use std::cast;
use std::libc::{c_int, c_uint};
use std::libc;
use std::ptr;
use std::vec;

#[allow(non_camel_case_types)]
pub type EVP_PKEY = *libc::c_void;

#[allow(non_camel_case_types)]
pub type ANYKEY = *libc::c_void;

#[allow(non_camel_case_types)]
pub type RSA = *libc::c_void;

mod libcrypto {
    use super::*;
    use std::libc::{c_int, c_uint};

    #[link_args = "-lcrypto"]
    extern "C" {
        fn EVP_PKEY_new() -> *EVP_PKEY;
        fn EVP_PKEY_free(k: *EVP_PKEY);
        fn EVP_PKEY_assign(k: *EVP_PKEY, t: c_int, inner: *ANYKEY) -> c_int;
        fn EVP_PKEY_get1_RSA(k: *EVP_PKEY) -> *RSA;

        fn i2d_PublicKey(k: *EVP_PKEY, buf: **mut u8) -> c_int;
        fn d2i_PublicKey(t: c_int, k: **EVP_PKEY, buf: **u8, len: c_uint) -> *EVP_PKEY;
        fn i2d_PrivateKey(k: *EVP_PKEY, buf: **mut u8) -> c_int;
        fn d2i_PrivateKey(t: c_int, k: **EVP_PKEY, buf: **u8, len: c_uint) -> *EVP_PKEY;

        fn RSA_generate_key(modsz: c_uint, e: c_uint, cb: *u8, cbarg: *u8) -> *RSA;
        fn RSA_size(k: *RSA) -> c_uint;

        fn RSA_public_encrypt(flen: c_uint, from: *u8, to: *mut u8, k: *RSA,
                              pad: c_int) -> c_int;
        fn RSA_private_decrypt(flen: c_uint, from: *u8, to: *mut u8, k: *RSA,
                               pad: c_int) -> c_int;
        fn RSA_sign(t: c_int, m: *u8, mlen: c_uint, sig: *mut u8, siglen: *mut c_uint,
                    k: *RSA) -> c_int;
        fn RSA_verify(t: c_int, m: *u8, mlen: c_uint, sig: *u8, siglen: c_uint,
                      k: *RSA) -> c_int;
    }
}

enum Parts {
    Neither,
    Public,
    Both
}

#[doc = "Represents a role an asymmetric key might be appropriate for."]
pub enum Role {
    Encrypt,
    Decrypt,
    Sign,
    Verify
}

fn rsa_to_any(rsa: *RSA) -> *ANYKEY {
    unsafe {
        cast::transmute(rsa)
    }
}

fn any_to_rsa(anykey: *ANYKEY) -> *RSA {
    unsafe {
        cast::transmute(anykey)
    }
}

pub struct PKey {
    priv evp: *EVP_PKEY,
    priv parts: Parts,
}

pub fn PKey() -> PKey {
    PKey {
        evp: unsafe { libcrypto::EVP_PKEY_new() },
        parts: Neither
    }
}

///Represents a public key, optionally with a private key attached.
impl PKey {
    fn _tostr(&self, f: extern "C" unsafe fn(*EVP_PKEY, **mut u8) -> c_int) -> ~[u8] {
        unsafe {
            let len = f(self.evp, ptr::null());
            if len < 0 as c_int { return ~[]; }
            let mut s = vec::from_elem(len as uint, 0u8);

            let r = do s.as_mut_buf |buf, _| {
                f(self.evp, &buf)
            };

            s.truncate(r as uint);
            s
        }
    }

    fn _fromstr(&mut self, s: &[u8], f: extern "C" unsafe fn(c_int, **EVP_PKEY, **u8, c_uint) -> *EVP_PKEY) {
        do s.as_imm_buf |ps, len| {
            let evp = ptr::null();
            unsafe {
                f(6 as c_int, &evp, &ps, len as c_uint);
            }
            self.evp = evp;
        }
    }

    pub fn gen(&mut self, keysz: uint) {
        unsafe {
            let rsa = libcrypto::RSA_generate_key(
                keysz as c_uint,
                65537u as c_uint,
                ptr::null(),
                ptr::null()
            );

            let rsa_ = rsa_to_any(rsa);
            // XXX: 6 == NID_rsaEncryption
            libcrypto::EVP_PKEY_assign(self.evp, 6 as c_int, rsa_);
            self.parts = Both;
        }
    }

