//! Extensions available to token mints and accounts

use {
    crate::{
        error::TokenError,
        extension::{
            confidential_transfer::{ConfidentialTransferAccount, ConfidentialTransferMint},
            default_account_state::DefaultAccountState,
            immutable_owner::ImmutableOwner,
            memo_transfer::MemoTransfer,
            mint_close_authority::MintCloseAuthority,
            transfer_fee::{TransferFeeAmount, TransferFeeConfig},
        },
        pod::*,
        state::{Account, Mint, Multisig},
    },
    bytemuck::{Pod, Zeroable},
    num_enum::{IntoPrimitive, TryFromPrimitive},
    solana_program::{
        program_error::ProgramError,
        program_pack::{IsInitialized, Pack},
    },
    std::{
        convert::{TryFrom, TryInto},
        mem::size_of,
    },
};

/// Confidential Transfer extension
pub mod confidential_transfer;
/// Default Account State extension
pub mod default_account_state;
/// Immutable Owner extension
pub mod immutable_owner;
/// Memo Transfer extension
pub mod memo_transfer;
/// Mint Close Authority extension
pub mod mint_close_authority;
/// Utility to reallocate token accounts
pub mod reallocate;
/// Transfer Fee extension
pub mod transfer_fee;

/// Length in TLV structure
#[derive(Clone, Copy, Debug, Default, PartialEq, Pod, Zeroable)]
#[repr(transparent)]
pub struct Length(PodU16);
impl From<Length> for usize {
    fn from(n: Length) -> Self {
        Self::from(u16::from(n.0))
    }
}
impl TryFrom<usize> for Length {
    type Error = ProgramError;
    fn try_from(n: usize) -> Result<Self, Self::Error> {
        u16::try_from(n)
            .map(|v| Self(PodU16::from(v)))
            .map_err(|_| ProgramError::AccountDataTooSmall)
    }
}

/// Helper function to get the current TlvIndices from the current spot
fn get_tlv_indices(type_start: usize) -> TlvIndices {
    let length_start = type_start.saturating_add(size_of::<ExtensionType>());
    let value_start = length_start.saturating_add(pod_get_packed_len::<Length>());
    TlvIndices {
        type_start,
        length_start,
        value_start,
    }
}

/// Helper struct for returning the indices of the type, length, and value in
/// a TLV entry
#[derive(Debug)]
struct TlvIndices {
    pub type_start: usize,
    pub length_start: usize,
    pub value_start: usize,
}
fn get_extension_indices<V: Extension>(
    tlv_data: &[u8],
    init: bool,
) -> Result<TlvIndices, ProgramError> {
    let mut start_index = 0;
    let v_account_type = V::TYPE.get_account_type();
    while start_index < tlv_data.len() {
        let tlv_indices = get_tlv_indices(start_index);
        if tlv_data.len() < tlv_indices.value_start {
            return Err(ProgramError::InvalidAccountData);
        }
        let extension_type =
            ExtensionType::try_from(&tlv_data[tlv_indices.type_start..tlv_indices.length_start])?;
        let account_type = extension_type.get_account_type();
        // got to an empty spot, can init here, or move forward if not initing
        if extension_type == ExtensionType::Uninitialized {
            if init {
                return Ok(tlv_indices);
            } else {
                start_index = tlv_indices.length_start;
            }
        } else if extension_type == V::TYPE {
            // found an instance of the extension that we're initializing, return!
            return Ok(tlv_indices);
        } else if v_account_type != account_type {
            return Err(TokenError::ExtensionTypeMismatch.into());
        } else {
            let length = pod_from_bytes::<Length>(
                &tlv_data[tlv_indices.length_start..tlv_indices.value_start],
            )?;
            let value_end_index = tlv_indices.value_start.saturating_add(usize::from(*length));
            start_index = value_end_index;
        }
    }
    Err(ProgramError::InvalidAccountData)
}

fn get_extension_types(tlv_data: &[u8]) -> Result<Vec<ExtensionType>, ProgramError> {
    let mut extension_types = vec![];
    let mut start_index = 0;
    while start_index < tlv_data.len() {
        let tlv_indices = get_tlv_indices(start_index);
        if tlv_data.len() < tlv_indices.value_start {
            return Ok(extension_types);
        }
        let extension_type =
            ExtensionType::try_from(&tlv_data[tlv_indices.type_start..tlv_indices.length_start])?;
        if extension_type == ExtensionType::Uninitialized {
            return Ok(extension_types);
        } else {
            extension_types.push(extension_type);
            let length = pod_from_bytes::<Length>(
                &tlv_data[tlv_indices.length_start..tlv_indices.value_start],
            )?;

            let value_end_index = tlv_indices.value_start.saturating_add(usize::from(*length));
            start_index = value_end_index;
        }
    }
    Ok(extension_types)
}

fn get_first_extension_type(tlv_data: &[u8]) -> Result<Option<ExtensionType>, ProgramError> {
    if tlv_data.is_empty() {
        Ok(None)
    } else {
        let tlv_indices = get_tlv_indices(0);
        if tlv_data.len() <= tlv_indices.length_start {
            return Ok(None);
        }
        let extension_type =
            ExtensionType::try_from(&tlv_data[tlv_indices.type_start..tlv_indices.length_start])?;
        if extension_type == ExtensionType::Uninitialized {
            Ok(None)
        } else {
            Ok(Some(extension_type))
        }
    }
}

fn check_min_len_and_not_multisig(input: &[u8], minimum_len: usize) -> Result<(), ProgramError> {
    if input.len() == Multisig::LEN || input.len() < minimum_len {
        Err(ProgramError::InvalidAccountData)
    } else {
        Ok(())
    }
}

fn check_account_type<S: BaseState>(account_type: AccountType) -> Result<(), ProgramError> {
    if account_type != S::ACCOUNT_TYPE {
        Err(ProgramError::InvalidAccountData)
    } else {
        Ok(())
    }
}

/// Any account with extensions must be at least `Account::LEN`.  Both mints and
/// accounts can have extensions
/// A mint with extensions that takes it past 165 could be indiscernible from an
/// Account with an extension, even if we add the account type. For example,
/// let's say we have:
///
/// Account: 165 bytes... + [2, 0, 3, 0, 100, ....]
///                          ^     ^       ^     ^
///                     acct type  extension length data...
///
/// Mint: 82 bytes... + 83 bytes of other extension data + [2, 0, 3, 0, 100, ....]
///                                                         ^ data in extension just happens to look like this
///
/// With this approach, we only start writing the TLV data after Account::LEN,
/// which means we always know that the account type is going to be right after
/// that. We do a special case checking for a Multisig length, because those
/// aren't extensible under any circumstances.
const BASE_ACCOUNT_LENGTH: usize = Account::LEN;

fn type_and_tlv_indices<S: BaseState>(
    rest_input: &[u8],
) -> Result<Option<(usize, usize)>, ProgramError> {
    if rest_input.is_empty() {
        Ok(None)
    } else {
        let account_type_index = BASE_ACCOUNT_LENGTH.saturating_sub(S::LEN);
        // check padding is all zeroes
        let tlv_start_index = account_type_index.saturating_add(size_of::<AccountType>());
        if rest_input.len() <= tlv_start_index {
            return Err(ProgramError::InvalidAccountData);
        }
        if rest_input[..account_type_index] != vec![0; account_type_index] {
            Err(ProgramError::InvalidAccountData)
        } else {
            Ok(Some((account_type_index, tlv_start_index)))
        }
    }
}

