use std::cmp;
use std::ptr;
use libc::c_int;
use ffi;

use {cvt, cvt_p};
use error::ErrorStack;

#[derive(Copy, Clone)]
pub enum Mode {
    Encrypt,
    Decrypt,
}

#[derive(Copy, Clone)]
pub struct Cipher(*const ffi::EVP_CIPHER);

impl Cipher {
    pub fn aes_128_ecb() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_ecb())
        }
    }

    pub fn aes_128_cbc() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_cbc())
        }
    }

    pub fn aes_128_xts() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_xts())
        }
    }

    pub fn aes_128_ctr() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_ctr())
        }
    }

    pub fn aes_128_cfb1() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_cfb1())
        }
    }

    pub fn aes_128_cfb128() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_cfb128())
        }
    }

    pub fn aes_128_cfb8() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_128_cfb8())
        }
    }

    pub fn aes_256_ecb() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_ecb())
        }
    }

    pub fn aes_256_cbc() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_cbc())
        }
    }

    pub fn aes_256_xts() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_xts())
        }
    }

    pub fn aes_256_ctr() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_ctr())
        }
    }

    pub fn aes_256_cfb1() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_cfb1())
        }
    }

    pub fn aes_256_cfb128() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_cfb128())
        }
    }

    pub fn aes_256_cfb8() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_aes_256_cfb8())
        }
    }

    pub fn des_cbc() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_des_cbc())
        }
    }

    pub fn des_ecb() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_des_ecb())
        }
    }

    pub fn rc4() -> Cipher {
        unsafe {
            Cipher(ffi::EVP_rc4())
        }
    }

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

    /// Returns the length of keys used with this cipher.
    pub fn key_len(&self) -> usize {
        unsafe {
            EVP_CIPHER_key_length(self.0) as usize
        }
    }

    /// Returns the length of the IV used with this cipher, or `None` if the
    /// cipher does not use an IV.
    pub fn iv_len(&self) -> Option<usize> {
        unsafe {
            let len = EVP_CIPHER_iv_length(self.0) as usize;
            if len == 0 {
                None
            } else {
                Some(len)
            }
        }
    }

    /// Returns the block size of the cipher.
    ///
    /// # Note
    ///
    /// Stream ciphers such as RC4 have a block size of 1.
    pub fn block_size(&self) -> usize {
        unsafe {
            EVP_CIPHER_block_size(self.0) as usize
        }
    }
}

/// Represents a symmetric cipher context.
pub struct Crypter {
    ctx: *mut ffi::EVP_CIPHER_CTX,
    block_size: usize,
}

impl Crypter {
    /// Creates a new `Crypter`.
    ///
    /// # Panics
    ///
    /// Panics if an IV is required by the cipher but not provided, or if the
    /// IV's length does not match the expected length (see `Cipher::iv_len`).
    pub fn new(t: Cipher, mode: Mode, key: &[u8], iv: Option<&[u8]>) -> Result<Crypter, ErrorStack> {
        ffi::init();

        unsafe {
            let ctx = try!(cvt_p(ffi::EVP_CIPHER_CTX_new()));
            let crypter = Crypter {
                ctx: ctx,
                block_size: t.block_size(),
            };

            let mode = match mode {
                Mode::Encrypt => 1,
                Mode::Decrypt => 0,
            };

            try!(cvt(ffi::EVP_CipherInit_ex(crypter.ctx,
                                             t.as_ptr(),
                                             ptr::null_mut(),
                                             ptr::null_mut(),
                                             ptr::null_mut(),
                                             mode)));

            assert!(key.len() <= c_int::max_value() as usize);
            try!(cvt(ffi::EVP_CIPHER_CTX_set_key_length(crypter.ctx, key.len() as c_int)));

            let key = key.as_ptr() as *mut _;
            let iv = match (iv, t.iv_len()) {
                (Some(iv), Some(len)) => {
                    assert!(iv.len() == len);
                    iv.as_ptr() as *mut _
                }
                (Some(_), None) | (None, None) => ptr::null_mut(),
                (None, Some(_)) => panic!("an IV is required for this cipher"),
            };
            try!(cvt(ffi::EVP_CipherInit_ex(crypter.ctx,
                                            ptr::null(),
                                            ptr::null_mut(),
                                            key,
                                            iv,
                                            mode)));

