// SPDX-License-Identifier: CC0-1.0

//! BIP-0032 implementation.
//!
//! Implementation of BIP-0032 hierarchical deterministic wallets, as defined
//! at <https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki>.

use core::convert::Infallible;
use core::ops::Index;
use core::str::FromStr;
use core::{fmt, slice};

use hashes::{hash160, hash_newtype, sha512, Hash, HashEngine, Hmac, HmacEngine};
use internals::array::ArrayExt;
use internals::write_err;

use crate::crypto::key::{CompressedPublicKey, Keypair, PrivateKey, XOnlyPublicKey};
use crate::internal_macros;
use crate::network::NetworkKind;
use crate::prelude::{String, Vec};

/// Version bytes for extended public keys on the Bitcoin network.
const VERSION_BYTES_MAINNET_PUBLIC: [u8; 4] = [0x04, 0x88, 0xB2, 0x1E];
/// Version bytes for extended private keys on the Bitcoin network.
const VERSION_BYTES_MAINNET_PRIVATE: [u8; 4] = [0x04, 0x88, 0xAD, 0xE4];
/// Version bytes for extended public keys on any of the testnet networks.
const VERSION_BYTES_TESTNETS_PUBLIC: [u8; 4] = [0x04, 0x35, 0x87, 0xCF];
/// Version bytes for extended private keys on any of the testnet networks.
const VERSION_BYTES_TESTNETS_PRIVATE: [u8; 4] = [0x04, 0x35, 0x83, 0x94];

/// The old name for xpub, extended public key.
#[deprecated(since = "0.31.0", note = "use `Xpub` instead")]
pub type ExtendedPubKey = Xpub;

/// The old name for xpriv, extended public key.
#[deprecated(since = "0.31.0", note = "use `Xpriv` instead")]
pub type ExtendedPrivKey = Xpriv;

/// A chain code
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct ChainCode([u8; 32]);
internals::impl_array_newtype!(ChainCode, u8, 32);
internal_macros::impl_array_newtype_stringify!(ChainCode, 32);

impl ChainCode {
    fn from_hmac(hmac: Hmac<sha512::Hash>) -> Self {
        Self(*hmac.as_byte_array().split_array::<32, 32>().1)
    }

    /// Copies the underlying bytes into a new `Vec`.
    #[inline]
    #[deprecated(since = "TBD", note = "use to_vec instead")]
    pub fn to_bytes(self) -> alloc::vec::Vec<u8> { self.to_vec() }
}

/// A fingerprint
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
pub struct Fingerprint([u8; 4]);
internals::impl_array_newtype!(Fingerprint, u8, 4);
internal_macros::impl_array_newtype_stringify!(Fingerprint, 4);

hash_newtype! {
    /// Extended key identifier as defined in BIP-0032.
    pub struct XKeyIdentifier(hash160::Hash);
}

hashes::impl_hex_for_newtype!(XKeyIdentifier);
#[cfg(feature = "serde")]
hashes::impl_serde_for_newtype!(XKeyIdentifier);

/// Extended private key
#[derive(Copy, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "std", derive(Debug))]
pub struct Xpriv {
    /// The network this key is to be used on
    pub network: NetworkKind,
    /// How many derivations this key is from the master (which is 0)
    pub depth: u8,
    /// Fingerprint of the parent key (0 for master)
    pub parent_fingerprint: Fingerprint,
    /// Child number of the key used to derive from parent (0 for master)
    pub child_number: ChildNumber,
    /// Private key
    pub private_key: secp256k1::SecretKey,
    /// Chain code
    pub chain_code: ChainCode,
}
#[cfg(feature = "serde")]
internals::serde_string_impl!(Xpriv, "a BIP-0032 extended private key");

#[cfg(not(feature = "std"))]
impl fmt::Debug for Xpriv {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Xpriv")
            .field("network", &self.network)
            .field("depth", &self.depth)
            .field("parent_fingerprint", &self.parent_fingerprint)
            .field("child_number", &self.child_number)
            .field("chain_code", &self.chain_code)
            .field("private_key", &"[SecretKey]")
            .finish()
    }
}

/// Extended public key
#[derive(Copy, Clone, PartialEq, Eq, Debug, PartialOrd, Ord, Hash)]
pub struct Xpub {
    /// The network kind this key is to be used on
    pub network: NetworkKind,
    /// How many derivations this key is from the master (which is 0)
    pub depth: u8,
    /// Fingerprint of the parent key
    pub parent_fingerprint: Fingerprint,
    /// Child number of the key used to derive from parent (0 for master)
    pub child_number: ChildNumber,
    /// Public key
    pub public_key: secp256k1::PublicKey,
    /// Chain code
    pub chain_code: ChainCode,
}
#[cfg(feature = "serde")]
internals::serde_string_impl!(Xpub, "a BIP-0032 extended public key");

/// A child number for a derived key
#[derive(Copy, Clone, PartialEq, Eq, Debug, PartialOrd, Ord, Hash)]
pub enum ChildNumber {
    /// Non-hardened key
    Normal {
        /// Key index, within [0, 2^31 - 1]
        index: u32,
    },
    /// Hardened key
    Hardened {
        /// Key index, within [0, 2^31 - 1]
        index: u32,
    },
}
impl ChildNumber {
    /// Normal child number with index 0.
    pub const ZERO_NORMAL: Self = Self::Normal { index: 0 };

    /// Normal child number with index 1.
    pub const ONE_NORMAL: Self = Self::Normal { index: 1 };

    /// Hardened child number with index 0.
    pub const ZERO_HARDENED: Self = Self::Hardened { index: 0 };

    /// Hardened child number with index 1.
    pub const ONE_HARDENED: Self = Self::Hardened { index: 1 };

    /// Constructs a new [`Normal`] from an index, returns an error if the index is not within
    /// [0, 2^31 - 1].
    ///
    /// [`Normal`]: #variant.Normal
    pub fn from_normal_idx(index: u32) -> Result<Self, IndexOutOfRangeError> {
        if index & (1 << 31) == 0 {
            Ok(Self::Normal { index })
        } else {
            Err(IndexOutOfRangeError { index })
        }
    }

    /// Constructs a new [`Hardened`] from an index, returns an error if the index is not within
    /// [0, 2^31 - 1].
    ///
    /// [`Hardened`]: #variant.Hardened
    pub fn from_hardened_idx(index: u32) -> Result<Self, IndexOutOfRangeError> {
        if index & (1 << 31) == 0 {
            Ok(Self::Hardened { index })
        } else {
            Err(IndexOutOfRangeError { index })
        }
    }

    /// Returns `true` if the child number is a [`Normal`] value.
    ///
    /// [`Normal`]: #variant.Normal
    pub fn is_normal(&self) -> bool { !self.is_hardened() }

    /// Returns `true` if the child number is a [`Hardened`] value.
    ///
    /// [`Hardened`]: #variant.Hardened
    pub fn is_hardened(&self) -> bool {
        match self {
            Self::Hardened { .. } => true,
            Self::Normal { .. } => false,
        }
    }

    /// Returns the child number that is a single increment from this one.
    pub fn increment(self) -> Result<Self, IndexOutOfRangeError> {
        // Bare addition in this function is okay, because we have an invariant that
        // `index` is always within [0, 2^31 - 1]. FIXME this is not actually an
        // invariant because the fields are public.
        match self {
            Self::Normal { index: idx } => Self::from_normal_idx(idx + 1),
            Self::Hardened { index: idx } => Self::from_hardened_idx(idx + 1),
        }
    }

