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use cipher::{
    crypto_common::{InnerInit, InnerUser},
    generic_array::ArrayLength,
    inout::InOut,
    AlgorithmName, Block, BlockBackend, BlockCipher, BlockClosure, BlockDecryptMut, BlockSizeUser,
    ParBlocks, ParBlocksSizeUser,
};
use core::fmt;

#[cfg(feature = "zeroize")]
use cipher::zeroize::{Zeroize, ZeroizeOnDrop};

/// ECB mode decryptor.
#[derive(Clone)]
pub struct Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher,
{
    cipher: C,
}

impl<C> BlockSizeUser for Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher,
{
    type BlockSize = C::BlockSize;
}

impl<C> BlockDecryptMut for Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher,
{
    fn decrypt_with_backend_mut(&mut self, f: impl BlockClosure<BlockSize = Self::BlockSize>) {
        let Self { cipher } = self;
        cipher.decrypt_with_backend_mut(Closure { f })
    }
}

impl<C> InnerUser for Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher,
{
    type Inner = C;
}

impl<C> InnerInit for Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher,
{
    #[inline]
    fn inner_init(cipher: C) -> Self {
        Self { cipher }
    }
}

impl<C> AlgorithmName for Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher + AlgorithmName,
{
    fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("ecb::Decryptor<")?;
        <C as AlgorithmName>::write_alg_name(f)?;
        f.write_str(">")
    }
}

impl<C> fmt::Debug for Decryptor<C>
where
    C: BlockDecryptMut + BlockCipher + AlgorithmName,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("ecb::Decryptor<")?;
        <C as AlgorithmName>::write_alg_name(f)?;
        f.write_str("> { ... }")
    }
}

#[cfg(feature = "zeroize")]
#[cfg_attr(docsrs, doc(cfg(feature = "zeroize")))]
impl<C: BlockDecryptMut + BlockCipher> Drop for Decryptor<C> {
    fn drop(&mut self) {
        self.iv.zeroize();
    }
}

#[cfg(feature = "zeroize")]
#[cfg_attr(docsrs, doc(cfg(feature = "zeroize")))]
impl<C: BlockDecryptMut + BlockCipher + ZeroizeOnDrop> ZeroizeOnDrop for Decryptor<C> {}

struct Closure<BS, BC>
where
    BS: ArrayLength<u8>,
    BC: BlockClosure<BlockSize = BS>,
{
    f: BC,
}

impl<BS, BC> BlockSizeUser for Closure<BS, BC>
where
    BS: ArrayLength<u8>,
    BC: BlockClosure<BlockSize = BS>,
{
    type BlockSize = BS;
}

impl<BS, BC> BlockClosure for Closure<BS, BC>
where
    BS: ArrayLength<u8>,
    BC: BlockClosure<BlockSize = BS>,
{
    #[inline(always)]
    fn call<B: BlockBackend<BlockSize = Self::BlockSize>>(self, backend: &mut B) {
        let Self { f } = self;
        f.call(&mut Backend { backend });
    }
}

struct Backend<'a, BS, BK>
where
    BS: ArrayLength<u8>,
    BK: BlockBackend<BlockSize = BS>,
{
    backend: &'a mut BK,
}

impl<'a, BS, BK> BlockSizeUser for Backend<'a, BS, BK>
where
    BS: ArrayLength<u8>,
    BK: BlockBackend<BlockSize = BS>,
{
    type BlockSize = BS;
}

impl<'a, BS, BK> ParBlocksSizeUser for Backend<'a, BS, BK>
where
    BS: ArrayLength<u8>,
    BK: BlockBackend<BlockSize = BS>,
{
    type ParBlocksSize = BK::ParBlocksSize;
}

impl<'a, BS, BK> BlockBackend for Backend<'a, BS, BK>
where
    BS: ArrayLength<u8>,
    BK: BlockBackend<BlockSize = BS>,
{
    #[inline(always)]
    fn proc_block(&mut self, block: InOut<'_, '_, Block<Self>>) {
        self.backend.proc_block(block);
    }

    #[inline(always)]
    fn proc_par_blocks(&mut self, blocks: InOut<'_, '_, ParBlocks<Self>>) {
        self.backend.proc_par_blocks(blocks);
    }
}