Orderbook: Add GetDepth to Base

[gbjk]

Base.GetDepth returns the concrete book of which Base is a copy This is probably useful for immutably monitoring orderbook health and state whereas FetchOrderbook would trigger a refresh.

Type of change

• New feature (non-breaking change which adds functionality)

How has this been tested

• go test ./... -race
• golangci-lint run

[gloriousCode]

Base already has access to the fields to make the call for GetDepth, but this is still a nice enough helper to avoid needing to provide params anyway.

[shazbert]

One nit.

[gbjk]

@gloriousCode

Base already has access to the fields to make the call for GetDepth, but this is still a nice enough helper to avoid needing to provide params anyway.

Base does, but nothing outside it does, right?
In the case of a consumer of the Bitfinex exchange, calling FetchOrderbook formats the pair, and then fetches the orderbook.
You can't call GetDepth without knowing the pair, and you can't find out if the orderbook is valid without risking a fetch.
There's a few other options, but this felt easiest.

[gbjk]

All comments addressed.

We discussed why this method is helpful, and with some refactoring/improvement/something in bitfinex maybe we could get away with calling FormatExchangePair before calling Fetch ever, or something.
But it's a can of worms so for now this solves my need and isn't too code-rotty.

[gbjk]

Ah. This is failing when run as a whole suite. Will work out why.
Probably service is populated by prev test

[gbjk]

Yep. It was that. Fixed.

[shazbert]

tACK. Thanks.

[gloriousCode]

tACK! Thanks for making those changes