use k256::{Scalar, elliptic_curve::PrimeField as _};
use nssa_core::{NullifierPublicKey, encryption::ViewingPublicKey};
use serde::{Deserialize, Serialize};

use crate::key_management::{
    KeyChain,
    key_tree::traits::KeyNode,
    secret_holders::{PrivateKeyHolder, SecretSpendingKey},
};

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct ChildKeysPrivate {
    pub value: (KeyChain, nssa::Account),
    pub ccc: [u8; 32],
    /// Can be [`None`] if root.
    pub cci: Option<u32>,
}

impl KeyNode for ChildKeysPrivate {
    fn root(seed: [u8; 64]) -> Self {
        let hash_value = hmac_sha512::HMAC::mac(seed, b"LEE_master_priv");

        let ssk = SecretSpendingKey(
            *hash_value
                .first_chunk::<32>()
                .expect("hash_value is 64 bytes, must be safe to get first 32"),
        );
        let ccc = *hash_value
            .last_chunk::<32>()
            .expect("hash_value is 64 bytes, must be safe to get last 32");

        let nsk = ssk.generate_nullifier_secret_key(None);
        let vsk = ssk.generate_viewing_secret_key(None);

        let npk = NullifierPublicKey::from(&nsk);
        let vpk = ViewingPublicKey::from_scalar(vsk);

        Self {
            value: (
                KeyChain {
                    secret_spending_key: ssk,
                    nullifier_public_key: npk,
                    viewing_public_key: vpk,
                    private_key_holder: PrivateKeyHolder {
                        nullifier_secret_key: nsk,
                        viewing_secret_key: vsk,
                    },
                },
                nssa::Account::default(),
            ),
            ccc,
            cci: None,
        }
    }

    fn nth_child(&self, cci: u32) -> Self {
        #[expect(clippy::arithmetic_side_effects, reason = "TODO: fix later")]
        let parent_pt =
            Scalar::from_repr(self.value.0.private_key_holder.nullifier_secret_key.into())
                .expect("Key generated as scalar, must be valid representation")
                * Scalar::from_repr(self.value.0.private_key_holder.viewing_secret_key.into())
                    .expect("Key generated as scalar, must be valid representation");
        let mut input = vec![];

        input.extend_from_slice(b"LEE_seed_priv");
        input.extend_from_slice(&parent_pt.to_bytes());
        #[expect(clippy::big_endian_bytes, reason = "BIP-032 uses big endian")]
        input.extend_from_slice(&cci.to_be_bytes());

        let hash_value = hmac_sha512::HMAC::mac(input, self.ccc);

        let ssk = SecretSpendingKey(
            *hash_value
                .first_chunk::<32>()
                .expect("hash_value is 64 bytes, must be safe to get first 32"),
        );
        let ccc = *hash_value
            .last_chunk::<32>()
            .expect("hash_value is 64 bytes, must be safe to get last 32");

        let nsk = ssk.generate_nullifier_secret_key(Some(cci));
        let vsk = ssk.generate_viewing_secret_key(Some(cci));

        let npk = NullifierPublicKey::from(&nsk);
        let vpk = ViewingPublicKey::from_scalar(vsk);

        Self {
            value: (
                KeyChain {
                    secret_spending_key: ssk,
                    nullifier_public_key: npk,
                    viewing_public_key: vpk,
                    private_key_holder: PrivateKeyHolder {
                        nullifier_secret_key: nsk,
                        viewing_secret_key: vsk,
                    },
                },
                nssa::Account::default(),
            ),
            ccc,
            cci: Some(cci),
        }
    }

    fn chain_code(&self) -> &[u8; 32] {
        &self.ccc
    }

    fn child_index(&self) -> Option<u32> {
        self.cci
    }

    fn account_id(&self) -> nssa::AccountId {
        nssa::AccountId::from(&self.value.0.nullifier_public_key)
    }
}

#[expect(
    clippy::single_char_lifetime_names,
    reason = "TODO add meaningful name"
)]
impl<'a> From<&'a ChildKeysPrivate> for &'a (KeyChain, nssa::Account) {
    fn from(value: &'a ChildKeysPrivate) -> Self {
        &value.value
    }
}

#[expect(
    clippy::single_char_lifetime_names,
    reason = "TODO add meaningful name"
)]
impl<'a> From<&'a mut ChildKeysPrivate> for &'a mut (KeyChain, nssa::Account) {
    fn from(value: &'a mut ChildKeysPrivate) -> Self {
        &mut value.value
    }
}

#[cfg(test)]
mod tests {
    use nssa_core::{NullifierPublicKey, NullifierSecretKey};

    use super::*;
    use crate::key_management::{self, secret_holders::ViewingSecretKey};

