# isFirstSupply
## Overview
* [x] cache
* [x] updateState
* [x] validateSupply
* [x] updateInterestRates
* [x] transfer & mint
* [ ] If isFirstSupply
This is the last execution block for a supply action. This if block only executes in the event of a user's very first supply action for a specific asset.
If on minting ATokens, `isFirstSupply` is returned as `TRUE`, and the nested `validateUseAsCollateral` returns `TRUE` as well,
* `isFirstSupply` : `TRUE` => user's first time supplying this specific asset
* `validateUseAsCollateral` : `TRUE` => either:
* `isUsingAnyCollateralAny`: `TRUE` => user never supplied any asset ever,
* OR,
* `!isolationMode && getDebtCeiling == 0`: TRUE => there is no debt ceiling on incoming supplied asset AND the user is not in isolation mode.
## isFirstSupply
* captures the return value from `mint`
* `TRUE` if user has no prior supply actions, and therefore a pre-dating zero supply balance
If `TRUE`, execution moves into the nested if block, with the return value of `validateUseAsCollateral` as the condition.
### validateUseAsCollateral
This function checks if the incoming asset can be used as collateral. If the user is previously in [isolated mode](https://calnix.gitbook.io/aave-book/aave-features/risk-management/isolation-mode), other assets cannot be supplied as collateral at the same time.
{% hint style="info" %}
Supplied assets are automatically treated as collateral, if possible.
{% endhint %}
#### isUsingAsCollateralAny
* checks if user has been supplying ANY asset as collateral
* returns `FALSE` if user has NOT supplied ANY asset so far
{% hint style="info" %}
[`isUsingAsCollateralAny` breakdown](https://calnix.gitbook.io/aave-book/functions/supply/isfirstsupply/isusingascollateralone-isusingascollateralany)
{% endhint %}
If the user has never supplied any assets to date, (`isUsingAsCollateralAny` returns `FALSE`) `validateUseAsCollateral` will exit early and return `TRUE`.
* Execution will then proceed to [`setUsingAsCollateral`](#setusingascollateral); this will engage in first-time user configuration setup.
{% hint style="success" %}
User cannot be in isolation mode if he has no supplied action to date.
{% endhint %}
However, if `isUsingAsCollateralAny` is true; user has executed supply action sometime before. This means, we must check if the user is currently in **isolation mode;** achieved by `getIsolationMode`.
* If he is, it could cause conflict with the new supply action.
* Additionally, there would be no need to execute `setUsingAsCollateral`, as this is not a first-time user.
### `getIsolationMode`
* if user is supplying only one type of collateral, get the debt ceiling of the collateral to check if its an isolated asset.
* returns `TRUE`, along with value of debt ceiling
* If the user is supplying multiple types of collateral, clearly he is not in isolation mode, returns `FALSE`.
#### Visual aid
* isUsingCollateralOne: checks if the user has been supplying only 1 asset as collateral
#### return (!isolationMode && getDebtCeiling == 0)
`!isolationMode && getDebtCeiling == 0`:
* TRUE => there is no debt ceiling on incoming supplied asset AND the user is not in isolation mode.
## setUsingAsCollateral
#### `(reserveIndex << 1) + 1`
* This bitwise operation doubles the index and increments it by 1
* Creates the necessary offset to manipulate the relevant bits to the asset of specified index
* For more in-depth explanation see: [isUsingCollateral](https://calnix.gitbook.io/aave-book/withdraw/collateral-check#example-check-if-the-user-has-been-using-the-reserve-at-index-2-as-collateral)
#### **`bit = 1 << offset`**
If `usingAsCollateral` is **true**, indicating that the reserve should be marked as used for collateral,
* bitwise OR operation between `data` and the `bit` value (`self.data |= bit`).
* sets the corresponding bit in the `self.data` variable to `1`
If `usingAsCollateral` is **false**, indicating that the reserve should NOT be marked as collateral
* bitwise AND operation between `data` and the `bit` value (`self.data &= bit`).
* sets the corresponding bit in the `self.data` variable to `0`
## isFirstSupply
* captures the return value from `mint`
* `TRUE` if user has no prior supply actions, and therefore a pre-dating zero supply balance
If `TRUE`, execution moves into the nested if block, with the return value of `validateUseAsCollateral` as the condition.
### validateUseAsCollateral
This function checks if the incoming asset can be used as collateral. If the user is previously in [isolated mode](https://calnix.gitbook.io/aave-book/aave-features/risk-management/isolation-mode), other assets cannot be supplied as collateral at the same time.
{% hint style="info" %}
Supplied assets are automatically treated as collateral, if possible.
{% endhint %}
* isUsingCollateralOne: checks if the user has been supplying only 1 asset as collateral
#### return (!isolationMode && getDebtCeiling == 0)
`!isolationMode && getDebtCeiling == 0`:
* TRUE => there is no debt ceiling on incoming supplied asset AND the user is not in isolation mode.
## setUsingAsCollateral
If `usingAsCollateral` is **true**, indicating that the reserve should be marked as used for collateral,
* bitwise OR operation between `data` and the `bit` value (`self.data |= bit`).
* sets the corresponding bit in the `self.data` variable to `1`
If `usingAsCollateral` is **false**, indicating that the reserve should NOT be marked as collateral
* bitwise AND operation between `data` and the `bit` value (`self.data &= bit`).
* sets the corresponding bit in the `self.data` variable to `0`