let client;
try {
  const redis = require("redis");
  console.log("trying to create");
  client = redis.createClient();
  client.on("error", function(err) {
    client.quit();
    console.error("Missing redis-configurations..");
    client = {
      rpush: function() {
        console.log("redis-dummy lpush", arguments);
        if (typeof arguments[arguments.length - 1] == "function") {
          arguments[arguments.length - 1](null);
        }
      },
      lrange: function() {
        console.log("redis-dummy lrange", arguments);
        if (typeof arguments[arguments.length - 1] == "function") {
          arguments[arguments.length - 1](null);
        }
      },
      del: function() {
        console.log("redis-dummy del", arguments);
        if (typeof arguments[arguments.length - 1] == "function") {
          arguments[arguments.length - 1](null);
        }
      }
    };
  });
} catch (e) {}

const addMessage = message => {
  const json = JSON.stringify(message);
  client.rpush("messages", json);

  return message;
};

const history = (skip = 0, take = 20) => {
  skip = (1 + skip) * -1; // negate to get FIFO
  return new Promise((resolve, reject) =>
    client.lrange("messages", skip * take, skip, (err, data) => {
      if (err) {
        console.log(err);
        reject(err);
      }

      data = data.map(data => JSON.parse(data));
      resolve(data);
    })
  );
};

const clearHistory = () => {
  return new Promise((resolve, reject) =>
    client.del("messages", (err, success) => {
      if (err) {
        console.log(err);
        reject(err);
      }
      resolve(success == 1 ? true : false);
    })
  );
};

module.exports = {
  addMessage,
  history,
  clearHistory
};