/*******************************************************************************
 * Copyright (c) 2015, 2016 EclipseSource.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 ******************************************************************************/
package com.restfb.json;

import java.io.IOException;
import java.io.Reader;
import java.util.Arrays;
import java.util.Objects;

/**
 * This class serves as the entry point to the minimal-json API.
 * <p>
 * To <strong>parse</strong> a given JSON input, use the <code>parse()</code> methods like in this example:
 * </p>
 * 
 * <pre>
 * JsonObject object = Json.parse(string).asObject();
 * </pre>
 * <p>
 * To <strong>create</strong> a JSON data structure to be serialized, use the methods <code>value()</code>,
 * <code>array()</code>, and <code>object()</code>. For example, the following snippet will produce the JSON string
 * <em>{"foo": 23, "bar": true}</em>:
 * </p>
 * 
 * <pre>
 * String string = Json.object().add("foo", 23).add("bar", true).toString();
 * </pre>
 * <p>
 * To create a JSON array from a given Java array, you can use one of the <code>array()</code> methods with varargs
 * parameters:
 * </p>
 * 
 * <pre>
 * String[] names = ...
 * JsonArray array = Json.array(names);
 * </pre>
 */
public final class Json {

  // String constants
  private static final String VALUES_IS_NULL = "values is null";
  private static final String STRING_IS_NULL = "string is null";
  private static final String READER_IS_NULL = "reader is null";
  private static final String INFINITE_AND_NAN = "Infinite and NaN values not permitted in JSON";

  private Json() {
    // not meant to be instantiated
  }

  /**
   * Represents the JSON literal <code>null</code>.
   */
  public static final JsonValue NULL = new JsonLiteral("null");

  /**
   * Represents the JSON literal <code>true</code>.
   */
  public static final JsonValue TRUE = new JsonLiteral("true");

  /**
   * Represents the JSON literal <code>false</code>.
   */
  public static final JsonValue FALSE = new JsonLiteral("false");

  /**
   * Returns a JsonValue instance that represents the given <code>int</code> value.
   *
   * @param value
   *          the value to get a JSON representation for
   * @return a JSON value that represents the given value
   */
  public static JsonValue value(int value) {
    return new JsonNumber(Integer.toString(value, 10));
  }

  /**
   * Returns a JsonValue instance that represents the given <code>long</code> value.
   *
   * @param value
   *          the value to get a JSON representation for
   * @return a JSON value that represents the given value
   */
  public static JsonValue value(long value) {
    return new JsonNumber(Long.toString(value, 10));
  }

  /**
   * Returns a JsonValue instance that represents the given <code>float</code> value.
   *
   * @param value
   *          the value to get a JSON representation for
   * @return a JSON value that represents the given value
   */
  public static JsonValue value(float value) {
    if (Float.isInfinite(value) || Float.isNaN(value)) {
      throw new IllegalArgumentException(INFINITE_AND_NAN);
    }
    return new JsonNumber(cutOffPointZero(Float.toString(value)));
  }

  /**
   * Returns a JsonValue instance that represents the given <code>double</code> value.
   *
   * @param value
   *          the value to get a JSON representation for
   * @return a JSON value that represents the given value
   */
  public static JsonValue value(double value) {
    if (Double.isInfinite(value) || Double.isNaN(value)) {
      throw new IllegalArgumentException(INFINITE_AND_NAN);
    }
    return new JsonNumber(cutOffPointZero(Double.toString(value)));
  }

  /**
   * Returns a JsonValue instance that represents the given string.
   *
   * @param string
   *          the string to get a JSON representation for
   * @return a JSON value that represents the given string
   */
  public static JsonValue value(String string) {
    return string == null ? NULL : new JsonString(string);
  }

  /**
   * Returns a JsonValue instance that represents the given <code>boolean</code> value.
   *
   * @param value
   *          the value to get a JSON representation for
   * @return a JSON value that represents the given value
   */
  public static JsonValue value(boolean value) {
    return value ? TRUE : FALSE;
  }

  /**
   * Creates a new empty JsonArray. This is equivalent to creating a new JsonArray using the constructor.
   *
   * @return a new empty JSON array
   */
  public static JsonArray array() {
    return new JsonArray();
  }

  /**
   * Creates a new JsonArray that contains the JSON representations of the given <code>int</code> values.
   *
   * @param values
   *          the values to be included in the new JSON array
   * @return a new JSON array that contains the given values
   */
  public static JsonArray array(int... values) {
    Objects.requireNonNull(values, VALUES_IS_NULL);
    JsonArray array = new JsonArray();
    Arrays.stream(values).forEach(array::add);
    return array;
  }