    /// Formats the child number using the provided formatting function.
    ///
    /// For hardened child numbers appends a `'` or `hardened_alt_suffix`
    /// depending on the formatter.
    fn format_with<F>(
        &self,
        f: &mut fmt::Formatter,
        format_fn: F,
        hardened_alt_suffix: &str,
    ) -> fmt::Result
    where
        F: Fn(&u32, &mut fmt::Formatter) -> fmt::Result,
    {
        match *self {
            Self::Hardened { index } => {
                format_fn(&index, f)?;
                let alt = f.alternate();
                f.write_str(if alt { hardened_alt_suffix } else { "'" })
            }
            Self::Normal { index } => format_fn(&index, f),
        }
    }
}

impl From<u32> for ChildNumber {
    fn from(number: u32) -> Self {
        if number & (1 << 31) != 0 {
            Self::Hardened { index: number ^ (1 << 31) }
        } else {
            Self::Normal { index: number }
        }
    }
}

impl From<ChildNumber> for u32 {
    fn from(cnum: ChildNumber) -> Self {
        match cnum {
            ChildNumber::Normal { index } => index,
            ChildNumber::Hardened { index } => index | (1 << 31),
        }
    }
}

impl fmt::Display for ChildNumber {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.format_with(f, fmt::Display::fmt, "h")
    }
}

impl fmt::LowerHex for ChildNumber {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.format_with(f, fmt::LowerHex::fmt, "h")
    }
}

impl fmt::UpperHex for ChildNumber {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.format_with(f, fmt::UpperHex::fmt, "H")
    }
}

impl fmt::Octal for ChildNumber {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.format_with(f, fmt::Octal::fmt, "h")
    }
}

impl fmt::Binary for ChildNumber {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.format_with(f, fmt::Binary::fmt, "h")
    }
}

impl FromStr for ChildNumber {
    type Err = ParseChildNumberError;

    fn from_str(inp: &str) -> Result<Self, Self::Err> {
        let is_hardened = inp.chars().last().is_some_and(|l| l == '\'' || l == 'h');
        Ok(if is_hardened {
            Self::from_hardened_idx(
                inp[0..inp.len() - 1].parse().map_err(ParseChildNumberError::ParseInt)?,
            )
            .map_err(ParseChildNumberError::IndexOutOfRange)?
        } else {
            Self::from_normal_idx(inp.parse().map_err(ParseChildNumberError::ParseInt)?)
                .map_err(ParseChildNumberError::IndexOutOfRange)?
        })
    }
}

impl AsRef<[Self]> for ChildNumber {
    fn as_ref(&self) -> &[Self] { slice::from_ref(self) }
}

#[cfg(feature = "serde")]
impl<'de> serde::Deserialize<'de> for ChildNumber {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        u32::deserialize(deserializer).map(Self::from)
    }
}

#[cfg(feature = "serde")]
impl serde::Serialize for ChildNumber {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        u32::from(*self).serialize(serializer)
    }
}

/// Trait that allows possibly failable conversion from a type into a
/// derivation path
pub trait IntoDerivationPath {
    /// Converts a given type into a [`DerivationPath`] with possible error
    fn into_derivation_path(self) -> Result<DerivationPath, ParseChildNumberError>;
}

/// A BIP-0032 derivation path.
#[derive(Clone, PartialEq, Eq, Ord, PartialOrd, Hash)]
pub struct DerivationPath(Vec<ChildNumber>);

#[cfg(feature = "serde")]
internals::serde_string_impl!(DerivationPath, "a BIP-0032 derivation path");

impl<I> Index<I> for DerivationPath
where
    Vec<ChildNumber>: Index<I>,
{
    type Output = <Vec<ChildNumber> as Index<I>>::Output;

    #[inline]
    fn index(&self, index: I) -> &Self::Output { &self.0[index] }
}

impl Default for DerivationPath {
    fn default() -> Self { Self::master() }
}

impl<T> IntoDerivationPath for T
where
    T: Into<DerivationPath>,
{
    fn into_derivation_path(self) -> Result<DerivationPath, ParseChildNumberError> {
        Ok(self.into())
    }
}

impl IntoDerivationPath for String {
    fn into_derivation_path(self) -> Result<DerivationPath, ParseChildNumberError> { self.parse() }
}

impl IntoDerivationPath for &'_ str {
    fn into_derivation_path(self) -> Result<DerivationPath, ParseChildNumberError> { self.parse() }
}

impl From<Vec<ChildNumber>> for DerivationPath {
    fn from(numbers: Vec<ChildNumber>) -> Self { Self(numbers) }
}

impl From<DerivationPath> for Vec<ChildNumber> {
    fn from(path: DerivationPath) -> Self { path.0 }
}

impl<'a> From<&'a [ChildNumber]> for DerivationPath {
    fn from(numbers: &'a [ChildNumber]) -> Self { Self(numbers.to_vec()) }
}

impl core::iter::FromIterator<ChildNumber> for DerivationPath {
    fn from_iter<T>(iter: T) -> Self
    where
        T: IntoIterator<Item = ChildNumber>,
    {
        Self(Vec::from_iter(iter))
    }
}

impl<'a> core::iter::IntoIterator for &'a DerivationPath {
    type Item = &'a ChildNumber;
    type IntoIter = slice::Iter<'a, ChildNumber>;
    fn into_iter(self) -> Self::IntoIter { self.0.iter() }
}

impl AsRef<[ChildNumber]> for DerivationPath {
    fn as_ref(&self) -> &[ChildNumber] { &self.0 }
}

impl FromStr for DerivationPath {
    type Err = ParseChildNumberError;

    fn from_str(path: &str) -> Result<Self, Self::Err> {
        if path.is_empty() || path == "m" || path == "m/" {
            return Ok(vec![].into());
        }

        let path = path.strip_prefix("m/").unwrap_or(path);

        let parts = path.split('/');
        let ret: Result<Vec<ChildNumber>, _> = parts.map(str::parse).collect();
        Ok(Self(ret?))
    }
}

/// An iterator over children of a [DerivationPath].
///
/// It is returned by the methods [DerivationPath::children_from],
/// [DerivationPath::normal_children] and [DerivationPath::hardened_children].
pub struct DerivationPathIterator<'a> {
    base: &'a DerivationPath,
    next_child: Option<ChildNumber>,
}

impl<'a> DerivationPathIterator<'a> {
    /// Starts a new [DerivationPathIterator] at the given child.
    pub fn start_from(path: &'a DerivationPath, start: ChildNumber) -> Self {
        DerivationPathIterator { base: path, next_child: Some(start) }
    }
}

impl Iterator for DerivationPathIterator<'_> {
    type Item = DerivationPath;

    fn next(&mut self) -> Option<Self::Item> {
        let ret = self.next_child?;
        self.next_child = ret.increment().ok();
        Some(self.base.child(ret))
    }
}

impl DerivationPath {
    /// Returns length of the derivation path
    pub fn len(&self) -> usize { self.0.len() }

    /// Returns `true` if the derivation path is empty
    pub fn is_empty(&self) -> bool { self.0.is_empty() }

    /// Returns derivation path for a master key (i.e. empty derivation path)
    pub fn master() -> Self { Self(vec![]) }

    /// Returns whether derivation path represents master key (i.e. it's length
    /// is empty). True for `m` path.
    pub fn is_master(&self) -> bool { self.0.is_empty() }

    /// Constructs a new [DerivationPath] that is a child of this one.
    pub fn child(&self, cn: ChildNumber) -> Self {
        let mut path = self.0.clone();
        path.push(cn);
        Self(path)
    }

    /// Converts into a [DerivationPath] that is a child of this one.
    pub fn into_child(self, cn: ChildNumber) -> Self {
        let mut path = self.0;
        path.push(cn);
        Self(path)
    }

    /// Gets an [Iterator] over the children of this [DerivationPath]
    /// starting with the given [ChildNumber].
    pub fn children_from(&self, cn: ChildNumber) -> DerivationPathIterator<'_> {
        DerivationPathIterator::start_from(self, cn)
    }

    /// Gets an [Iterator] over the unhardened children of this [DerivationPath].
    pub fn normal_children(&self) -> DerivationPathIterator<'_> {
        DerivationPathIterator::start_from(self, ChildNumber::Normal { index: 0 })
    }

    /// Gets an [Iterator] over the hardened children of this [DerivationPath].
    pub fn hardened_children(&self) -> DerivationPathIterator<'_> {
        DerivationPathIterator::start_from(self, ChildNumber::Hardened { index: 0 })
    }

    /// Concatenate `self` with `path` and return the resulting new path.
    ///
    /// ```
    /// use bitcoin::bip32::{DerivationPath, ChildNumber};
    ///
    /// let base = "m/42".parse::<DerivationPath>().unwrap();
    ///
    /// let deriv_1 = base.extend("0/1".parse::<DerivationPath>().unwrap());
    /// let deriv_2 = base.extend(&[
    ///     ChildNumber::ZERO_NORMAL,
    ///     ChildNumber::ONE_NORMAL
    /// ]);
    ///
    /// assert_eq!(deriv_1, deriv_2);
    /// ```
    pub fn extend<T: AsRef<[ChildNumber]>>(&self, path: T) -> Self {
        let mut new_path = self.clone();
        new_path.0.extend_from_slice(path.as_ref());
        new_path
    }

