use ffi;
use std::fmt;
use std::ptr;
use std::mem;
use libc::{c_int, c_void, c_char, c_ulong};

use bn::{BigNum, BigNumRef};
use bio::{MemBio, MemBioSlice};
use error::ErrorStack;
use HashTypeInternals;
use crypto::hash;
use crypto::util::{CallbackState, invoke_passwd_cb};

pub struct RSA(*mut ffi::RSA);

impl Drop for RSA {
    fn drop(&mut self) {
        unsafe {
            ffi::RSA_free(self.0);
        }
    }
}

impl RSA {
    /// only useful for associating the key material directly with the key, it's safer to use
    /// the supplied load and save methods for DER formatted keys.
    pub fn from_public_components(n: BigNum, e: BigNum) -> Result<RSA, ErrorStack> {
        unsafe {
            let rsa = try_ssl_null!(ffi::RSA_new());
            (*rsa).n = n.as_ptr();
            (*rsa).e = e.as_ptr();
            mem::forget(n);
            mem::forget(e);
            Ok(RSA(rsa))
        }
    }

    pub fn from_private_components(n: BigNum,
                                   e: BigNum,
                                   d: BigNum,
                                   p: BigNum,
                                   q: BigNum,
                                   dp: BigNum,
                                   dq: BigNum,
                                   qi: BigNum)
                                   -> Result<RSA, ErrorStack> {
        unsafe {
            let rsa = try_ssl_null!(ffi::RSA_new());
            (*rsa).n = n.as_ptr();
            (*rsa).e = e.as_ptr();
            (*rsa).d = d.as_ptr();
            (*rsa).p = p.as_ptr();
            (*rsa).q = q.as_ptr();
            (*rsa).dmp1 = dp.as_ptr();
            (*rsa).dmq1 = dq.as_ptr();
            (*rsa).iqmp = qi.as_ptr();
            mem::forget(n);
            mem::forget(e);
            mem::forget(d);
            mem::forget(p);
            mem::forget(q);
            mem::forget(dp);
            mem::forget(dq);
            mem::forget(qi);
            Ok(RSA(rsa))
        }
    }

    pub unsafe fn from_raw(rsa: *mut ffi::RSA) -> RSA {
        RSA(rsa)
    }

    /// Generates a public/private key pair with the specified size.
    ///
    /// The public exponent will be 65537.
    pub fn generate(bits: u32) -> Result<RSA, ErrorStack> {
        unsafe {
            let rsa = try_ssl_null!(ffi::RSA_new());
            let rsa = RSA(rsa);
            let e = try!(BigNum::new_from(ffi::RSA_F4 as c_ulong));

            try_ssl!(ffi::RSA_generate_key_ex(rsa.0, bits as c_int, e.as_ptr(), ptr::null_mut()));

            Ok(rsa)
        }
    }

    /// Reads an RSA private key from PEM formatted data.
    pub fn private_key_from_pem(buf: &[u8]) -> Result<RSA, ErrorStack> {
        let mem_bio = try!(MemBioSlice::new(buf));
        unsafe {
            let rsa = try_ssl_null!(ffi::PEM_read_bio_RSAPrivateKey(mem_bio.handle(),
                                                                    ptr::null_mut(),
                                                                    None,
                                                                    ptr::null_mut()));
            Ok(RSA(rsa))
        }
    }

    /// Reads an RSA private key from PEM formatted data and supplies a password callback.
    pub fn private_key_from_pem_cb<F>(buf: &[u8], pass_cb: F) -> Result<RSA, ErrorStack>
        where F: FnOnce(&mut [c_char]) -> usize
    {
        let mut cb = CallbackState::new(pass_cb);
        let mem_bio = try!(MemBioSlice::new(buf));

        unsafe {
            let cb_ptr = &mut cb as *mut _ as *mut c_void;
            let rsa = try_ssl_null!(ffi::PEM_read_bio_RSAPrivateKey(mem_bio.handle(),
                                                                    ptr::null_mut(),
                                                                    Some(invoke_passwd_cb::<F>),
                                                                    cb_ptr));

