#![cfg(feature = "full")]

use {
    crate::{
        derivation_path::DerivationPath,
        pubkey::Pubkey,
        signature::Signature,
        signer::{Signer, SignerError},
    },
    ed25519_dalek::Signer as DalekSigner,
    ed25519_dalek_bip32::Error as Bip32Error,
    hmac::Hmac,
    rand::{rngs::OsRng, CryptoRng, RngCore},
    std::{
        error,
        fs::{self, File, OpenOptions},
        io::{Read, Write},
        path::Path,
    },
};

/// A vanilla Ed25519 key pair
#[derive(Debug)]
pub struct Keypair(ed25519_dalek::Keypair);

impl Keypair {
    /// Constructs a new, random `Keypair` using a caller-proveded RNG
    pub fn generate<R>(csprng: &mut R) -> Self
    where
        R: CryptoRng + RngCore,
    {
        Self(ed25519_dalek::Keypair::generate(csprng))
    }

    /// Constructs a new, random `Keypair` using `OsRng`
    pub fn new() -> Self {
        let mut rng = OsRng::default();
        Self::generate(&mut rng)
    }

    /// Recovers a `Keypair` from a byte array
    pub fn from_bytes(bytes: &[u8]) -> Result<Self, ed25519_dalek::SignatureError> {
        ed25519_dalek::Keypair::from_bytes(bytes).map(Self)
    }

    /// Returns this `Keypair` as a byte array
    pub fn to_bytes(&self) -> [u8; 64] {
        self.0.to_bytes()
    }

    /// Recovers a `Keypair` from a base58-encoded string
    pub fn from_base58_string(s: &str) -> Self {
        Self::from_bytes(&bs58::decode(s).into_vec().unwrap()).unwrap()
    }

    /// Returns this `Keypair` as a base58-encoded string
    pub fn to_base58_string(&self) -> String {
        bs58::encode(&self.0.to_bytes()).into_string()
    }

    /// Gets this `Keypair`'s SecretKey
    pub fn secret(&self) -> &ed25519_dalek::SecretKey {
        &self.0.secret
    }
}

impl Signer for Keypair {
    fn pubkey(&self) -> Pubkey {
        Pubkey::new(self.0.public.as_ref())
    }

    fn try_pubkey(&self) -> Result<Pubkey, SignerError> {
        Ok(self.pubkey())
    }

    fn sign_message(&self, message: &[u8]) -> Signature {
        Signature::new(&self.0.sign(message).to_bytes())
    }

    fn try_sign_message(&self, message: &[u8]) -> Result<Signature, SignerError> {
        Ok(self.sign_message(message))
    }
}

impl<T> PartialEq<T> for Keypair
where
    T: Signer,
{
    fn eq(&self, other: &T) -> bool {
        self.pubkey() == other.pubkey()
    }
}

/// Reads a JSON-encoded `Keypair` from a `Reader` implementor
pub fn read_keypair<R: Read>(reader: &mut R) -> Result<Keypair, Box<dyn error::Error>> {
    let bytes: Vec<u8> = serde_json::from_reader(reader)?;
    let dalek_keypair = ed25519_dalek::Keypair::from_bytes(&bytes)
        .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, e.to_string()))?;
    Ok(Keypair(dalek_keypair))
}

/// Reads a `Keypair` from a file
pub fn read_keypair_file<F: AsRef<Path>>(path: F) -> Result<Keypair, Box<dyn error::Error>> {
    let mut file = File::open(path.as_ref())?;
    read_keypair(&mut file)
}

/// Writes a `Keypair` to a `Write` implementor with JSON-encoding
pub fn write_keypair<W: Write>(
    keypair: &Keypair,
    writer: &mut W,
) -> Result<String, Box<dyn error::Error>> {
    let keypair_bytes = keypair.0.to_bytes();
    let serialized = serde_json::to_string(&keypair_bytes.to_vec())?;
    writer.write_all(&serialized.clone().into_bytes())?;
    Ok(serialized)
}

/// Writes a `Keypair` to a file with JSON-encoding
pub fn write_keypair_file<F: AsRef<Path>>(
    keypair: &Keypair,
    outfile: F,
) -> Result<String, Box<dyn error::Error>> {
    let outfile = outfile.as_ref();

    if let Some(outdir) = outfile.parent() {
        fs::create_dir_all(outdir)?;
    }

    let mut f = {
        #[cfg(not(unix))]
        {
            OpenOptions::new()
        }
        #[cfg(unix)]
        {
            use std::os::unix::fs::OpenOptionsExt;
            OpenOptions::new().mode(0o600)
        }
    }
    .write(true)
    .truncate(true)
    .create(true)
    .open(outfile)?;

    write_keypair(keypair, &mut f)
}

/// Constructs a `Keypair` from caller-provided seed entropy
pub fn keypair_from_seed(seed: &[u8]) -> Result<Keypair, Box<dyn error::Error>> {
    if seed.len() < ed25519_dalek::SECRET_KEY_LENGTH {
        return Err("Seed is too short".into());
    }
    let secret = ed25519_dalek::SecretKey::from_bytes(&seed[..ed25519_dalek::SECRET_KEY_LENGTH])
        .map_err(|e| e.to_string())?;
    let public = ed25519_dalek::PublicKey::from(&secret);
    let dalek_keypair = ed25519_dalek::Keypair { secret, public };
    Ok(Keypair(dalek_keypair))
}

/// Generates a Keypair using Bip32 Hierarchical Derivation if derivation-path is provided;
/// otherwise generates the base Bip44 Safecoin keypair from the seed
pub fn keypair_from_seed_and_derivation_path(
    seed: &[u8],
    derivation_path: Option<DerivationPath>,
) -> Result<Keypair, Box<dyn error::Error>> {
    let derivation_path = derivation_path.unwrap_or_else(DerivationPath::default);
    bip32_derived_keypair(seed, derivation_path).map_err(|err| err.to_string().into())
}