    /// Returns the derivation path as a vector of u32 integers.
    /// Unhardened elements are copied as is.
    /// 0x80000000 is added to the hardened elements.
    ///
    /// ```
    /// use bitcoin::bip32::DerivationPath;
    ///
    /// let path = "m/84'/0'/0'/0/1".parse::<DerivationPath>().unwrap();
    /// const HARDENED: u32 = 0x80000000;
    /// assert_eq!(path.to_u32_vec(), vec![84 + HARDENED, HARDENED, HARDENED, 0, 1]);
    /// ```
    pub fn to_u32_vec(&self) -> Vec<u32> { self.into_iter().map(|&el| el.into()).collect() }

    /// Constructs a new derivation path from a slice of u32s.
    /// ```
    /// use bitcoin::bip32::DerivationPath;
    ///
    /// const HARDENED: u32 = 0x80000000;
    /// let expected = vec![84 + HARDENED, HARDENED, HARDENED, 0, 1];
    /// let path = DerivationPath::from_u32_slice(expected.as_slice());
    /// assert_eq!(path.to_u32_vec(), expected);
    /// ```
    pub fn from_u32_slice(numbers: &[u32]) -> Self {
        numbers.iter().map(|&n| ChildNumber::from(n)).collect()
    }
}

impl fmt::Display for DerivationPath {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut iter = self.0.iter();
        if let Some(first_element) = iter.next() {
            if f.alternate() {
                write!(f, "{:#}", first_element)?;
            } else {
                write!(f, "{}", first_element)?;
            }
        }
        for cn in iter {
            f.write_str("/")?;
            if f.alternate() {
                write!(f, "{:#}", cn)?;
            } else {
                write!(f, "{}", cn)?;
            }
        }
        Ok(())
    }
}

impl fmt::Debug for DerivationPath {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::Display::fmt(&self, f) }
}

/// Full information on the used extended public key: fingerprint of the
/// master extended public key and a derivation path from it.
pub type KeySource = (Fingerprint, DerivationPath);

/// A BIP-0032 error
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum ParseError {
    /// A secp256k1 error occurred
    Secp256k1(secp256k1::Error),
    /// Unknown version magic bytes
    UnknownVersion([u8; 4]),
    /// Encoded extended key data has wrong length
    WrongExtendedKeyLength(usize),
    /// Base58 encoding error
    Base58(base58::Error),
    /// Base58 decoded data was an invalid length.
    InvalidBase58PayloadLength(InvalidBase58PayloadLengthError),
    /// Invalid private key prefix (byte 45 must be 0)
    InvalidPrivateKeyPrefix,
    /// Non-zero parent fingerprint for a master key (depth 0)
    NonZeroParentFingerprintForMasterKey,
    /// Non-zero child number for a master key (depth 0)
    NonZeroChildNumberForMasterKey,
}

impl From<Infallible> for ParseError {
    fn from(never: Infallible) -> Self { match never {} }
}

impl fmt::Display for ParseError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::Secp256k1(ref e) => write_err!(f, "secp256k1 error"; e),
            Self::UnknownVersion(ref bytes) =>
                write!(f, "unknown version magic bytes: {:?}", bytes),
            Self::WrongExtendedKeyLength(ref len) =>
                write!(f, "encoded extended key data has wrong length {}", len),
            Self::Base58(ref e) => write_err!(f, "base58 encoding error"; e),
            Self::InvalidBase58PayloadLength(ref e) => write_err!(f, "base58 payload"; e),
            Self::InvalidPrivateKeyPrefix =>
                f.write_str("invalid private key prefix, byte 45 must be 0 as required by BIP-0032"),
            Self::NonZeroParentFingerprintForMasterKey =>
                f.write_str("non-zero parent fingerprint in master key"),
            Self::NonZeroChildNumberForMasterKey =>
                f.write_str("non-zero child number in master key"),
        }
    }
}

#[cfg(feature = "std")]
impl std::error::Error for ParseError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            Self::Secp256k1(ref e) => Some(e),
            Self::Base58(ref e) => Some(e),
            Self::InvalidBase58PayloadLength(ref e) => Some(e),
            Self::UnknownVersion(_) | Self::WrongExtendedKeyLength(_) => None,
            Self::InvalidPrivateKeyPrefix => None,
            Self::NonZeroParentFingerprintForMasterKey => None,
            Self::NonZeroChildNumberForMasterKey => None,
        }
    }
}

impl From<secp256k1::Error> for ParseError {
    fn from(e: secp256k1::Error) -> Self { Self::Secp256k1(e) }
}

impl From<base58::Error> for ParseError {
    fn from(err: base58::Error) -> Self { Self::Base58(err) }
}

impl From<InvalidBase58PayloadLengthError> for ParseError {
    fn from(e: InvalidBase58PayloadLengthError) -> Self { Self::InvalidBase58PayloadLength(e) }
}

/// A BIP-0032 error
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum DerivationError {
    /// Attempted to derive a hardened child from an xpub.
    ///
    /// You can only derive hardened children from xprivs.
    CannotDeriveHardenedChild,
    /// Attempted to derive a child of depth 256 or higher.
    ///
    /// There is no way to encode such xkeys.
    MaximumDepthExceeded,
}

#[cfg(feature = "std")]
impl std::error::Error for DerivationError {}

impl fmt::Display for DerivationError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Self::CannotDeriveHardenedChild =>
                f.write_str("cannot derive hardened child of public key"),
            Self::MaximumDepthExceeded => f.write_str("cannot derive child of depth 256 or higher"),
        }
    }
}

/// Out-of-range index when constructing a child number.
///
/// *Indices* are always in the range [0, 2^31 - 1]. Normal child numbers have the
/// same range, while hardened child numbers lie in the range [2^31, 2^32 - 1].
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub struct IndexOutOfRangeError {
    /// The index that was out of range for a child number.
    pub index: u32,
}

#[cfg(feature = "std")]
impl std::error::Error for IndexOutOfRangeError {}

impl From<Infallible> for IndexOutOfRangeError {
    fn from(never: Infallible) -> Self { match never {} }
}

impl fmt::Display for IndexOutOfRangeError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "index {} out of range [0, 2^31 - 1] (do you have a hardened child number, rather than an index?)", self.index)
    }
}

/// Error parsing a child number.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ParseChildNumberError {
    /// Parsed the child number as an integer, but the integer was out of range.
    IndexOutOfRange(IndexOutOfRangeError),
    /// Failed to parse the child number as an integer.
    ParseInt(core::num::ParseIntError),
}

impl From<Infallible> for ParseChildNumberError {
    fn from(never: Infallible) -> Self { match never {} }
}

#[cfg(feature = "std")]
impl std::error::Error for ParseChildNumberError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match *self {
            Self::IndexOutOfRange(ref e) => Some(e),
            Self::ParseInt(ref e) => Some(e),
        }
    }
}

impl fmt::Display for ParseChildNumberError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Self::IndexOutOfRange(ref e) => e.fmt(f),
            Self::ParseInt(ref e) => e.fmt(f),
        }
    }
}

impl Xpriv {
    /// Constructs a new master key from a seed value
    pub fn new_master(network: impl Into<NetworkKind>, seed: &[u8]) -> Self {
        let mut engine = HmacEngine::<sha512::HashEngine>::new(b"Bitcoin seed");
        engine.input(seed);
        let hmac = engine.finalize();

        Self {
            network: network.into(),
            depth: 0,
            parent_fingerprint: Default::default(),
            child_number: ChildNumber::ZERO_NORMAL,
            private_key: secp256k1::SecretKey::from_secret_bytes(
                *hmac.as_byte_array().split_array::<32, 32>().0,
            )
            .expect("cryptographically unreachable"),
            chain_code: ChainCode::from_hmac(hmac),
        }
    }

    /// Constructs a new ECDSA compressed private key matching internal secret key representation.
    #[deprecated(since = "TBD", note = "use `to_private_key()` instead")]
    pub fn to_priv(self) -> PrivateKey { self.to_private_key() }

    /// Constructs a new ECDSA compressed private key matching internal secret key representation.
    pub fn to_private_key(self) -> PrivateKey {
        PrivateKey::from_secp(self.private_key, self.network)
    }