  /**
   * Creates a new JsonArray that contains the JSON representations of the given <code>long</code> values.
   *
   * @param values
   *          the values to be included in the new JSON array
   * @return a new JSON array that contains the given values
   */
  public static JsonArray array(long... values) {
    Objects.requireNonNull(values, VALUES_IS_NULL);
    JsonArray array = new JsonArray();
    Arrays.stream(values).forEach(array::add);
    return array;
  }

  /**
   * Creates a new JsonArray that contains the JSON representations of the given <code>float</code> values.
   *
   * @param values
   *          the values to be included in the new JSON array
   * @return a new JSON array that contains the given values
   */
  public static JsonArray array(float... values) {
    Objects.requireNonNull(values, VALUES_IS_NULL);
    JsonArray array = new JsonArray();
    for (float value : values) {
      array.add(value);
    }
    return array;
  }

  /**
   * Creates a new JsonArray that contains the JSON representations of the given <code>double</code> values.
   *
   * @param values
   *          the values to be included in the new JSON array
   * @return a new JSON array that contains the given values
   */
  public static JsonArray array(double... values) {
    Objects.requireNonNull(values, VALUES_IS_NULL);
    JsonArray array = new JsonArray();
    Arrays.stream(values).forEach(array::add);
    return array;
  }

  /**
   * Creates a new JsonArray that contains the JSON representations of the given <code>boolean</code> values.
   *
   * @param values
   *          the values to be included in the new JSON array
   * @return a new JSON array that contains the given values
   */
  public static JsonArray array(boolean... values) {
    Objects.requireNonNull(values, VALUES_IS_NULL);
    JsonArray array = new JsonArray();
    for (boolean value : values) {
      array.add(value);
    }
    return array;
  }

  /**
   * Creates a new JsonArray that contains the JSON representations of the given strings.
   *
   * @param strings
   *          the strings to be included in the new JSON array
   * @return a new JSON array that contains the given strings
   */
  public static JsonArray array(String... strings) {
    Objects.requireNonNull(strings, VALUES_IS_NULL);
    JsonArray array = new JsonArray();
    Arrays.stream(strings).forEach(array::add);
    return array;
  }

  /**
   * Creates a new empty JsonObject. This is equivalent to creating a new JsonObject using the constructor.
   *
   * @return a new empty JSON object
   */
  public static JsonObject object() {
    return new JsonObject();
  }

  /**
   * Parses the given input string as JSON. The input must contain a valid JSON value, optionally padded with
   * whitespace.
   *
   * @param string
   *          the input string, must be valid JSON
   * @return a value that represents the parsed JSON
   * @throws ParseException
   *           if the input is not valid JSON
   */
  public static JsonValue parse(String string) {
    Objects.requireNonNull(string, STRING_IS_NULL);
    DefaultHandler handler = new DefaultHandler();
    new JsonParser(handler).parse(string);
    return handler.getValue();
  }

  /**
   * Reads the entire input from the given reader and parses it as JSON. The input must contain a
   * valid JSON value, optionally padded with whitespace.
   * <p>
   * Characters are read in chunks into an input buffer. Hence, wrapping a reader in an additional
   * <code>BufferedReader</code> likely won't improve reading performance.
   * </p>
   *
   * @param reader
   *          the reader to read the JSON value from
   * @return a value that represents the parsed JSON
   * @throws IOException
   *           if an I/O error occurs in the reader
   * @throws ParseException
   *           if the input is not valid JSON
   */
  public static JsonValue parse(Reader reader) throws IOException {
    Objects.requireNonNull(reader, READER_IS_NULL);
    DefaultHandler handler = new DefaultHandler();
    new JsonParser(handler).parse(reader);
    return handler.getValue();
  }

  private static String cutOffPointZero(String string) {
    if (string.endsWith(".0")) {
      return string.substring(0, string.length() - 2);
    }
    return string;
  }

  static class DefaultHandler extends JsonHandler<JsonArray, JsonObject> {

    protected JsonValue value;

    @Override
    public JsonArray startArray() {
      return new JsonArray();
    }

    @Override
    public JsonObject startObject() {
      return new JsonObject();
    }

    @Override
    public void endNull() {
      value = NULL;
    }

    @Override
    public void endBoolean(boolean bool) {
      value = bool ? TRUE : FALSE;
    }

    @Override
    public void endString(String string) {
      value = new JsonString(string);
    }

    @Override
    public void endNumber(String string) {
      value = new JsonNumber(string);
    }

    @Override
    public void endArray(JsonArray array) {
      value = array;
    }

    @Override
    public void endObject(JsonObject object) {
      value = object;
    }

    @Override
    public void endArrayValue(JsonArray array) {
      array.add(value);
    }

    @Override
    public void endObjectValue(JsonObject object, String name) {
      object.add(name, value);
    }

    JsonValue getValue() {
      return value;
    }

  }

}