            Ok(RSA(rsa))
        }
    }

    /// Reads an RSA public key from PEM formatted data.
    pub fn public_key_from_pem(buf: &[u8]) -> Result<RSA, ErrorStack> {
        let mem_bio = try!(MemBioSlice::new(buf));
        unsafe {
            let rsa = try_ssl_null!(ffi::PEM_read_bio_RSA_PUBKEY(mem_bio.handle(),
                                                                 ptr::null_mut(),
                                                                 None,
                                                                 ptr::null_mut()));
            Ok(RSA(rsa))
        }
    }

    /// Writes an RSA private key as unencrypted PEM formatted data
    pub fn private_key_to_pem(&self) -> Result<Vec<u8>, ErrorStack> {
        let mem_bio = try!(MemBio::new());

        unsafe {
            try_ssl!(ffi::PEM_write_bio_RSAPrivateKey(mem_bio.handle(),
                                             self.0,
                                             ptr::null(),
                                             ptr::null_mut(),
                                             0,
                                             None,
                                             ptr::null_mut()));
        }
        Ok(mem_bio.get_buf().to_owned())
    }

    /// Writes an RSA public key as PEM formatted data
    pub fn public_key_to_pem(&self) -> Result<Vec<u8>, ErrorStack> {
        let mem_bio = try!(MemBio::new());

        unsafe {
            try_ssl!(ffi::PEM_write_bio_RSA_PUBKEY(mem_bio.handle(), self.0))
        };

        Ok(mem_bio.get_buf().to_owned())
    }

    pub fn size(&self) -> Option<u32> {
        if self.n().is_some() {
            unsafe { Some(ffi::RSA_size(self.0) as u32) }
        } else {
            None
        }
    }

    pub fn sign(&self, hash: hash::Type, message: &[u8]) -> Result<Vec<u8>, ErrorStack> {
        let k_len = self.size().expect("RSA missing an n");
        let mut sig = vec![0; k_len as usize];
        let mut sig_len = k_len;

        unsafe {
            try_ssl!(ffi::RSA_sign(hash.as_nid() as c_int,
                                   message.as_ptr(),
                                   message.len() as u32,
                                   sig.as_mut_ptr(),
                                   &mut sig_len,
                                   self.0));
            assert!(sig_len == k_len);
            Ok(sig)
        }
    }

    pub fn verify(&self, hash: hash::Type, message: &[u8], sig: &[u8]) -> Result<(), ErrorStack> {
        unsafe {
            try_ssl!(ffi::RSA_verify(hash.as_nid() as c_int,
                                     message.as_ptr(),
                                     message.len() as u32,
                                     sig.as_ptr(),
                                     sig.len() as u32,
                                     self.0));
        }
        Ok(())
    }

    pub fn as_ptr(&self) -> *mut ffi::RSA {
        self.0
    }

    pub fn n<'a>(&'a self) -> Option<BigNumRef<'a>> {
        unsafe {
            let n = (*self.0).n;
            if n.is_null() {
                None
            } else {
                Some(BigNumRef::from_ptr(n))
            }
        }
    }

    pub fn d<'a>(&self) -> Option<BigNumRef<'a>> {
        unsafe {
            let d = (*self.0).d;
            if d.is_null() {
                None
            } else {
                Some(BigNumRef::from_ptr(d))
            }
        }
    }

    pub fn e<'a>(&'a self) -> Option<BigNumRef<'a>> {
        unsafe {
            let e = (*self.0).e;
            if e.is_null() {
                None
            } else {
                Some(BigNumRef::from_ptr(e))
            }
        }
    }

    pub fn p<'a>(&'a self) -> Option<BigNumRef<'a>> {
        unsafe {
            let p = (*self.0).p;
            if p.is_null() {
                None
            } else {
                Some(BigNumRef::from_ptr(p))
            }
        }
    }

    pub fn q<'a>(&'a self) -> Option<BigNumRef<'a>> {
        unsafe {
            let q = (*self.0).q;
            if q.is_null() {
                None
            } else {
                Some(BigNumRef::from_ptr(q))
            }
        }
    }
}

impl fmt::Debug for RSA {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "RSA")
    }
}