/// Checks a base buffer to verify if it is an Account without having to completely deserialize it
fn is_initialized_account(input: &[u8]) -> Result<bool, ProgramError> {
    const ACCOUNT_INITIALIZED_INDEX: usize = 108; // See state.rs#L99

    if input.len() != BASE_ACCOUNT_LENGTH {
        return Err(ProgramError::InvalidAccountData);
    }
    Ok(input[ACCOUNT_INITIALIZED_INDEX] != 0)
}

fn get_extension<S: BaseState, V: Extension>(tlv_data: &[u8]) -> Result<&V, ProgramError> {
    if V::TYPE.get_account_type() != S::ACCOUNT_TYPE {
        return Err(ProgramError::InvalidAccountData);
    }
    let TlvIndices {
        type_start: _,
        length_start,
        value_start,
    } = get_extension_indices::<V>(tlv_data, false)?;
    // get_extension_indices has checked that tlv_data is long enough to include these indices
    let length = pod_from_bytes::<Length>(&tlv_data[length_start..value_start])?;
    let value_end = value_start.saturating_add(usize::from(*length));
    pod_from_bytes::<V>(&tlv_data[value_start..value_end])
}

/// Encapsulates owned immutable base state data (mint or account) with possible extensions
#[derive(Debug, PartialEq)]
pub struct StateWithExtensionsOwned<S: BaseState> {
    /// Unpacked base data
    pub base: S,
    /// Raw TLV data, deserialized on demand
    tlv_data: Vec<u8>,
}
impl<S: BaseState> StateWithExtensionsOwned<S> {
    /// Unpack base state, leaving the extension data as a slice
    ///
    /// Fails if the base state is not initialized.
    pub fn unpack(mut input: Vec<u8>) -> Result<Self, ProgramError> {
        check_min_len_and_not_multisig(&input, S::LEN)?;
        let mut rest = input.split_off(S::LEN);
        let base = S::unpack(&input)?;
        if let Some((account_type_index, tlv_start_index)) = type_and_tlv_indices::<S>(&rest)? {
            // type_and_tlv_indices() checks that returned indexes are within range
            let account_type = AccountType::try_from(rest[account_type_index])
                .map_err(|_| ProgramError::InvalidAccountData)?;
            check_account_type::<S>(account_type)?;
            let tlv_data = rest.split_off(tlv_start_index);
            Ok(Self { base, tlv_data })
        } else {
            Ok(Self {
                base,
                tlv_data: vec![],
            })
        }
    }

    /// Unpack a portion of the TLV data as the desired type
    pub fn get_extension<V: Extension>(&self) -> Result<&V, ProgramError> {
        get_extension::<S, V>(&self.tlv_data)
    }

    /// Iterates through the TLV entries, returning only the types
    pub fn get_extension_types(&self) -> Result<Vec<ExtensionType>, ProgramError> {
        get_extension_types(&self.tlv_data)
    }
}

/// Encapsulates immutable base state data (mint or account) with possible extensions
#[derive(Debug, PartialEq)]
pub struct StateWithExtensions<'data, S: BaseState> {
    /// Unpacked base data
    pub base: S,
    /// Slice of data containing all TLV data, deserialized on demand
    tlv_data: &'data [u8],
}
impl<'data, S: BaseState> StateWithExtensions<'data, S> {
    /// Unpack base state, leaving the extension data as a slice
    ///
    /// Fails if the base state is not initialized.
    pub fn unpack(input: &'data [u8]) -> Result<Self, ProgramError> {
        check_min_len_and_not_multisig(input, S::LEN)?;
        let (base_data, rest) = input.split_at(S::LEN);
        let base = S::unpack(base_data)?;
        if let Some((account_type_index, tlv_start_index)) = type_and_tlv_indices::<S>(rest)? {
            // type_and_tlv_indices() checks that returned indexes are within range
            let account_type = AccountType::try_from(rest[account_type_index])
                .map_err(|_| ProgramError::InvalidAccountData)?;
            check_account_type::<S>(account_type)?;
            Ok(Self {
                base,
                tlv_data: &rest[tlv_start_index..],
            })
        } else {
            Ok(Self {
                base,
                tlv_data: &[],
            })
        }
    }

    /// Unpack a portion of the TLV data as the desired type
    pub fn get_extension<V: Extension>(&self) -> Result<&V, ProgramError> {
        get_extension::<S, V>(self.tlv_data)
    }

    /// Iterates through the TLV entries, returning only the types
    pub fn get_extension_types(&self) -> Result<Vec<ExtensionType>, ProgramError> {
        get_extension_types(self.tlv_data)
    }
}

/// Encapsulates mutable base state data (mint or account) with possible extensions
#[derive(Debug, PartialEq)]
pub struct StateWithExtensionsMut<'data, S: BaseState> {
    /// Unpacked base data
    pub base: S,
    /// Raw base data
    base_data: &'data mut [u8],
    /// Writable account type
    account_type: &'data mut [u8],
    /// Slice of data containing all TLV data, deserialized on demand
    tlv_data: &'data mut [u8],
}
impl<'data, S: BaseState> StateWithExtensionsMut<'data, S> {
    /// Unpack base state, leaving the extension data as a mutable slice
    ///
    /// Fails if the base state is not initialized.
    pub fn unpack(input: &'data mut [u8]) -> Result<Self, ProgramError> {
        check_min_len_and_not_multisig(input, S::LEN)?;
        let (base_data, rest) = input.split_at_mut(S::LEN);
        let base = S::unpack(base_data)?;
        if let Some((account_type_index, tlv_start_index)) = type_and_tlv_indices::<S>(rest)? {
            // type_and_tlv_indices() checks that returned indexes are within range
            let account_type = AccountType::try_from(rest[account_type_index])
                .map_err(|_| ProgramError::InvalidAccountData)?;
            check_account_type::<S>(account_type)?;
            let (account_type, tlv_data) = rest.split_at_mut(tlv_start_index);
            Ok(Self {
                base,
                base_data,
                account_type: &mut account_type[account_type_index..tlv_start_index],
                tlv_data,
            })
        } else {
            Ok(Self {
                base,
                base_data,
                account_type: &mut [],
                tlv_data: &mut [],
            })
        }
    }

