NewOperationFlow sets up the StartState, so transitions will be reported to `listener`.

States are emitted in Transitions and contain a certain Update type.

States are emitted in Transitions and contain a certain Update type.

States are emitted in Transitions and contain a certain Update type.

BaseState contains the shared structure among all states.

ExchangeRateWindow holds a map of exchange rates from BTC to every currency we handle.

FeeWindow holds a map of target block to fee rate for a given time.

MonetaryAmount holds an amount of money in a certain currency.

NextTransactionSize is a struct used for calculating fees in terms of the unspent outputs required to perform a transaction.

PaymentContext stores data required to analyze and validate an operation.

PaymentIntent contains the resolved payment intent and does not change during the flow.

State is an interface implemented by every state type, containing flow-level properties.

TransitionListener allows app-level code to receive state updates asynchronously, preserving concrete types across the bridge and enforcing type safety.