ebean/src/main/java/com/avaje/ebean/text/json/EJsonReader.java

package com.avaje.ebean.text.json;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;

import com.avaje.ebeaninternal.server.type.ModifyAwareFlag;
import com.avaje.ebeaninternal.server.type.ModifyAwareList;
import com.avaje.ebeaninternal.server.type.ModifyAwareMap;
import com.avaje.ebeaninternal.server.type.ModifyAwareOwner;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;

class EJsonReader {

  static final JsonFactory json = new JsonFactory();

  @SuppressWarnings("unchecked")
  static Map<String, Object> parseObject(String json, boolean modifyAware) throws IOException  {
    return (Map<String, Object>) parse(json, modifyAware);
  }

  @SuppressWarnings("unchecked")
  static Map<String, Object> parseObject(String json) throws IOException  {
    return (Map<String, Object>) parse(json);
  }
  
  @SuppressWarnings("unchecked")
  static Map<String, Object> parseObject(Reader reader) throws IOException {
    return (Map<String, Object>) parse(reader);
  }

  @SuppressWarnings("unchecked")
  static Map<String, Object> parseObject(Reader reader, boolean modifyAware) throws IOException {
    return (Map<String, Object>) parse(reader, modifyAware);
  }

  @SuppressWarnings("unchecked")
  static Map<String, Object> parseObject(JsonParser parser) throws IOException {
    return (Map<String, Object>) parse(parser);
  }

  @SuppressWarnings("unchecked")
  static Map<String, Object> parseObject(JsonParser parser, JsonToken token) throws IOException {
    return (Map<String, Object>)parse(parser, token, false);
  }

  @SuppressWarnings("unchecked")
  static List<Object> parseList(String json, boolean modifyAware) throws IOException {
    return (List<Object>) parse(json, modifyAware);
  }

  @SuppressWarnings("unchecked")
  static List<Object> parseList(String json) throws IOException {
    return (List<Object>) parse(json);
  }
  
  @SuppressWarnings("unchecked")
  static List<Object> parseList(Reader reader) throws IOException {
    return (List<Object>) parse(reader);
  }
  
  @SuppressWarnings("unchecked")
  static List<Object> parseList(JsonParser parser, boolean modifyAware) throws IOException {
    return (List<Object>) parse(parser, modifyAware);
  }

  static Object parse(String json) throws IOException {
    if (json == null) {
      return null;
    }
    return parse(new StringReader(json));
  }

  static Object parse(String json, boolean modifyAware) throws IOException {
    if (json == null) {
      return null;
    }
    return parse(new StringReader(json), modifyAware);
  }

  static Object parse(Reader reader) throws IOException {
    return parse(json.createParser(reader));
  }

  static Object parse(Reader reader, boolean modifyAware) throws IOException {
    return parse(json.createParser(reader), modifyAware);
  }

  static Object parse(JsonParser parser) throws IOException {
    return parse(parser, null, false);
  }

  static Object parse(JsonParser parser, boolean modifyAware) throws IOException {
    return parse(parser, null, modifyAware);
  }

  static Object parse(JsonParser parser, JsonToken token, boolean modifyAware) throws IOException {
    return new EJsonReader(parser, modifyAware).parseJson(token);
  }

  private final JsonParser parser;

  private final boolean modifyAware;

  private final ModifyAwareFlag modifyAwareOwner;

  private int depth;
  
  private Stack stack;

  private Context currentContext;

 EJsonReader(JsonParser parser, boolean modifyAware) {
    this.parser = parser;
    this.modifyAware = modifyAware;
    this.modifyAwareOwner = (modifyAware) ? new ModifyAwareFlag() : null;
  }

  private void startArray() {
    depth++;
    stack.push(currentContext);
    currentContext = modifyAware ? new ArrayContext(modifyAwareOwner) : new ArrayContext();
  }

  private void startObject() {
    depth++;
    stack.push(currentContext);
    currentContext = modifyAware ? new ObjectContext(modifyAwareOwner) : new ObjectContext();
  }

