// ***************************************************************************************************************************
// * 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.juneau.json;

import static org.apache.juneau.common.internal.StringUtils.*;
import static org.apache.juneau.internal.CollectionUtils.*;

import java.io.*;
import java.lang.reflect.*;
import java.nio.charset.*;
import java.util.*;
import java.util.function.*;

import org.apache.juneau.*;
import org.apache.juneau.collections.*;
import org.apache.juneau.common.internal.*;
import org.apache.juneau.httppart.*;
import org.apache.juneau.internal.*;
import org.apache.juneau.parser.*;
import org.apache.juneau.swap.*;

/**
 * Session object that lives for the duration of a single use of {@link JsonParser}.
 *
 * <h5 class='section'>Notes:</h5><ul>
 *    <li class='warn'>This class is not thread safe and is typically discarded after one use.
 * </ul>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="../../../../index.html#jm.JsonDetails">JSON Details</a>

 * </ul>
 */
@SuppressWarnings({ "unchecked", "rawtypes" })
public final class JsonParserSession extends ReaderParserSession {

   //-------------------------------------------------------------------------------------------------------------------
   // Static
   //-------------------------------------------------------------------------------------------------------------------

   private static final AsciiSet decChars = AsciiSet.create().ranges("0-9").build();

   /**
    * Creates a new builder for this object.
    *
    * @param ctx The context creating this session.
    * @return A new builder.
    */
   public static Builder create(JsonParser ctx) {
      return new Builder(ctx);
   }

   //-------------------------------------------------------------------------------------------------------------------
   // Builder
   //-------------------------------------------------------------------------------------------------------------------

   /**
    * Builder class.
    */
   @FluentSetters
   public static class Builder extends ReaderParserSession.Builder {

      JsonParser ctx;

      /**
       * Constructor
       *
       * @param ctx The context creating this session.
       */
      protected Builder(JsonParser ctx) {
         super(ctx);
         this.ctx = ctx;
      }

      @Override
      public JsonParserSession build() {
         return new JsonParserSession(this);
      }

      // <FluentSetters>

      @Override /* GENERATED - org.apache.juneau.ContextSession.Builder */
      public <T> Builder apply(Class<T> type, Consumer<T> apply) {
         super.apply(type, apply);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.ContextSession.Builder */
      public Builder debug(Boolean value) {
         super.debug(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.ContextSession.Builder */
      public Builder properties(Map<String,Object> value) {
         super.properties(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.ContextSession.Builder */
      public Builder property(String key, Object value) {
         super.property(key, value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.ContextSession.Builder */
      public Builder unmodifiable() {
         super.unmodifiable();
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.BeanSession.Builder */
      public Builder locale(Locale value) {
         super.locale(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.BeanSession.Builder */
      public Builder localeDefault(Locale value) {
         super.localeDefault(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.BeanSession.Builder */
      public Builder mediaType(MediaType value) {
         super.mediaType(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.BeanSession.Builder */
      public Builder mediaTypeDefault(MediaType value) {
         super.mediaTypeDefault(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.BeanSession.Builder */
      public Builder timeZone(TimeZone value) {
         super.timeZone(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.BeanSession.Builder */
      public Builder timeZoneDefault(TimeZone value) {
         super.timeZoneDefault(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.parser.ParserSession.Builder */
      public Builder javaMethod(Method value) {
         super.javaMethod(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.parser.ParserSession.Builder */
      public Builder outer(Object value) {
         super.outer(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.parser.ParserSession.Builder */
      public Builder schema(HttpPartSchema value) {
         super.schema(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.parser.ParserSession.Builder */
      public Builder schemaDefault(HttpPartSchema value) {
         super.schemaDefault(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.parser.ReaderParserSession.Builder */
      public Builder fileCharset(Charset value) {
         super.fileCharset(value);
         return this;
      }

