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use std::io;

use nom::{be_u8, rest_len};
use num_traits::FromPrimitive;
use zeroize::Zeroize;

use crate::crypto::public_key::PublicKeyAlgorithm;
use crate::crypto::sym::SymmetricKeyAlgorithm;
use crate::errors::Result;
use crate::ser::Serialize;
use crate::types::*;

/// A list of params that are used to represent the values of possibly encrypted key,
/// from imports and exports.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum SecretParams {
    Plain(PlainSecretParams),
    Encrypted(EncryptedSecretParams),
}

impl Zeroize for SecretParams {
    fn zeroize(&mut self) {
        match self {
            SecretParams::Plain(p) => p.zeroize(),
            SecretParams::Encrypted(_) => { /* encrypted params do not need zeroing */ }
        }
    }
}

impl SecretParams {
    pub fn is_encrypted(&self) -> bool {
        match self {
            SecretParams::Plain(_) => false,
            SecretParams::Encrypted(_) => true,
        }
    }

    pub fn from_slice(data: &[u8], alg: PublicKeyAlgorithm) -> Result<Self> {
        let (_, (params, cs)) = parse_secret_fields(data, alg)?;

        params.compare_checksum(cs)?;

        Ok(params)
    }

    pub fn string_to_key_id(&self) -> u8 {
        match self {
            SecretParams::Plain(k) => k.string_to_key_id(),
            SecretParams::Encrypted(k) => k.string_to_key_id(),
        }
    }

    pub fn compare_checksum(&self, other: Option<&[u8]>) -> Result<()> {
        match self {
            SecretParams::Plain(k) => k.as_ref().compare_checksum_simple(other),
            SecretParams::Encrypted(k) => k.compare_checksum(other),
        }
    }

    pub fn checksum(&self) -> Option<Vec<u8>> {
        match self {
            SecretParams::Plain(k) => Some(k.checksum_simple()),
            SecretParams::Encrypted(k) => k.checksum(),
        }
    }
}

impl Serialize for SecretParams {
    fn to_writer<W: io::Write>(&self, writer: &mut W) -> Result<()> {
        match self {
            SecretParams::Plain(k) => k.to_writer(writer),
            SecretParams::Encrypted(k) => k.to_writer(writer),
        }
    }
}

// Parse possibly encrypted private fields of a key.
#[rustfmt::skip]
named_args!(parse_secret_fields(alg: PublicKeyAlgorithm) <(SecretParams, Option<&[u8]>)>, do_parse!(
          s2k_typ: be_u8
    >> enc_params: switch!(value!(s2k_typ),
                   // 0 is no encryption
                   0       => value!((None, None, None)) |
                   // symmetric key algorithm
                   1..=253 => do_parse!(
                          sym_alg: map_opt!(
                                    value!(s2k_typ),
                                    SymmetricKeyAlgorithm::from_u8
                                )
                       >>      iv: take!(sym_alg.block_size())
                       >> (Some(sym_alg), Some(iv), None)
                   ) |
                   // symmetric key + string-to-key
                   254..=255 => do_parse!(
                             sym_alg: map_opt!(
                                        be_u8,
                                        SymmetricKeyAlgorithm::from_u8
                                      )
                       >>        s2k: s2k_parser
                       >>         iv: take!(sym_alg.block_size())
                       >> (Some(sym_alg), Some(iv), Some(s2k))
                   )
    )
    >> checksum_len: switch!(value!(s2k_typ),
        // 20 octect hash at the end, but part of the encrypted part
        254 => value!(0) |
        // 2 octet checksum at the end
        _   => value!(2)
    )
    >> data_len: map!(rest_len, |r| r - checksum_len)
    >>     data: take!(data_len)
    >> checksum: cond!(checksum_len > 0, take!(checksum_len))
    >> ({
        let encryption_algorithm = enc_params.0;
        let iv = enc_params.1.map(|iv| iv.to_vec());
        let string_to_key = enc_params.2;

        let res = match s2k_typ {
            0 => {
                let repr = PlainSecretParams::from_slice(data, alg)?;
                SecretParams::Plain(repr)
            }
            _ => {
                SecretParams::Encrypted(EncryptedSecretParams::new(
                    data.to_vec(),
                    iv.expect("encrypted"),
                    encryption_algorithm.expect("encrypted"),
                    string_to_key.expect("encrypted"),
                    s2k_typ,
                ))
            }
        };
        (res, checksum)
    })
));