    /// Unpack an uninitialized base state, leaving the extension data as a mutable slice
    ///
    /// Fails if the base state has already been initialized.
    pub fn unpack_uninitialized(input: &'data mut [u8]) -> Result<Self, ProgramError> {
        check_min_len_and_not_multisig(input, S::LEN)?;
        let (base_data, rest) = input.split_at_mut(S::LEN);
        let base = S::unpack_unchecked(base_data)?;
        if base.is_initialized() {
            return Err(TokenError::AlreadyInUse.into());
        }
        if let Some((account_type_index, tlv_start_index)) = type_and_tlv_indices::<S>(rest)? {
            // type_and_tlv_indices() checks that returned indexes are within range
            let account_type = AccountType::try_from(rest[account_type_index])
                .map_err(|_| ProgramError::InvalidAccountData)?;
            if account_type != AccountType::Uninitialized {
                return Err(ProgramError::InvalidAccountData);
            }
            let (account_type, tlv_data) = rest.split_at_mut(tlv_start_index);
            let state = Self {
                base,
                base_data,
                account_type: &mut account_type[account_type_index..tlv_start_index],
                tlv_data,
            };
            if let Some(extension_type) = state.get_first_extension_type()? {
                let account_type = extension_type.get_account_type();
                if account_type != S::ACCOUNT_TYPE {
                    return Err(TokenError::ExtensionBaseMismatch.into());
                }
            }
            Ok(state)
        } else {
            Ok(Self {
                base,
                base_data,
                account_type: &mut [],
                tlv_data: &mut [],
            })
        }
    }

    fn init_or_get_extension<V: Extension>(&mut self, init: bool) -> Result<&mut V, ProgramError> {
        if V::TYPE.get_account_type() != S::ACCOUNT_TYPE {
            return Err(ProgramError::InvalidAccountData);
        }
        let TlvIndices {
            type_start,
            length_start,
            value_start,
        } = get_extension_indices::<V>(self.tlv_data, init)?;

        if self.tlv_data[type_start..].len() < V::TYPE.get_tlv_len() {
            return Err(ProgramError::InvalidAccountData);
        }
        if init {
            // write extension type
            let extension_type_array: [u8; 2] = V::TYPE.into();
            let extension_type_ref = &mut self.tlv_data[type_start..length_start];
            extension_type_ref.copy_from_slice(&extension_type_array);
            // write length
            let length_ref =
                pod_from_bytes_mut::<Length>(&mut self.tlv_data[length_start..value_start])?;
            // maybe this becomes smarter later for dynamically sized extensions
            let length = pod_get_packed_len::<V>();
            *length_ref = Length::try_from(length).unwrap();

            let value_end = value_start.saturating_add(length);
            let extension_ref =
                pod_from_bytes_mut::<V>(&mut self.tlv_data[value_start..value_end])?;
            *extension_ref = V::default();
            Ok(extension_ref)
        } else {
            let length = pod_from_bytes::<Length>(&self.tlv_data[length_start..value_start])?;
            let value_end = value_start.saturating_add(usize::from(*length));
            pod_from_bytes_mut::<V>(&mut self.tlv_data[value_start..value_end])
        }
    }

    /// Unpack a portion of the TLV data as the desired type that allows modifying the type
    pub fn get_extension_mut<V: Extension>(&mut self) -> Result<&mut V, ProgramError> {
        self.init_or_get_extension(false)
    }

    /// Unpack a portion of the TLV data as the desired type
    pub fn get_extension<V: Extension>(&self) -> Result<&V, ProgramError> {
        if V::TYPE.get_account_type() != S::ACCOUNT_TYPE {
            return Err(ProgramError::InvalidAccountData);
        }
        let TlvIndices {
            type_start,
            length_start,
            value_start,
        } = get_extension_indices::<V>(self.tlv_data, false)?;

        if self.tlv_data[type_start..].len() < V::TYPE.get_tlv_len() {
            return Err(ProgramError::InvalidAccountData);
        }
        let length = pod_from_bytes::<Length>(&self.tlv_data[length_start..value_start])?;
        let value_end = value_start.saturating_add(usize::from(*length));
        pod_from_bytes::<V>(&self.tlv_data[value_start..value_end])
    }

    /// Packs base state data into the base data portion
    pub fn pack_base(&mut self) {
        S::pack_into_slice(&self.base, self.base_data);
    }

    /// Packs the default extension data into an open slot if not already found in the
    /// data buffer, otherwise overwrites the existing extension with the default state
    pub fn init_extension<V: Extension>(&mut self) -> Result<&mut V, ProgramError> {
        self.init_or_get_extension(true)
    }

    /// If `extension_type` is an Account-associated ExtensionType that requires initialization on
    /// InitializeAccount, this method packs the default relevant Extension of an ExtensionType
    /// into an open slot if not already found in the data buffer, otherwise overwrites the
    /// existing extension with the default state. For all other ExtensionTypes, this is a no-op.
    pub fn init_account_extension_from_type(
        &mut self,
        extension_type: ExtensionType,
    ) -> Result<(), ProgramError> {
        if extension_type.get_account_type() != AccountType::Account {
            return Ok(());
        }
        match extension_type {
            ExtensionType::TransferFeeAmount => {
                self.init_extension::<TransferFeeAmount>().map(|_| ())
            }
            // ConfidentialTransfers are currently opt-in only, so this is a no-op for extra safety
            // on InitializeAccount
            ExtensionType::ConfidentialTransferAccount => Ok(()),
            #[cfg(test)]
            ExtensionType::AccountPaddingTest => {
                self.init_extension::<AccountPaddingTest>().map(|_| ())
            }
            _ => unreachable!(),
        }
    }

    /// Write the account type into the buffer, done during the base
    /// state initialization
    /// Noops if there is no room for an extension in the account, needed for
    /// pure base mints / accounts.
    pub fn init_account_type(&mut self) -> Result<(), ProgramError> {
        if !self.account_type.is_empty() {
            if let Some(extension_type) = self.get_first_extension_type()? {
                let account_type = extension_type.get_account_type();
                if account_type != S::ACCOUNT_TYPE {
                    return Err(TokenError::ExtensionBaseMismatch.into());
                }
            }
            self.account_type[0] = S::ACCOUNT_TYPE.into();
        }
        Ok(())
    }

    /// Iterates through the TLV entries, returning only the types
    pub fn get_extension_types(&self) -> Result<Vec<ExtensionType>, ProgramError> {
        get_extension_types(self.tlv_data)
    }

    fn get_first_extension_type(&self) -> Result<Option<ExtensionType>, ProgramError> {
        get_first_extension_type(self.tlv_data)
    }
}

/// If AccountType is uninitialized, set it to the BaseState's ACCOUNT_TYPE;
/// if AccountType is already set, check is set correctly for BaseState
/// This method assumes that the `base_data` has already been packed with data of the desired type.
pub fn set_account_type<S: BaseState>(input: &mut [u8]) -> Result<(), ProgramError> {
    check_min_len_and_not_multisig(input, S::LEN)?;
    let (base_data, rest) = input.split_at_mut(S::LEN);
    if S::ACCOUNT_TYPE == AccountType::Account && !is_initialized_account(base_data)? {
        return Err(ProgramError::InvalidAccountData);
    }
    if let Some((account_type_index, _tlv_start_index)) = type_and_tlv_indices::<S>(rest)? {
        let mut account_type = AccountType::try_from(rest[account_type_index])
            .map_err(|_| ProgramError::InvalidAccountData)?;
        if account_type == AccountType::Uninitialized {
            rest[account_type_index] = S::ACCOUNT_TYPE.into();
            account_type = S::ACCOUNT_TYPE;
        }
        check_account_type::<S>(account_type)?;
        Ok(())
    } else {
        Err(ProgramError::InvalidAccountData)
    }
}

/// Different kinds of accounts. Note that `Mint`, `Account`, and `Multisig` types
/// are determined exclusively by the size of the account, and are not included in
/// the account data. `AccountType` is only included if extensions have been
/// initialized.
#[repr(u8)]
#[derive(Clone, Copy, Debug, PartialEq, TryFromPrimitive, IntoPrimitive)]
pub enum AccountType {
    /// Marker for 0 data
    Uninitialized,
    /// Mint account with additional extensions
    Mint,
    /// Token holding account with additional extensions
    Account,
}
impl Default for AccountType {
    fn default() -> Self {
        Self::Uninitialized
    }
}

