# Pre/Post Expiry Exits

```mermaid
sequenceDiagram
  actor User
  participant Router as Router (ActionMiscV3)
  participant Market as FiraMarket
  participant FW as FW
  participant CT as CouponToken (CT)
  participant BT as BondToken (BT)

  alt Pre-expiry exit (exitPreExpToToken/Fw)
    Note over User,Router: User approves LP/BT/CT tokens to Router
    User->>Router: exitPreExpToToken(receiver, market, netBtIn, netCtIn, netLpIn, output, limit)

    opt LP provided (netLpIn > 0)
      Router->>Market: transfer LP from user to market
      Router->>Market: burn(fwReceiver, Router, netLpIn)
      Market-->>Router: FW out (to fwReceiver), BT out (to Router)
    end

    opt Additional BT provided (netBtIn > 0)
      Router->>Router: pull BT from user
    end

    Note over Router: Match BT with CT for BC redemption (most efficient path)
    Note over Router: netBcRedeem = min(totalBt, netCtIn)
    opt netBcRedeem > 0
      Router->>CT: transfer BT to CT contract
      Router->>CT: transfer CT from user to CT contract
      Router->>CT: redeemBC(fwReceiver) — burns both BT + CT → FW
      CT-->>Router: FW from redemption
    end

    Note over Router: Handle remaining unmatched tokens
    opt Remaining BT (not matched with CT)
      Router->>Market: swapExactBtForFw — swap surplus BT → FW via AMM
      Market-->>Router: FW from swap
    end
    opt Remaining CT (not matched with BT)
      Router->>Market: swapExactCtForFw — swap surplus CT → FW via AMM
      Market-->>Router: FW from swap
    end

    Router->>FW: redeem all collected FW → tokenOut
    FW-->>Router: tokenOut
    Router-->>User: tokenOut to receiver

  else Post-expiry exit (exitPostExpToToken/Fw)
    Note over User,Router: User approves LP/BT tokens to Router
    User->>Router: exitPostExpToToken(receiver, market, netBtIn, netLpIn, output)

    opt LP provided (netLpIn > 0)
      Router->>Market: transfer LP from user to market
      Router->>Market: burn(fwReceiver, CT, netLpIn)
      Market-->>FW: FW out (to fwReceiver)
      Market-->>CT: BT out (sent to CT contract for redemption)
    end

    opt Additional BT provided (netBtIn > 0)
      Router->>CT: transfer BT from user directly to CT contract
    end

    Router->>CT: redeemBC(fwReceiver) — burns BT only, CT NOT burned
    CT-->>Router: FW from redemption (at bcIndex rate)

    Router->>FW: redeem all collected FW → tokenOut
    FW-->>Router: tokenOut
    Router-->>User: tokenOut to receiver
    Note over CT: Post-expiry yield difference accrues to treasury
  end
```

**Key references**: `IPActionMiscV3.exitPreExpToToken/Fw`, `exitPostExpToToken/Fw`.

## Details

* **Goal**: Unwind LP/BT/CT positions to a single token or FW.
* **Pre-expiry**: Router first matches BT with CT for redemption (cheaper than swapping), then swaps any remaining unmatched BT or CT to FW via the AMM. Finally redeems FW to desired token.
* **Post-expiry**: BT is sent to the CT contract. `CT.redeemBC()` burns only BT (not CT). FW returned at current `bcIndex` rate. Post-expiry yield accrual goes to treasury, not the redeemer.

{% hint style="info" %}
**Implementation note**: `exitPostExpToFw` has a parameter named `netFwOut` that should be `netBtIn` (naming bug in implementation, no functional impact).
{% endhint %}

## Views and events

**Views**

* Market: `isExpired()`, `readTokens()`, `observe(...)`.
* Lending: `getUserPosition` if exiting borrow-adjacent strategies.

**Events**

* Router: `ExitPreExpToToken`, `ExitPreExpToFw`, `ExitPostExpToToken`, `ExitPostExpToFw`.
* Market: `Burn`, subsequent `Swap` if executed.
* CT: `Burn` (for BC redemption step).