            Ok(crypter)
        }
    }

    /// Enables or disables padding.
    ///
    /// If padding is disabled, total amount of data encrypted/decrypted must
    /// be a multiple of the cipher's block size.
    pub fn pad(&mut self, padding: bool) {
        unsafe { ffi::EVP_CIPHER_CTX_set_padding(self.ctx, padding as c_int); }
    }

    /// Feeds data from `input` through the cipher, writing encrypted/decrypted
    /// bytes into `output`.
    ///
    /// The number of bytes written to `output` is returned. Note that this may
    /// not be equal to the length of `input`.
    ///
    /// # Panics
    ///
    /// Panics if `output.len() < input.len() + block_size` where
    /// `block_size` is the block size of the cipher (see `Cipher::block_size`),
    /// or if `output.len() > c_int::max_value()`.
    pub fn update(&mut self, input: &[u8], output: &mut [u8]) -> Result<usize, ErrorStack> {
        unsafe {
            assert!(output.len() >= input.len() + self.block_size);
            assert!(output.len() <= c_int::max_value() as usize);
            let mut outl = output.len() as c_int;
            let inl = input.len() as c_int;

            try!(cvt(ffi::EVP_CipherUpdate(self.ctx,
                                           output.as_mut_ptr(),
                                           &mut outl,
                                           input.as_ptr(),
                                           inl)));

            Ok(outl as usize)
        }
    }

    /// Finishes the encryption/decryption process, writing any remaining data
    /// to `output`.
    ///
    /// The number of bytes written to `output` is returned.
    ///
    /// `update` should not be called after this method.
    ///
    /// # Panics
    ///
    /// Panics if `output` is less than the cipher's block size.
    pub fn finalize(&mut self, output: &mut [u8]) -> Result<usize, ErrorStack> {
        unsafe {
            assert!(output.len() >= self.block_size);
            let mut outl = cmp::min(output.len(), c_int::max_value() as usize) as c_int;

            try!(cvt(ffi::EVP_CipherFinal(self.ctx, output.as_mut_ptr(), &mut outl)));

            Ok(outl as usize)
        }
    }
}

impl Drop for Crypter {
    fn drop(&mut self) {
        unsafe {
            ffi::EVP_CIPHER_CTX_free(self.ctx);
        }
    }
}

/**
 * Encrypts data, using the specified crypter type in encrypt mode with the
 * specified key and iv; returns the resulting (encrypted) data.
 */
pub fn encrypt(t: Cipher,
               key: &[u8],
               iv: Option<&[u8]>,
               data: &[u8])
               -> Result<Vec<u8>, ErrorStack> {
    cipher(t, Mode::Encrypt, key, iv, data)
}

/**
 * Decrypts data, using the specified crypter type in decrypt mode with the
 * specified key and iv; returns the resulting (decrypted) data.
 */
pub fn decrypt(t: Cipher,
               key: &[u8],
               iv: Option<&[u8]>,
               data: &[u8])
               -> Result<Vec<u8>, ErrorStack> {
    cipher(t, Mode::Decrypt, key, iv, data)
}

fn cipher(t: Cipher,
          mode: Mode,
          key: &[u8],
          iv: Option<&[u8]>,
          data: &[u8])
          -> Result<Vec<u8>, ErrorStack> {
    let mut c = try!(Crypter::new(t, mode, key, iv));
    let mut out = vec![0; data.len() + t.block_size()];
    let count = try!(c.update(data, &mut out));
    let rest = try!(c.finalize(&mut out[count..]));
    out.truncate(count + rest);
    Ok(out)
}

#[cfg(ossl110)]
use ffi::{EVP_CIPHER_iv_length, EVP_CIPHER_block_size, EVP_CIPHER_key_length};

#[cfg(ossl10x)]
#[allow(bad_style)]
mod compat {
    use libc::c_int;
    use ffi::EVP_CIPHER;

    pub unsafe fn EVP_CIPHER_iv_length(ptr: *const EVP_CIPHER) -> c_int {
        (*ptr).iv_len
    }

    pub unsafe fn EVP_CIPHER_block_size(ptr: *const EVP_CIPHER) -> c_int {
        (*ptr).block_size
    }

    pub unsafe fn EVP_CIPHER_key_length(ptr: *const EVP_CIPHER) -> c_int {
        (*ptr).key_len
    }
}
#[cfg(ossl10x)]
use self::compat::*;

