Cleanup codes with clean code principle

Cleanup codes with clean code principle

- Extract codes into functions to reduce function size.
- Apply early-return policy to reduce indentation depth.
- Integrate duplicate operation logic into one function.
- Remove unnecessary comments.
- Add blank lines for readability.

Change-Id: I5e9cca6e1854dbe781daf5099cc29a5103369698
Signed-off-by: Junghyun Yeon <jungh.yeon@samsung.com>