use base64;
use byteorder::{BigEndian, ByteOrder};
use aes::Aes192;
use hmac::Hmac;
use sha1::{Sha1, Digest};
use pbkdf2::pbkdf2;
use protobuf::ProtobufEnum;
use serde;
use serde_json;
use std::fs::File;
use std::io::{self, Read, Write};
use std::ops::FnOnce;
use std::path::Path;

use protocol::authentication::AuthenticationType;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Credentials {
    pub username: String,

    #[serde(serialize_with = "serialize_protobuf_enum")]
    #[serde(deserialize_with = "deserialize_protobuf_enum")]
    pub auth_type: AuthenticationType,

    #[serde(serialize_with = "serialize_base64")]
    #[serde(deserialize_with = "deserialize_base64")]
    pub auth_data: Vec<u8>,
}

impl Credentials {
    pub fn with_password(username: String, password: String) -> Credentials {
        Credentials {
            username: username,
            auth_type: AuthenticationType::AUTHENTICATION_USER_PASS,
            auth_data: password.into_bytes(),
        }
    }

    pub fn with_blob(username: String, encrypted_blob: &str, device_id: &str) -> Credentials {
        fn read_u8<R: Read>(stream: &mut R) -> io::Result<u8> {
            let mut data = [0u8];
            try!(stream.read_exact(&mut data));
            Ok(data[0])
        }

        fn read_int<R: Read>(stream: &mut R) -> io::Result<u32> {
            let lo = try!(read_u8(stream)) as u32;
            if lo & 0x80 == 0 {
                return Ok(lo);
            }

            let hi = try!(read_u8(stream)) as u32;
            Ok(lo & 0x7f | hi << 7)
        }

        fn read_bytes<R: Read>(stream: &mut R) -> io::Result<Vec<u8>> {
            let length = try!(read_int(stream));
            let mut data = vec![0u8; length as usize];
            try!(stream.read_exact(&mut data));

            Ok(data)
        }

        let secret = Sha1::digest(device_id.as_bytes());

        let key = {
            let mut key = [0u8; 24];
            pbkdf2::<Hmac<Sha1>>(&secret, username.as_bytes(), 0x100, &mut key[0..20]);

            let hash = &Sha1::digest(&key[..20]);
            key[..20].copy_from_slice(hash);
            BigEndian::write_u32(&mut key[20..], 20);
            key
        };

        // decrypt data using ECB mode without padding
        let blob = {
            use aes::block_cipher_trait::BlockCipher;
            use aes::block_cipher_trait::generic_array::GenericArray;
            use aes::block_cipher_trait::generic_array::typenum::Unsigned;

            let mut data = base64::decode(encrypted_blob).unwrap();
            let cipher = Aes192::new(GenericArray::from_slice(&key));
            let block_size = <Aes192 as BlockCipher>::BlockSize::to_usize();
            assert_eq!(data.len() % block_size, 0);
            // replace to chunks_exact_mut with MSRV bump to 1.31
            for chunk in data.chunks_mut(block_size) {
                cipher.decrypt_block(GenericArray::from_mut_slice(chunk));
            }

            let l = data.len();
            for i in 0..l - 0x10 {
                data[l - i - 1] ^= data[l - i - 0x11];
            }

            data
        };

        let mut cursor = io::Cursor::new(&blob);
        read_u8(&mut cursor).unwrap();
        read_bytes(&mut cursor).unwrap();
        read_u8(&mut cursor).unwrap();
        let auth_type = read_int(&mut cursor).unwrap();
        let auth_type = AuthenticationType::from_i32(auth_type as i32).unwrap();
        read_u8(&mut cursor).unwrap();
        let auth_data = read_bytes(&mut cursor).unwrap();

        Credentials {
            username: username,
            auth_type: auth_type,
            auth_data: auth_data,
        }
    }

    fn from_reader<R: Read>(mut reader: R) -> Credentials {
        let mut contents = String::new();
        reader.read_to_string(&mut contents).unwrap();

        serde_json::from_str(&contents).unwrap()
    }

    pub(crate) fn from_file<P: AsRef<Path>>(path: P) -> Option<Credentials> {
        File::open(path).ok().map(Credentials::from_reader)
    }

    fn save_to_writer<W: Write>(&self, writer: &mut W) {
        let contents = serde_json::to_string(&self.clone()).unwrap();
        writer.write_all(contents.as_bytes()).unwrap();
    }

    pub(crate) fn save_to_file<P: AsRef<Path>>(&self, path: P) {
        let mut file = File::create(path).unwrap();
        self.save_to_writer(&mut file)
    }
}

fn serialize_protobuf_enum<T, S>(v: &T, ser: S) -> Result<S::Ok, S::Error>
where
    T: ProtobufEnum,
    S: serde::Serializer,
{
    serde::Serialize::serialize(&v.value(), ser)
}

fn deserialize_protobuf_enum<'de, T, D>(de: D) -> Result<T, D::Error>
where
    T: ProtobufEnum,
    D: serde::Deserializer<'de>,
{
    let v: i32 = try!(serde::Deserialize::deserialize(de));
    T::from_i32(v).ok_or_else(|| serde::de::Error::custom("Invalid enum value"))
}

fn serialize_base64<T, S>(v: &T, ser: S) -> Result<S::Ok, S::Error>
where
    T: AsRef<[u8]>,
    S: serde::Serializer,
{
    serde::Serialize::serialize(&base64::encode(v.as_ref()), ser)
}

fn deserialize_base64<'de, D>(de: D) -> Result<Vec<u8>, D::Error>
where
    D: serde::Deserializer<'de>,
{
    let v: String = try!(serde::Deserialize::deserialize(de));
    base64::decode(&v).map_err(|e| serde::de::Error::custom(e.to_string()))
}

pub fn get_credentials<F: FnOnce(&String) -> String>(
    username: Option<String>,
    password: Option<String>,
    cached_credentials: Option<Credentials>,
    prompt: F,
) -> Option<Credentials> {
    match (username, password, cached_credentials) {
        (Some(username), Some(password), _) => Some(Credentials::with_password(username, password)),

        (Some(ref username), _, Some(ref credentials)) if *username == credentials.username => {
            Some(credentials.clone())
        }

        (Some(username), None, _) => {
            Some(Credentials::with_password(username.clone(), prompt(&username)))
        }

        (None, _, Some(credentials)) => Some(credentials),

        (None, _, None) => None,
    }
}