#[cfg(test)]
mod tests {
    use serialize::hex::{FromHex, ToHex};

    // Test vectors from FIPS-197:
    // http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
    #[test]
    fn test_aes_256_ecb() {
        let k0 = [0x00u8, 0x01u8, 0x02u8, 0x03u8, 0x04u8, 0x05u8, 0x06u8, 0x07u8, 0x08u8, 0x09u8,
                  0x0au8, 0x0bu8, 0x0cu8, 0x0du8, 0x0eu8, 0x0fu8, 0x10u8, 0x11u8, 0x12u8, 0x13u8,
                  0x14u8, 0x15u8, 0x16u8, 0x17u8, 0x18u8, 0x19u8, 0x1au8, 0x1bu8, 0x1cu8, 0x1du8,
                  0x1eu8, 0x1fu8];
        let p0 = [0x00u8, 0x11u8, 0x22u8, 0x33u8, 0x44u8, 0x55u8, 0x66u8, 0x77u8, 0x88u8, 0x99u8,
                  0xaau8, 0xbbu8, 0xccu8, 0xddu8, 0xeeu8, 0xffu8];
        let c0 = [0x8eu8, 0xa2u8, 0xb7u8, 0xcau8, 0x51u8, 0x67u8, 0x45u8, 0xbfu8, 0xeau8, 0xfcu8,
                  0x49u8, 0x90u8, 0x4bu8, 0x49u8, 0x60u8, 0x89u8];
        let mut c = super::Crypter::new(super::Cipher::aes_256_ecb(),
                                        super::Mode::Encrypt,
                                        &k0,
                                        None).unwrap();
        c.pad(false);
        let mut r0 = vec![0; c0.len() + super::Cipher::aes_256_ecb().block_size()];
        let count = c.update(&p0, &mut r0).unwrap();
        let rest = c.finalize(&mut r0[count..]).unwrap();
        r0.truncate(count + rest);
        assert_eq!(r0.to_hex(), c0.to_hex());

        let mut c = super::Crypter::new(super::Cipher::aes_256_ecb(),
                                        super::Mode::Decrypt,
                                        &k0,
                                        None).unwrap();
        c.pad(false);
        let mut p1 = vec![0; r0.len() + super::Cipher::aes_256_ecb().block_size()];
        let count = c.update(&r0, &mut p1).unwrap();
        let rest = c.finalize(&mut p1[count..]).unwrap();
        p1.truncate(count + rest);
        assert_eq!(p1.to_hex(), p0.to_hex());
    }

    #[test]
    fn test_aes_256_cbc_decrypt() {
        let iv = [4_u8, 223_u8, 153_u8, 219_u8, 28_u8, 142_u8, 234_u8, 68_u8, 227_u8, 69_u8,
                  98_u8, 107_u8, 208_u8, 14_u8, 236_u8, 60_u8];
        let data = [143_u8, 210_u8, 75_u8, 63_u8, 214_u8, 179_u8, 155_u8, 241_u8, 242_u8, 31_u8,
                    154_u8, 56_u8, 198_u8, 145_u8, 192_u8, 64_u8, 2_u8, 245_u8, 167_u8, 220_u8,
                    55_u8, 119_u8, 233_u8, 136_u8, 139_u8, 27_u8, 71_u8, 242_u8, 119_u8, 175_u8,
                    65_u8, 207_u8];
        let ciphered_data = [0x4a_u8, 0x2e_u8, 0xe5_u8, 0x6_u8, 0xbf_u8, 0xcf_u8, 0xf2_u8,
                             0xd7_u8, 0xea_u8, 0x2d_u8, 0xb1_u8, 0x85_u8, 0x6c_u8, 0x93_u8,
                             0x65_u8, 0x6f_u8];
        let mut cr = super::Crypter::new(super::Cipher::aes_256_cbc(),
                                         super::Mode::Decrypt,
                                         &data,
                                         Some(&iv)).unwrap();
        cr.pad(false);
        let mut unciphered_data = vec![0; data.len() + super::Cipher::aes_256_cbc().block_size()];
        let count = cr.update(&ciphered_data, &mut unciphered_data).unwrap();
        let rest = cr.finalize(&mut unciphered_data[count..]).unwrap();
        unciphered_data.truncate(count + rest);