      @Override /* GENERATED - org.apache.juneau.parser.ReaderParserSession.Builder */
      public Builder streamCharset(Charset value) {
         super.streamCharset(value);
         return this;
      }

      // </FluentSetters>
   }

   //-------------------------------------------------------------------------------------------------------------------
   // Instance
   //-------------------------------------------------------------------------------------------------------------------

   private final JsonParser ctx;

   /**
    * Constructor.
    *
    * @param builder The builder for this object.
    */
   protected JsonParserSession(Builder builder) {
      super(builder);
      ctx = builder.ctx;
   }

   /**
    * Returns <jk>true</jk> if the specified character is whitespace.
    *
    * <p>
    * The definition of whitespace is different for strict vs lax mode.
    * Strict mode only interprets 0x20 (space), 0x09 (tab), 0x0A (line feed) and 0x0D (carriage return) as whitespace.
    * Lax mode uses {@link Character#isWhitespace(int)} to make the determination.
    *
    * @param cp The codepoint.
    * @return <jk>true</jk> if the specified character is whitespace.
    */
   protected final boolean isWhitespace(int cp) {
      if (isStrict())
            return cp <= 0x20 && (cp == 0x09 || cp == 0x0A || cp == 0x0D || cp == 0x20);
      return Character.isWhitespace(cp);
   }

   /**
    * Returns <jk>true</jk> if the specified character is whitespace or '/'.
    *
    * @param cp The codepoint.
    * @return <jk>true</jk> if the specified character is whitespace or '/'.
    */
   protected final boolean isCommentOrWhitespace(int cp) {
      if (cp == '/')
         return true;
      if (isStrict())
         return cp <= 0x20 && (cp == 0x09 || cp == 0x0A || cp == 0x0D || cp == 0x20);
      return Character.isWhitespace(cp);
   }

   @Override /* ParserSession */
   protected <T> T doParse(ParserPipe pipe, ClassMeta<T> type) throws IOException, ParseException, ExecutableException {
      try (ParserReader r = pipe.getParserReader()) {
         if (r == null)
            return null;
         T o = parseAnything(type, r, getOuter(), null);
         validateEnd(r);
         return o;
      }
   }

   @Override /* ReaderParserSession */
   protected <K,V> Map<K,V> doParseIntoMap(ParserPipe pipe, Map<K,V> m, Type keyType, Type valueType) throws IOException, ParseException, ExecutableException {
      try (ParserReader r = pipe.getParserReader()) {
         m = parseIntoMap2(r, m, (ClassMeta<K>)getClassMeta(keyType), (ClassMeta<V>)getClassMeta(valueType), null);
         validateEnd(r);
         return m;
      }
   }

   @Override /* ReaderParserSession */
   protected <E> Collection<E> doParseIntoCollection(ParserPipe pipe, Collection<E> c, Type elementType) throws IOException, ParseException, ExecutableException {
      try (ParserReader r = pipe.getParserReader()) {
         c = parseIntoCollection2(r, c, getClassMeta(elementType), null);
         validateEnd(r);
         return c;
      }
   }

   private <T> T parseAnything(ClassMeta<?> eType, ParserReader r, Object outer, BeanPropertyMeta pMeta) throws IOException, ParseException, ExecutableException {

      if (eType == null)
         eType = object();
      ObjectSwap<T,Object> swap = (ObjectSwap<T,Object>)eType.getSwap(this);
      BuilderSwap<T,Object> builder = (BuilderSwap<T,Object>)eType.getBuilderSwap(this);
      ClassMeta<?> sType = null;
      if (builder != null)
         sType = builder.getBuilderClassMeta(this);
      else if (swap != null)
         sType = swap.getSwapClassMeta(this);
      else
         sType = eType;

      if (sType.isOptional())
         return (T)optional(parseAnything(eType.getElementType(), r, outer, pMeta));

      setCurrentClass(sType);
      String wrapperAttr = getJsonClassMeta(sType).getWrapperAttr();