    /// Constructs a new extended public key from this extended private key.
    pub fn to_xpub(self) -> Xpub { Xpub::from_xpriv(&self) }

    /// Constructs a new BIP-0340 keypair for Schnorr signatures and Taproot use matching the internal
    /// secret key representation.
    pub fn to_keypair(self) -> Keypair { Keypair::from_secret_key(&self.private_key) }

    /// Derives an extended private key from a path.
    ///
    /// The `path` argument can be both of type `DerivationPath` or `Vec<ChildNumber>`.
    #[deprecated(since = "TBD", note = "use `derive_xpriv()` instead")]
    pub fn derive_priv<P: AsRef<[ChildNumber]>>(&self, path: P) -> Result<Self, DerivationError> {
        self.derive_xpriv(path)
    }

    /// Derives an extended private key from a path.
    ///
    /// The `path` argument can be both of type `DerivationPath` or `Vec<ChildNumber>`.
    pub fn derive_xpriv<P: AsRef<[ChildNumber]>>(&self, path: P) -> Result<Self, DerivationError> {
        let mut sk: Self = *self;
        for cnum in path.as_ref() {
            sk = sk.ckd_priv(*cnum)?;
        }
        Ok(sk)
    }

    /// Private->Private child key derivation
    fn ckd_priv(&self, i: ChildNumber) -> Result<Self, DerivationError> {
        let mut engine = HmacEngine::<sha512::HashEngine>::new(&self.chain_code[..]);
        match i {
            ChildNumber::Normal { .. } => {
                // Non-hardened key: compute public data and use that
                engine.input(
                    &secp256k1::PublicKey::from_secret_key(&self.private_key).serialize()[..],
                );
            }
            ChildNumber::Hardened { .. } => {
                // Hardened key: use only secret data to prevent public derivation
                engine.input(&[0u8]);
                engine.input(&self.private_key[..]);
            }
        }

        engine.input(&u32::from(i).to_be_bytes());
        let hmac: Hmac<sha512::Hash> = engine.finalize();
        let sk = secp256k1::SecretKey::from_secret_bytes(
            *hmac.as_byte_array().split_array::<32, 32>().0,
        )
        .expect("statistically impossible to hit");
        let tweaked =
            sk.add_tweak(&self.private_key.into()).expect("statistically impossible to hit");

        Ok(Self {
            network: self.network,
            depth: self.depth.checked_add(1).ok_or(DerivationError::MaximumDepthExceeded)?,
            parent_fingerprint: self.fingerprint(),
            child_number: i,
            private_key: tweaked,
            chain_code: ChainCode::from_hmac(hmac),
        })
    }

    /// Decoding extended private key from binary data according to BIP-0032
    pub fn decode(data: &[u8]) -> Result<Self, ParseError> {
        let Common { network, depth, parent_fingerprint, child_number, chain_code, key } =
            Common::decode(data)?;

        let network = match network {
            VERSION_BYTES_MAINNET_PRIVATE => NetworkKind::Main,
            VERSION_BYTES_TESTNETS_PRIVATE => NetworkKind::Test,
            unknown => return Err(ParseError::UnknownVersion(unknown)),
        };

        let (&zero, private_key) = key.split_first();
        if zero != 0 {
            return Err(ParseError::InvalidPrivateKeyPrefix);
        }

        Ok(Self {
            network,
            depth,
            parent_fingerprint,
            child_number,
            chain_code,
            private_key: secp256k1::SecretKey::from_secret_bytes(*private_key)?,
        })
    }

    /// Extended private key binary encoding according to BIP-0032
    pub fn encode(&self) -> [u8; 78] {
        let mut ret = [0; 78];
        ret[0..4].copy_from_slice(&match self.network {
            NetworkKind::Main => VERSION_BYTES_MAINNET_PRIVATE,
            NetworkKind::Test => VERSION_BYTES_TESTNETS_PRIVATE,
        });
        ret[4] = self.depth;
        ret[5..9].copy_from_slice(&self.parent_fingerprint[..]);
        ret[9..13].copy_from_slice(&u32::from(self.child_number).to_be_bytes());
        ret[13..45].copy_from_slice(&self.chain_code[..]);
        ret[45] = 0;
        ret[46..78].copy_from_slice(&self.private_key[..]);
        ret
    }

    /// Returns the HASH160 of the public key belonging to the xpriv
    pub fn identifier(&self) -> XKeyIdentifier { Xpub::from_xpriv(self).identifier() }

    /// Returns the first four bytes of the identifier
    pub fn fingerprint(&self) -> Fingerprint {
        self.identifier().as_byte_array().sub_array::<0, 4>().into()
    }
}

impl Xpub {
    /// Constructs a new extended public key from an extended private key.
    #[deprecated(since = "TBD", note = "use `from_xpriv()` instead")]
    pub fn from_priv(sk: &Xpriv) -> Self { Self::from_xpriv(sk) }

    /// Constructs a new extended public key from an extended private key.
    pub fn from_xpriv(xpriv: &Xpriv) -> Self {
        Self {
            network: xpriv.network,
            depth: xpriv.depth,
            parent_fingerprint: xpriv.parent_fingerprint,
            child_number: xpriv.child_number,
            public_key: secp256k1::PublicKey::from_secret_key(&xpriv.private_key),
            chain_code: xpriv.chain_code,
        }
    }

    /// Constructs a new ECDSA compressed public key matching internal public key representation.
    #[deprecated(since = "TBD", note = "use `to_public_key()` instead")]
    pub fn to_pub(self) -> CompressedPublicKey { self.to_public_key() }

    /// Constructs a new ECDSA compressed public key matching internal public key representation.
    pub fn to_public_key(self) -> CompressedPublicKey {
        CompressedPublicKey::from_secp(self.public_key)
    }

    /// Constructs a new BIP-0340 x-only public key for BIP-0340 signatures and Taproot use matching
    /// the internal public key representation.
    #[deprecated(since = "TBD", note = "use `to_x_only_public_key()` instead")]
    pub fn to_x_only_pub(self) -> XOnlyPublicKey { self.to_x_only_public_key() }

    /// Constructs a new BIP-0340 x-only public key for BIP-0340 signatures and Taproot use matching
    /// the internal public key representation.
    pub fn to_x_only_public_key(self) -> XOnlyPublicKey { XOnlyPublicKey::from(self.public_key) }

    /// Attempts to derive an extended public key from a path.
    ///
    /// The `path` argument can be any type implementing `AsRef<ChildNumber>`, such as `DerivationPath`, for instance.
    #[deprecated(since = "TBD", note = "use `derive_xpub()` instead")]
    pub fn derive_pub<P: AsRef<[ChildNumber]>>(&self, path: P) -> Result<Self, DerivationError> {
        self.derive_xpub(path)
    }

    /// Attempts to derive an extended public key from a path.
    ///
    /// The `path` argument can be any type implementing `AsRef<ChildNumber>`, such as `DerivationPath`, for instance.
    pub fn derive_xpub<P: AsRef<[ChildNumber]>>(&self, path: P) -> Result<Self, DerivationError> {
        let mut pk: Self = *self;
        for cnum in path.as_ref() {
            pk = pk.ckd_pub(*cnum)?
        }
        Ok(pk)
    }

    /// Computes the scalar tweak added to this key to get a child key
    pub fn ckd_pub_tweak(
        &self,
        i: ChildNumber,
    ) -> Result<(secp256k1::SecretKey, ChainCode), DerivationError> {
        match i {
            ChildNumber::Hardened { .. } => Err(DerivationError::CannotDeriveHardenedChild),
            ChildNumber::Normal { index: n } => {
                let mut engine = HmacEngine::<sha512::HashEngine>::new(&self.chain_code[..]);
                engine.input(&self.public_key.serialize()[..]);
                engine.input(&n.to_be_bytes());

                let hmac = engine.finalize();
                let private_key = secp256k1::SecretKey::from_secret_bytes(
                    *hmac.as_byte_array().split_array::<32, 32>().0,
                )
                .expect("cryptographically unreachable");
                let chain_code = ChainCode::from_hmac(hmac);
                Ok((private_key, chain_code))
            }
        }
    }

    /// Public->Public child key derivation
    pub fn ckd_pub(&self, i: ChildNumber) -> Result<Self, DerivationError> {
        let (sk, chain_code) = self.ckd_pub_tweak(i)?;
        let tweaked =
            self.public_key.add_exp_tweak(&sk.into()).expect("cryptographically unreachable");