  private void endArray() {
    end();
  }

  private void endObject() {
    end();
  }

  private void end() {
    depth--;
    if (!stack.isEmpty()) {
      currentContext = stack.pop(currentContext);
    }
    if (modifyAwareOwner != null) {
      modifyAwareOwner.resetMarkedDirty();
    }
  }

  private void setValue(Object value) {
    currentContext.setValue(value);
  }

  private void setValueNull() {
    currentContext.setValueNull();
  }

  private Object parseJson(JsonToken token) throws IOException {

    if (token == null) {
      token = parser.nextToken();
      // if it is a simple value just return it
      switch (token) {
        case VALUE_NULL: return null;
        case VALUE_FALSE: return Boolean.FALSE;
        case VALUE_TRUE: return Boolean.TRUE;
        case VALUE_STRING: return parser.getText();
        case VALUE_NUMBER_INT: return parser.getLongValue();
        case VALUE_NUMBER_FLOAT: return parser.getDecimalValue();
      }
    }

    // it is a object or array, process the first JsonToken
    stack = new Stack();
    processJsonToken(token);

    // process the rest of the object or array
    while (depth > 0) {
      token = parser.nextToken();
      processJsonToken(token);
    }

    return currentContext.getValue();
  }

  /**
   * Process the JsonToken for objects and arrays.
   */
  private void processJsonToken(JsonToken token) throws IOException {
    switch (token) {

    case START_ARRAY:
      startArray();
      break;

    case START_OBJECT:
      startObject();
      break;

    case FIELD_NAME:
      currentContext.setKey(parser.getCurrentName());
      break;

    case VALUE_STRING:
      setValue(parser.getValueAsString());
      break;

    case VALUE_NUMBER_INT:
      setValue(parser.getLongValue());
      break;
      
    case VALUE_NUMBER_FLOAT:
      setValue(parser.getDecimalValue());
      break;

    case VALUE_TRUE:
      setValue(Boolean.TRUE);
      break;

    case VALUE_FALSE:
      setValue(Boolean.FALSE);
      break;

    case VALUE_NULL:
      setValueNull();
      break;

    case END_OBJECT:
      endObject();
      break;

    case END_ARRAY:
      endArray();
      break;

    default:
      break;
    }
  }
  
  private static final class Stack {
    
    private Context head;
    
    private void push(Context context) {
      if (context != null) {
        context.next = head;
        head = context;
      }
    }

    private Context pop(Context endingContext) {
      if (head == null) {
        throw new NoSuchElementException();
      }
      Context temp = head;
      head = head.next;
      temp.popContext(endingContext);
      return temp;
    }

    private boolean isEmpty() {
      return head == null;
    }
  }

  private static abstract class Context {
    Context next;
    abstract void popContext(Context temp);
    abstract Object getValue();
    abstract void setKey(String key);
    abstract void setValue(Object value);
    abstract void setValueNull();
  }
  
  private static class ObjectContext extends Context {
        
    private final Map<String, Object> map;

    private String key;

    ObjectContext() {
      map = new LinkedHashMap<String, Object>();
    }

    ObjectContext(ModifyAwareOwner owner) {
      map = new ModifyAwareMap<String, Object>(owner, new LinkedHashMap<String, Object>());
    }

    public void popContext(Context temp) {
      setValue(temp.getValue());
    }

    Object getValue() {
      return map;
    }

    void setKey(String key) {
      this.key = key;
    }

    void setValue(Object value) {
      map.put(key, value);
    }

    void setValueNull() {
      map.put(key, null);
    }
  }

  private static class ArrayContext extends Context {
    
    private final List<Object> values;

    ArrayContext() {
      values = new ArrayList<Object>();
    }

    ArrayContext(ModifyAwareOwner owner) {
      values = new ModifyAwareList<Object>(owner, new ArrayList<Object>());
    }

    public void popContext(Context temp) {
      values.add(temp.getValue());
    }

    Object getValue() {
      return values;
    }
    
    void setValue(Object value) {
      values.add(value);
    }

    void setValueNull() {
      // ignore
    }
    void setKey(String key) {  
      // not expected
    }
  }

}