# R&D - What will happen if Cli broke in the middle ?
## How to break
- Quit signal, for example `ctrl+c`
- Panics, if it happens while executing something through cli

## Related problem
- Multiple user trying to install the same package at the same time.

## How currently works
- At the beginning the package information related to its name and version are stored
- Then the installation block is executed
- After installation is completed, the package is stored in `install database`
- Same for remove, gets removed then stored at `removed database`

## Scenarios
### 1 : exits before installing
- there will not be any issues

### 2 : exits during installation
- for apt installs
- there will be no issues,as apt can install same package multiple times
- so if while installing cli breaks, it will not be installed in the system and will not be stored in database
- others
- may be problematic
- need to check in details

### 3 : exits after installation but before storing to db
- for apt installs
- even though the system has package installed, theres no record of it in the databse
- again trying to install there will be no issues,as apt can install same package multiple times, and the database has no entry
- others
- may be problematic
- need to check in details

## How to solve ?
- Through help of database and another process
- when executing each stage we can assign state of that installation
- Before install status : install starting
- after install status : install completed
- after db entry : added to db
- ....
- pros
- we can track exactly where the program exited, and take decisions based on that
- cons
- easy solutin but complex logic will arise, for example a lot of conditionals on installation, such as check state of the package, if package in certain state, do this and so on.
- need another process that will check the state of package, if installed and not in database, it will push to `install database` same for the remove

- Using graceful shutdown
- the idea is to detect the exit signal , but rather than terminating instantly, wait for the installation to complete and then exit program
- pros
- it will make sure that everything goes right
- cons
- for panics it will not work
- the user might want to exit instantly but rather he will have to wait, violating the purpose of the user

- Using Database and CLI
- Database stores states of each installation
- We can track at what level the installation is
- started
- completed
- Fetch pending installs, or the broken ones
- Run cleanup
- Remove everything of that package
- Now we can fresh install