        Ok(Self {
            network: self.network,
            depth: self.depth.checked_add(1).ok_or(DerivationError::MaximumDepthExceeded)?,
            parent_fingerprint: self.fingerprint(),
            child_number: i,
            public_key: tweaked,
            chain_code,
        })
    }

    /// Decoding extended public key from binary data according to BIP-0032
    pub fn decode(data: &[u8]) -> Result<Self, ParseError> {
        let Common { network, depth, parent_fingerprint, child_number, chain_code, key } =
            Common::decode(data)?;

        let network = match network {
            VERSION_BYTES_MAINNET_PUBLIC => NetworkKind::Main,
            VERSION_BYTES_TESTNETS_PUBLIC => NetworkKind::Test,
            unknown => return Err(ParseError::UnknownVersion(unknown)),
        };

        Ok(Self {
            network,
            depth,
            parent_fingerprint,
            child_number,
            chain_code,
            public_key: secp256k1::PublicKey::from_slice(&key)?,
        })
    }

    /// Extended public key binary encoding according to BIP-0032
    pub fn encode(&self) -> [u8; 78] {
        let mut ret = [0; 78];
        ret[0..4].copy_from_slice(&match self.network {
            NetworkKind::Main => VERSION_BYTES_MAINNET_PUBLIC,
            NetworkKind::Test => VERSION_BYTES_TESTNETS_PUBLIC,
        });
        ret[4] = self.depth;
        ret[5..9].copy_from_slice(&self.parent_fingerprint[..]);
        ret[9..13].copy_from_slice(&u32::from(self.child_number).to_be_bytes());
        ret[13..45].copy_from_slice(&self.chain_code[..]);
        ret[45..78].copy_from_slice(&self.public_key.serialize()[..]);
        ret
    }

    /// Returns the HASH160 of the public key component of the xpub
    pub fn identifier(&self) -> XKeyIdentifier {
        XKeyIdentifier(hash160::Hash::hash(&self.public_key.serialize()))
    }

    /// Returns the first four bytes of the identifier
    pub fn fingerprint(&self) -> Fingerprint {
        self.identifier().as_byte_array().sub_array::<0, 4>().into()
    }
}

impl fmt::Display for Xpriv {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        base58::encode_check_to_fmt(fmt, &self.encode()[..])
    }
}

impl FromStr for Xpriv {
    type Err = ParseError;

    fn from_str(inp: &str) -> Result<Self, ParseError> {
        let data = base58::decode_check(inp)?;

        if data.len() != 78 {
            return Err(InvalidBase58PayloadLengthError { length: data.len() }.into());
        }

        Self::decode(&data)
    }
}

impl fmt::Display for Xpub {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        base58::encode_check_to_fmt(fmt, &self.encode()[..])
    }
}

impl FromStr for Xpub {
    type Err = ParseError;

    fn from_str(inp: &str) -> Result<Self, ParseError> {
        let data = base58::decode_check(inp)?;

        if data.len() != 78 {
            return Err(InvalidBase58PayloadLengthError { length: data.len() }.into());
        }

        Self::decode(&data)
    }
}

impl From<Xpub> for XKeyIdentifier {
    fn from(key: Xpub) -> Self { key.identifier() }
}

impl From<&Xpub> for XKeyIdentifier {
    fn from(key: &Xpub) -> Self { key.identifier() }
}

/// Decoded base58 data was an invalid length.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct InvalidBase58PayloadLengthError {
    /// The base58 payload length we got after decoding xpriv/xpub string.
    pub(crate) length: usize,
}

impl InvalidBase58PayloadLengthError {
    /// Returns the invalid payload length.
    pub fn invalid_base58_payload_length(&self) -> usize { self.length }
}

impl fmt::Display for InvalidBase58PayloadLengthError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "decoded base58 xpriv/xpub data was an invalid length: {} (expected 78)",
            self.length
        )
    }
}

#[cfg(feature = "std")]
impl std::error::Error for InvalidBase58PayloadLengthError {}

// Helps unify decoding
struct Common {
    network: [u8; 4],
    depth: u8,
    parent_fingerprint: Fingerprint,
    child_number: ChildNumber,
    chain_code: ChainCode,
    // public key (compressed) or 0 byte followed by a private key
    key: [u8; 33],
}

impl Common {
    fn decode(data: &[u8]) -> Result<Self, ParseError> {
        let data: &[u8; 78] =
            data.try_into().map_err(|_| ParseError::WrongExtendedKeyLength(data.len()))?;

        let (&network, data) = data.split_array::<4, 74>();
        let (&depth, data) = data.split_first::<73>();
        let (&parent_fingerprint, data) = data.split_array::<4, 69>();
        let (&child_number, data) = data.split_array::<4, 65>();
        let (&chain_code, &key) = data.split_array::<32, 33>();

        if depth == 0 {
            if parent_fingerprint != [0u8; 4] {
                return Err(ParseError::NonZeroParentFingerprintForMasterKey);
            }

            if child_number != [0u8; 4] {
                return Err(ParseError::NonZeroChildNumberForMasterKey);
            }
        }

        Ok(Self {
            network,
            depth,
            parent_fingerprint: parent_fingerprint.into(),
            child_number: u32::from_be_bytes(child_number).into(),
            chain_code: chain_code.into(),
            key,
        })
    }
}

#[cfg(test)]
mod tests {
    use hex_lit::hex;
    #[cfg(feature = "serde")]
    use internals::serde_round_trip;

    use super::ChildNumber::{Hardened, Normal};
    use super::*;

    #[test]
    fn parse_derivation_path_invalid_format() {
        let invalid_paths = ["n/0'/0", "4/m/5", "//3/0'", "0h/0x"];
        for path in &invalid_paths {
            assert!(matches!(
                path.parse::<DerivationPath>(),
                Err(ParseChildNumberError::ParseInt(..)),
            ));
        }
    }

    #[test]
    fn test_derivation_path_display() {
        let path = DerivationPath::from_str("m/84'/0'/0'/0/0").unwrap();
        assert_eq!(format!("{}", path), "84'/0'/0'/0/0");
        assert_eq!(format!("{:#}", path), "84h/0h/0h/0/0");
    }

    #[test]
    fn test_lowerhex_formatting() {
        let normal = Normal { index: 42 };
        let hardened = Hardened { index: 42 };

        assert_eq!(format!("{:x}", normal), "2a");
        assert_eq!(format!("{:#x}", normal), "0x2a");

        assert_eq!(format!("{:x}", hardened), "2a'");
        assert_eq!(format!("{:#x}", hardened), "0x2ah");
    }

    #[test]
    fn test_upperhex_formatting() {
        let normal = Normal { index: 42 };
        let hardened = Hardened { index: 42 };

        assert_eq!(format!("{:X}", normal), "2A");
        assert_eq!(format!("{:#X}", normal), "0x2A");

        assert_eq!(format!("{:X}", hardened), "2A'");
        assert_eq!(format!("{:#X}", hardened), "0x2AH");
    }

    #[test]
    fn test_octal_formatting() {
        let normal = Normal { index: 42 };
        let hardened = Hardened { index: 42 };

        assert_eq!(format!("{:o}", normal), "52");
        assert_eq!(format!("{:#o}", normal), "0o52");

        assert_eq!(format!("{:o}", hardened), "52'");
        assert_eq!(format!("{:#o}", hardened), "0o52h");
    }

    #[test]
    fn test_binary_formatting() {
        let normal = Normal { index: 42 };
        let hardened = Hardened { index: 42 };

        assert_eq!(format!("{:b}", normal), "101010");
        assert_eq!(format!("{:#b}", normal), "0b101010");

        assert_eq!(format!("{:b}", hardened), "101010'");
        assert_eq!(format!("{:#b}", hardened), "0b101010h");
    }

    #[test]
    fn parse_derivation_path_out_of_range() {
        let invalid_path = "2147483648";
        assert_eq!(
            invalid_path.parse::<DerivationPath>(),
            Err(ParseChildNumberError::IndexOutOfRange(IndexOutOfRangeError { index: 2147483648 })),
        );
    }

