter> converterClass = null;
 
         for (int i = converterId.length(); i > 0 && converterClass == null; i--) {
             converterName = converterName.substring(0, i);
 
             if (converterClass == null && rules != null) {
                 converterClass = rules.get(converterName);
             }
         }
 
         if (converterClass == null) {
             LOGGER.error("Unrecognized format specifier [" + converterId + "]");
             return null;
         }
 
         // Work around the regression bug in Class.getDeclaredMethods() in Oracle Java in version > 1.6.0_17:
         // http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6815786
         final Method[] methods = converterClass.getDeclaredMethods();
         Method newInstanceMethod = null;
         for (final Method method : methods) {
             if (Modifier.isStatic(method.getModifiers()) && method.getDeclaringClass().equals(converterClass) &&
                     method.getName().equals("newInstance")) {
                 if (newInstanceMethod == null) {
                     newInstanceMethod = method;
                 } else if (method.getReturnType().equals(newInstanceMethod.getReturnType())) {
                     LOGGER.error("Class " + converterClass + " cannot contain multiple static newInstance methods");
                     return null;
                 }
             }
         }
         if (newInstanceMethod == null) {
             LOGGER.error("Class " + converterClass + " does not contain a static newInstance method");
             return null;
         }
 
         final Class<?>[] parmTypes = newInstanceMethod.getParameterTypes();
         final Object [] parms = parmTypes.length > 0 ? new Object[parmTypes.length] : null;
 
         if (parms != null) {
             int i = 0;
             boolean errors = false;
             for (final Class<?> clazz : parmTypes) {
                 if (clazz.isArray() && clazz.getName().equals("[Ljava.lang.String;")) {
                     final String[] optionsArray = options.toArray(new String[options.size()]);
                     parms[i] = optionsArray;
                 } else if (clazz.isAssignableFrom(Configuration.class)) {
                     parms[i] = config;
                 } else {
                     LOGGER.error("Unknown parameter type " + clazz.getName() + " for static newInstance method of " +
                         converterClass.getName());
                     errors = true;
                 }
                 ++i;
             }
             if (errors) {
                 return null;
             }
         }
 
         try {
             final Object newObj = newInstanceMethod.invoke(null, parms);
 
             if (newObj instanceof PatternConverter) {
                 currentLiteral.delete(0, currentLiteral.length()
                         - (converterId.length() - converterName.length()));
 
                 return (PatternConverter) newObj;
             } else {
                 LOGGER.warn("Class " + converterClass.getName() + " does not extend PatternConverter.");
             }
         } catch (final Exception ex) {
             LOGGER.error("Error creating converter for " + converterId, ex);
         }
 
         return null;
     }
 
     /**
      * Processes a format specifier sequence.
      *
      * @param c                 initial character of format specifier.
      * @param pattern           conversion pattern
      * @param i                 current position in conversion pattern.
      * @param currentLiteral    current literal.
      * @param formattingInfo    current field specifier.
      * @param rules             map of stock pattern converters keyed by format specifier.
      * @param patternConverters list to receive parsed pattern converter.
      * @param formattingInfos   list to receive corresponding field specifier.
      * @return position after format specifier sequence.
      */
     private int finalizeConverter(final char c, final String pattern, int i,
             final StringBuilder currentLiteral, final FormattingInfo formattingInfo,
             final Map<String, Class<PatternConverter>> rules,
             final List<PatternConverter> patternConverters, final List<FormattingInfo> formattingInfos) {
         final StringBuilder convBuf = new StringBuilder();
         i = extractConverter(c, pattern, i, convBuf, currentLiteral);
 
         final String converterId = convBuf.toString();
 
         final List<String> options = new ArrayList<String>();
         i = extractOptions(pattern, i, options);
 
         final PatternConverter pc = createConverter(converterId, currentLiteral, rules, options);
 
         if (pc == null) {
             StringBuilder msg;
 
             if (Strings.isEmpty(converterId)) {
                 msg = new StringBuilder("Empty conversion specifier starting at position ");
             } else {
                 msg = new StringBuilder("Unrecognized conversion specifier [");
                 msg.append(converterId);
                 msg.append("] starting at position ");
             }
 
             msg.append(Integer.toString(i));
             msg.append(" in conversion pattern.");
 
             LOGGER.error(msg.toString());
 
             patternConverters.add(new LiteralPatternConverter(config, currentLiteral.toString()));
             formattingInfos.add(FormattingInfo.getDefault());
         } else {
             patternConverters.add(pc);
             formattingInfos.add(formattingInfo);
 
             if (currentLiteral.length() > 0) {
                 patternConverters.add(new LiteralPatternConverter(config, currentLiteral.toString()));
                 formattingInfos.add(FormattingInfo.getDefault());
             }
         }
 
         currentLiteral.setLength(0);
 
         return i;
     }
 }