// [Phase 2 -- Coming Soon]
// Pseudocode illustrating the intended API

let tx = CrossVprogTransaction::new()
    // Read accounts (r(x)) -- state we need to inspect
    .read(lending_vprog, borrower_account)
    .read(dex_vprog, kas_stable_pool)
    .read(staking_vprog, stable_vault)

    // Write accounts (w(x)) -- state we will modify
    // Constraint: w(x) must be a subset of r(x)
    .write(lending_vprog, borrower_account)
    .write(dex_vprog, kas_stable_pool)
    .write(staking_vprog, stable_vault)

    // Witness set -- dependency resolution data
    .witness(lending_vprog, lending_state_proof)
    .witness(dex_vprog, dex_state_proof)
    .witness(staking_vprog, staking_state_proof);

// [Phase 2 -- Coming Soon]

/// Execute a borrow-swap-stake operation across three vProgs.
/// All operations are computed off-chain; only the proof goes to L1.
fn borrow_swap_stake(
    // Current state of all involved accounts
    lending_state: &LendingAccountState,
    dex_state: &DexPoolState,
    staking_state: &StakingVaultState,
    // Operation parameters
    borrow_amount: u64,
    min_stable_out: u64,
) -> Result<CompositeTransition, TransitionError> {

    // Step 1: Borrow from lending vProg
    let (new_lending_state, borrowed_kas) = lending_transition(
        lending_state,
        LendingAction::Borrow {
            amount: borrow_amount,
            collateral_ratio: 150,  // 150% collateralized
        },
    )?;

    // Step 2: Swap KAS -> stablecoin on DEX vProg
    let (new_dex_state, stable_received) = dex_transition(
        dex_state,
        DexAction::Swap {
            input_token: Token::KAS,
            input_amount: borrowed_kas,
            output_token: Token::KUSD,
            min_output: min_stable_out,
        },
    )?;

    // Step 3: Stake stablecoin on yield vProg
    let (new_staking_state, stake_receipt) = staking_transition(
        staking_state,
        StakingAction::Stake {
            token: Token::KUSD,
            amount: stable_received,
        },
    )?;

    // Return the composite transition
    Ok(CompositeTransition {
        transitions: vec![
            (LENDING_VPROG_ID, new_lending_state),
            (DEX_VPROG_ID, new_dex_state),
            (STAKING_VPROG_ID, new_staking_state),
        ],
        receipt: stake_receipt,
    })
}

// [Phase 2 -- Coming Soon]

/// Generate a single ZK proof covering all three state transitions.
/// Proof stitching combines individual transition proofs into one
/// composite proof that L1 can verify in constant time.
fn prove_composite(
    composite: &CompositeTransition,
    witnesses: &[ConciseWitness],
) -> Result<Proof, ProvingError> {
    let prover = Prover::new(ZkBackend::RiscZero);

    // Each vProg transition is proven independently
    let lending_proof = prover.prove_transition(
        &composite.transitions[0],
        &witnesses[0],
    )?;
    let dex_proof = prover.prove_transition(
        &composite.transitions[1],
        &witnesses[1],
    )?;
    let staking_proof = prover.prove_transition(
        &composite.transitions[2],
        &witnesses[2],
    )?;

    // Stitch proofs together into a single composite proof
    let composite_proof = prover.stitch(vec![
        lending_proof,
        dex_proof,
        staking_proof,
    ])?;

    Ok(composite_proof)
}

// [Phase 2 -- Coming Soon]

async fn submit_composite(
    client: &VprogsClient,
    tx: CrossVprogTransaction,
    proof: Proof,
) -> Result<TxId, SubmitError> {
    // L1 validates:
    // 1. All read/write set declarations are consistent
    // 2. Concise witnesses prove correct prior state
    // 3. ZK proof attests to correct execution of ALL transitions
    // 4. No conflicting writes with concurrent transactions
    let tx_id = client.submit_composite_proof(tx, proof).await?;

    // DagKnight provides instant finality
    println!("Composite transaction finalized: {}", tx_id);
    Ok(tx_id)
}