    #[test]
    fn parse_derivation_path_valid_empty_master() {
        // Sanity checks.
        assert_eq!(DerivationPath::master(), DerivationPath(vec![]));
        assert_eq!(DerivationPath::master(), "".parse::<DerivationPath>().unwrap());
        assert_eq!(DerivationPath::master(), DerivationPath::default());

        // Empty is the same as with an `m`.
        assert_eq!("".parse::<DerivationPath>().unwrap(), DerivationPath(vec![]));
        assert_eq!("m".parse::<DerivationPath>().unwrap(), DerivationPath(vec![]));
        assert_eq!("m/".parse::<DerivationPath>().unwrap(), DerivationPath(vec![]));
    }

    #[test]
    fn parse_derivation_path_valid() {
        let valid_paths = [
            ("0'", vec![ChildNumber::ZERO_HARDENED]),
            ("0'/1", vec![ChildNumber::ZERO_HARDENED, ChildNumber::ONE_NORMAL]),
            (
                "0h/1/2'",
                vec![
                    ChildNumber::ZERO_HARDENED,
                    ChildNumber::ONE_NORMAL,
                    ChildNumber::from_hardened_idx(2).unwrap(),
                ],
            ),
            (
                "0'/1/2h/2",
                vec![
                    ChildNumber::ZERO_HARDENED,
                    ChildNumber::ONE_NORMAL,
                    ChildNumber::from_hardened_idx(2).unwrap(),
                    ChildNumber::from_normal_idx(2).unwrap(),
                ],
            ),
            (
                "0'/1/2'/2/1000000000",
                vec![
                    ChildNumber::ZERO_HARDENED,
                    ChildNumber::ONE_NORMAL,
                    ChildNumber::from_hardened_idx(2).unwrap(),
                    ChildNumber::from_normal_idx(2).unwrap(),
                    ChildNumber::from_normal_idx(1000000000).unwrap(),
                ],
            ),
        ];
        for (path, expected) in valid_paths {
            // Access the inner private field so we don't have to clone expected.
            assert_eq!(path.parse::<DerivationPath>().unwrap().0, expected);
            // Test with the leading `m` for good measure.
            let prefixed = format!("m/{}", path);
            assert_eq!(prefixed.parse::<DerivationPath>().unwrap().0, expected);
        }
    }

    #[test]
    fn parse_derivation_path_same_as_into_derivation_path() {
        let s = "0'/50/3'/5/545456";
        assert_eq!(s.parse::<DerivationPath>(), s.into_derivation_path());
        assert_eq!(s.parse::<DerivationPath>(), s.to_string().into_derivation_path());

        let s = "m/0'/50/3'/5/545456";
        assert_eq!(s.parse::<DerivationPath>(), s.into_derivation_path());
        assert_eq!(s.parse::<DerivationPath>(), s.to_string().into_derivation_path());
    }

    #[test]
    fn derivation_path_conversion_index() {
        let path = "0h/1/2'".parse::<DerivationPath>().unwrap();
        let numbers: Vec<ChildNumber> = path.clone().into();
        let path2: DerivationPath = numbers.into();
        assert_eq!(path, path2);
        assert_eq!(&path[..2], &[ChildNumber::ZERO_HARDENED, ChildNumber::ONE_NORMAL]);
        let indexed: DerivationPath = path[..2].into();
        assert_eq!(indexed, "0h/1".parse::<DerivationPath>().unwrap());
        assert_eq!(indexed.child(ChildNumber::from_hardened_idx(2).unwrap()), path);
    }

    fn test_path(
        network: NetworkKind,
        seed: &[u8],
        path: DerivationPath,
        expected_sk: &str,
        expected_pk: &str,
    ) {
        let mut sk = Xpriv::new_master(network, seed);
        let mut pk = Xpub::from_xpriv(&sk);

        // Check derivation convenience method for Xpriv
        assert_eq!(&sk.derive_xpriv(&path).unwrap().to_string()[..], expected_sk);

        // Check derivation convenience method for Xpub, should error
        // appropriately if any ChildNumber is hardened
        if path.0.iter().any(|cnum| cnum.is_hardened()) {
            assert_eq!(pk.derive_xpub(&path), Err(DerivationError::CannotDeriveHardenedChild));
        } else {
            assert_eq!(&pk.derive_xpub(&path).unwrap().to_string()[..], expected_pk);
        }

        // Derive keys, checking hardened and non-hardened derivation one-by-one
        for &num in path.0.iter() {
            sk = sk.ckd_priv(num).unwrap();
            match num {
                Normal { .. } => {
                    let pk2 = pk.ckd_pub(num).unwrap();
                    pk = Xpub::from_xpriv(&sk);
                    assert_eq!(pk, pk2);
                }
                Hardened { .. } => {
                    assert_eq!(pk.ckd_pub(num), Err(DerivationError::CannotDeriveHardenedChild));
                    pk = Xpub::from_xpriv(&sk);
                }
            }
        }

        // Check result against expected base58
        assert_eq!(&sk.to_string()[..], expected_sk);
        assert_eq!(&pk.to_string()[..], expected_pk);
        // Check decoded base58 against result
        let decoded_sk = expected_sk.parse::<Xpriv>();
        let decoded_pk = expected_pk.parse::<Xpub>();
        assert_eq!(Ok(sk), decoded_sk);
        assert_eq!(Ok(pk), decoded_pk);
    }

    #[test]
    fn increment() {
        let idx = 9345497; // randomly generated, I promise
        let cn = ChildNumber::from_normal_idx(idx).unwrap();
        assert_eq!(cn.increment().ok(), Some(ChildNumber::from_normal_idx(idx + 1).unwrap()));
        let cn = ChildNumber::from_hardened_idx(idx).unwrap();
        assert_eq!(cn.increment().ok(), Some(ChildNumber::from_hardened_idx(idx + 1).unwrap()));

        let max = (1 << 31) - 1;
        let cn = ChildNumber::from_normal_idx(max).unwrap();
        assert_eq!(cn.increment(), Err(IndexOutOfRangeError { index: 1 << 31 }),);
        let cn = ChildNumber::from_hardened_idx(max).unwrap();
        assert_eq!(cn.increment(), Err(IndexOutOfRangeError { index: 1 << 31 }),);

        let cn = ChildNumber::from_normal_idx(350).unwrap();
        let path = "42'".parse::<DerivationPath>().unwrap();
        let mut iter = path.children_from(cn);
        assert_eq!(iter.next(), Some("42'/350".parse().unwrap()));
        assert_eq!(iter.next(), Some("42'/351".parse().unwrap()));

        let path = "42'/350'".parse::<DerivationPath>().unwrap();
        let mut iter = path.normal_children();
        assert_eq!(iter.next(), Some("42'/350'/0".parse().unwrap()));
        assert_eq!(iter.next(), Some("42'/350'/1".parse().unwrap()));

        let path = "42'/350'".parse::<DerivationPath>().unwrap();
        let mut iter = path.hardened_children();
        assert_eq!(iter.next(), Some("42'/350'/0'".parse().unwrap()));
        assert_eq!(iter.next(), Some("42'/350'/1'".parse().unwrap()));

        let cn = ChildNumber::from_hardened_idx(42350).unwrap();
        let path = "42'".parse::<DerivationPath>().unwrap();
        let mut iter = path.children_from(cn);
        assert_eq!(iter.next(), Some("42'/42350'".parse().unwrap()));
        assert_eq!(iter.next(), Some("42'/42351'".parse().unwrap()));

        let cn = ChildNumber::from_hardened_idx(max).unwrap();
        let path = "42'".parse::<DerivationPath>().unwrap();
        let mut iter = path.children_from(cn);
        assert!(iter.next().is_some());
        assert!(iter.next().is_none());
    }

    #[test]
    fn vector_1() {
        let seed = hex!("000102030405060708090a0b0c0d0e0f");

        // m
        test_path(NetworkKind::Main, &seed, "m".parse().unwrap(),
                  "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi",
                  "xpub661MyMwAqRbcFtXgS5sYJABqqG9YLmC4Q1Rdap9gSE8NqtwybGhePY2gZ29ESFjqJoCu1Rupje8YtGqsefD265TMg7usUDFdp6W1EGMcet8");

        // m/0h
        test_path(NetworkKind::Main, &seed, "m/0h".parse().unwrap(),
                  "xprv9uHRZZhk6KAJC1avXpDAp4MDc3sQKNxDiPvvkX8Br5ngLNv1TxvUxt4cV1rGL5hj6KCesnDYUhd7oWgT11eZG7XnxHrnYeSvkzY7d2bhkJ7",
                  "xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw");