/// Extensions that can be applied to mints or accounts.  Mint extensions must only be
/// applied to mint accounts, and account extensions must only be applied to token holding
/// accounts.
#[repr(u16)]
#[derive(Clone, Copy, Debug, PartialEq, TryFromPrimitive, IntoPrimitive)]
pub enum ExtensionType {
    /// Used as padding if the account size would otherwise be 355, same as a multisig
    Uninitialized,
    /// Includes transfer fee rate info and accompanying authorities to withdraw and set the fee
    TransferFeeConfig,
    /// Includes withheld transfer fees
    TransferFeeAmount,
    /// Includes an optional mint close authority
    MintCloseAuthority,
    /// Auditor configuration for confidential transfers
    ConfidentialTransferMint,
    /// State for confidential transfers
    ConfidentialTransferAccount,
    /// Specifies the default Account::state for new Accounts
    DefaultAccountState,
    /// Indicates that the Account owner authority cannot be changed
    ImmutableOwner,
    /// Require inbound transfers to have memo
    MemoTransfer,
    /// Padding extension used to make an account exactly Multisig::LEN, used for testing
    #[cfg(test)]
    AccountPaddingTest = u16::MAX - 1,
    /// Padding extension used to make a mint exactly Multisig::LEN, used for testing
    #[cfg(test)]
    MintPaddingTest = u16::MAX,
}
impl TryFrom<&[u8]> for ExtensionType {
    type Error = ProgramError;
    fn try_from(a: &[u8]) -> Result<Self, Self::Error> {
        Self::try_from(u16::from_le_bytes(
            a.try_into().map_err(|_| ProgramError::InvalidAccountData)?,
        ))
        .map_err(|_| ProgramError::InvalidAccountData)
    }
}
impl From<ExtensionType> for [u8; 2] {
    fn from(a: ExtensionType) -> Self {
        u16::from(a).to_le_bytes()
    }
}
impl ExtensionType {
    /// Get the data length of the type associated with the enum
    pub fn get_type_len(&self) -> usize {
        match self {
            ExtensionType::Uninitialized => 0,
            ExtensionType::TransferFeeConfig => pod_get_packed_len::<TransferFeeConfig>(),
            ExtensionType::TransferFeeAmount => pod_get_packed_len::<TransferFeeAmount>(),
            ExtensionType::MintCloseAuthority => pod_get_packed_len::<MintCloseAuthority>(),
            ExtensionType::ImmutableOwner => pod_get_packed_len::<ImmutableOwner>(),
            ExtensionType::ConfidentialTransferMint => {
                pod_get_packed_len::<ConfidentialTransferMint>()
            }
            ExtensionType::ConfidentialTransferAccount => {
                pod_get_packed_len::<ConfidentialTransferAccount>()
            }
            ExtensionType::DefaultAccountState => pod_get_packed_len::<DefaultAccountState>(),
            ExtensionType::MemoTransfer => pod_get_packed_len::<MemoTransfer>(),
            #[cfg(test)]
            ExtensionType::AccountPaddingTest => pod_get_packed_len::<AccountPaddingTest>(),
            #[cfg(test)]
            ExtensionType::MintPaddingTest => pod_get_packed_len::<MintPaddingTest>(),
        }
    }

    /// Get the TLV length for an ExtensionType
    fn get_tlv_len(&self) -> usize {
        self.get_type_len()
            .saturating_add(size_of::<ExtensionType>())
            .saturating_add(pod_get_packed_len::<Length>())
    }

    /// Get the TLV length for a set of ExtensionTypes
    fn get_total_tlv_len(extension_types: &[Self]) -> usize {
        // dedupe extensions
        let mut extensions = vec![];
        for extension_type in extension_types {
            if !extensions.contains(&extension_type) {
                extensions.push(extension_type);
            }
        }
        let tlv_len: usize = extensions.iter().map(|e| e.get_tlv_len()).sum();
        if tlv_len
            == Multisig::LEN
                .saturating_sub(BASE_ACCOUNT_LENGTH)
                .saturating_sub(size_of::<AccountType>())
        {
            tlv_len.saturating_add(size_of::<ExtensionType>())
        } else {
            tlv_len
        }
    }

    /// Get the required account data length for the given ExtensionTypes
    pub fn get_account_len<S: BaseState>(extension_types: &[Self]) -> usize {
        if extension_types.is_empty() {
            S::LEN
        } else {
            let extension_size = Self::get_total_tlv_len(extension_types);
            extension_size
                .saturating_add(BASE_ACCOUNT_LENGTH)
                .saturating_add(size_of::<AccountType>())
        }
    }

    /// Get the associated account type
    pub fn get_account_type(&self) -> AccountType {
        match self {
            ExtensionType::Uninitialized => AccountType::Uninitialized,
            ExtensionType::TransferFeeConfig
            | ExtensionType::MintCloseAuthority
            | ExtensionType::ConfidentialTransferMint
            | ExtensionType::DefaultAccountState => AccountType::Mint,
            ExtensionType::ImmutableOwner
            | ExtensionType::TransferFeeAmount
            | ExtensionType::ConfidentialTransferAccount
            | ExtensionType::MemoTransfer => AccountType::Account,
            #[cfg(test)]
            ExtensionType::AccountPaddingTest => AccountType::Account,
            #[cfg(test)]
            ExtensionType::MintPaddingTest => AccountType::Mint,
        }
    }

    /// Based on a set of AccountType::Mint ExtensionTypes, get the list of AccountType::Account
    /// ExtensionTypes required on InitializeAccount
    pub fn get_required_init_account_extensions(mint_extension_types: &[Self]) -> Vec<Self> {
        let mut account_extension_types = vec![];
        for extension_type in mint_extension_types {
            #[allow(clippy::single_match)]
            match extension_type {
                ExtensionType::TransferFeeConfig => {
                    account_extension_types.push(ExtensionType::TransferFeeAmount);
                }
                #[cfg(test)]
                ExtensionType::MintPaddingTest => {
                    account_extension_types.push(ExtensionType::AccountPaddingTest);
                }
                _ => {}
            }
        }
        account_extension_types
    }
}

/// Trait for base states, specifying the associated enum
pub trait BaseState: Pack + IsInitialized {
    /// Associated extension type enum, checked at the start of TLV entries
    const ACCOUNT_TYPE: AccountType;
}
impl BaseState for Account {
    const ACCOUNT_TYPE: AccountType = AccountType::Account;
}
impl BaseState for Mint {
    const ACCOUNT_TYPE: AccountType = AccountType::Mint;
}

/// Trait to be implemented by all extension states, specifying which extension
/// and account type they are associated with
pub trait Extension: Pod + Default {
    /// Associated extension type enum, checked at the start of TLV entries
    const TYPE: ExtensionType;
}