      Object o = null;

      skipCommentsAndSpace(r);
      if (wrapperAttr != null)
         skipWrapperAttrStart(r, wrapperAttr);
      int c = r.peek();
      if (c == -1) {
         if (isStrict())
            throw new ParseException(this, "Empty input.");
         // Let o be null.
      } else if ((c == ',' || c == '}' || c == ']')) {
         if (isStrict())
            throw new ParseException(this, "Missing value detected.");
         // Handle bug in Cognos 10.2.1 that can product non-existent values.
         // Let o be null;
      } else if (c == 'n') {
         parseKeyword("null", r);
      } else if (sType.isObject()) {
         if (c == '{') {
            JsonMap m2 = new JsonMap(this);
            parseIntoMap2(r, m2, string(), object(), pMeta);
            o = cast(m2, pMeta, eType);
         } else if (c == '[') {
            o = parseIntoCollection2(r, new JsonList(this), object(), pMeta);
         } else if (c == '\'' || c == '"') {
            o = parseString(r);
            if (sType.isChar())
               o = parseCharacter(o);
         } else if (c >= '0' && c <= '9' || c == '-' || c == '.') {
            o = parseNumber(r, null);
         } else if (c == 't') {
            parseKeyword("true", r);
            o = Boolean.TRUE;
         } else {
            parseKeyword("false", r);
            o = Boolean.FALSE;
         }
      } else if (sType.isBoolean()) {
         o = parseBoolean(r);
      } else if (sType.isCharSequence()) {
         o = parseString(r);
      } else if (sType.isChar()) {
         o = parseCharacter(parseString(r));
      } else if (sType.isNumber()) {
         o = parseNumber(r, (Class<? extends Number>)sType.getInnerClass());
      } else if (sType.isMap()) {
         Map m = (sType.canCreateNewInstance(outer) ? (Map)sType.newInstance(outer) : newGenericMap(sType));
         o = parseIntoMap2(r, m, sType.getKeyType(), sType.getValueType(), pMeta);
      } else if (sType.isCollection()) {
         if (c == '{') {
            JsonMap m = new JsonMap(this);
            parseIntoMap2(r, m, string(), object(), pMeta);
            o = cast(m, pMeta, eType);
         } else {
            Collection l = (sType.canCreateNewInstance(outer) ? (Collection)sType.newInstance() : new JsonList(this));
            o = parseIntoCollection2(r, l, sType, pMeta);
         }
      } else if (builder != null) {
         BeanMap m = toBeanMap(builder.create(this, eType));
         o = builder.build(this, parseIntoBeanMap2(r, m).getBean(), eType);
      } else if (sType.canCreateNewBean(outer)) {
         BeanMap m = newBeanMap(outer, sType.getInnerClass());
         o = parseIntoBeanMap2(r, m).getBean();
      } else if (sType.canCreateNewInstanceFromString(outer) && (c == '\'' || c == '"')) {
         o = sType.newInstanceFromString(outer, parseString(r));
      } else if (sType.isArray() || sType.isArgs()) {
         if (c == '{') {
            JsonMap m = new JsonMap(this);
            parseIntoMap2(r, m, string(), object(), pMeta);
            o = cast(m, pMeta, eType);
         } else {
            ArrayList l = (ArrayList)parseIntoCollection2(r, list(), sType, pMeta);
            o = toArray(sType, l);
         }
      } else if (c == '{') {
         Map m = new JsonMap(this);
         parseIntoMap2(r, m, sType.getKeyType(), sType.getValueType(), pMeta);
         if (m.containsKey(getBeanTypePropertyName(eType)))
            o = cast((JsonMap)m, pMeta, eType);
         else if (sType.getProxyInvocationHandler() != null)
            o = newBeanMap(outer, sType.getInnerClass()).load(m).getBean();
         else
            throw new ParseException(this, "Class ''{0}'' could not be instantiated.  Reason: ''{1}''",
                  sType.getInnerClass().getName(), sType.getNotABeanReason());
      } else if (sType.canCreateNewInstanceFromString(outer) && ! isStrict()) {
         o = sType.newInstanceFromString(outer, parseString(r));
      } else {
         throw new ParseException(this, "Unrecognized syntax for class type ''{0}'', starting character ''{1}''",
            sType, (char)c);
      }

