public/subjects/personal-shopper/README.md

personal-shopper

Instructions

You know your guests, but don't forget you have to feed them if you want to be considered as a good host.

Create a personal-shopper.mjs script that:

• Takes a file as first argument, for example shopping-list.json
• Takes one of these keywords as second argument:
  • create: create the file
  • delete: delete the file
  • add: add a new element to the list in the file.
    • This command line must take a third argument which is the name of the new entry in your list. If no third argument is passed, console must print this error: No elem specified..
    • This command line could take a fourth argument which is the number of elements you want for this new entry.
      • If there is no 4rth argument or the 4rth argument is NaN, 1 would be the value by default.
      • If the entry already exists, it would add 1 or more to the original value.
      • Using a negative number must behave as rm command.
  • rm: remove an element from the list in the file
    • This command line must take a third argument which is the name of the entry to remove from the list.
      • If no third argument is passed, console must print this error: No elem specified..
      • If the entry does not exists, it does nothing.
    • This command line could take a fourth argument which is the number of elements you want to delete from this entry.
      • If there is no 4rth argument: it remove the entry.
      • If the 4rth argument is NaN, nothing is removed and console must print this error Unexpected request: nothing has been removed.
      • If the 4rth argument is a number, it will substract this number from the original value (if the new value is <= 0, it will remove the entry).
      • Using a negative number must behave as add command.
  • help: print all the command lines available, with a description of it (specifications in the examples)
  • ls or no more arguments: print the list in the console.
    • Each line is formated like this: - element (number)
    • If the list is empty, this message should appear in console: Empty list..

Examples

• node personal-shopper.mjs shopping-list.json create would create the file

• node personal-shopper.mjs shopping-list.json delete would remove the file

• node personal-shopper.mjs shopping-list.json add "tzatziki pot" would update the content of the file like:

'{
  "tzatziki pot": 1
}'

• node personal-shopper.mjs shopping-list.json add carrots 5 would update the content of the file like:

'{
  "tzatziki pot": 1,
  "carrots": 5
}'

• node personal-shopper.mjs shopping-list.json add carrots 2 would update the content of the file like:

'{
  "tzatziki pot": 1,
  "carrots": 7
}'

• node personal-shopper.mjs shopping-list.json rm carrots 4 would update the content of the file like:

'{
  "tzatziki pot": 1,
  "carrots": 3
}'

• node personal-shopper.mjs shopping-list.json rm carrots would update the content of the file like:

'{
  "tzatziki pot": 1
}'

• node personal-shopper.mjs shopping-list.json rm carrots -3 would update the content of the file like:

'{
  "tzatziki pot": 1,
  "carrots": 3
}'

• node personal-shopper.mjs shopping-list.json add carrots -3 would update the content of the file like:

'{
  "tzatziki pot": 1
}'

• node personal-shopper.mjs shopping-list.json ls would print the list in your console like this:

- tzatziki pot (1)

• node personal-shopper.mjs help would print a list of all available commands in your console :

Commands:
- create: takes a filename as argument and create it (should have `.json` extension specified)
- delete: takes a filename as argument and delete it
<!-- etc. -->

Notions

• Node file system: rm
• Node file system: writeFile
• JSON.parse()
• JSON.stringify()
• isNaN()
• Number()
• console.error()