        // m/0h/1
        test_path(NetworkKind::Main, &seed, "m/0h/1".parse().unwrap(),
                   "xprv9wTYmMFdV23N2TdNG573QoEsfRrWKQgWeibmLntzniatZvR9BmLnvSxqu53Kw1UmYPxLgboyZQaXwTCg8MSY3H2EU4pWcQDnRnrVA1xe8fs",
                   "xpub6ASuArnXKPbfEwhqN6e3mwBcDTgzisQN1wXN9BJcM47sSikHjJf3UFHKkNAWbWMiGj7Wf5uMash7SyYq527Hqck2AxYysAA7xmALppuCkwQ");

        // m/0h/1/2h
        test_path(NetworkKind::Main, &seed, "m/0h/1/2h".parse().unwrap(),
                  "xprv9z4pot5VBttmtdRTWfWQmoH1taj2axGVzFqSb8C9xaxKymcFzXBDptWmT7FwuEzG3ryjH4ktypQSAewRiNMjANTtpgP4mLTj34bhnZX7UiM",
                  "xpub6D4BDPcP2GT577Vvch3R8wDkScZWzQzMMUm3PWbmWvVJrZwQY4VUNgqFJPMM3No2dFDFGTsxxpG5uJh7n7epu4trkrX7x7DogT5Uv6fcLW5");

        // m/0h/1/2h/2
        test_path(NetworkKind::Main, &seed, "m/0h/1/2h/2".parse().unwrap(),
                  "xprvA2JDeKCSNNZky6uBCviVfJSKyQ1mDYahRjijr5idH2WwLsEd4Hsb2Tyh8RfQMuPh7f7RtyzTtdrbdqqsunu5Mm3wDvUAKRHSC34sJ7in334",
                  "xpub6FHa3pjLCk84BayeJxFW2SP4XRrFd1JYnxeLeU8EqN3vDfZmbqBqaGJAyiLjTAwm6ZLRQUMv1ZACTj37sR62cfN7fe5JnJ7dh8zL4fiyLHV");

        // m/0h/1/2h/2/1000000000
        test_path(NetworkKind::Main, &seed, "m/0h/1/2h/2/1000000000".parse().unwrap(),
                  "xprvA41z7zogVVwxVSgdKUHDy1SKmdb533PjDz7J6N6mV6uS3ze1ai8FHa8kmHScGpWmj4WggLyQjgPie1rFSruoUihUZREPSL39UNdE3BBDu76",
                  "xpub6H1LXWLaKsWFhvm6RVpEL9P4KfRZSW7abD2ttkWP3SSQvnyA8FSVqNTEcYFgJS2UaFcxupHiYkro49S8yGasTvXEYBVPamhGW6cFJodrTHy");
    }

    #[test]
    fn vector_2() {
        let seed = hex!("fffcf9f6f3f0edeae7e4e1dedbd8d5d2cfccc9c6c3c0bdbab7b4b1aeaba8a5a29f9c999693908d8a8784817e7b7875726f6c696663605d5a5754514e4b484542");

        // m
        test_path(NetworkKind::Main, &seed, "m".parse().unwrap(),
                  "xprv9s21ZrQH143K31xYSDQpPDxsXRTUcvj2iNHm5NUtrGiGG5e2DtALGdso3pGz6ssrdK4PFmM8NSpSBHNqPqm55Qn3LqFtT2emdEXVYsCzC2U",
                  "xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB");

        // m/0
        test_path(NetworkKind::Main, &seed, "m/0".parse().unwrap(),
                  "xprv9vHkqa6EV4sPZHYqZznhT2NPtPCjKuDKGY38FBWLvgaDx45zo9WQRUT3dKYnjwih2yJD9mkrocEZXo1ex8G81dwSM1fwqWpWkeS3v86pgKt",
                  "xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH");

        // m/0/2147483647h
        test_path(NetworkKind::Main, &seed, "m/0/2147483647h".parse().unwrap(),
                  "xprv9wSp6B7kry3Vj9m1zSnLvN3xH8RdsPP1Mh7fAaR7aRLcQMKTR2vidYEeEg2mUCTAwCd6vnxVrcjfy2kRgVsFawNzmjuHc2YmYRmagcEPdU9",
                  "xpub6ASAVgeehLbnwdqV6UKMHVzgqAG8Gr6riv3Fxxpj8ksbH9ebxaEyBLZ85ySDhKiLDBrQSARLq1uNRts8RuJiHjaDMBU4Zn9h8LZNnBC5y4a");

        // m/0/2147483647h/1
        test_path(NetworkKind::Main, &seed, "m/0/2147483647h/1".parse().unwrap(),
                  "xprv9zFnWC6h2cLgpmSA46vutJzBcfJ8yaJGg8cX1e5StJh45BBciYTRXSd25UEPVuesF9yog62tGAQtHjXajPPdbRCHuWS6T8XA2ECKADdw4Ef",
                  "xpub6DF8uhdarytz3FWdA8TvFSvvAh8dP3283MY7p2V4SeE2wyWmG5mg5EwVvmdMVCQcoNJxGoWaU9DCWh89LojfZ537wTfunKau47EL2dhHKon");

        // m/0/2147483647h/1/2147483646h
        test_path(NetworkKind::Main, &seed, "m/0/2147483647h/1/2147483646h".parse().unwrap(),
                  "xprvA1RpRA33e1JQ7ifknakTFpgNXPmW2YvmhqLQYMmrj4xJXXWYpDPS3xz7iAxn8L39njGVyuoseXzU6rcxFLJ8HFsTjSyQbLYnMpCqE2VbFWc",
                  "xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL");

        // m/0/2147483647h/1/2147483646h/2
        test_path(NetworkKind::Main, &seed, "m/0/2147483647h/1/2147483646h/2".parse().unwrap(),
                  "xprvA2nrNbFZABcdryreWet9Ea4LvTJcGsqrMzxHx98MMrotbir7yrKCEXw7nadnHM8Dq38EGfSh6dqA9QWTyefMLEcBYJUuekgW4BYPJcr9E7j",
                  "xpub6FnCn6nSzZAw5Tw7cgR9bi15UV96gLZhjDstkXXxvCLsUXBGXPdSnLFbdpq8p9HmGsApME5hQTZ3emM2rnY5agb9rXpVGyy3bdW6EEgAtqt");
    }

    #[test]
    fn vector_3() {
        let seed = hex!("4b381541583be4423346c643850da4b320e46a87ae3d2a4e6da11eba819cd4acba45d239319ac14f863b8d5ab5a0d0c64d2e8a1e7d1457df2e5a3c51c73235be");

        // m
        test_path(NetworkKind::Main, &seed, "m".parse().unwrap(),
                  "xprv9s21ZrQH143K25QhxbucbDDuQ4naNntJRi4KUfWT7xo4EKsHt2QJDu7KXp1A3u7Bi1j8ph3EGsZ9Xvz9dGuVrtHHs7pXeTzjuxBrCmmhgC6",
                  "xpub661MyMwAqRbcEZVB4dScxMAdx6d4nFc9nvyvH3v4gJL378CSRZiYmhRoP7mBy6gSPSCYk6SzXPTf3ND1cZAceL7SfJ1Z3GC8vBgp2epUt13");

        // m/0h
        test_path(NetworkKind::Main, &seed, "m/0h".parse().unwrap(),
                  "xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L",
                  "xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y");
    }

    #[test]
    fn test_reject_xpriv_with_non_zero_byte_at_index_45() {
        let mut xpriv = base58::decode_check("xprv9wSp6B7kry3Vj9m1zSnLvN3xH8RdsPP1Mh7fAaR7aRLcQMKTR2vidYEeEg2mUCTAwCd6vnxVrcjfy2kRgVsFawNzmjuHc2YmYRmagcEPdU9").unwrap();

        // Modify byte at index 45 to be non-zero (e.g., 1)
        xpriv[45] = 1;

        let result = Xpriv::decode(&xpriv);
        assert!(result.is_err());

        match result {
            Err(ParseError::InvalidPrivateKeyPrefix) => {}
            _ => panic!("Expected InvalidPrivateKeyPrefix error, got {:?}", result),
        }
    }

