Tiny app for converting currencies quickly

kirillt commented 2 years ago

Basically, the app must perform multi-conversion of currencies. E.g. we have 2 USD, 3 EUR, 1000 RSD and 250 TRY. This is "input" of our multi-conversion.

For the conversion we need 6 exchange rates:

USD-EUR (0.98 at July 19, 2022)
USD-RSD (115.5 at July 19, 2022)
USD-TRY (17.48 at July 19, 2022)
~EUR-USD~ (the same as USD-EUR)
EUR-RSD (117.4 at July 19, 2022)
EUR-TRY (17.76 at July 19, 2022)
~RSD-USD~ (the same as USD-RSD)
~RSD-EUR~ (the same as EUR-RSD)
RSD-TRY (0.15 at July 19, 2022)
~TRY-...~ (repeating one of the above)

The output would be list of conversions of total amount (2 USD + 3 EUR + 1000 RSD + 250 TRY) into each of the currency USD, EUR, RSD or TRY separately:

28.01 USD
27.38 EUR
3215.3 RSD
492.08 TRY

The app must consist of 2 screens:

"Input" screen — list of currencies user has.
- There must be a list of currency inputs:
- each row has number input, default is 0, no need to save the input between app launches
- each row has currency symbol or abbreviation ($ or USD for U.S. dollars)
- each row has [-] button for deleting the currency
- There must be a button [next], which loads next screen (passing user inputs into it).
"Output" screen - result of conversion. This screen accepts all user inputs from "Input" screen.
- There must be a list of all currency outputs:
- each row (for currency T):
  - has list of exchange rates, i.e. for each currency S, exchange rate between S and T must be displayed
  - all "input" currencies must be converted into currency T and summed up
  - total number must be displayed
- There must be a button [back], which loads previous screen
Both screens must have [add_curr] button, presenting a dialog for adding new currency to the lists:
- the dialog has drop-down list for choosing currency
- the dialog has [add] button saving the choice
  - after adding, list of currencies must contain new row with corresponding currency
  - selected currencies must be stored between app launches
- the dialog has [x] button for closing it without changes

List of chosen currencies is the same in "Input" and "Output" screen, must be saved into user data and be loaded during next app startup. Exchange rates must be taken from good source like Bloomberg, but can be other source if it's API is better.