/// Generates a Keypair using Bip32 Hierarchical Derivation
fn bip32_derived_keypair(
    seed: &[u8],
    derivation_path: DerivationPath,
) -> Result<Keypair, Bip32Error> {
    let extended = ed25519_dalek_bip32::ExtendedSecretKey::from_seed(seed)
        .and_then(|extended| extended.derive(&derivation_path))?;
    let extended_public_key = extended.public_key();
    Ok(Keypair(ed25519_dalek::Keypair {
        secret: extended.secret_key,
        public: extended_public_key,
    }))
}

pub fn generate_seed_from_seed_phrase_and_passphrase(
    seed_phrase: &str,
    passphrase: &str,
) -> Vec<u8> {
    const PBKDF2_ROUNDS: u32 = 2048;
    const PBKDF2_BYTES: usize = 64;

    let salt = format!("mnemonic{}", passphrase);

    let mut seed = vec![0u8; PBKDF2_BYTES];
    pbkdf2::pbkdf2::<Hmac<sha2::Sha512>>(
        seed_phrase.as_bytes(),
        salt.as_bytes(),
        PBKDF2_ROUNDS,
        &mut seed,
    );
    seed
}

pub fn keypair_from_seed_phrase_and_passphrase(
    seed_phrase: &str,
    passphrase: &str,
) -> Result<Keypair, Box<dyn error::Error>> {
    keypair_from_seed(&generate_seed_from_seed_phrase_and_passphrase(
        seed_phrase,
        passphrase,
    ))
}

#[cfg(test)]
mod tests {
    use {
        super::*,
        bip39::{Language, Mnemonic, MnemonicType, Seed},
        std::mem,
    };

    fn tmp_file_path(name: &str) -> String {
        use std::env;
        let out_dir = env::var("FARF_DIR").unwrap_or_else(|_| "farf".to_string());
        let keypair = Keypair::new();

        format!("{}/tmp/{}-{}", out_dir, name, keypair.pubkey())
    }

    #[test]
    fn test_write_keypair_file() {
        let outfile = tmp_file_path("test_write_keypair_file.json");
        let serialized_keypair = write_keypair_file(&Keypair::new(), &outfile).unwrap();
        let keypair_vec: Vec<u8> = serde_json::from_str(&serialized_keypair).unwrap();
        assert!(Path::new(&outfile).exists());
        assert_eq!(
            keypair_vec,
            read_keypair_file(&outfile).unwrap().0.to_bytes().to_vec()
        );

        #[cfg(unix)]
        {
            use std::os::unix::fs::PermissionsExt;
            assert_eq!(
                File::open(&outfile)
                    .expect("open")
                    .metadata()
                    .expect("metadata")
                    .permissions()
                    .mode()
                    & 0o777,
                0o600
            );
        }

        assert_eq!(
            read_keypair_file(&outfile).unwrap().pubkey().as_ref().len(),
            mem::size_of::<Pubkey>()
        );
        fs::remove_file(&outfile).unwrap();
        assert!(!Path::new(&outfile).exists());
    }

    #[test]
    fn test_write_keypair_file_overwrite_ok() {
        let outfile = tmp_file_path("test_write_keypair_file_overwrite_ok.json");

        write_keypair_file(&Keypair::new(), &outfile).unwrap();
        write_keypair_file(&Keypair::new(), &outfile).unwrap();
    }

    #[test]
    fn test_write_keypair_file_truncate() {
        let outfile = tmp_file_path("test_write_keypair_file_truncate.json");

        write_keypair_file(&Keypair::new(), &outfile).unwrap();
        read_keypair_file(&outfile).unwrap();

        // Ensure outfile is truncated
        {
            let mut f = File::create(&outfile).unwrap();
            f.write_all(String::from_utf8([b'a'; 2048].to_vec()).unwrap().as_bytes())
                .unwrap();
        }
        write_keypair_file(&Keypair::new(), &outfile).unwrap();
        read_keypair_file(&outfile).unwrap();
    }

    #[test]
    fn test_keypair_from_seed() {
        let good_seed = vec![0; 32];
        assert!(keypair_from_seed(&good_seed).is_ok());

        let too_short_seed = vec![0; 31];
        assert!(keypair_from_seed(&too_short_seed).is_err());
    }

    #[test]
    fn test_keypair_from_seed_phrase_and_passphrase() {
        let mnemonic = Mnemonic::new(MnemonicType::Words12, Language::English);
        let passphrase = "42";
        let seed = Seed::new(&mnemonic, passphrase);
        let expected_keypair = keypair_from_seed(seed.as_bytes()).unwrap();
        let keypair =
            keypair_from_seed_phrase_and_passphrase(mnemonic.phrase(), passphrase).unwrap();
        assert_eq!(keypair.pubkey(), expected_keypair.pubkey());
    }

    #[test]
    fn test_keypair() {
        let keypair = keypair_from_seed(&[0u8; 32]).unwrap();
        let pubkey = keypair.pubkey();
        let data = [1u8];
        let sig = keypair.sign_message(&data);

        // Signer
        assert_eq!(keypair.try_pubkey().unwrap(), pubkey);
        assert_eq!(keypair.pubkey(), pubkey);
        assert_eq!(keypair.try_sign_message(&data).unwrap(), sig);
        assert_eq!(keypair.sign_message(&data), sig);

        // PartialEq
        let keypair2 = keypair_from_seed(&[0u8; 32]).unwrap();
        assert_eq!(keypair, keypair2);
    }
}