      if (wrapperAttr != null)
         skipWrapperAttrEnd(r);

      if (swap != null && o != null)
         o = unswap(swap, o, eType);

      if (outer != null)
         setParent(eType, o, outer);

      return (T)o;
   }

   private Number parseNumber(ParserReader r, Class<? extends Number> type) throws IOException, ParseException {
      int c = r.peek();
      if (c == '\'' || c == '"')
         return parseNumber(r, parseString(r), type);
      return parseNumber(r, r.parseNumberString(), type);
   }

   private Number parseNumber(ParserReader r, String s, Class<? extends Number> type) throws ParseException {

      // JSON has slightly different number rules from Java.
      // Strict mode enforces these different rules, lax does not.
      if (isStrict()) {

         // Lax allows blank strings to represent 0.
         // Strict does not allow blank strings.
         if (s.length() == 0)
            throw new ParseException(this, "Invalid JSON number: ''{0}''", s);

         // Need to weed out octal and hexadecimal formats:  0123,-0123,0x123,-0x123.
         // Don't weed out 0 or -0.
         boolean isNegative = false;
         char c = s.charAt(0);
         if (c == '-') {
            isNegative = true;
            c = (s.length() == 1 ? 'x' : s.charAt(1));
         }

         // JSON doesn't allow '.123' and '-.123'.
         if (c == '.')
            throw new ParseException(this, "Invalid JSON number: ''{0}''", s);

         // '01' is not a valid number, but '0.1', '0e1', '0e+1' are valid.
         if (c == '0' && s.length() > (isNegative ? 2 : 1)) {
            char c2 = s.charAt((isNegative ? 2 : 1));
            if (c2 != '.' && c2 != 'e' && c2 != 'E')
               throw new ParseException(this, "Invalid JSON number: ''{0}''", s);
         }

         // JSON doesn't allow '1.' or '0.e1'.
         int i = s.indexOf('.');
         if (i != -1 && (s.length() == (i+1) || ! decChars.contains(s.charAt(i+1))))
            throw new ParseException(this, "Invalid JSON number: ''{0}''", s);

      }
      return StringUtils.parseNumber(s, type);
   }

   private Boolean parseBoolean(ParserReader r) throws IOException, ParseException {
      int c = r.peek();
      if (c == '\'' || c == '"')
         return Boolean.valueOf(parseString(r));
      if (c == 't') {
         parseKeyword("true", r);
         return Boolean.TRUE;
      } else if (c == 'f') {
         parseKeyword("false", r);
         return Boolean.FALSE;
      } else {
         throw new ParseException(this, "Unrecognized syntax.  Expected boolean value, actual=''{0}''", r.read(100));
      }
   }

   private <K,V> Map<K,V> parseIntoMap2(ParserReader r, Map<K,V> m, ClassMeta<K> keyType,
         ClassMeta<V> valueType, BeanPropertyMeta pMeta) throws IOException, ParseException, ExecutableException {

      if (keyType == null)
         keyType = (ClassMeta<K>)string();

      int S0=0; // Looking for outer {
      int S1=1; // Looking for attrName start.
      int S3=3; // Found attrName end, looking for :.
      int S4=4; // Found :, looking for valStart: { [ " ' LITERAL.
      int S5=5; // Looking for , or }
      int S6=6; // Found , looking for attr start.

