validate(_DbConn, req#{body = <<>>}) ->
  {error, "No body provided"};
validate(DbConn, req#{body = ReqJsonStr}) ->
  parse_json(DbConn, ReqJsonStr).

parse_json(DbConn, ReqJsonStr) ->
  case json:parse(ReqJsonStr) of
    {error, Reason} ->  {error, Reason};
    {ok, ReqJson} -> decode_json(DbConn, ReqJson)
  end

decode_json(DbConn, ReqJson) ->
  case validate_and_decode_login_request(ReqJson) of
    {ok, #login_request{username = Username, password = Password}}) ->
      db_find_user(DbConn, Username, Password)
  end.

db_find_user(DbConn, Username, Password) ->
  case db.find_user(DbConn, Username, Password) of
    {:error, Reason} -> {:error, Reason};
    {:ok, #user_details{hashed_password = HashedPassword}} ->
      check_password(Username, Password, HashedPassword)
  end.

check_password(Username, Password, HashedPassword) ->
  case does_password_match(HashedPassword, Password) of
    {error, Reason} ->
      {error, Reason};
    {ok, false} ->
      {error, "Invalid username or password"}
    {ok, true} ->
      generateJwtToken(Username)
  end.

generateJwtToken(Username) ->
  case jwt.generateToken(Username) of
    {error, Reason} ->
      {error, Reason};
    {ok, jwtToken} ->
      {ok, 200, json:encode([{"token", jwtToken}])}
  end.