//! The `signature` module provides functionality for public, and private keys.

use crate::pubkey::Pubkey;
use bs58;
use ed25519_dalek;
use generic_array::typenum::U64;
use generic_array::GenericArray;
use rand::rngs::OsRng;
use serde_json;
use std::error;
use std::fmt;
use std::fs::{self, File};
use std::io::Write;
use std::path::Path;

pub type Keypair = ed25519_dalek::Keypair;

#[derive(Serialize, Deserialize, Clone, Copy, Default, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct Signature(GenericArray<u8, U64>);

impl Signature {
    pub fn new(signature_slice: &[u8]) -> Self {
        Self(GenericArray::clone_from_slice(&signature_slice))
    }

    pub fn verify(&self, pubkey_bytes: &[u8], message_bytes: &[u8]) -> bool {
        let pubkey = ed25519_dalek::PublicKey::from_bytes(pubkey_bytes);
        let signature = ed25519_dalek::Signature::from_bytes(self.0.as_slice());
        if pubkey.is_err() || signature.is_err() {
            return false;
        }
        pubkey
            .unwrap()
            .verify(message_bytes, &signature.unwrap())
            .is_ok()
    }
}

pub trait Signable {
    fn sign(&mut self, keypair: &Keypair) {
        let data = self.signable_data();
        self.set_signature(keypair.sign_message(&data));
    }
    fn verify(&self) -> bool {
        self.get_signature()
            .verify(&self.pubkey().as_ref(), &self.signable_data())
    }

    fn pubkey(&self) -> Pubkey;
    fn signable_data(&self) -> Vec<u8>;
    fn get_signature(&self) -> Signature;
    fn set_signature(&mut self, signature: Signature);
}

impl AsRef<[u8]> for Signature {
    fn as_ref(&self) -> &[u8] {
        &self.0[..]
    }
}

impl fmt::Debug for Signature {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", bs58::encode(self.0).into_string())
    }
}

impl fmt::Display for Signature {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", bs58::encode(self.0).into_string())
    }
}

pub trait KeypairUtil {
    fn new() -> Self;
    fn pubkey(&self) -> Pubkey;
    fn sign_message(&self, message: &[u8]) -> Signature;
}

impl KeypairUtil for Keypair {
    /// Return a new ED25519 keypair
    fn new() -> Self {
        let mut rng = OsRng::new().unwrap();
        Keypair::generate(&mut rng)
    }

    /// Return the public key for the given keypair
    fn pubkey(&self) -> Pubkey {
        Pubkey::new(&self.public.as_ref())
    }

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

pub fn read_keypair(path: &str) -> Result<Keypair, Box<error::Error>> {
    let file = File::open(path.to_string())?;
    let bytes: Vec<u8> = serde_json::from_reader(file)?;
    let keypair = Keypair::from_bytes(&bytes).unwrap();
    Ok(keypair)
}

pub fn gen_keypair_file(outfile: String) -> Result<String, Box<error::Error>> {
    let keypair_bytes = Keypair::new().to_bytes();
    let serialized = serde_json::to_string(&keypair_bytes.to_vec())?;

    if outfile != "-" {
        if let Some(outdir) = Path::new(&outfile).parent() {
            fs::create_dir_all(outdir)?;
        }
        let mut f = File::create(outfile)?;
        f.write_all(&serialized.clone().into_bytes())?;
    }
    Ok(serialized)
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::mem;

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

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

    #[test]
    fn test_gen_keypair_file() {
        let outfile = tmp_file_path("test_gen_keypair_file.json");
        let serialized_keypair = gen_keypair_file(outfile.to_string()).unwrap();
        let keypair_vec: Vec<u8> = serde_json::from_str(&serialized_keypair).unwrap();
        assert!(Path::new(&outfile).exists());
        assert_eq!(
            keypair_vec,
            read_keypair(&outfile).unwrap().to_bytes().to_vec()
        );
        assert_eq!(
            read_keypair(&outfile).unwrap().pubkey().as_ref().len(),
            mem::size_of::<Pubkey>()
        );
        fs::remove_file(&outfile).unwrap();
        assert!(!Path::new(&outfile).exists());
    }
}