      skipCommentsAndSpace(r);
      int state = S0;
      String currAttr = null;
      int c = 0;
      while (c != -1) {
         c = r.read();
         if (state == S0) {
            if (c == '{')
               state = S1;
            else
               break;
         } else if (state == S1) {
            if (c == '}') {
               return m;
            } else if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else {
               currAttr = parseFieldName(r.unread());
               state = S3;
            }
         } else if (state == S3) {
            if (c == ':')
               state = S4;
         } else if (state == S4) {
            if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else {
               K key = convertAttrToType(m, currAttr, keyType);
               V value = parseAnything(valueType, r.unread(), m, pMeta);
               setName(valueType, value, key);
               m.put(key, value);
               state = S5;
            }
         } else if (state == S5) {
            if (c == ',') {
               state = S6;
            } else if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else if (c == '}') {
               return m;
            } else {
               break;
            }
         } else if (state == S6) {
            if (c == '}') {
               break;
            } else if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else {
               currAttr = parseFieldName(r.unread());
               state = S3;
            }
         }
      }
      if (state == S0)
         throw new ParseException(this, "Expected '{' at beginning of JSON object.");
      if (state == S1)
         throw new ParseException(this, "Could not find attribute name on JSON object.");
      if (state == S3)
         throw new ParseException(this, "Could not find ':' following attribute name on JSON object.");
      if (state == S4)
         throw new ParseException(this, "Expected one of the following characters: {,[,',\",LITERAL.");
      if (state == S5)
         throw new ParseException(this, "Could not find '}' marking end of JSON object.");
      if (state == S6)
         throw new ParseException(this, "Unexpected '}' found in JSON object.");

      return null; // Unreachable.
   }

   /*
    * Parse a JSON attribute from the character array at the specified position, then
    * set the position marker to the last character in the field name.
    */
   private String parseFieldName(ParserReader r) throws IOException, ParseException {
      int c = r.peek();
      if (c == '\'' || c == '"')
         return parseString(r);
      if (isStrict())
         throw new ParseException(this, "Unquoted attribute detected.");
      if (! VALID_BARE_CHARS.contains(c))
         throw new ParseException(this, "Could not find the start of the field name.");
      r.mark();
      // Look for whitespace.
      while (c != -1) {
         c = r.read();
         if (! VALID_BARE_CHARS.contains(c)) {
            r.unread();
            String s = r.getMarked().intern();
            return s.equals("null") ? null : s;
         }
      }
      throw new ParseException(this, "Could not find the end of the field name.");
   }

   private static final AsciiSet VALID_BARE_CHARS = AsciiSet.create().range('A','Z').range('a','z').range('0','9').chars("$_-.").build();

   private <E> Collection<E> parseIntoCollection2(ParserReader r, Collection<E> l,
         ClassMeta<?> type, BeanPropertyMeta pMeta) throws IOException, ParseException, ExecutableException {

      int S0=0; // Looking for outermost [
      int S1=1; // Looking for starting [ or { or " or ' or LITERAL or ]
      int S2=2; // Looking for , or ]
      int S3=3; // Looking for starting [ or { or " or ' or LITERAL

      int argIndex = 0;

      int state = S0;
      int c = 0;
      while (c != -1) {
         c = r.read();
         if (state == S0) {
            if (c == '[')
               state = S1;
            else if (isCommentOrWhitespace(c))
               skipCommentsAndSpace(r.unread());
            else
               break;  // Invalid character found.
         } else if (state == S1) {
            if (c == ']') {
               return l;
            } else if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else if (c != -1) {
               l.add((E)parseAnything(type.isArgs() ? type.getArg(argIndex++) : type.getElementType(), r.unread(), l, pMeta));
               state = S2;
            }
         } else if (state == S2) {
            if (c == ',') {
               state = S3;
            } else if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else if (c == ']') {
               return l;
            } else {
               break;  // Invalid character found.
            }
         } else if (state == S3) {
            if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else if (c == ']') {
               break;
            } else if (c != -1) {
               l.add((E)parseAnything(type.isArgs() ? type.getArg(argIndex++) : type.getElementType(), r.unread(), l, pMeta));
               state = S2;
            }
         }
      }
      if (state == S0)
         throw new ParseException(this, "Expected '[' at beginning of JSON array.");
      if (state == S1)
         throw new ParseException(this, "Expected one of the following characters: {,[,',\",LITERAL.");
      if (state == S2)
         throw new ParseException(this, "Expected ',' or ']'.");
      if (state == S3)
         throw new ParseException(this, "Unexpected trailing comma in array.");

