Transaction finalization

[Klakurka]

Mark transactions as finalized in the db as they happen and show this to the user in some way.

[Klakurka]

Show this instead of a block confirmation for XEC.

From Fabien:

when you subscribe to a script you get events for tx_added_to_mempool, tx_removed_from_mempool, tx_confirmed and tx_finalized

tx_finalized is what we're looking for.

[Klakurka]

This also involves changing the 'CONFIRMED' table header text to 'FINALIZED'.

[chedieck]

I would like to understand better the difference between "finalized" and "confirmed". Chronik supports the following messages:

export type SubscribeMsg =
  | Error
  | MsgAddedToMempool
  | MsgRemovedFromMempool
  | MsgConfirmed
  | MsgReorg
  | MsgBlockConnected
  | MsgBlockDisconnected

... which doesn't seem to include the "finalized" logic.

---

more info about each message from chronik code:

/** A transaction has been added to the mempool. */
export interface MsgAddedToMempool {
  type: "AddedToMempool"
  /** txid of the transaction, in 'human-readable' (big-endian) hex encoding. */
  txid: string
}

/** A transaction has been removed from the mempool,
 * but not because of a confirmation (e.g. expiry, conflict, etc.).
 */
export interface MsgRemovedFromMempool {
  type: "RemovedFromMempool"
  /** txid of the transaction, in 'human-readable' (big-endian) hex encoding. */
  txid: string
}

/** A transaction has been confirmed in a block. */
export interface MsgConfirmed {
  type: "Confirmed"
  /** txid of the transaction, in 'human-readable' (big-endian) hex encoding. */
  txid: string
}

/** A transaction used to be part of a block but now got re-orged.
 * Usually, unless something malicious occurs, a "Confirmed" message is sent
 * immediately afterwards.
 */
export interface MsgReorg {
  type: "Reorg"
  /** txid of the transaction, in 'human-readable' (big-endian) hex encoding. */
  txid: string
}

/** A new block has been added to the chain. Sent regardless of subscriptions. */
export interface MsgBlockConnected {
  type: "BlockConnected"
  /** block hash of the block, in 'human-readable' (big-endian) hex encoding. */
  blockHash: string
}

/** A block has been removed from the chain. Sent regardless of subscriptions. */
export interface MsgBlockDisconnected {
  type: "BlockDisconnected"
  /** block hash of the block, in 'human-readable' (big-endian) hex encoding. */
  blockHash: string
}

[Klakurka]

We need to wait for the next version of chronik to be available which has this.

Finalization currently happens about 1-2 seconds after making it into a block. In the future (with the pre-consensus upgrade), it will happen 1-2 seconds after hitting the mempool.

Finalization means that a transaction can no longer be double spent by a conflicting tx.

A "confirmation" refers to the fact that a new block has come in that either includes the transaction in question (1 confirmation) or that a new block has come in on top of it (2+ confirmations).

Without finalization (eg. on Bitcoin), it's technically possible for a transaction to be double spent even after it has made it into a block (1 confirmation). Each confirmation makes it less and less likely for this to happen but it's still technically possible several blocks deep. This is especially true on low-hash minority forks like BCH or XEC.

[Klakurka]

It's less important while pre-consensus isn't yet live.