### Description of Strategy
This strategy has been designed using one of the highest TVL strategies from Yearn Finance: [Generic-Lender](https://github.com/Grandthrax/yearnV2-generic-lender-strat). This strategy uses a lender-agnostic approach to optimize the routing of new deposits withdraws across an arbitrary number of lending platforms according to best-APY. This is done by using "plug-in" contracts which map the various platform APIs back to the common Generic Lender strategy API (shown in the diagram below). Although RAI only exists on limited lending platforms today, there are pre-written plugins that exist for the following lending platforms that can be leveraged immediately if RAI were to be added:
- Compound
- Aave
- Fuse
- Alpha Homora
- Cream
- DyDx

This codebase has been both reviewed and formally audited, and is utilized on just about every production v2 vault that Yearn has.


#### Generic Lender Overview and Key Advantages
The Generic Lender strategy contract is designed to allow a vault to lend funds to multiple lending platforms and autobalances in order to achieve the best APY. This strategy offers a highly omptimized, gas efficient methodology for allowing RAI holders to maximize the yield on their assets over time.

Whenever the `harvest` function is called (e.g. once daily), depending on the conditions of the vault, funds may be added to the strategy or removed from the strategy. In both cases, the Generic Lender optimizes which lenders to remove or add funds to. It does this by cycling through the available lenders and rebalance by:
1. Identifying the lowest yielding platform and determining the amount that should be withdrawn from that platform
2. Identifying the highest yielding platform and determining the amount that should be deposited into it

Importantly, the expected yield on the platform that is being deposited is calculated _post-deposit_ ensuring that if large deposits are being made, the strategy is properly accounting for any downward pressure on yields that this could create.

If ever necessary, a function is made available to authorized users to define a custom allocation across available lenders, effectively overriding the strategy's default behavior.

Similar to how we optimize allocation of inbound funds, there are efficiencies realized on outbound funds. Whenever a user calls `withdraw`, the strategy will similarly cycle through the various platforms and identify the lowest yielding one and selectively withdraw funds from that one. If not enough funds are available from the lowest yielding platform to fulfill the withdrawal, the process repeats.

The net effect of these features is that every time funds are deposited, they are allocated to the highest yielding option, and when funds are withdrawn they are withdrawn from the lowest yielding option. This results in the overall vault APY increasing each time a user withdraws from the vault.

One additional feature of this strategy is that it implements `tend` function that identifies whether the yield gains of rebalancing outweight gas costs. There is also a `tendTrigger` function which automates this decision and signals to keepers when it makes sense to call `tend`.

# RAI Strategy

## Links
- [Gitcoin Bounty](https://gitcoin.co/issue/reflexer-labs/geb-safe-saviours/3/100025561)

### Code resources
- [GenLender](https://github.com/Grandthrax/yearnV2-generic-lender-strat/blob/master/contracts/Strategy.sol)
- Sam's generic lender strategy
- [Generic Cream](https://etherscan.io/address/0xC53a7A7bEB51141b750b2752cD1276150a511daa#code)
- [Generic DyDx](https://etherscan.io/address/0xed2F20ACbb4809BB2F62da75cbE3A0Df557d955E#code)
- [Brownie-strategy-mix](https://github.com/yearn/brownie-strategy-mix)
- This is the template used to begin work on a strategy. Comes with basic dependencies and tests.
- [Yearn BaseStrategy](https://github.com/yearn/yearn-vaults/blob/master/contracts/BaseStrategy.sol)
- Reference for BaseStrategy, which is inhereited by all strategiest
- [Yearn Vault.vy](https://github.com/yearn/yearn-vaults/blob/master/contracts/Vault.vy)
- Reference for how the vault works

- [Deployment Process](https://github.com/yearn/yearn-vaults/tree/master/docs)
- Use this when it comes time to deploy

## Write Up
- Price per share on deposit/withdraw

#### Platform-Specific Plugins
The plugin contracts allow our Generic Lender to inferface with lending platforms. For the purposes of this submission, plugins for Cream and Fuse have been implemented. A major benefit of the approach taken is that adding new lending platforms such as Aave or Compound can be easily achieved, plugins can be updated as needed and also removed if they are no longer desired.

## Questions
- Strategist rewards on live vault
- Funding for keepers
- Expectation that this goes live on Yearn.finance
- Expected APY + expected deposits
- Any guidance/preference on post-save CRatio (if user is liquidated for being <145%, we need to assign a value to how much debt should be repaid by the keeper)
- Is Compound out of scope? Is there already existing saviour for this.

- How should tests be delivered? Preferred testing suite? Yearn strategy
- Kovan requirement... requires FUSE/Cream/Yearn
- Will standard Yearn 2/20 fee structure be used

## To-do list
- [ ] Genlender strategy study
- How the optimization works
- Any shortcomings to highlight?
-
- [ ] Fully integrated test in brownie
- [ ] Test saviour using Stefan tests
- [ ] Write-up
- make the case for our submission
- flow diagram with Yearn vault management?

# Write up outline

### How the strategy works
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