      return null;  // Unreachable.
   }

   private <T> BeanMap<T> parseIntoBeanMap2(ParserReader r, BeanMap<T> m) throws IOException, ParseException, ExecutableException {

      int S0=0; // Looking for outer {
      int S1=1; // Looking for attrName start.
      int S3=3; // Found attrName end, looking for :.
      int S4=4; // Found :, looking for valStart: { [ " ' LITERAL.
      int S5=5; // Looking for , or }

      int state = S0;
      String currAttr = "";
      int c = 0;
      mark();
      try {
         while (c != -1) {
            c = r.read();
            if (state == S0) {
               if (c == '{') {
                  state = S1;
               } else if (isCommentOrWhitespace(c)) {
                  skipCommentsAndSpace(r.unread());
               } else {
                  break;
               }
            } else if (state == S1) {
               if (c == '}') {
                  return m;
               } else if (isCommentOrWhitespace(c)) {
                  skipCommentsAndSpace(r.unread());
               } else {
                  r.unread();
                  mark();
                  currAttr = parseFieldName(r);
                  state = S3;
               }
            } else if (state == S3) {
               if (c == ':')
                  state = S4;
            } else if (state == S4) {
               if (isCommentOrWhitespace(c)) {
                  skipCommentsAndSpace(r.unread());
               } else {
                  if (! currAttr.equals(getBeanTypePropertyName(m.getClassMeta()))) {
                     BeanPropertyMeta pMeta = m.getPropertyMeta(currAttr);
                     setCurrentProperty(pMeta);
                     if (pMeta == null) {
                        onUnknownProperty(currAttr, m, parseAnything(object(), r.unread(), m.getBean(false), null));
                        unmark();
                     } else {
                        unmark();
                        ClassMeta<?> cm = pMeta.getClassMeta();
                        Object value = parseAnything(cm, r.unread(), m.getBean(false), pMeta);
                        setName(cm, value, currAttr);
                        try {
                           pMeta.set(m, currAttr, value);
                        } catch (BeanRuntimeException e) {
                           onBeanSetterException(pMeta, e);
                           throw e;
                        }
                     }
                     setCurrentProperty(null);
                  }
                  state = S5;
               }
            } else if (state == S5) {
               if (c == ',')
                  state = S1;
               else if (isCommentOrWhitespace(c))
                  skipCommentsAndSpace(r.unread());
               else if (c == '}') {
                  return m;
               }
            }
         }
         if (state == S0)
            throw new ParseException(this, "Expected '{' at beginning of JSON object.");
         if (state == S1)
            throw new ParseException(this, "Could not find attribute name on JSON object.");
         if (state == S3)
            throw new ParseException(this, "Could not find ':' following attribute name on JSON object.");
         if (state == S4)
            throw new ParseException(this, "Expected one of the following characters: {,[,',\",LITERAL.");
         if (state == S5)
            throw new ParseException(this, "Could not find '}' marking end of JSON object.");
      } finally {
         unmark();
      }

