New Feature: Allow users to buy some tokens with eth directly

[kongliangzhong]

Allow users buy some tokens with ETH directly.
This feature should be implemented in a new function in IRingSubmitter.
Should we allow users buy tokens from some addresses directly(need a price service, like Kyber) or from a sell order? (need some discussion here)

[Brechtpd]

I'd limit it to orders that sell for WETH/ETH. I don't really see a need to allow buying tokens with ETH in a different market.

We actually still have a choice here:

Support ETH directly:

Good:

• Seller receives ETH directly if he wants

Bad:

• Different markets for ETH and WETH
• We will need to support ETH everywhere (transfers/fee contracts)

Support ETH by automatic conversion to WETH

For example, before we transfer the tokens we check how much WETH we need and convert the ETH to WETH so everything works like usual. This way we only convert the actual amount needed for the trades.

Good:

• Single WETH market
• No need to really support ETH anywhere except adding some special cases (like spendables for the owner of the ETH needs to be set to msg.value)

Bad:

• Seller always receives WETH, never ETH

[kongliangzhong]

I think the second one: support ETH by conversion to WETH will be a good choice for us.