    #[test]
    fn test_reject_xpriv_with_zero_depth_and_non_zero_index() {
        let result = "xprv9s21ZrQH4r4TsiLvyLXqM9P7k1K3EYhA1kkD6xuquB5i39AU8KF42acDyL3qsDbU9NmZn6MsGSUYZEsuoePmjzsB3eFKSUEh3Gu1N3cqVUN".parse::<Xpriv>();
        assert!(result.is_err());

        match result {
            Err(ParseError::NonZeroChildNumberForMasterKey) => {}
            _ => panic!("Expected NonZeroChildNumberForMasterKey error, got {:?}", result),
        }
    }

    #[test]
    fn test_reject_xpriv_with_zero_depth_and_non_zero_parent_fingerprint() {
        let result = "xprv9s2SPatNQ9Vc6GTbVMFPFo7jsaZySyzk7L8n2uqKXJen3KUmvQNTuLh3fhZMBoG3G4ZW1N2kZuHEPY53qmbZzCHshoQnNf4GvELZfqTUrcv".parse::<Xpriv>();
        assert!(result.is_err());

        match result {
            Err(ParseError::NonZeroParentFingerprintForMasterKey) => {}
            _ => panic!("Expected NonZeroParentFingerprintForMasterKey error, got {:?}", result),
        }
    }

    #[test]
    #[cfg(feature = "serde")]
    pub fn encode_decode_childnumber() {
        serde_round_trip!(ChildNumber::ZERO_NORMAL);
        serde_round_trip!(ChildNumber::ONE_NORMAL);
        serde_round_trip!(ChildNumber::from_normal_idx((1 << 31) - 1).unwrap());
        serde_round_trip!(ChildNumber::ZERO_HARDENED);
        serde_round_trip!(ChildNumber::ONE_HARDENED);
        serde_round_trip!(ChildNumber::from_hardened_idx((1 << 31) - 1).unwrap());
    }

    #[test]
    #[cfg(feature = "serde")]
    pub fn encode_fingerprint_chaincode() {
        use serde_json;
        let fp = Fingerprint::from([1u8, 2, 3, 42]);
        #[rustfmt::skip]
        let cc = ChainCode::from(
            [1u8,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2]
        );

        serde_round_trip!(fp);
        serde_round_trip!(cc);

        assert_eq!("\"0102032a\"", serde_json::to_string(&fp).unwrap());
        assert_eq!(
            "\"0102030405060708090001020304050607080900010203040506070809000102\"",
            serde_json::to_string(&cc).unwrap()
        );
        assert_eq!("0102032a", fp.to_string());
        assert_eq!(
            "0102030405060708090001020304050607080900010203040506070809000102",
            cc.to_string()
        );
    }

    #[test]
    fn fmt_child_number() {
        assert_eq!("000005h", &format!("{:#06}", ChildNumber::from_hardened_idx(5).unwrap()));
        assert_eq!("5h", &format!("{:#}", ChildNumber::from_hardened_idx(5).unwrap()));
        assert_eq!("000005'", &format!("{:06}", ChildNumber::from_hardened_idx(5).unwrap()));
        assert_eq!("5'", &format!("{}", ChildNumber::from_hardened_idx(5).unwrap()));
        assert_eq!("42", &format!("{}", ChildNumber::from_normal_idx(42).unwrap()));
        assert_eq!("000042", &format!("{:06}", ChildNumber::from_normal_idx(42).unwrap()));
    }

    #[test]
    #[should_panic(expected = "Secp256k1(InvalidSecretKey)")]
    fn schnorr_broken_privkey_zeros() {
        /* this is how we generate key:
        let mut sk = secp256k1::key::ONE_KEY;

        let zeros = [0u8; 32];
        unsafe {
            sk.as_mut_ptr().copy_from(zeros.as_ptr(), 32);
        }

        let xpriv = Xpriv {
            network: NetworkKind::Main,
            depth: 0,
            parent_fingerprint: Default::default(),
            child_number: ChildNumber::Normal { index: 0 },
            private_key: sk,
            chain_code: ChainCode::from([0u8; 32])
        };

        println!("{}", xpriv);
         */

        // Xpriv having secret key set to all zeros
        let xpriv_str = "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzF93Y5wvzdUayhgkkFoicQZcP3y52uPPxFnfoLZB21Teqt1VvEHx";
        xpriv_str.parse::<Xpriv>().unwrap();
    }

    #[test]
    #[should_panic(expected = "Secp256k1(InvalidSecretKey)")]
    fn schnorr_broken_privkey_ffs() {
        // Xpriv having secret key set to all 0xFF's
        let xpriv_str = "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzFAzHGBP2UuGCqWLTAPLcMtD9y5gkZ6Eq3Rjuahrv17fENZ3QzxW";
        xpriv_str.parse::<Xpriv>().unwrap();
    }

    #[test]
    fn official_vectors_5() {
        let invalid_keys = [
            "xpub661MyMwAqRbcEYS8w7XLSVeEsBXy79zSzH1J8vCdxAZningWLdN3zgtU6LBpB85b3D2yc8sfvZU521AAwdZafEz7mnzBBsz4wKY5fTtTQBm",
            "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzFGTQQD3dC4H2D5GBj7vWvSQaaBv5cxi9gafk7NF3pnBju6dwKvH",
            "xpub661MyMwAqRbcEYS8w7XLSVeEsBXy79zSzH1J8vCdxAZningWLdN3zgtU6Txnt3siSujt9RCVYsx4qHZGc62TG4McvMGcAUjeuwZdduYEvFn",
            "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzFGpWnsj83BHtEy5Zt8CcDr1UiRXuWCmTQLxEK9vbz5gPstX92JQ",
            "xpub661MyMwAqRbcEYS8w7XLSVeEsBXy79zSzH1J8vCdxAZningWLdN3zgtU6N8ZMMXctdiCjxTNq964yKkwrkBJJwpzZS4HS2fxvyYUA4q2Xe4",
            "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzFAzHGBP2UuGCqWLTAPLcMtD9y5gkZ6Eq3Rjuahrv17fEQ3Qen6J",
            "xprv9s2SPatNQ9Vc6GTbVMFPFo7jsaZySyzk7L8n2uqKXJen3KUmvQNTuLh3fhZMBoG3G4ZW1N2kZuHEPY53qmbZzCHshoQnNf4GvELZfqTUrcv",
            "xpub661no6RGEX3uJkY4bNnPcw4URcQTrSibUZ4NqJEw5eBkv7ovTwgiT91XX27VbEXGENhYRCf7hyEbWrR3FewATdCEebj6znwMfQkhRYHRLpJ",
            "xprv9s21ZrQH4r4TsiLvyLXqM9P7k1K3EYhA1kkD6xuquB5i39AU8KF42acDyL3qsDbU9NmZn6MsGSUYZEsuoePmjzsB3eFKSUEh3Gu1N3cqVUN",
            "xpub661MyMwAuDcm6CRQ5N4qiHKrJ39Xe1R1NyfouMKTTWcguwVcfrZJaNvhpebzGerh7gucBvzEQWRugZDuDXjNDRmXzSZe4c7mnTK97pTvGS8",
            "DMwo58pR1QLEFihHiXPVykYB6fJmsTeHvyTp7hRThAtCX8CvYzgPcn8XnmdfHGMQzT7ayAmfo4z3gY5KfbrZWZ6St24UVf2Qgo6oujFktLHdHY4",
            "DMwo58pR1QLEFihHiXPVykYB6fJmsTeHvyTp7hRThAtCX8CvYzgPcn8XnmdfHPmHJiEDXkTiJTVV9rHEBUem2mwVbbNfvT2MTcAqj3nesx8uBf9",
            "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzF93Y5wvzdUayhgkkFoicQZcP3y52uPPxFnfoLZB21Teqt1VvEHx",
            "xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzFAzHGBP2UuGCqWLTAPLcMtD5SDKr24z3aiUvKr9bJpdrcLg1y3G",
            "xpub661MyMwAqRbcEYS8w7XLSVeEsBXy79zSzH1J8vCdxAZningWLdN3zgtU6Q5JXayek4PRsn35jii4veMimro1xefsM58PgBMrvdYre8QyULY",
            "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHL",
        ];
        for key in invalid_keys {
            if key.starts_with("xpub") {
                key.parse::<Xpub>().unwrap_err();
            } else {
                key.parse::<Xpriv>().unwrap_err();
            }
        }
    }
}