      return null; // Unreachable.
   }

   /*
    * Starting from the specified position in the character array, returns the
    * position of the character " or '.
    * If the string consists of a concatenation of strings (e.g. 'AAA' + "BBB"), this method
    * will automatically concatenate the strings and return the result.
    */
   private String parseString(ParserReader r) throws IOException, ParseException {
      r.mark();
      int qc = r.read();      // The quote character being used (" or ')
      if (qc != '"' && isStrict()) {
         String msg = (
            qc == '\''
            ? "Invalid quote character \"{0}\" being used."
            : "Did not find quote character marking beginning of string.  Character=\"{0}\""
         );
         throw new ParseException(this, msg, (char)qc);
      }
      final boolean isQuoted = (qc == '\'' || qc == '"');
      String s = null;
      boolean isInEscape = false;
      int c = 0;
      while (c != -1) {
         c = r.read();
         // Strict syntax requires that all control characters be escaped.
         if (isStrict() && c <= 0x1F)
            throw new ParseException(this, "Unescaped control character encountered: ''0x{0}''", String.format("%04X", c));
         if (isInEscape) {
            switch (c) {
               case 'n': r.replace('\n'); break;
               case 'r': r.replace('\r'); break;
               case 't': r.replace('\t'); break;
               case 'f': r.replace('\f'); break;
               case 'b': r.replace('\b'); break;
               case '\\': r.replace('\\'); break;
               case '/': r.replace('/'); break;
               case '\'': r.replace('\''); break;
               case '"': r.replace('"'); break;
               case 'u': {
                  String n = r.read(4);
                  try {
                     r.replace(Integer.parseInt(n, 16), 6);
                  } catch (NumberFormatException e) {
                     throw new ParseException(this, "Invalid Unicode escape sequence in string.");
                  }
                  break;
               }
               default:
                  throw new ParseException(this, "Invalid escape sequence in string.");
            }
            isInEscape = false;
         } else {
            if (c == '\\') {
               isInEscape = true;
               r.delete();
            } else if (isQuoted) {
               if (c == qc) {
                  s = r.getMarked(1, -1);
                  break;
               }
            } else {
               if (c == ',' || c == '}' || c == ']' || isWhitespace(c)) {
                  s = r.getMarked(0, -1);
                  r.unread();
                  break;
               } else if (c == -1) {
                  s = r.getMarked(0, 0);
                  break;
               }
            }
         }
      }
      if (s == null)
         throw new ParseException(this, "Could not find expected end character ''{0}''.", (char)qc);

      // Look for concatenated string (i.e. whitespace followed by +).
      skipCommentsAndSpace(r);
      if (r.peek() == '+') {
         if (isStrict())
            throw new ParseException(this, "String concatenation detected.");
         r.read();   // Skip past '+'
         skipCommentsAndSpace(r);
         s += parseString(r);
      }
      return trim(s); // End of input reached.
   }

   /*
    * Looks for the keywords true, false, or null.
    * Throws an exception if any of these keywords are not found at the specified position.
    */
   private void parseKeyword(String keyword, ParserReader r) throws IOException, ParseException {
      try {
         String s = r.read(keyword.length());
         if (s.equals(keyword))
            return;
         throw new ParseException(this, "Unrecognized syntax.  Expected=''{0}'', Actual=''{1}''", keyword, s);
      } catch (IndexOutOfBoundsException e) {
         throw new ParseException(this, "Unrecognized syntax.  Expected=''{0}'', found end-of-file.", keyword);
      }
   }

   /*
    * Doesn't actually parse anything, but moves the position beyond any whitespace or comments.
    * If positionOnNext is 'true', then the cursor will be set to the point immediately after
    * the comments and whitespace.  Otherwise, the cursor will be set to the last position of
    * the comments and whitespace.
    */
   private void skipCommentsAndSpace(ParserReader r) throws IOException, ParseException {
      int c = 0;
      while ((c = r.read()) != -1) {
         if (! isWhitespace(c)) {
            if (c == '/') {
               if (isStrict())
                  throw new ParseException(this, "Javascript comment detected.");
               skipComments(r);
            } else {
               r.unread();
               return;
            }
         }
      }
   }

