use crate::decode;
use crate::sled::Db;

// Contract payment totals are stored as a packed list of u64 values
// under the loan contract key.
fn deserialize_value(bytes: &[u8]) -> Option<Vec<u64>> {
    let mut vec = vec![];
    let mut offset = 0;
    while offset + 8 <= bytes.len() {
        vec.push(u64::from_le_bytes([
            bytes[offset],
            bytes[offset + 1],
            bytes[offset + 2],
            bytes[offset + 3],
            bytes[offset + 4],
            bytes[offset + 5],
            bytes[offset + 6],
            bytes[offset + 7],
        ]));
        offset += 8;
    }
    if offset == bytes.len() {
        Some(vec)
    } else {
        None
    }
}

pub async fn get_total_payments(db: &Db, contract_id: &str) -> u64 {
    // Consensus loan state only includes payments already saved in blocks.
    // Pending mempool payments are intentionally excluded so block validation
    // cannot depend on each node's local unconfirmed transaction set.
    let tree = db.open_tree("contract_payments").unwrap();
    let contract_key = match decode(contract_id) {
        Ok(bytes) => bytes,
        Err(_) => return 0,
    };

    let payments: Option<Vec<u64>> = match tree.get(contract_key) {
        Ok(Some(p)) => deserialize_value(&p),
        _ => None,
    };

    match payments {
        Some(p) => p.iter().sum(),
        None => 0,
    }
}