Add a max piece size to storage asks

[arajasek]

We should probably put something in that ensures that the new max piece size is less than or equal to the sector size.

This PR also includes a commit that makes the Storage Market client refuse to propose a deal if piece size > sector size.

[hannahhoward]

See comment about functional options pattern -- this will allow us to support more features on the StorageAsk in the future

[hannahhoward]

So I actually had something slightly different in mind when I mentioned variadic arguments -- I was talking about the functional options pattern:
https://www.sohamkamani.com/golang/options-pattern/

I would define the function this way:

type StorageAskOption func(*storagemarket.StorageAsk)
func (p *Provider) AddAsk(price abi.TokenAmount, duration abi.ChainEpoch, options ...StorageAskOption)

and then you can define:

func MinPieceSize(minPieceSize abi.PaddedPieceSize) StorageAskOptions {
   return func(sa *storagemarket.StorageAsk) {
      sa.MinPieceSize = minPieceSize
   }
}

and so on for other options (leave the price + duration as fixed arguments -- those are always required)

And then, in storedAsk.AddAsk, you can just do:

ask := &storagemarket.StorageAsk{
		Price:        price,
		Timestamp:    height,
		Expiry:       height + duration,
		Miner:        s.actor,
		SeqNo:        seqno,
		MinPieceSize: defaultMinPieceSize,
                  MaxPieceSize: defaultMaxPieceSize,
}
for _, option := range options {
   option(ask)
}

[hannahhoward]

Great idea to do this check early -- even if the provider would reject the deal eventually we should go ahead and error if we know the deal won't be accepted

[arajasek]

Ah, my bad, I definitely didn't know what functional options meant! Thanks for the detailed explanation, I've implemented it (and like the pattern, it's much better than what I had)!

[hannahhoward]

Hey was about to approve this but looks like you have an import cycle in your code. I would move StorageAskOption up to storagemarket/types.go and also change the signature for the function on the interface.

[codecov-io]

Codecov Report

Merging #188 into master will decrease coverage by 0.32%.
The diff coverage is 23.53%.

@@            Coverage Diff             @@
##           master     #188      +/-   ##
==========================================
- Coverage   68.00%   67.68%   -0.31%     
==========================================
  Files          39       39              
  Lines        2065     2079      +14     
==========================================
+ Hits         1404     1407       +3     
- Misses        559      569      +10     
- Partials      102      103       +1     

Impacted Files	Coverage Δ
storagemarket/impl/client.go	0.00% <0.00%> (ø)
storagemarket/impl/provider.go	6.99% <0.00%> (ø)
...oragemarket/impl/providerstates/provider_states.go	87.65% <0.00%> (-1.57%)	⬇️
storagemarket/types.go	33.34% <0.00%> (-66.66%)	⬇️
storagemarket/impl/storedask/storedask.go	80.52% <100.00%> (+0.79%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 731e6ca...5b9acf9. Read the comment docs.