Change wallet currentTip from SlotId to BlockHeader

[Anviking]

Issue Number

#219

Overview

• Change the tip from SlotId to BlockHeader

Comments

• Remake of First exploration: Jörmungandr NetworkLayer #366
• The gist of it should be here, but I'll go through and polish / self-review it
• I have a concern about if we want to extend BlockHeader in the future
• We could still parameterise over the tip (but even if we solve the Sqlite schema by storing Either tip1 tip2 as (Maybe tip1, Maybe tip2), we introduce a new dimension of complexity in the database, which might be undesired)

[Anviking]

This will never work 😕

BlockHeader stores the blockId of the parent. So if the tip is n we must call getDescendants on (n-1). This was fine, I thought — but of course we can't ask for the descendants of block -1 to fetch block 0.

But, I think we can't go wrong with data Cursor = { blockId :: Hash "BlockHeader", header :: BlockHeader }, which also happens to be the exact type used for the current networkTip.

[KtorZ]

👍

[KtorZ]

rebased on top of master + improved comment for defaultRetryPolicy as suggested in #400

[Anviking]

Squashed relevant commits into Change type of tip from SlotId to BlockHeader.

[KtorZ]

@Anviking Not so sure about the squash here. I think some commits deserved to be separated for readability. Styling stuff and indentation fixes, sure; but structural changes were better off separated IMO.