#[cfg(feature = "nostr")]
use frost_secp256k1_tr as frost;
#[cfg(feature = "nostr")]
use rand::thread_rng;
#[cfg(feature = "nostr")]
use std::collections::BTreeMap;

/// A simplified ROAST Coordinator that manages signing sessions
#[cfg(feature = "nostr")]
struct RoastCoordinator {
    min_signers: u16,
    _message: Vec<u8>,
    commitments: BTreeMap<frost::Identifier, frost::round1::SigningCommitments>,
    nonces: BTreeMap<frost::Identifier, frost::round1::SigningNonces>,
    shares: BTreeMap<frost::Identifier, frost::round2::SignatureShare>,
}

#[cfg(feature = "nostr")]
impl RoastCoordinator {
    fn new(min_signers: u16, message: &[u8]) -> Self {
        Self {
            min_signers,
            _message: message.to_vec(),
            commitments: BTreeMap::new(),
            nonces: BTreeMap::new(),
            shares: BTreeMap::new(),
        }
    }

    /// ROAST Logic: Collect commitments until we hit the threshold.
    /// In a real P2P system, this would be an async stream handler.
    fn add_commitment(&mut self, id: frost::Identifier, comms: frost::round1::SigningCommitments, nonces: frost::round1::SigningNonces) {
        if self.commitments.len() < self.min_signers as usize {
            self.commitments.insert(id, comms);
            self.nonces.insert(id, nonces);
        }
    }

    /// ROAST Logic: Collect signature shares.
    fn add_share(&mut self, id: frost::Identifier, share: frost::round2::SignatureShare) {
        if self.shares.len() < self.min_signers as usize {
            self.shares.insert(id, share);
        }
    }

    fn is_ready_to_sign(&self) -> bool {
        self.commitments.len() >= self.min_signers as usize
    }

    fn is_ready_to_aggregate(&self) -> bool {
        self.shares.len() >= self.min_signers as usize
    }
}

#[cfg(feature = "nostr")]
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut rng = thread_rng();
    let (max_signers, min_signers) = (5, 3);
    let message = b"BIP-64MOD Context: ROAST Coordination";

    // 1. Setup: Generate keys (Dealer mode for simulation)
    let (key_shares, pubkey_package) = frost::keys::generate_with_dealer(
        max_signers,
        min_signers,
        frost::keys::IdentifierList::Default,
        &mut rng,
    )?;

    let mut coordinator = RoastCoordinator::new(min_signers, message);

    // 2. Round 1: Asynchronous Commitment Collection
    // Simulate signers 1, 3, and 5 responding first (ROAST skips 2 and 4)
    for &id_num in &[1, 3, 5] {
        let id = frost::Identifier::try_from(id_num as u16)?;
        let (nonces, comms) = frost::round1::commit(key_shares[&id].signing_share(), &mut rng);
        
        // Signers store their nonces locally, send comms to coordinator
        coordinator.add_commitment(id, comms, nonces);
        
        // Note: Signer 2 was "offline", but ROAST doesn't care because we hit 3/5.
    }

    // 3. Round 2: Signing
    if coordinator.is_ready_to_sign() {
        let signing_package = frost::SigningPackage::new(coordinator.commitments.clone(), message);
        
        let mut temp_shares = BTreeMap::new();
        for &id in coordinator.commitments.keys() {
            // In reality, coordinator sends signing_package to signers
            // Here we simulate the signers producing shares

            let nonces = &coordinator.nonces[&id];
            
            let key_package: frost::keys::KeyPackage = key_shares[&id].clone().try_into()?;
            let share = frost::round2::sign(&signing_package, &nonces, &key_package)?;
            temp_shares.insert(id, share);
        }
        for (id, share) in temp_shares {
            coordinator.add_share(id, share);
        }
    }

    // 4. Finalization: Aggregation
    if coordinator.is_ready_to_aggregate() {
        let signing_package = frost::SigningPackage::new(coordinator.commitments.clone(), message);
        let group_signature = frost::aggregate(
            &signing_package,
            &coordinator.shares,
            &pubkey_package,
        )?;

        pubkey_package.verifying_key().verify(message, &group_signature)?;
        println!("ROAST-coordinated signature verified!");
    }

    Ok(())
}

#[cfg(not(feature = "nostr"))]
fn main() {
    println!("This example requires the 'nostr' feature. Please run with: cargo run --example roast-experiment --features nostr");
}