/// Padding a mint account to be exactly Multisig::LEN.
/// We need to pad 185 bytes, since Multisig::LEN = 355, Account::LEN = 165,
/// size_of AccountType = 1, size_of ExtensionType = 2, size_of Length = 2.
/// 355 - 165 - 1 - 2 - 2 = 185
#[cfg(test)]
#[repr(C)]
#[derive(Clone, Copy, Debug, PartialEq, Pod, Zeroable)]
pub struct MintPaddingTest {
    /// Largest value under 185 that implements Pod
    pub padding1: [u8; 128],
    /// Largest value under 57 that implements Pod
    pub padding2: [u8; 48],
    /// Exact value needed to finish the padding
    pub padding3: [u8; 9],
}
#[cfg(test)]
impl Extension for MintPaddingTest {
    const TYPE: ExtensionType = ExtensionType::MintPaddingTest;
}
#[cfg(test)]
impl Default for MintPaddingTest {
    fn default() -> Self {
        Self {
            padding1: [1; 128],
            padding2: [2; 48],
            padding3: [3; 9],
        }
    }
}
/// Account version of the MintPadding
#[cfg(test)]
#[repr(C)]
#[derive(Clone, Copy, Debug, Default, PartialEq, Pod, Zeroable)]
pub struct AccountPaddingTest(MintPaddingTest);
#[cfg(test)]
impl Extension for AccountPaddingTest {
    const TYPE: ExtensionType = ExtensionType::AccountPaddingTest;
}

#[cfg(test)]
mod test {
    use {
        super::*,
        crate::state::test::{TEST_ACCOUNT, TEST_ACCOUNT_SLICE, TEST_MINT, TEST_MINT_SLICE},
        solana_program::pubkey::Pubkey,
        transfer_fee::test::test_transfer_fee_config,
    };

    const MINT_WITH_EXTENSION: &[u8] = &[
        // base mint
        1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 42, 0, 0, 0, 0, 0, 0, 0, 7, 1, 1, 0, 0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // padding
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // account type
        1, // extension type
        3, 0, // length
        32, 0, // data
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1,
    ];

    #[test]
    fn unpack_opaque_buffer() {
        let state = StateWithExtensions::<Mint>::unpack(MINT_WITH_EXTENSION).unwrap();
        assert_eq!(state.base, TEST_MINT);
        let extension = state.get_extension::<MintCloseAuthority>().unwrap();
        let close_authority = OptionalNonZeroPubkey::try_from(Some(Pubkey::new(&[1; 32]))).unwrap();
        assert_eq!(extension.close_authority, close_authority);
        assert_eq!(
            state.get_extension::<TransferFeeConfig>(),
            Err(ProgramError::InvalidAccountData)
        );
        assert_eq!(
            StateWithExtensions::<Account>::unpack(MINT_WITH_EXTENSION),
            Err(ProgramError::InvalidAccountData)
        );

        let state = StateWithExtensions::<Mint>::unpack(TEST_MINT_SLICE).unwrap();
        assert_eq!(state.base, TEST_MINT);

        let mut test_mint = TEST_MINT_SLICE.to_vec();
        let state = StateWithExtensionsMut::<Mint>::unpack(&mut test_mint).unwrap();
        assert_eq!(state.base, TEST_MINT);
    }

    #[test]
    fn fail_unpack_opaque_buffer() {
        // input buffer too small
        let mut buffer = vec![0, 3];
        assert_eq!(
            StateWithExtensions::<Mint>::unpack(&buffer),
            Err(ProgramError::InvalidAccountData)
        );
        assert_eq!(
            StateWithExtensionsMut::<Mint>::unpack(&mut buffer),
            Err(ProgramError::InvalidAccountData)
        );
        assert_eq!(
            StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer),
            Err(ProgramError::InvalidAccountData)
        );

        // tweak the account type
        let mut buffer = MINT_WITH_EXTENSION.to_vec();
        buffer[BASE_ACCOUNT_LENGTH] = 3;
        assert_eq!(
            StateWithExtensions::<Mint>::unpack(&buffer),
            Err(ProgramError::InvalidAccountData)
        );

        // clear the mint initialized byte
        let mut buffer = MINT_WITH_EXTENSION.to_vec();
        buffer[45] = 0;
        assert_eq!(
            StateWithExtensions::<Mint>::unpack(&buffer),
            Err(ProgramError::UninitializedAccount)
        );

        // tweak the padding
        let mut buffer = MINT_WITH_EXTENSION.to_vec();
        buffer[Mint::LEN] = 100;
        assert_eq!(
            StateWithExtensions::<Mint>::unpack(&buffer),
            Err(ProgramError::InvalidAccountData)
        );

        // tweak the extension type
        let mut buffer = MINT_WITH_EXTENSION.to_vec();
        buffer[BASE_ACCOUNT_LENGTH + 1] = 2;
        let state = StateWithExtensions::<Mint>::unpack(&buffer).unwrap();
        assert_eq!(
            state.get_extension::<TransferFeeConfig>(),
            Err(ProgramError::Custom(
                TokenError::ExtensionTypeMismatch as u32
            ))
        );

        // tweak the length, too big
        let mut buffer = MINT_WITH_EXTENSION.to_vec();
        buffer[BASE_ACCOUNT_LENGTH + 3] = 100;
        let state = StateWithExtensions::<Mint>::unpack(&buffer).unwrap();
        assert_eq!(
            state.get_extension::<TransferFeeConfig>(),
            Err(ProgramError::InvalidAccountData)
        );

        // tweak the length, too small
        let mut buffer = MINT_WITH_EXTENSION.to_vec();
        buffer[BASE_ACCOUNT_LENGTH + 3] = 10;
        let state = StateWithExtensions::<Mint>::unpack(&buffer).unwrap();
        assert_eq!(
            state.get_extension::<TransferFeeConfig>(),
            Err(ProgramError::InvalidAccountData)
        );
    }

    #[test]
    fn mint_with_extension_pack_unpack() {
        let mint_size = ExtensionType::get_account_len::<Mint>(&[
            ExtensionType::MintCloseAuthority,
            ExtensionType::TransferFeeConfig,
        ]);
        let mut buffer = vec![0; mint_size];

        // fail unpack
        assert_eq!(
            StateWithExtensionsMut::<Mint>::unpack(&mut buffer),
            Err(ProgramError::UninitializedAccount),
        );

        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        // fail init account extension
        assert_eq!(
            state.init_extension::<TransferFeeAmount>(),
            Err(ProgramError::InvalidAccountData),
        );

        // success write extension
        let close_authority = OptionalNonZeroPubkey::try_from(Some(Pubkey::new(&[1; 32]))).unwrap();
        let extension = state.init_extension::<MintCloseAuthority>().unwrap();
        extension.close_authority = close_authority;
        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[ExtensionType::MintCloseAuthority]
        );

        // fail unpack as account, a mint extension was written
        assert_eq!(
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer),
            Err(ProgramError::Custom(
                TokenError::ExtensionBaseMismatch as u32
            ))
        );

        // fail unpack again, still no base data
        assert_eq!(
            StateWithExtensionsMut::<Mint>::unpack(&mut buffer.clone()),
            Err(ProgramError::UninitializedAccount),
        );

        // write base mint
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_MINT;
        state.pack_base();
        state.init_account_type().unwrap();

        // check raw buffer
        let mut expect = TEST_MINT_SLICE.to_vec();
        expect.extend_from_slice(&[0; BASE_ACCOUNT_LENGTH - Mint::LEN]); // padding
        expect.push(AccountType::Mint.into());
        expect.extend_from_slice(&(ExtensionType::MintCloseAuthority as u16).to_le_bytes());
        expect
            .extend_from_slice(&(pod_get_packed_len::<MintCloseAuthority>() as u16).to_le_bytes());
        expect.extend_from_slice(&[1; 32]); // data
        expect.extend_from_slice(&[0; size_of::<ExtensionType>()]);
        expect.extend_from_slice(&[0; size_of::<Length>()]);
        expect.extend_from_slice(&[0; size_of::<TransferFeeConfig>()]);
        assert_eq!(expect, buffer);

