Incorrect 100x amount in payment notification when currency is HUF

[openoms]

Describe the bug
The amount is shown as 100x in the notification when using HUF as the display currency.

To Reproduce
Steps to reproduce the behavior:
The padding in the notification should be the same as in the history with two digits accuracy.

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
Notification showing +364 506Ft

The correct amount history is
Notification showing +3654.06Ft

Smartphone (please complete the following information):

• Device: Pixel5
• OS: GraphenOS
• Version 2.2.263

Additional context
Add any other context about the problem here.

[amitamrutiya]

Hey @openoms, I want to work on this issue. I think it's a good one to explore in this repository.

[thevaibhav-dixit]

@openoms is there any trace for this ?

[openoms]

shared in DM with @thevaibhav-dixit .

Turns out HUF is special as it does not have a minor exponent https://leejo.github.io/2015/08/02/a_lot_of_huf/ :

        HUF : {
            exponent: 0,
            iso_alpha_code: "HUF",
            iso_numeric_code: "348",
            locale: EnBy,
            minor_units: 5,
            name: "Hungarian Forint",
            symbol: "Ft",
            symbol_first: false,
        },

It is causing the problem in the notifications, but not in the transaction history.

[openoms]

The issue is likely related to the difference between the libraries used (or how they are handled) in the backend (https://github.com/galoymoney/blink) vs this repo for the mobile app.

Excerpt from an example notification trace from the backend :

app.handle_transaction_occurred_event

TransactionOccurred { transaction_type: LightningReceipt, settlement_amount: TransactionAmount { minor_units: 16000, currency: Crypto(Currency { code: "BTC", exponent: 8, locale: EnUs, minor_units: 100000000, name: "Bitcoin", symbol: "₿", symbol_first: true }) }, display_amount: Some(TransactionAmount { minor_units: 366519, currency: Iso(Currency { iso_alpha_code: "HUF", exponent: 0, iso_numeric_code: "348", locale: EnBy, minor_units: 5, name: "Hungarian Forint", symbol: "Ft", symbol_first: false }) }) }

[mlori]

The final text of the txNotification is presented based on this metadata:

    minor_units: 366519, 
    currency: Iso(Currency {
      iso_alpha_code: "HUF", 
      exponent: 0, 
      iso_numeric_code: "348", 
      locale: EnBy, 
      minor_units: 5, 
      name: "Hungarian Forint", 
      symbol: "Ft", 
      symbol_first: false
    })
  }

I asume the text prestended in the push notifcation is renderred on backend side. While the text presented in tx history and other places is renderred on UI side.
Is it possible to override the above setup for HUF in the backend library, with a custom formatter?
Options:

1. On backend side set exponent = 2, this implies, the minor_units should be 500 (so it will be expressed in fillér) - In this case i think no UI side change is required.
2. keep exponent = 0 and round the amount so minor_units = 3665.
   Drawback of 2.: we lost the decimals and In this case the UI side has to be adapted too.
   somewhere around this point: https://github.com/GaloyMoney/blink-mobile/blob/main/app/hooks/use-display-currency.ts#L146