#[macro_use]
extern crate serde_derive;

use simpl::err;
use std::*;
use std::str::FromStr;
use openssl::sign::Signer;
use openssl::pkey::{PKey, Private};
use openssl::hash::MessageDigest;
use base64::encode_config;

use serde::ser::Serialize;

use std::io::prelude::*;
use std::fs::File;

err!(JwtErr,
    {
        Json@serde_json::Error;
        OpenSsl@openssl::error::ErrorStack;
        Io@std::io::Error;
    });

#[derive(Debug)]
pub enum Algorithm {
    HS256,
    RS256,
}

impl Algorithm {
    fn signer(&self) -> openssl::hash::MessageDigest {
        match *self {
            Algorithm::HS256 => unimplemented!(),
            Algorithm::RS256 => MessageDigest::sha256(),
        }
    }
}

impl fmt::Display for Algorithm {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Algorithm::HS256 => write!(f, "HS256"),
            Algorithm::RS256 => write!(f, "RS256")
        }
    }
}

#[derive(Serialize, Deserialize, Debug)]
pub struct JwtHeader {
    alg: String,
    typ: String,
}

impl fmt::Display for JwtHeader {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "JwtHeader: {}", serde_json::to_string_pretty(&self).unwrap())
    }
}

pub struct RSAKey {
    key: PKey<Private>
}

impl RSAKey {
    pub fn from_pem(filename: &str) -> Result<Self, JwtErr> {
        Ok(RSAKey { key: Self::read_keyfile(filename)? })
    }

    pub fn from_pkey(pkey: PKey<Private>) -> Result<Self, JwtErr> {
        Ok(RSAKey { key: pkey })
    }

    fn read_keyfile(keyfile: &str) -> Result<PKey<Private>, JwtErr> {
        let mut f = File::open(keyfile)?;
        let mut buffer = Vec::new();
        let _ = f.read_to_end(&mut buffer);
        Ok(PKey::private_key_from_pem(&buffer)?)
    }

    fn produce_key(&self) -> &PKey<Private> {
        &self.key
    }
}

impl FromStr for RSAKey {
    type Err = JwtErr;
    fn from_str(s: &str) -> Result<Self, JwtErr> {
        Ok(RSAKey { key: PKey::private_key_from_pem(s.as_bytes())? })
    }
}

pub struct Jwt<T> {
    body: T,
    pkey: RSAKey,
    algo: Algorithm,
}

impl<T: serde::ser::Serialize> fmt::Display for Jwt<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Jwt: \n header: {} \n body: {}, \n algorithm: {}",
               serde_json::to_string_pretty(&self.header().unwrap()).unwrap(),
               serde_json::to_string_pretty(&self.body).unwrap(),
               &self.algo)
    }
}

/// Jwt can be finalized to produce an encoded and signed string representation
///
/// ### Example
///
/// ```
///
/// #[macro_use]
/// extern crate serde_derive;
/// extern crate serde;
/// extern crate smpl_jwt;
///
/// use serde::Serialize;
/// use smpl_jwt::{Jwt, RSAKey};
///
/// fn main() {
///   #[derive(Serialize)]
///   struct ExampleStruct {
///     field: String
///   }
///
///   let rsa_key = match RSAKey::from_pem("random_rsa_for_testing") {
///     Ok(x) => x,
///     Err(e) => panic!("{}", e)
///   };
///
///   let jwt = Jwt::new(ExampleStruct{field: String::from("test")},
///                     rsa_key,
///                     None);
///
///   println!("{}", jwt);
/// }
/// ```

impl<T> Jwt<T> where
    T: Serialize {
    fn input(&self) -> Result<String, JwtErr> {
        let header = &self.encode_header()?;
        let body = Self::encode(&self.body)?;
        Ok(format!("{}.{}", header, body))
    }

    fn encode(param: &T) -> Result<String, JwtErr> {
        Ok(encode_config(serde_json::to_string(&param)?.as_bytes(), base64::URL_SAFE).to_owned())
    }

    fn encode_header(&self) -> Result<String, JwtErr> {
        Ok(encode_config(serde_json::to_string(&self.header()?)?.as_bytes(), base64::URL_SAFE).to_owned())
    }

    fn header(&self) -> Result<JwtHeader, JwtErr> {
        Ok(JwtHeader {
            alg: self.algo.to_string(),
            typ: "JWT".to_string(),
        })
    }

    fn sign(&self) -> Result<String, JwtErr> {
        let pkey = self.pkey.produce_key();
        let mut signer = Signer::new(self.algo.signer(), pkey)?;
        signer.update(self.input()?.as_bytes())?;
        let signed: Vec<u8> = signer.sign_to_vec()?;
        Ok(encode_config(&signed, base64::URL_SAFE))
    }

    pub fn finalize(&self) -> Result<String, JwtErr> {
        Ok(format!("{}.{}", &self.input()?, &self.sign()?))
    }

    pub fn new(body: T, jwt_key: RSAKey, algo: Option<Algorithm>) -> Jwt<T> {
        Jwt {
            body,
            pkey: jwt_key,
            algo: algo.unwrap_or(Algorithm::RS256),
        }
    }
}

#[test]
fn test_sign() {
    //  Verified with https://jwt.io/

    #[derive(Serialize)]
    struct TestBody {
        serialize: String
    }

    let rsa_key = match RSAKey::from_pem("random_rsa_for_testing") {
        Ok(x) => x,
        Err(e) => panic!("{}", e)
    };

    let jwt = Jwt::new(TestBody { serialize: "me".to_string() },
                       rsa_key,
                       None);
    assert_eq!(jwt.finalize().unwrap(), "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJzZXJpYWxpemUiOiJtZSJ9.nJIFpAKQWE5Mt1TQS2eDqoLVANJf809pCegB7herGYZ0Lqb1eV9MAv_Cz6lyaq87v1StC48e-U3Lp6oVezsQ-mUg5h92hFEEkzKIoJOYE6N-BEaVuy73Qf2s7c6W3ZdD0U3oR6PiEO9-FnB5bsiQlIfgzykmDUSjo2CmYpAypF9sT43by4tvSMwUwNZ_NuTI3ASPqdk5wKAkrCOJjayhyKZR7KrqeUmZdqS0Un8NSpr53Zd6SdCYTpDSGsKF_mwYV309q7zAbzRhWN-YTYsdB6Em5QoXo0ZUuNIigfprOQP1MVFvznbeonQvu6OHzJMIFhhUip8UCFNp6wzsqm4syQ==");
}