    #[expect(clippy::redundant_type_annotations, reason = "TODO: clippy requires")]
    #[test]
    fn master_key_generation() {
        let seed: [u8; 64] = [
            252, 56, 204, 83, 232, 123, 209, 188, 187, 167, 39, 213, 71, 39, 58, 65, 125, 134, 255,
            49, 43, 108, 92, 53, 173, 164, 94, 142, 150, 74, 21, 163, 43, 144, 226, 87, 199, 18,
            129, 223, 176, 198, 5, 150, 157, 70, 210, 254, 14, 105, 89, 191, 246, 27, 52, 170, 56,
            114, 39, 38, 118, 197, 205, 225,
        ];

        let keys = ChildKeysPrivate::root(seed);

        let expected_ssk: SecretSpendingKey = key_management::secret_holders::SecretSpendingKey([
            246, 79, 26, 124, 135, 95, 52, 51, 201, 27, 48, 194, 2, 144, 51, 219, 245, 128, 139,
            222, 42, 195, 105, 33, 115, 97, 186, 0, 97, 14, 218, 191,
        ]);

        let expected_ccc = [
            56, 114, 70, 249, 67, 169, 206, 9, 192, 11, 180, 168, 149, 129, 42, 95, 43, 157, 130,
            111, 13, 5, 195, 75, 20, 255, 162, 85, 40, 251, 8, 168,
        ];

        let expected_nsk: NullifierSecretKey = [
            154, 102, 103, 5, 34, 235, 227, 13, 22, 182, 226, 11, 7, 67, 110, 162, 99, 193, 174,
            34, 234, 19, 222, 2, 22, 12, 163, 252, 88, 11, 0, 163,
        ];

        let expected_npk: NullifierPublicKey = nssa_core::NullifierPublicKey([
            7, 123, 125, 191, 233, 183, 201, 4, 20, 214, 155, 210, 45, 234, 27, 240, 194, 111, 97,
            247, 155, 113, 122, 246, 192, 0, 70, 61, 76, 71, 70, 2,
        ]);
        let expected_vsk = [
            155, 90, 54, 75, 228, 130, 68, 201, 129, 251, 180, 195, 250, 64, 34, 230, 241, 204,
            216, 50, 149, 156, 10, 67, 208, 74, 9, 10, 47, 59, 50, 202,
        ];

        let expected_vpk_as_bytes: [u8; 33] = [
            2, 191, 99, 102, 114, 40, 131, 109, 166, 8, 222, 186, 107, 29, 156, 106, 206, 96, 127,
            80, 170, 66, 217, 79, 38, 80, 11, 74, 147, 123, 221, 159, 166,
        ];

        assert!(expected_ssk == keys.value.0.secret_spending_key);
        assert!(expected_ccc == keys.ccc);
        assert!(expected_nsk == keys.value.0.private_key_holder.nullifier_secret_key);
        assert!(expected_npk == keys.value.0.nullifier_public_key);
        assert!(expected_vsk == keys.value.0.private_key_holder.viewing_secret_key);
        assert!(expected_vpk_as_bytes == keys.value.0.viewing_public_key.to_bytes());
    }

    #[test]
    fn child_keys_generation() {
        let seed: [u8; 64] = [
            252, 56, 204, 83, 232, 123, 209, 188, 187, 167, 39, 213, 71, 39, 58, 65, 125, 134, 255,
            49, 43, 108, 92, 53, 173, 164, 94, 142, 150, 74, 21, 163, 43, 144, 226, 87, 199, 18,
            129, 223, 176, 198, 5, 150, 157, 70, 210, 254, 14, 105, 89, 191, 246, 27, 52, 170, 56,
            114, 39, 38, 118, 197, 205, 225,
        ];

        let root_node = ChildKeysPrivate::root(seed);
        let child_node = ChildKeysPrivate::nth_child(&root_node, 42_u32);

        let expected_ccc: [u8; 32] = [
            27, 73, 133, 213, 214, 63, 217, 184, 164, 17, 172, 140, 223, 95, 255, 157, 11, 0, 58,
            53, 82, 147, 121, 120, 199, 50, 30, 28, 103, 24, 121, 187,
        ];

        let expected_nsk: NullifierSecretKey = [
            124, 61, 40, 92, 33, 135, 3, 41, 200, 234, 3, 69, 102, 184, 57, 191, 106, 151, 194,
            192, 103, 132, 141, 112, 249, 108, 192, 117, 24, 48, 70, 216,
        ];
        let expected_npk = nssa_core::NullifierPublicKey([
            116, 231, 246, 189, 145, 240, 37, 59, 219, 223, 216, 246, 116, 171, 223, 55, 197, 200,
            134, 192, 221, 40, 218, 167, 239, 5, 11, 95, 147, 247, 162, 226,
        ]);

        let expected_vsk: ViewingSecretKey = [
            33, 155, 68, 60, 102, 70, 47, 105, 194, 129, 44, 26, 143, 198, 44, 244, 185, 31, 236,
            252, 205, 89, 138, 107, 39, 38, 154, 73, 109, 166, 41, 114,
        ];
        let expected_vpk_as_bytes: [u8; 33] = [
            2, 78, 213, 113, 117, 105, 162, 248, 175, 68, 128, 232, 106, 204, 208, 159, 11, 78, 48,
            244, 127, 112, 46, 0, 93, 184, 1, 77, 132, 160, 75, 152, 88,
        ];

        assert!(expected_ccc == child_node.ccc);
        assert!(expected_nsk == child_node.value.0.private_key_holder.nullifier_secret_key);
        assert!(expected_npk == child_node.value.0.nullifier_public_key);
        assert!(expected_vsk == child_node.value.0.private_key_holder.viewing_secret_key);
        assert!(expected_vpk_as_bytes == child_node.value.0.viewing_public_key.to_bytes());
    }
}