hashmessages handling collisions

shamessages.js

let getMessageHash = function(hash, fn) {
    dm.settings.log("getmessage hash", hash);

    dm.rcmsg.get("m:"+ hash, function(err, data) {
      if (err) {
        dm.settings.log('message hash error', err);
      }

      if (!data) {
        dm.settings.log("message hash not found?!", hash)
        return fn(null,{message: 'messagehash error', message_text: 'messagehash error', hash: hash})
      }
      var j = JSON.parse(data);
      dm.settings.log("messagehash", j);
      return fn(err, j);
    });
  }



  
  let saveMessageHash = function(mj, fn) {

  
      var hash = crypto.createHash('sha256').update(mj.message_text).digest("hex");
      
      dm.rcmsg.exists("m:" + hash, function(err, exists) {
        if (exists) {
          dm.rcmsg.get("m:" +hash, function(err, existing) {
            var j = JSON.parse(existing);
            if (j.message_text === mj.message_text) {
              //dm.settings.log("hash found")
              return fn(null, hash);
            } else {
              dm.settings.log("sha256 collision");
              dm.rcmsg.incr("c:" + hash, function(err, id) {
                var newhash = hash + id.toString();

                var data = {message_text: mj.message_text, message: mj.message };
                console.log("saving hash", newhash, data);

                dm.rcmsg.set("m:" + newhash, JSON.stringify(data), function(err, done) {
                  return fn(null, newhash);
                });
              })
            } 
          })
            
        } else {
            var data = {message_text: mj.message_text, message: mj.message};

            console.log("saving message", hash, data);

          dm.rcmsg.set("m:" + hash, JSON.stringify(data), function(err, done) {
            return fn(null, hash);
          })
        }
      })
  }