package com.example.Whatever.setup;

import com.example.Whatever.WhateverApplication;
import lombok.Getter;
import lombok.NonNull;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class JSONUpdater {
  @NonNull private String configFilePath;
  @Getter private JSONObject configuration;
  private long timestamp;
  private static final transient Logger logger =
          LoggerFactory.getLogger(WhateverApplication.class);

  /**
   * This instantiates the JSONUpdater. Trigger {@link JSONUpdater#update()} before active use.
   * @param configFilePath the path to the configuration file in JSON format
   */
  public JSONUpdater (String configFilePath) {
    this.configFilePath = configFilePath;
    this.timestamp = 0;
  }

  /**
   * update the fields
   * @throws IOException if an error occurred while opening / reading the file
   * @throws ParseException if an error occurred parsing the JSON file
   */
  public void update() throws IOException, ParseException {
    long latestTimestamp = getLatestTimestamp(this.configFilePath);
    if (this.timestamp == latestTimestamp)
      return;

    logger.info("Configuration file was modified. " +
            "Current timestamp: " + this.timestamp
            + " | New timestamp: " + latestTimestamp);
    this.configuration = this.parse(this.configFilePath);
    logger.trace("JSON Parsing done");
    this.timestamp = latestTimestamp;
  }

  private long getLatestTimestamp(String configFilePath) {
    return new File(configFilePath).lastModified();
  }

  private JSONObject parse(String configFilePath) throws IOException, ParseException {
    JSONParser jsonParser = new JSONParser();
    return (JSONObject) jsonParser.parse(new FileReader(configFilePath));
  }

}