cancel_listing in marketplace does not revert invoice NFT status from Listed back to Created

[Mac-5]

Description

When an invoice is listed on the marketplace via list_invoice, the contract makes a cross-contract call to InvoiceNftContract::set_listed to transition the NFT's status from Created → Listed.

However, when a listing is cancelled via cancel_listing (contracts/marketplace/src/lib.rs lines 217–239), the marketplace only marks its own Listing.is_active = false. It does not call the NFT contract to revert the status:

pub fn cancel_listing(env: Env, caller: Address, invoice_id: u64) -> Result<(), KoraError> {
    // ...validation...
    listing.is_active = false;
    env.storage().persistent().set(&DataKey::Listing(invoice_id), &listing);
    events::listing_cancelled(&env, invoice_id, &listing.seller);
    Ok(())
    // ← no call to nft_client.set_cancelled() or equivalent
}

After cancellation, the NFT remains in the Listed status permanently. The SME cannot re-list the invoice (because set_listed requires Created status) and cannot mint a replacement (the original NFT is stuck). The invoice is effectively dead.

Fix

Add a reverse-status transition. Either:

• Option A: Add a set_cancelled or set_created function to InvoiceNftContract and call it from cancel_listing.
• Option B: Add a generic revert_to_created(caller, invoice_id) on the NFT contract callable only by the authorized marketplace.

Acceptance Criteria

• After cancel_listing, the Invoice NFT status is Created (not Listed).
• The SME can re-list the same invoice after cancellation.
• A test covers: list → cancel → re-list succeeds.
• Unauthorized addresses cannot call the new status revert function.

Complexity: Medium (150 points)