Report live value of d parameter in decentralizationLevel.

[jonathanknowles]

Context

Task #1692 will have added a skeletal decentralizationLevel parameter to the ApiNetworkParameters object.

Decision

Adjust the code so that this parameter reflects the true value of the d parameter, as reported by the network.

Acceptance Criteria

• The GetNetworkParameters API endpoint must return a decentralization level percentage that reflects the true value of the d parameter, as reported by the network.

Development

• (Introduce ProtocolParameters type. #1700)
  Introduce ProtocolParameters type to hold (a subset of) the protocol parameters defined in a Formal Specification of the Cardano Ledger.

  data ProtocolParameters = ProtocolParameters  
      { decentralizationLevel
          :: Quantity "percent" Percentage      
      , txParameters
          :: TxParameters       
      }

• (Introduce ProtocolParameters type. #1700)
  Rewrite the GenesisBlockParameters type to include a ProtocolParameters value (whose type is defined above):

  - data GenesisBlockParameters = GenesisBlockParameters
  -     { staticParameters :: BlockchainParameters
  -     ,     txParameters ::         TxParameters
  -     }
  + data NetworkParameters = NetworkParameters
  +     {  genesisParameters ::  GenesisParameters
  +     , protocolParameters :: ProtocolParameters
  +     }

• (Introduce ProtocolParameters type. #1700)
  Change the type of toApiNetworkParameters to:

  - toApiNetworkParameters :: BlockchainParameters -> ApiNetworkParameters
  + toApiNetworkParameters ::    NetworkParameters -> ApiNetworkParameters

• (Revise documentation for NetworkParameters and related types. #1715)
  Revise documentation comments for the following types:

  • NetworkParameters
  • GenesisParameters
  • ProtocolParameters
    
    

• (Report live value of decentralization parameter d. #1725)
  Generalize the wallet, network, and database layers to use ProtocolParameters instead of TxParameters. (ProtocolParameters includes TxParameters).

• (Report live value of decentralization parameter d. #1725)
  Adjust the chain-following code to retrieve the current value of the d parameter, in the same way we already do for transaction parameters.

• (Report live value of decentralization parameter d. #1725)
  Introduce a DecentralizationLevel type (based on the Percentage type).

  Greater values should indicate greater levels of decentralization, as follows:

  Value	Meaning
  0%	Network is completely federalized
  100%	Network is completely decentralized

• (Report live value of decentralization parameter d. #1725)
  Add a function to convert from d parameter values to values of type DecentralizationLevel, performing the following mapping:

  {1 → 0%, 0.9 → 10%, 0.8 → 20%, ..., 0 → 100%}
  

QA

• Create unit and property tests to check that we correctly convert from values of d (provided by cardano-node) to values of DecentralizationLevel.
• Add unit test to lib/byron/test/unit/Cardano/Wallet/Byron/NetworkSpec.hs to see that decentralization parameter is updated ⇒ Add unit test to check updates of decentralizationLevel #1736.
• Add integration test NETWORK_PARAMS - Able to fetch network parameters to check that decentralization parameter is correct (this is not checking parameter updates however) ⇒ Add unit test to check updates of decentralizationLevel #1736.

[jonathanknowles]

@rvl wrote:

I suspect that you will hook in to the same place that TxParameters are updated (fromPParams), and possibly rename/embed TxParameters to something more general.

[piotr-iohk]

lgtm.