   /*
    * Doesn't actually parse anything, but moves the position beyond the construct "{wrapperAttr:" when
    * the @Json(wrapperAttr) annotation is used on a class.
    */
   private void skipWrapperAttrStart(ParserReader r, String wrapperAttr) throws IOException, ParseException {

      int S0=0; // Looking for outer {
      int S1=1; // Looking for attrName start.
      int S3=3; // Found attrName end, looking for :.
      int S4=4; // Found :, looking for valStart: { [ " ' LITERAL.

      int state = S0;
      String currAttr = null;
      int c = 0;
      while (c != -1) {
         c = r.read();
         if (state == S0) {
            if (c == '{')
               state = S1;
         } else if (state == S1) {
            if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else {
               currAttr = parseFieldName(r.unread());
               if (! currAttr.equals(wrapperAttr))
                  throw new ParseException(this,
                     "Expected to find wrapper attribute ''{0}'' but found attribute ''{1}''", wrapperAttr, currAttr);
               state = S3;
            }
         } else if (state == S3) {
            if (c == ':')
               state = S4;
         } else if (state == S4) {
            if (isCommentOrWhitespace(c)) {
               skipCommentsAndSpace(r.unread());
            } else {
               r.unread();
               return;
            }
         }
      }
      if (state == S0)
         throw new ParseException(this, "Expected '{' at beginning of JSON object.");
      if (state == S1)
         throw new ParseException(this, "Could not find attribute name on JSON object.");
      if (state == S3)
         throw new ParseException(this, "Could not find ':' following attribute name on JSON object.");
      if (state == S4)
         throw new ParseException(this, "Expected one of the following characters: {,[,',\",LITERAL.");
   }

   /*
    * Doesn't actually parse anything, but moves the position beyond the construct "}" when
    * the @Json(wrapperAttr) annotation is used on a class.
    */
   private void skipWrapperAttrEnd(ParserReader r) throws ParseException, IOException {
      int c = 0;
      while ((c = r.read()) != -1) {
         if (! isWhitespace(c)) {
            if (c == '/') {
               if (isStrict())
                  throw new ParseException(this, "Javascript comment detected.");
               skipComments(r);
            } else if (c == '}') {
               return;
            } else {
               throw new ParseException(this, "Could not find '}' at the end of JSON wrapper object.");
            }
         }
      }
   }

   /*
    * Doesn't actually parse anything, but when positioned at the beginning of comment,
    * it will move the pointer to the last character in the comment.
    */
   private void skipComments(ParserReader r) throws ParseException, IOException {
      int c = r.read();
      //  "/* */" style comments
      if (c == '*') {
         while (c != -1)
            if ((c = r.read()) == '*')
               if ((c = r.read()) == '/')
                  return;
      //  "//" style comments
      } else if (c == '/') {
         while (c != -1) {
            c = r.read();
            if (c == -1 || c == '\n')
               return;
         }
      }
      throw new ParseException(this, "Open ended comment.");
   }

   /*
    * Call this method after you've finished a parsing a string to make sure that if there's any
    * remainder in the input, that it consists only of whitespace and comments.
    */
   private void validateEnd(ParserReader r) throws IOException, ParseException {
      if (! isValidateEnd())
         return;
      skipCommentsAndSpace(r);
      int c = r.read();
      if (c != -1 && c != ';')  // var x = {...}; expressions can end with a semicolon.
         throw new ParseException(this, "Remainder after parse: ''{0}''.", (char)c);
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Properties
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Validate end.
    *
    * @see JsonParser.Builder#validateEnd()
    * @return
    *    <jk>true</jk> if after parsing a POJO from the input, verifies that the remaining input in
    *    the stream consists of only comments or whitespace.
    */
   protected final boolean isValidateEnd() {
      return ctx.isValidateEnd();
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Extended metadata
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Returns the language-specific metadata on the specified class.
    *
    * @param cm The class to return the metadata on.
    * @return The metadata.
    */
   protected JsonClassMeta getJsonClassMeta(ClassMeta<?> cm) {
      return ctx.getJsonClassMeta(cm);
   }
}