The problem was that the restriction on the JOIN clause does not properly filter the complete set, but actually results in wrongly joining the CFDs.
This resulted in two CFDs returned, where one was wrongly assembled (the id of the first one, but the data of the second one).
In a cases where the wrong one is the first one in the list of returned CFDs we would run into an error when inserting a new state, because we would try to alter the state of a wrong CFD.
Fixed by joining on the id and filtering for the order.uuid in the where clause.
Note:
I also tested to add the `and orders.uuid = ?` restriction to the first join clause (in addition to the id clause) which might theoretically be more optimized.
That would work as well, but I found it harder to reason about it. As part of the overall where clause one can see the restriction to exactly this value more clearly.
Includes validating that the amount the other party commits to is the expected amount based on calculating the counterparty margin out of the CFD values.
Note: We could also remove the lock amount from the messages and use the calculation on both sides - that would simplify things.
Flattening the Cfd out in the internal mode has caused duplication and confusion.
This refactor puts the Order into the Cfd to make relations clearer.
Note that once we have multiple leverage the leverage and liquidation price will have to move into the Cfd because they depend on the user's choice then.
This should be trivial to do.
The buy margin is calculated from `initial_price`, `quantity` and `leverage`.
The sell margin is calculated from `initial_price` and `quantity` (no leverage trading for the seller at the moment).
Includes several refactors:
- Separate API interface for `Cfd` and `CfdOffer` when mapping `toSseEvent`. This allows internal modelling to be different than the exposed API.
- Remove the profit calculation internally, it is only relevant on the UI feed API level.
- Move code that is specific to taker/maker http API from `model` to the respective `routes` module.
- Some simplification of the calculation model of `Usd` (could be further improved by deriving calculation traits)
- Introduces `OfferOrigin` used to save the offer's origin as `mine` and `others` in the database. This is used to properly derive the CFD position from the offer.
Daniel Karzel