        // unpack uninitialized will now fail because the Mint is now initialized
        assert_eq!(
            StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer.clone()),
            Err(TokenError::AlreadyInUse.into()),
        );

        // check unpacking
        let mut state = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap();

        // update base
        state.base = TEST_MINT;
        state.base.supply += 100;
        state.pack_base();

        // check unpacking
        let mut unpacked_extension = state.get_extension_mut::<MintCloseAuthority>().unwrap();
        assert_eq!(*unpacked_extension, MintCloseAuthority { close_authority });

        // update extension
        let close_authority = OptionalNonZeroPubkey::try_from(None).unwrap();
        unpacked_extension.close_authority = close_authority;

        // check updates are propagated
        let base = state.base;
        let state = StateWithExtensions::<Mint>::unpack(&buffer).unwrap();
        assert_eq!(state.base, base);
        let unpacked_extension = state.get_extension::<MintCloseAuthority>().unwrap();
        assert_eq!(*unpacked_extension, MintCloseAuthority { close_authority });

        // check raw buffer
        let mut expect = vec![0; Mint::LEN];
        Mint::pack_into_slice(&base, &mut expect);
        expect.extend_from_slice(&[0; BASE_ACCOUNT_LENGTH - Mint::LEN]); // padding
        expect.push(AccountType::Mint.into());
        expect.extend_from_slice(&(ExtensionType::MintCloseAuthority as u16).to_le_bytes());
        expect
            .extend_from_slice(&(pod_get_packed_len::<MintCloseAuthority>() as u16).to_le_bytes());
        expect.extend_from_slice(&[0; 32]);
        expect.extend_from_slice(&[0; size_of::<ExtensionType>()]);
        expect.extend_from_slice(&[0; size_of::<Length>()]);
        expect.extend_from_slice(&[0; size_of::<TransferFeeConfig>()]);
        assert_eq!(expect, buffer);

        // fail unpack as an account
        assert_eq!(
            StateWithExtensions::<Account>::unpack(&buffer),
            Err(ProgramError::InvalidAccountData),
        );

        let mut state = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap();
        // init one more extension
        let mint_transfer_fee = test_transfer_fee_config();
        let new_extension = state.init_extension::<TransferFeeConfig>().unwrap();
        new_extension.transfer_fee_config_authority =
            mint_transfer_fee.transfer_fee_config_authority;
        new_extension.withdraw_withheld_authority = mint_transfer_fee.withdraw_withheld_authority;
        new_extension.withheld_amount = mint_transfer_fee.withheld_amount;
        new_extension.older_transfer_fee = mint_transfer_fee.older_transfer_fee;
        new_extension.newer_transfer_fee = mint_transfer_fee.newer_transfer_fee;

        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[
                ExtensionType::MintCloseAuthority,
                ExtensionType::TransferFeeConfig
            ]
        );

        // check raw buffer
        let mut expect = vec![0; Mint::LEN];
        Mint::pack_into_slice(&base, &mut expect);
        expect.extend_from_slice(&[0; BASE_ACCOUNT_LENGTH - Mint::LEN]); // padding
        expect.push(AccountType::Mint.into());
        expect.extend_from_slice(&(ExtensionType::MintCloseAuthority as u16).to_le_bytes());
        expect
            .extend_from_slice(&(pod_get_packed_len::<MintCloseAuthority>() as u16).to_le_bytes());
        expect.extend_from_slice(&[0; 32]); // data
        expect.extend_from_slice(&(ExtensionType::TransferFeeConfig as u16).to_le_bytes());
        expect.extend_from_slice(&(pod_get_packed_len::<TransferFeeConfig>() as u16).to_le_bytes());
        expect.extend_from_slice(pod_bytes_of(&mint_transfer_fee));
        assert_eq!(expect, buffer);

        // fail to init one more extension that does not fit
        let mut state = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap();
        assert_eq!(
            state.init_extension::<MintPaddingTest>(),
            Err(ProgramError::InvalidAccountData),
        );
    }

    #[test]
    fn mint_extension_any_order() {
        let mint_size = ExtensionType::get_account_len::<Mint>(&[
            ExtensionType::MintCloseAuthority,
            ExtensionType::TransferFeeConfig,
        ]);
        let mut buffer = vec![0; mint_size];

        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        // write extensions
        let close_authority = OptionalNonZeroPubkey::try_from(Some(Pubkey::new(&[1; 32]))).unwrap();
        let extension = state.init_extension::<MintCloseAuthority>().unwrap();
        extension.close_authority = close_authority;

        let mint_transfer_fee = test_transfer_fee_config();
        let extension = state.init_extension::<TransferFeeConfig>().unwrap();
        extension.transfer_fee_config_authority = mint_transfer_fee.transfer_fee_config_authority;
        extension.withdraw_withheld_authority = mint_transfer_fee.withdraw_withheld_authority;
        extension.withheld_amount = mint_transfer_fee.withheld_amount;
        extension.older_transfer_fee = mint_transfer_fee.older_transfer_fee;
        extension.newer_transfer_fee = mint_transfer_fee.newer_transfer_fee;

        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[
                ExtensionType::MintCloseAuthority,
                ExtensionType::TransferFeeConfig
            ]
        );

        // write base mint
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_MINT;
        state.pack_base();
        state.init_account_type().unwrap();

        let mut other_buffer = vec![0; mint_size];
        let mut state =
            StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut other_buffer).unwrap();

        // write base mint
        state.base = TEST_MINT;
        state.pack_base();
        state.init_account_type().unwrap();

        // write extensions in a different order
        let mint_transfer_fee = test_transfer_fee_config();
        let extension = state.init_extension::<TransferFeeConfig>().unwrap();
        extension.transfer_fee_config_authority = mint_transfer_fee.transfer_fee_config_authority;
        extension.withdraw_withheld_authority = mint_transfer_fee.withdraw_withheld_authority;
        extension.withheld_amount = mint_transfer_fee.withheld_amount;
        extension.older_transfer_fee = mint_transfer_fee.older_transfer_fee;
        extension.newer_transfer_fee = mint_transfer_fee.newer_transfer_fee;

        let close_authority = OptionalNonZeroPubkey::try_from(Some(Pubkey::new(&[1; 32]))).unwrap();
        let extension = state.init_extension::<MintCloseAuthority>().unwrap();
        extension.close_authority = close_authority;

        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[
                ExtensionType::TransferFeeConfig,
                ExtensionType::MintCloseAuthority
            ]
        );

        // buffers are NOT the same because written in a different order
        assert_ne!(buffer, other_buffer);
        let state = StateWithExtensions::<Mint>::unpack(&buffer).unwrap();
        let other_state = StateWithExtensions::<Mint>::unpack(&other_buffer).unwrap();

        // BUT mint and extensions are the same
        assert_eq!(
            state.get_extension::<TransferFeeConfig>().unwrap(),
            other_state.get_extension::<TransferFeeConfig>().unwrap()
        );
        assert_eq!(
            state.get_extension::<MintCloseAuthority>().unwrap(),
            other_state.get_extension::<MintCloseAuthority>().unwrap()
        );
        assert_eq!(state.base, other_state.base);
    }

