# getIsolationModeState
## Overview
* [x] cache
* [x] updateState
* [ ] getIsolationMode
* [ ] validateBorrow
* [ ] mint debt token
* [ ] setBorrowing
* [ ] update IsolationMode debt
* [ ] updateInterestRates
* [ ] transfer underlying to user
## getIsolationModeState
Check if user is in isolation mode, if so, return the isolated asset address and its corresponding debt ceiling.
{% hint style="info" %}
Isolation mode: user can only use the specific isolation asset as collateral
{% endhint %}
There 3 other functions within `getIsolationModeState` which we will cover:
1. `isUsingAsCollateralOne`
2. `_getFirstAssetIdByMask`
3. `getDebtCeiling`
Essentially,
1. `isUsingAsCollateralOne`: check if user has ONLY ONE asset as collateral (any one).
2. If check returns true, possible that the user is in isolation mode.
* get and return isolation details: `(true, assetAddress, debtCeiling)`
3. `_getFirstAssetIdByMask` is used to obtain the `assetID` of this asset.
* Since `isUsingAsCollateralOne` is `true`,
* only 1 asset to ID, no need to worry about multiple assets
4. If `isUsingAsCollateralOne` is `false`
* user has multiple reserves as collateral
* not in Isolation mode
* return `(false, address(0), 0)`
### `isUsingAsCollateralOne`
Check if user has ONLY ONE asset as collateral (any one).
This function was explained previously when covering the `supply` function: [isUsingCollateralOne](https://calnix.gitbook.io/aave-book/supply/isfirstsupply/isusingascollateralone-isusingascollateralany#isusingcollateralone)
### `_getFirstAssetIdByMask`
Returns the address of the first asset flagged in the bitmap given the corresponding bitmask.
* if collateral\_mask, find the first asset which has its collateral bit set to `1`
```solidity
uint256 internal constant COLLATERAL_MASK =
0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
```
* `COLLATERAL_MASK` is passed as `mask`
* `bitmapData` is the binary string comprising of isolated collateral bits as explained in: [isUsingAsCollateralAny](https://calnix.gitbook.io/aave-book/supply/isfirstsupply/isusingascollateralone-isusingascollateralany#isusingascollateralany)
As we can see, we can end with id of value 1 -> index of the first asset which has its collateral bit set to `1` is 1.
### `getDebtCeiling`
With the previously obtained asset index, we can retrieve the `assetAddress` by the `reserveList` mapping. With the address, we can retrieve its corresponding `reservesData` struct, using it to obtain the debt ceiling.
```solidity
address assetAddress = reserveList[assetId]; //declared on PoolStorage.sol
uint256 ceiling = reservesData[assetAddress].configuration.getDebtCeiling();
```
`getDebtCeiling` will extract the debt ceiling value held within bits 212-251 in the `ReserveConfigurationMap`.
Reference: ReserveConfigurationMap
`getDebtCeiling` utilizes the same approach as explained in [getReserveFactor](https://calnix.gitbook.io/aave-book/primer/bitmap-and-masks#getreservefactor); see that section for an in-depth explanation.
{% hint style="info" %}
The debt ceiling value has decimals as dictated in **`ReserveConfiguration::DEBT_CEILING_DECIMALS`**, like so:
```solidity
uint256 public constant DEBT_CEILING_DECIMALS = 2;
```
{% endhint %}
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## getIsolationModeState
Check if user is in isolation mode, if so, return the isolated asset address and its corresponding debt ceiling.
{% hint style="info" %}
Isolation mode: user can only use the specific isolation asset as collateral
{% endhint %}
There 3 other functions within `getIsolationModeState` which we will cover:
1. `isUsingAsCollateralOne`
2. `_getFirstAssetIdByMask`
3. `getDebtCeiling`
Essentially,
1. `isUsingAsCollateralOne`: check if user has ONLY ONE asset as collateral (any one).
2. If check returns true, possible that the user is in isolation mode.
* get and return isolation details: `(true, assetAddress, debtCeiling)`
3. `_getFirstAssetIdByMask` is used to obtain the `assetID` of this asset.
* Since `isUsingAsCollateralOne` is `true`,
* only 1 asset to ID, no need to worry about multiple assets
4. If `isUsingAsCollateralOne` is `false`
* user has multiple reserves as collateral
* not in Isolation mode
* return `(false, address(0), 0)`
### `isUsingAsCollateralOne`
Check if user has ONLY ONE asset as collateral (any one).
As we can see, we can end with id of value 1 -> index of the first asset which has its collateral bit set to `1` is 1.
### `getDebtCeiling`
With the previously obtained asset index, we can retrieve the `assetAddress` by the `reserveList` mapping. With the address, we can retrieve its corresponding `reservesData` struct, using it to obtain the debt ceiling.
```solidity
address assetAddress = reserveList[assetId]; //declared on PoolStorage.sol
uint256 ceiling = reservesData[assetAddress].configuration.getDebtCeiling();
```