#[cfg(test)]
mod test {
    use std::io::Write;
    use libc::c_char;

    use super::*;
    use crypto::hash::*;

    fn signing_input_rs256() -> Vec<u8> {
        vec![101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 122, 73, 49, 78, 105, 74, 57,
             46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48,
             75, 73, 67, 74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107,
             122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76, 121,
             57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118, 98, 83, 57, 112, 99,
             49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48, 99, 110, 86, 108, 102, 81]
    }

    fn signature_rs256() -> Vec<u8> {
        vec![112, 46, 33, 137, 67, 232, 143, 209, 30, 181, 216, 45, 191, 120, 69, 243, 65, 6, 174,
             27, 129, 255, 247, 115, 17, 22, 173, 209, 113, 125, 131, 101, 109, 66, 10, 253, 60,
             150, 238, 221, 115, 162, 102, 62, 81, 102, 104, 123, 0, 11, 135, 34, 110, 1, 135, 237,
             16, 115, 249, 69, 229, 130, 173, 252, 239, 22, 216, 90, 121, 142, 232, 198, 109, 219,
             61, 184, 151, 91, 23, 208, 148, 2, 190, 237, 213, 217, 217, 112, 7, 16, 141, 178, 129,
             96, 213, 248, 4, 12, 167, 68, 87, 98, 184, 31, 190, 127, 249, 217, 46, 10, 231, 111,
             36, 242, 91, 51, 187, 230, 244, 74, 230, 30, 177, 4, 10, 203, 32, 4, 77, 62, 249, 18,
             142, 212, 1, 48, 121, 91, 212, 189, 59, 65, 238, 202, 208, 102, 171, 101, 25, 129,
             253, 228, 141, 247, 127, 55, 45, 195, 139, 159, 175, 221, 59, 239, 177, 139, 93, 163,
             204, 60, 46, 176, 47, 158, 58, 65, 214, 18, 202, 173, 21, 145, 18, 115, 160, 95, 35,
             185, 232, 56, 250, 175, 132, 157, 105, 132, 41, 239, 90, 30, 136, 121, 130, 54, 195,
             212, 14, 96, 69, 34, 165, 68, 200, 242, 122, 122, 45, 184, 6, 99, 209, 108, 247, 202,
             234, 86, 222, 64, 92, 178, 33, 90, 69, 178, 194, 85, 102, 181, 90, 193, 167, 72, 160,
             112, 223, 200, 163, 42, 70, 149, 67, 208, 25, 238, 251, 71]
    }

    #[test]
    pub fn test_sign() {
        let key = include_bytes!("../../test/rsa.pem");
        let private_key = RSA::private_key_from_pem(key).unwrap();

        let mut sha = Hasher::new(Type::SHA256).unwrap();
        sha.write_all(&signing_input_rs256()).unwrap();
        let digest = sha.finish().unwrap();

        let result = private_key.sign(Type::SHA256, &digest).unwrap();

        assert_eq!(result, signature_rs256());
    }

    #[test]
    pub fn test_verify() {
        let key = include_bytes!("../../test/rsa.pem.pub");
        let public_key = RSA::public_key_from_pem(key).unwrap();

        let mut sha = Hasher::new(Type::SHA256).unwrap();
        sha.write_all(&signing_input_rs256()).unwrap();
        let digest = sha.finish().unwrap();

        assert!(public_key.verify(Type::SHA256, &digest, &signature_rs256()).is_ok());
    }

    #[test]
    pub fn test_password() {
        let mut password_queried = false;
        let key = include_bytes!("../../test/rsa-encrypted.pem");
        RSA::private_key_from_pem_cb(key, |password| {
            password_queried = true;
            password[0] = b'm' as c_char;
            password[1] = b'y' as c_char;
            password[2] = b'p' as c_char;
            password[3] = b'a' as c_char;
            password[4] = b's' as c_char;
            password[5] = b's' as c_char;
            6
        }).unwrap();

        assert!(password_queried);
    }
}