    /**
     * Returns a serialized form of the public key, suitable for load_pub().
     */
    pub fn save_pub(&self) -> ~[u8] {
        self._tostr(libcrypto::i2d_PublicKey)
    }

    /**
     * Loads a serialized form of the public key, as produced by save_pub().
     */
    pub fn load_pub(&mut self, s: &[u8]) {
        self._fromstr(s, libcrypto::d2i_PublicKey);
        self.parts = Public;
    }

    /**
     * Returns a serialized form of the public and private keys, suitable for
     * load_priv().
     */
    pub fn save_priv(&self) -> ~[u8] {
        self._tostr(libcrypto::i2d_PrivateKey)
    }
    /**
     * Loads a serialized form of the public and private keys, as produced by
     * save_priv().
     */
    pub fn load_priv(&mut self, s: &[u8]) {
        self._fromstr(s, libcrypto::d2i_PrivateKey);
        self.parts = Both;
    }

    /**
     * Returns the size of the public key modulus.
     */
    pub fn size(&self) -> uint {
        unsafe {
            libcrypto::RSA_size(libcrypto::EVP_PKEY_get1_RSA(self.evp)) as uint
        }
    }

    /**
     * Returns whether this pkey object can perform the specified role.
     */
    pub fn can(&self, r: Role) -> bool {
        match r {
            Encrypt =>
                match self.parts {
                    Neither => false,
                    _ => true,
                },
            Verify =>
                match self.parts {
                    Neither => false,
                    _ => true,
                },
            Decrypt =>
                match self.parts {
                    Both => true,
                    _ => false,
                },
            Sign =>
                match self.parts {
                    Both => true,
                    _ => false,
                },
        }
    }

    /**
     * Returns the maximum amount of data that can be encrypted by an encrypt()
     * call.
     */
    pub fn max_data(&self) -> uint {
        unsafe {
            let rsa = libcrypto::EVP_PKEY_get1_RSA(self.evp);
            let len = libcrypto::RSA_size(rsa);

            // 41 comes from RSA_public_encrypt(3) for OAEP
            len as uint - 41u
        }
    }

    /**
     * Encrypts data using OAEP padding, returning the encrypted data. The
     * supplied data must not be larger than max_data().
     */
    pub fn encrypt(&self, s: &[u8]) -> ~[u8] {
        unsafe {
            let rsa = libcrypto::EVP_PKEY_get1_RSA(self.evp);
            let len = libcrypto::RSA_size(rsa);

            // 41 comes from RSA_public_encrypt(3) for OAEP
            assert!(s.len() < libcrypto::RSA_size(rsa) as uint - 41u);

            let mut r = vec::from_elem(len as uint + 1u, 0u8);

            let rv = do r.as_mut_buf |pr, _len| {
                do s.as_imm_buf |ps, s_len| {
                    // XXX: 4 == RSA_PKCS1_OAEP_PADDING
                    libcrypto::RSA_public_encrypt(
                        s_len as c_uint,
                        ps,
                        pr,
                        rsa, 4 as c_int
                    )
                }
            };

            if rv < 0 as c_int {
                ~[]
            } else {
                r.truncate(rv as uint);
                r
            }
        }
    }

    /**
     * Decrypts data, expecting OAEP padding, returning the decrypted data.
     */
    pub fn decrypt(&self, s: &[u8]) -> ~[u8] {
        unsafe {
            let rsa = libcrypto::EVP_PKEY_get1_RSA(self.evp);
            let len = libcrypto::RSA_size(rsa);

            assert!(s.len() as c_uint == libcrypto::RSA_size(rsa));

            let mut r = vec::from_elem(len as uint + 1u, 0u8);

            let rv = do r.as_mut_buf |pr, _len| {
                do s.as_imm_buf |ps, s_len| {
                    // XXX: 4 == RSA_PKCS1_OAEP_PADDING
                    libcrypto::RSA_private_decrypt(
                        s_len as c_uint,
                        ps,
                        pr,
                        rsa,
                        4 as c_int
                    )
                }
            };

            if rv < 0 as c_int {
                ~[]
            } else {
                r.truncate(rv as uint);
                r
            }
        }
    }

