package com.box.sdk;

import com.eclipsesource.json.Json;
import com.eclipsesource.json.JsonArray;
import com.eclipsesource.json.JsonObject;
import com.eclipsesource.json.JsonValue;
import java.util.HashMap;
import java.util.Map;

/**
 * The abstract base class for all types that contain JSON data returned by the Box API. The most
 * common implementation of BoxJSONObject is {@link BoxResource.Info} and its subclasses. Changes
 * made to a BoxJSONObject will be tracked locally until the pending changes are sent back to Box in
 * order to avoid unnecessary network requests.
 */
public abstract class BoxJSONObject {
  /**
   * A map of other BoxJSONObjects which will be lazily converted to a JsonObject once
   * getPendingChanges is called. This allows changes to be made to a child BoxJSONObject and still
   * have those changes reflected in the JSON string.
   */
  private final Map<String, BoxJSONObject> children;
  /**
   * The JsonObject that contains any local pending changes. When getPendingChanges is called, this
   * object will be encoded to a JSON string.
   */
  private JsonObject pendingChanges;
  /** The current JSON object. */
  private JsonObject jsonObject;

  /** Constructs an empty BoxJSONObject. */
  public BoxJSONObject() {
    this.children = new HashMap<String, BoxJSONObject>();
  }

  /**
   * Constructs a BoxJSONObject by decoding it from a JSON string.
   *
   * @param json the JSON string to decode.
   */
  public BoxJSONObject(String json) {
    this(Json.parse(json).asObject());
  }

  /**
   * Constructs a BoxJSONObject using an already parsed JSON object.
   *
   * @param jsonObject the parsed JSON object.
   */
  BoxJSONObject(JsonObject jsonObject) {
    this();

    this.update(jsonObject);
  }

  /** Clears any pending changes from this JSON object. */
  public void clearPendingChanges() {
    this.pendingChanges = null;
  }

  /**
   * Gets a JSON string containing any pending changes to this object that can be sent back to the
   * Box API.
   *
   * @return a JSON string containing the pending changes.
   */
  public String getPendingChanges() {
    JsonObject jsonObject = this.getPendingJSONObject();
    if (jsonObject == null) {
      return null;
    }

    return jsonObject.toString();
  }

  /**
   * Gets a JSON string containing any pending changes to this object that can be sent back to the
   * Box API.
   *
   * @return a JSON string containing the pending changes.
   */
  public JsonObject getPendingChangesAsJsonObject() {
    return this.getPendingJSONObject();
  }

  /**
   * Invoked with a JSON member whenever this object is updated or created from a JSON object.
   *
   * <p>Subclasses should override this method in order to parse any JSON members it knows about.
   * This method is a no-op by default.
   *
   * @param member the JSON member to be parsed.
   */
  void parseJSONMember(JsonObject.Member member) {}

  /**
   * Adds a pending field change that needs to be sent to the API. It will be included in the JSON
   * string the next time {@link #getPendingChanges} is called.
   *
   * @param key the name of the field.
   * @param value the new boolean value of the field.
   */
  void addPendingChange(String key, boolean value) {
    if (this.pendingChanges == null) {
      this.pendingChanges = new JsonObject();
    }

    this.pendingChanges.set(key, value);
  }

  /**
   * Adds a pending field change that needs to be sent to the API. It will be included in the JSON
   * string the next time {@link #getPendingChanges} is called.
   *
   * @param key the name of the field.
   * @param value the new String value of the field.
   */
  void addPendingChange(String key, String value) {
    this.addPendingChange(key, Json.value(value));
  }

  /**
   * Adds a pending field change that needs to be sent to the API. It will be included in the JSON
   * string the next time {@link #getPendingChanges} is called.
   *
   * @param key the name of the field.
   * @param value the new long value of the field.
   */
  void addPendingChange(String key, long value) {
    this.addPendingChange(key, Json.value(value));
  }

  /**
   * Adds a pending field change that needs to be sent to the API. It will be included in the JSON
   * string the next time {@link #getPendingChanges} is called.
   *
   * @param key the name of the field.
   * @param value the new JsonArray value of the field.
   */
  void addPendingChange(String key, JsonArray value) {
    this.addPendingChange(key, (JsonValue) value);
  }

  /**
   * Adds a pending field change that needs to be sent to the API. It will be included in the JSON
   * string the next time {@link #getPendingChanges} is called.
   *
   * @param key the name of the field.
   * @param value the new JsonObject value of the field.
   */
  void addPendingChange(String key, JsonObject value) {
    this.addPendingChange(key, (JsonValue) value);
  }

  void addChildObject(String fieldName, BoxJSONObject child) {
    if (child == null) {
      this.addPendingChange(fieldName, Json.NULL);
    } else {
      this.children.put(fieldName, child);
    }
  }

  void removeChildObject(String fieldName) {
    this.children.remove(fieldName);
  }

  /**
   * Adds a pending field change that needs to be sent to the API. It will be included in the JSON
   * string the next time {@link #getPendingChanges} is called.
   *
   * @param key the name of the field.
   * @param value the JsonValue of the field.
   */
  private void addPendingChange(String key, JsonValue value) {
    if (this.pendingChanges == null) {
      this.pendingChanges = new JsonObject();
    }

    this.pendingChanges.set(key, value);
  }

  void removePendingChange(String key) {
    if (this.pendingChanges != null) {
      this.pendingChanges.remove(key);
    }
  }

  /**
   * Updates this BoxJSONObject using the information in a JSON object and preserves the JSON
   * object.
   *
   * @param jsonObject the JSON object containing updated information.
   */
  void update(JsonObject jsonObject) {
    this.jsonObject = jsonObject;

    for (JsonObject.Member member : jsonObject) {
      if (member.getValue().isNull()) {
        continue;
      }

      this.parseJSONMember(member);
    }

    this.clearPendingChanges();
  }

  /**
   * Gets a JsonObject containing any pending changes to this object that can be sent back to the
   * Box API.
   *
   * @return a JsonObject containing the pending changes.
   */
  protected JsonObject getPendingJSONObject() {
    for (Map.Entry<String, BoxJSONObject> entry : this.children.entrySet()) {
      BoxJSONObject child = entry.getValue();
      JsonObject jsonObject = child.getPendingJSONObject();
      if (jsonObject != null) {
        if (this.pendingChanges == null) {
          this.pendingChanges = new JsonObject();
        }

        this.pendingChanges.set(entry.getKey(), jsonObject);
      }
    }
    return this.pendingChanges;
  }

  /**
   * Converts the JSON object into a string literal.
   *
   * @return a string representation of the JSON object.
   */
  public String getJson() {
    return this.jsonObject.toString();
  }
}