    #[test]
    fn mint_with_multisig_len() {
        let mut buffer = vec![0; Multisig::LEN];
        assert_eq!(
            StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer),
            Err(ProgramError::InvalidAccountData),
        );
        let mint_size = ExtensionType::get_account_len::<Mint>(&[ExtensionType::MintPaddingTest]);
        assert_eq!(mint_size, Multisig::LEN + size_of::<ExtensionType>());
        let mut buffer = vec![0; mint_size];

        // write base mint
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_MINT;
        state.pack_base();
        state.init_account_type().unwrap();

        // write padding
        let extension = state.init_extension::<MintPaddingTest>().unwrap();
        extension.padding1 = [1; 128];
        extension.padding2 = [1; 48];
        extension.padding3 = [1; 9];

        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[ExtensionType::MintPaddingTest]
        );

        // check raw buffer
        let mut expect = TEST_MINT_SLICE.to_vec();
        expect.extend_from_slice(&[0; BASE_ACCOUNT_LENGTH - Mint::LEN]); // padding
        expect.push(AccountType::Mint.into());
        expect.extend_from_slice(&(ExtensionType::MintPaddingTest as u16).to_le_bytes());
        expect.extend_from_slice(&(pod_get_packed_len::<MintPaddingTest>() as u16).to_le_bytes());
        expect.extend_from_slice(&vec![1; pod_get_packed_len::<MintPaddingTest>()]);
        expect.extend_from_slice(&(ExtensionType::Uninitialized as u16).to_le_bytes());
        assert_eq!(expect, buffer);
    }

    #[test]
    fn account_with_extension_pack_unpack() {
        let account_size =
            ExtensionType::get_account_len::<Account>(&[ExtensionType::TransferFeeAmount]);
        let mut buffer = vec![0; account_size];

        // fail unpack
        assert_eq!(
            StateWithExtensionsMut::<Account>::unpack(&mut buffer),
            Err(ProgramError::UninitializedAccount),
        );

        let mut state =
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer).unwrap();
        // fail init mint extension
        assert_eq!(
            state.init_extension::<TransferFeeConfig>(),
            Err(ProgramError::InvalidAccountData),
        );
        // success write extension
        let withheld_amount = PodU64::from(u64::MAX);
        let extension = state.init_extension::<TransferFeeAmount>().unwrap();
        extension.withheld_amount = withheld_amount;

        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[ExtensionType::TransferFeeAmount]
        );

        // fail unpack again, still no base data
        assert_eq!(
            StateWithExtensionsMut::<Account>::unpack(&mut buffer.clone()),
            Err(ProgramError::UninitializedAccount),
        );

        // write base account
        let mut state =
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_ACCOUNT;
        state.pack_base();
        state.init_account_type().unwrap();
        let base = state.base;

        // check raw buffer
        let mut expect = TEST_ACCOUNT_SLICE.to_vec();
        expect.push(AccountType::Account.into());
        expect.extend_from_slice(&(ExtensionType::TransferFeeAmount as u16).to_le_bytes());
        expect.extend_from_slice(&(pod_get_packed_len::<TransferFeeAmount>() as u16).to_le_bytes());
        expect.extend_from_slice(&u64::from(withheld_amount).to_le_bytes());
        assert_eq!(expect, buffer);

        // check unpacking
        let mut state = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, base);
        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[ExtensionType::TransferFeeAmount]
        );

        // update base
        state.base = TEST_ACCOUNT;
        state.base.amount += 100;
        state.pack_base();

        // check unpacking
        let mut unpacked_extension = state.get_extension_mut::<TransferFeeAmount>().unwrap();
        assert_eq!(*unpacked_extension, TransferFeeAmount { withheld_amount });

        // update extension
        let withheld_amount = PodU64::from(u32::MAX as u64);
        unpacked_extension.withheld_amount = withheld_amount;

        // check updates are propagated
        let base = state.base;
        let state = StateWithExtensions::<Account>::unpack(&buffer).unwrap();
        assert_eq!(state.base, base);
        let unpacked_extension = state.get_extension::<TransferFeeAmount>().unwrap();
        assert_eq!(*unpacked_extension, TransferFeeAmount { withheld_amount });

        // check raw buffer
        let mut expect = vec![0; Account::LEN];
        Account::pack_into_slice(&base, &mut expect);
        expect.push(AccountType::Account.into());
        expect.extend_from_slice(&(ExtensionType::TransferFeeAmount as u16).to_le_bytes());
        expect.extend_from_slice(&(pod_get_packed_len::<TransferFeeAmount>() as u16).to_le_bytes());
        expect.extend_from_slice(&u64::from(withheld_amount).to_le_bytes());
        assert_eq!(expect, buffer);

        // fail unpack as a mint
        assert_eq!(
            StateWithExtensions::<Mint>::unpack(&buffer),
            Err(ProgramError::InvalidAccountData),
        );
    }

    #[test]
    fn account_with_multisig_len() {
        let mut buffer = vec![0; Multisig::LEN];
        assert_eq!(
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer),
            Err(ProgramError::InvalidAccountData),
        );
        let account_size =
            ExtensionType::get_account_len::<Account>(&[ExtensionType::AccountPaddingTest]);
        assert_eq!(account_size, Multisig::LEN + size_of::<ExtensionType>());
        let mut buffer = vec![0; account_size];

        // write base account
        let mut state =
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_ACCOUNT;
        state.pack_base();
        state.init_account_type().unwrap();

        // write padding
        let extension = state.init_extension::<AccountPaddingTest>().unwrap();
        extension.0.padding1 = [2; 128];
        extension.0.padding2 = [2; 48];
        extension.0.padding3 = [2; 9];

        assert_eq!(
            &state.get_extension_types().unwrap(),
            &[ExtensionType::AccountPaddingTest]
        );

        // check raw buffer
        let mut expect = TEST_ACCOUNT_SLICE.to_vec();
        expect.push(AccountType::Account.into());
        expect.extend_from_slice(&(ExtensionType::AccountPaddingTest as u16).to_le_bytes());
        expect
            .extend_from_slice(&(pod_get_packed_len::<AccountPaddingTest>() as u16).to_le_bytes());
        expect.extend_from_slice(&vec![2; pod_get_packed_len::<AccountPaddingTest>()]);
        expect.extend_from_slice(&(ExtensionType::Uninitialized as u16).to_le_bytes());
        assert_eq!(expect, buffer);
    }

    #[test]
    fn test_set_account_type() {
        // account with buffer big enough for AccountType and Extension
        let mut buffer = TEST_ACCOUNT_SLICE.to_vec();
        let needed_len =
            ExtensionType::get_account_len::<Account>(&[ExtensionType::ImmutableOwner])
                - buffer.len();
        buffer.append(&mut vec![0; needed_len]);
        let err = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
        set_account_type::<Account>(&mut buffer).unwrap();
        // unpack is viable after manual set_account_type
        let mut state = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, TEST_ACCOUNT);
        assert_eq!(state.account_type[0], AccountType::Account as u8);
        state.init_extension::<ImmutableOwner>().unwrap(); // just confirming initialization works

        // account with buffer big enough for AccountType only
        let mut buffer = TEST_ACCOUNT_SLICE.to_vec();
        buffer.append(&mut vec![0; 2]);
        let err = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
        set_account_type::<Account>(&mut buffer).unwrap();
        // unpack is viable after manual set_account_type
        let state = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, TEST_ACCOUNT);
        assert_eq!(state.account_type[0], AccountType::Account as u8);

