Feature request/discussion: historical price data

[rating89us]

Transactions page should display fiat conversion of past transactions using historical price data. To avoid compromising user privacy, we should not retrieve prices using an external API.

Therefore, I see two possible implementations:

Option A: save current XMR price on wallet cache every time a transaction is sent/received

• Easier to implement.
• Historical prices can be exported to other Monero (software) wallets.
• More precise. Current price can be updated just before saving a transaction on the wallet.
• Transactions sent/received before implementation of Option A will not have fiat price conversion (unless we also implement Option B).

Option B: import historical price data from an external source (like this .csv file from Kraken)

• .csv file containing all XMRUSD trades of kraken (2017 until today) has ~80 MB.
• Requires an script to extract useful price information from this huge file. After selecting 2-3 price points for each day, I estimate it would have a size of less than 300 kB.
• How many price points will we use for each day? Should days with higher volatility have more price points? Should we use an average price for each day?
• Will this historical price data be small enough to be embedded in Monero GUI release? Or do we want extreme precision and offer the user to download 80 MB of data as an optional download?
• Will it only be updated on every GUI version release? Will an updated version of the .csv file be available between Monero GUI releases?