use std::{future::Future, pin::Pin, sync::Arc, task::Poll};

use keyfork_derive_util::request::{DerivationError, DerivationRequest, DerivationResponse};
use keyfork_mnemonic_util::Mnemonic;
use tower::Service;

// NOTE: All values implemented in Keyforkd must implement Clone with low overhead, either by
// using an Arc or by having a small signature. This is because Service<T> takes &mut self.

#[derive(thiserror::Error, Debug)]
pub enum KeyforkdRequestError {
    #[error("Invalid derivation length: Expected: 2, actual: {0}")]
    InvalidDerivationLength(usize),

    #[error("Derivation error: {0}")]
    Derivation(#[from] DerivationError),
}

#[derive(Clone, Debug)]
pub struct Keyforkd {
    mnemonic: Arc<Mnemonic>,
}

impl Keyforkd {
    pub fn new(mnemonic: Mnemonic) -> Self {
        Self {
            mnemonic: Arc::new(mnemonic),
        }
    }
}

impl Service<DerivationRequest> for Keyforkd {
    type Response = DerivationResponse;

    type Error = KeyforkdRequestError;

    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;

    fn poll_ready(
        &mut self,
        _cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Result<(), Self::Error>> {
        Poll::Ready(Ok(()))
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip(self)))]
    fn call(&mut self, req: DerivationRequest) -> Self::Future {
        let mnemonic = self.mnemonic.clone();
        Box::pin(async move {
            let len = req.path().len();
            if len < 2 {
                return Err(KeyforkdRequestError::InvalidDerivationLength(len));
            }
            req.derive_with_mnemonic(&mnemonic)
                .map_err(KeyforkdRequestError::from)
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use hex_literal::hex;
    use keyfork_derive_util::{request::*, DerivationPath};
    use keyfork_mnemonic_util::Wordlist;
    use std::str::FromStr;
    use tower::ServiceExt;

    #[tokio::test]
    async fn properly_derives_data() {
        // Pulled from keyfork-derive-util's tests, which is more extensively tested.
        let tests = [
            /*
             * Note: Tests excluded because the derivation path is not deep enough
             * for the API's preferences.
            (
                &hex!("000102030405060708090a0b0c0d0e0f")[..],
                DerivationPath::from_str("m").unwrap(),
                hex!("90046a93de5380a72b5e45010748567d5ea02bbf6522f979e05c0d8d8ca9fffb"),
                hex!("2b4be7f19ee27bbf30c667b642d5f4aa69fd169872f8fc3059c08ebae2eb19e7"),
                hex!("00a4b2856bfec510abab89753fac1ac0e1112364e7d250545963f135f2a33188ed"),
            ),
            (
                &hex!("000102030405060708090a0b0c0d0e0f")[..],
                DerivationPath::from_str("m/0'").unwrap(),
                hex!("8b59aa11380b624e81507a27fedda59fea6d0b779a778918a2fd3590e16e9c69"),
                hex!("68e0fe46dfb67e368c75379acec591dad19df3cde26e63b93a8e704f1dade7a3"),
                hex!("008c8a13df77a28f3445213a0f432fde644acaa215fc72dcdf300d5efaa85d350c"),
            ),
            */
            (
                &hex!("000102030405060708090a0b0c0d0e0f")[..],
                DerivationPath::from_str("m/0'/1'/2'/2'/1000000000'").unwrap(),
                hex!("68789923a0cac2cd5a29172a475fe9e0fb14cd6adb5ad98a3fa70333e7afa230"),
                hex!("8f94d394a8e8fd6b1bc2f3f49f5c47e385281d5c17e65324b0f62483e37e8793"),
                hex!("003c24da049451555d51a7014a37337aa4e12d41e485abccfa46b47dfb2af54b7a"),
            ),
        ];
        let wordlist = Wordlist::default().arc();
        for (seed, path, _, private_key, _) in tests {
            let mnemonic = Mnemonic::from_entropy(&seed[..], wordlist.clone()).unwrap();
            assert_eq!(mnemonic.seed(), seed);
            let req = DerivationRequest::new(DerivationAlgorithm::Ed25519, path);
            let mut keyforkd = Keyforkd::new(mnemonic);
            let response = keyforkd.ready().await.unwrap().call(req).await.unwrap();
            assert_eq!(response.data, private_key)
        }
    }

    #[should_panic]
    #[tokio::test]
    async fn errors_on_no_path() {
        let tests = [(
            &hex!("000102030405060708090a0b0c0d0e0f")[..],
            DerivationPath::from_str("m").unwrap(),
            hex!("90046a93de5380a72b5e45010748567d5ea02bbf6522f979e05c0d8d8ca9fffb"),
            hex!("2b4be7f19ee27bbf30c667b642d5f4aa69fd169872f8fc3059c08ebae2eb19e7"),
            hex!("00a4b2856bfec510abab89753fac1ac0e1112364e7d250545963f135f2a33188ed"),
        )];
        let wordlist = Wordlist::default().arc();
        for (seed, path, _, private_key, _) in tests {
            let mnemonic = Mnemonic::from_entropy(&seed[..], wordlist.clone()).unwrap();
            assert_eq!(mnemonic.seed(), seed);
            let req = DerivationRequest::new(DerivationAlgorithm::Ed25519, path);
            let mut keyforkd = Keyforkd::new(mnemonic);
            let response = keyforkd.ready().await.unwrap().call(req).await.unwrap();
            assert_eq!(response.data, private_key)
        }
    }

    #[should_panic]
    #[tokio::test]
    async fn errors_on_short_path() {
        let tests = [(
            &hex!("000102030405060708090a0b0c0d0e0f")[..],
            DerivationPath::from_str("m/0'").unwrap(),
            hex!("8b59aa11380b624e81507a27fedda59fea6d0b779a778918a2fd3590e16e9c69"),
            hex!("68e0fe46dfb67e368c75379acec591dad19df3cde26e63b93a8e704f1dade7a3"),
            hex!("008c8a13df77a28f3445213a0f432fde644acaa215fc72dcdf300d5efaa85d350c"),
        )];
        let wordlist = Wordlist::default().arc();
        for (seed, path, _, private_key, _) in tests {
            let mnemonic = Mnemonic::from_entropy(&seed[..], wordlist.clone()).unwrap();
            assert_eq!(mnemonic.seed(), seed);
            let req = DerivationRequest::new(DerivationAlgorithm::Ed25519, path);
            let mut keyforkd = Keyforkd::new(mnemonic);
            let response = keyforkd.ready().await.unwrap().call(req).await.unwrap();
            assert_eq!(response.data, private_key)
        }
    }
}