        // account with AccountType already set => noop
        let mut buffer = TEST_ACCOUNT_SLICE.to_vec();
        buffer.append(&mut vec![2, 0]);
        let _ = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap();
        set_account_type::<Account>(&mut buffer).unwrap();
        let state = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, TEST_ACCOUNT);
        assert_eq!(state.account_type[0], AccountType::Account as u8);

        // account with wrong AccountType fails
        let mut buffer = TEST_ACCOUNT_SLICE.to_vec();
        buffer.append(&mut vec![1, 0]);
        let err = StateWithExtensionsMut::<Account>::unpack(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
        let err = set_account_type::<Account>(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);

        // mint with buffer big enough for AccountType and Extension
        let mut buffer = TEST_MINT_SLICE.to_vec();
        let needed_len =
            ExtensionType::get_account_len::<Mint>(&[ExtensionType::MintCloseAuthority])
                - buffer.len();
        buffer.append(&mut vec![0; needed_len]);
        let err = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
        set_account_type::<Mint>(&mut buffer).unwrap();
        // unpack is viable after manual set_account_type
        let mut state = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, TEST_MINT);
        assert_eq!(state.account_type[0], AccountType::Mint as u8);
        state.init_extension::<MintCloseAuthority>().unwrap();

        // mint with buffer big enough for AccountType only
        let mut buffer = TEST_MINT_SLICE.to_vec();
        buffer.append(&mut vec![0; Account::LEN - Mint::LEN]);
        buffer.append(&mut vec![0; 2]);
        let err = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
        set_account_type::<Mint>(&mut buffer).unwrap();
        // unpack is viable after manual set_account_type
        let state = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, TEST_MINT);
        assert_eq!(state.account_type[0], AccountType::Mint as u8);

        // mint with AccountType already set => noop
        let mut buffer = TEST_MINT_SLICE.to_vec();
        buffer.append(&mut vec![0; Account::LEN - Mint::LEN]);
        buffer.append(&mut vec![1, 0]);
        set_account_type::<Mint>(&mut buffer).unwrap();
        let state = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap();
        assert_eq!(state.base, TEST_MINT);
        assert_eq!(state.account_type[0], AccountType::Mint as u8);

        // mint with wrong AccountType fails
        let mut buffer = TEST_MINT_SLICE.to_vec();
        buffer.append(&mut vec![0; Account::LEN - Mint::LEN]);
        buffer.append(&mut vec![2, 0]);
        let err = StateWithExtensionsMut::<Mint>::unpack(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
        let err = set_account_type::<Mint>(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
    }

    #[test]
    fn test_set_account_type_wrongly() {
        // try to set Account account_type to Mint
        let mut buffer = TEST_ACCOUNT_SLICE.to_vec();
        buffer.append(&mut vec![0; 2]);
        let err = set_account_type::<Mint>(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);

        // try to set Mint account_type to Account
        let mut buffer = TEST_MINT_SLICE.to_vec();
        buffer.append(&mut vec![0; Account::LEN - Mint::LEN]);
        buffer.append(&mut vec![0; 2]);
        let err = set_account_type::<Account>(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);
    }

    #[test]
    fn test_get_required_init_account_extensions() {
        // Some mint extensions with no required account extensions
        let mint_extensions = vec![
            ExtensionType::MintCloseAuthority,
            ExtensionType::Uninitialized,
        ];
        assert_eq!(
            ExtensionType::get_required_init_account_extensions(&mint_extensions),
            vec![]
        );

        // One mint extension with required account extension, one without
        let mint_extensions = vec![
            ExtensionType::TransferFeeConfig,
            ExtensionType::MintCloseAuthority,
        ];
        assert_eq!(
            ExtensionType::get_required_init_account_extensions(&mint_extensions),
            vec![ExtensionType::TransferFeeAmount]
        );

        // Some mint extensions both with required account extensions
        let mint_extensions = vec![
            ExtensionType::TransferFeeConfig,
            ExtensionType::MintPaddingTest,
        ];
        assert_eq!(
            ExtensionType::get_required_init_account_extensions(&mint_extensions),
            vec![
                ExtensionType::TransferFeeAmount,
                ExtensionType::AccountPaddingTest
            ]
        );

        // Demonstrate that method does not dedupe inputs or outputs
        let mint_extensions = vec![
            ExtensionType::TransferFeeConfig,
            ExtensionType::TransferFeeConfig,
        ];
        assert_eq!(
            ExtensionType::get_required_init_account_extensions(&mint_extensions),
            vec![
                ExtensionType::TransferFeeAmount,
                ExtensionType::TransferFeeAmount
            ]
        );
    }

    #[test]
    fn mint_without_extensions() {
        let space = ExtensionType::get_account_len::<Mint>(&[]);
        let mut buffer = vec![0; space];
        assert_eq!(
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer),
            Err(ProgramError::InvalidAccountData),
        );

        // write base account
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_MINT;
        state.pack_base();
        state.init_account_type().unwrap();

        // fail init extension
        assert_eq!(
            state.init_extension::<TransferFeeConfig>(),
            Err(ProgramError::InvalidAccountData),
        );

        assert_eq!(TEST_MINT_SLICE, buffer);
    }

    #[test]
    fn test_init_nonzero_default() {
        let mint_size = ExtensionType::get_account_len::<Mint>(&[ExtensionType::MintPaddingTest]);
        let mut buffer = vec![0; mint_size];
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_MINT;
        state.pack_base();
        state.init_account_type().unwrap();
        let extension = state.init_extension::<MintPaddingTest>().unwrap();
        assert_eq!(extension.padding1, [1; 128]);
        assert_eq!(extension.padding2, [2; 48]);
        assert_eq!(extension.padding3, [3; 9]);
    }

    #[test]
    fn test_init_buffer_too_small() {
        let mint_size =
            ExtensionType::get_account_len::<Mint>(&[ExtensionType::MintCloseAuthority]);
        let mut buffer = vec![0; mint_size - 1];
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        let err = state.init_extension::<MintCloseAuthority>().unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);

        state.tlv_data[0] = 3;
        state.tlv_data[2] = 32;
        let err = state.get_extension_mut::<MintCloseAuthority>().unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);

        let mut buffer = vec![0; Mint::LEN + 2];
        let err = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);

        let mut buffer = vec![0; BASE_ACCOUNT_LENGTH + 2];
        let mut state = StateWithExtensionsMut::<Mint>::unpack_uninitialized(&mut buffer).unwrap();
        let err = state.get_extension_mut::<MintCloseAuthority>().unwrap_err();
        assert_eq!(err, ProgramError::InvalidAccountData);

        assert_eq!(state.get_extension_types().unwrap(), vec![]);
    }

    #[test]
    fn test_extension_with_no_data() {
        let account_size =
            ExtensionType::get_account_len::<Account>(&[ExtensionType::ImmutableOwner]);
        let mut buffer = vec![0; account_size];
        let mut state =
            StateWithExtensionsMut::<Account>::unpack_uninitialized(&mut buffer).unwrap();
        state.base = TEST_ACCOUNT;
        state.pack_base();
        state.init_account_type().unwrap();
        state.init_extension::<ImmutableOwner>().unwrap();

        assert_eq!(
            get_first_extension_type(state.tlv_data).unwrap(),
            Some(ExtensionType::ImmutableOwner)
        );
        assert_eq!(
            get_extension_types(state.tlv_data).unwrap(),
            vec![ExtensionType::ImmutableOwner]
        );
    }
}