use std::rc::Rc;
use bc_crypto::ecdsa_new_private_key_using;
use bc_ur::prelude::*;
use crate::{tags, ECPrivateKey, Signature, ECKey, SigningPublicKey};
use bc_rand::{RandomNumberGenerator, SecureRandomNumberGenerator};
use anyhow::bail;

/// A private ECDSA key for signing.
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct SigningPrivateKey ([u8; Self::KEY_SIZE]);

impl SigningPrivateKey {
    pub const KEY_SIZE: usize = 32;

    /// Generate a new random `SigningPrivateKey`.
    pub fn new() -> Self {
        let mut rng = SecureRandomNumberGenerator;
        Self::new_using(&mut rng)
    }

    /// Generate a new random `SigningPrivateKey` using the given random number generator.
    ///
    /// For testing purposes only.
    pub fn new_using(rng: &mut impl RandomNumberGenerator) -> Self {
        Self(ecdsa_new_private_key_using(rng))
    }

    /// Restores a `SigningPrivateKey` from a vector of bytes.
    pub const fn from_data(data: [u8; Self::KEY_SIZE]) -> Self {
        Self(data)
    }

    /// Restores a `SigningPrivateKey` from a reference to a vector of bytes.
    pub fn from_data_ref(data: impl AsRef<[u8]>) -> anyhow::Result<Self> {
        let data = data.as_ref();
        if data.len() != Self::KEY_SIZE {
            bail!("Invalid signing private key size");
        }
        let mut arr = [0u8; Self::KEY_SIZE];
        arr.copy_from_slice(data);
        Ok(Self::from_data(arr))
    }

    /// Returns a reference to the vector of private key data.
    pub fn data(&self) -> &[u8; Self::KEY_SIZE] {
        self.into()
    }

    /// Restores a `SigningPrivateKey` from a hex string.
    ///
    /// # Panics
    ///
    /// Panics if the hex string is invalid or the length is not `SigningPrivateKey::KEY_SIZE * 2`.
    pub fn from_hex(hex: impl AsRef<str>) -> Self {
        Self::from_data_ref(hex::decode(hex.as_ref()).unwrap()).unwrap()
    }

    /// Returns the private key as a hex string.
    pub fn hex(&self) -> String {
        hex::encode(self.data())
    }

    /// Derives the ECDSA signing public key from this private key.
    pub fn ecdsa_public_key(&self) -> SigningPublicKey {
        SigningPublicKey::from_ecdsa(ECPrivateKey::from_data(*self.data()).public_key())
    }

    /// Derives the Schnorr signing public key from this private key.
    pub fn schnorr_public_key(&self) -> SigningPublicKey {
        SigningPublicKey::from_schnorr(ECPrivateKey::from_data(*self.data()).schnorr_public_key())
    }

    /// Derives a new `SigningPrivateKey` from the given key material.
    pub fn derive_from_key_material(key_material: impl AsRef<[u8]>) -> Self {
        Self::from_data(bc_crypto::x25519_derive_signing_private_key(key_material))
    }
}

impl SigningPrivateKey {
    pub fn ecdsa_sign(&self, message: impl AsRef<[u8]>) -> Signature {
        let private_key = ECPrivateKey::from_data(*self.data());
        let sig = private_key.ecdsa_sign(message);
        Signature::ecdsa_from_data(sig)
    }

    pub fn schnorr_sign_using(
        &self,
        message: impl AsRef<[u8]>,
        tag: impl AsRef<[u8]>,
        rng: &mut impl RandomNumberGenerator
    ) -> Signature {
        // let tag = tag.into();
        let private_key = ECPrivateKey::from_data(*self.data());
        let tag_copy = tag.as_ref().to_vec();
        let sig = private_key.schnorr_sign_using(message, tag, rng);
        Signature::schnorr_from_data(sig, tag_copy)
    }

    pub fn schnorr_sign(
        &self,
        message: impl AsRef<[u8]>,
        tag: impl AsRef<[u8]>,
    ) -> Signature {
        let mut rng = SecureRandomNumberGenerator;
        self.schnorr_sign_using(message, tag, &mut rng)
    }
}

impl<'a> From<&'a SigningPrivateKey> for &'a [u8; SigningPrivateKey::KEY_SIZE] {
    fn from(value: &'a SigningPrivateKey) -> Self {
        &value.0
    }
}

impl Default for SigningPrivateKey {
    fn default() -> Self {
        Self::new()
    }
}

impl AsRef<SigningPrivateKey> for SigningPrivateKey {
    fn as_ref(&self) -> &SigningPrivateKey {
        self
    }
}

impl From<Rc<SigningPrivateKey>> for SigningPrivateKey {
    fn from(value: Rc<SigningPrivateKey>) -> Self {
        value.as_ref().clone()
    }
}

impl CBORTagged for SigningPrivateKey {
    const CBOR_TAG: Tag = tags::SIGNING_PRIVATE_KEY;
}

impl CBOREncodable for SigningPrivateKey {
    fn cbor(&self) -> CBOR {
        self.tagged_cbor()
    }
}

impl From<SigningPrivateKey> for CBOR {
    fn from(value: SigningPrivateKey) -> Self {
        value.cbor()
    }
}

impl CBORTaggedEncodable for SigningPrivateKey {
    fn untagged_cbor(&self) -> CBOR {
        CBOR::byte_string(self.data())
    }
}

impl CBORDecodable for SigningPrivateKey {
    fn from_cbor(cbor: &CBOR) -> anyhow::Result<Self> {
        Self::from_tagged_cbor(cbor)
    }
}

impl TryFrom<CBOR> for SigningPrivateKey {
    type Error = anyhow::Error;

    fn try_from(cbor: CBOR) -> Result<Self, Self::Error> {
        Self::from_cbor(&cbor)
    }
}

impl TryFrom<&CBOR> for SigningPrivateKey {
    type Error = anyhow::Error;

    fn try_from(cbor: &CBOR) -> Result<Self, Self::Error> {
        Self::from_cbor(cbor)
    }
}

impl CBORTaggedDecodable for SigningPrivateKey {
    fn from_untagged_cbor(untagged_cbor: &CBOR) -> anyhow::Result<Self> {
        let data = CBOR::expect_byte_string(untagged_cbor)?;
        Self::from_data_ref(&data)
    }
}

impl UREncodable for SigningPrivateKey { }

impl URDecodable for SigningPrivateKey { }

impl URCodable for SigningPrivateKey { }

impl std::fmt::Debug for SigningPrivateKey {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "SigningPrivateKey")
    }
}

// Convert from a reference to a byte vector to a SigningPrivateKey.
impl From<&SigningPrivateKey> for SigningPrivateKey {
    fn from(key: &SigningPrivateKey) -> Self {
        key.clone()
    }
}

// Convert from a byte vector to a SigningPrivateKey.
impl From<SigningPrivateKey> for Vec<u8> {
    fn from(key: SigningPrivateKey) -> Self {
        key.0.to_vec()
    }
}

// Convert from a reference to a byte vector to a SigningPrivateKey.
impl From<&SigningPrivateKey> for Vec<u8> {
    fn from(key: &SigningPrivateKey) -> Self {
        key.0.to_vec()
    }
}