    /**
     * Signs data, using OpenSSL's default scheme and sha256. Unlike encrypt(),
     * can process an arbitrary amount of data; returns the signature.
     */
    pub fn sign(&self, s: &[u8]) -> ~[u8] {
        unsafe {
            let rsa = libcrypto::EVP_PKEY_get1_RSA(self.evp);
            let len = libcrypto::RSA_size(rsa);
            let mut r = vec::from_elem(len as uint + 1u, 0u8);

            let rv = do r.as_mut_buf |pr, _len| {
                do s.as_imm_buf |ps, s_len| {
                    let mut len = len;

                    // XXX: 672 == NID_sha256
                    libcrypto::RSA_sign(
                        672 as c_int,
                        ps,
                        s_len as c_uint,
                        pr,
                        &mut len,
                        rsa)
                }
            };

            if rv < 0 as c_int {
                ~[]
            } else {
                r.truncate(len as uint);
                r
            }
        }
    }

    /**
     * Verifies a signature s (using OpenSSL's default scheme and sha256) on a
     * message m. Returns true if the signature is valid, and false otherwise.
     */
    pub fn verify(&self, m: &[u8], s: &[u8]) -> bool {
        unsafe {
            let rsa = libcrypto::EVP_PKEY_get1_RSA(self.evp);

            do m.as_imm_buf |pm, m_len| {
                do s.as_imm_buf |ps, s_len| {
                    // XXX: 672 == NID_sha256
                    let rv = libcrypto::RSA_verify(
                        672 as c_int,
                        pm,
                        m_len as c_uint,
                        ps,
                        s_len as c_uint,
                        rsa
                    );

                    rv == 1 as c_int
                }
            }
        }
    }
}

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

    #[test]
    fn test_gen_pub() {
        let mut k0 = PKey();
        let mut k1 = PKey();
        k0.gen(512u);
        k1.load_pub(k0.save_pub());
        assert!(k0.save_pub() == k1.save_pub());
        assert!(k0.size() == k1.size());
        assert!(k0.can(Encrypt));
        assert!(k0.can(Decrypt));
        assert!(k0.can(Verify));
        assert!(k0.can(Sign));
        assert!(k1.can(Encrypt));
        assert!(!k1.can(Decrypt));
        assert!(k1.can(Verify));
        assert!(!k1.can(Sign));
    }

    #[test]
    fn test_gen_priv() {
        let mut k0 = PKey();
        let mut k1 = PKey();
        k0.gen(512u);
        k1.load_priv(k0.save_priv());
        assert!(k0.save_priv() == k1.save_priv());
        assert!(k0.size() == k1.size());
        assert!(k0.can(Encrypt));
        assert!(k0.can(Decrypt));
        assert!(k0.can(Verify));
        assert!(k0.can(Sign));
        assert!(k1.can(Encrypt));
        assert!(k1.can(Decrypt));
        assert!(k1.can(Verify));
        assert!(k1.can(Sign));
    }

    #[test]
    fn test_encrypt() {
        let mut k0 = PKey();
        let mut k1 = PKey();
        let msg = ~[0xdeu8, 0xadu8, 0xd0u8, 0x0du8];
        k0.gen(512u);
        k1.load_pub(k0.save_pub());
        let emsg = k1.encrypt(msg);
        let dmsg = k0.decrypt(emsg);
        assert!(msg == dmsg);
    }

    #[test]
    fn test_sign() {
        let mut k0 = PKey();
        let mut k1 = PKey();
        let msg = ~[0xdeu8, 0xadu8, 0xd0u8, 0x0du8];
        k0.gen(512u);
        k1.load_pub(k0.save_pub());
        let sig = k0.sign(msg);
        let rv = k1.verify(msg, sig);
        assert!(rv == true);
    }
}