        let expected_unciphered_data = b"I love turtles.\x01";

        assert_eq!(&unciphered_data, expected_unciphered_data);
    }

    fn cipher_test(ciphertype: super::Cipher, pt: &str, ct: &str, key: &str, iv: &str) {
        use serialize::hex::ToHex;

        let pt = pt.from_hex().unwrap();
        let ct = ct.from_hex().unwrap();
        let key = key.from_hex().unwrap();
        let iv = iv.from_hex().unwrap();

        let computed = super::decrypt(ciphertype, &key, Some(&iv), &ct).unwrap();
        let expected = pt;

        if computed != expected {
            println!("Computed: {}", computed.to_hex());
            println!("Expected: {}", expected.to_hex());
            if computed.len() != expected.len() {
                println!("Lengths differ: {} in computed vs {} expected",
                         computed.len(),
                         expected.len());
            }
            panic!("test failure");
        }
    }

    #[test]
    fn test_rc4() {

        let pt = "0000000000000000000000000000000000000000000000000000000000000000000000000000";
        let ct = "A68686B04D686AA107BD8D4CAB191A3EEC0A6294BC78B60F65C25CB47BD7BB3A48EFC4D26BE4";
        let key = "97CD440324DA5FD1F7955C1C13B6B466";
        let iv = "";

        cipher_test(super::Cipher::rc4(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes256_xts() {
        // Test case 174 from
        // http://csrc.nist.gov/groups/STM/cavp/documents/aes/XTSTestVectors.zip
        let pt = "77f4ef63d734ebd028508da66c22cdebdd52ecd6ee2ab0a50bc8ad0cfd692ca5fcd4e6dedc45df7f\
                  6503f462611dc542";
        let ct = "ce7d905a7776ac72f240d22aafed5e4eb7566cdc7211220e970da634ce015f131a5ecb8d400bc9e8\
                  4f0b81d8725dbbc7";
        let key = "b6bfef891f83b5ff073f2231267be51eb084b791fa19a154399c0684c8b2dfcb37de77d28bbda3b\
                   4180026ad640b74243b3133e7b9fae629403f6733423dae28";
        let iv = "db200efb7eaaa737dbdf40babb68953f";

        cipher_test(super::Cipher::aes_256_xts(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes128_ctr() {

        let pt = "6BC1BEE22E409F96E93D7E117393172AAE2D8A571E03AC9C9EB76FAC45AF8E5130C81C46A35CE411\
                  E5FBC1191A0A52EFF69F2445DF4F9B17AD2B417BE66C3710";
        let ct = "874D6191B620E3261BEF6864990DB6CE9806F66B7970FDFF8617187BB9FFFDFF5AE4DF3EDBD5D35E\
                  5B4F09020DB03EAB1E031DDA2FBE03D1792170A0F3009CEE";
        let key = "2B7E151628AED2A6ABF7158809CF4F3C";
        let iv = "F0F1F2F3F4F5F6F7F8F9FAFBFCFDFEFF";

        cipher_test(super::Cipher::aes_128_ctr(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes128_cfb1() {
        // Lifted from http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf

        let pt = "6bc1";
        let ct = "68b3";
        let key = "2b7e151628aed2a6abf7158809cf4f3c";
        let iv = "000102030405060708090a0b0c0d0e0f";

        cipher_test(super::Cipher::aes_128_cfb1(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes128_cfb128() {

        let pt = "6bc1bee22e409f96e93d7e117393172a";
        let ct = "3b3fd92eb72dad20333449f8e83cfb4a";
        let key = "2b7e151628aed2a6abf7158809cf4f3c";
        let iv = "000102030405060708090a0b0c0d0e0f";

        cipher_test(super::Cipher::aes_128_cfb128(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes128_cfb8() {

        let pt = "6bc1bee22e409f96e93d7e117393172aae2d";
        let ct = "3b79424c9c0dd436bace9e0ed4586a4f32b9";
        let key = "2b7e151628aed2a6abf7158809cf4f3c";
        let iv = "000102030405060708090a0b0c0d0e0f";

        cipher_test(super::Cipher::aes_128_cfb8(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes256_cfb1() {

        let pt = "6bc1";
        let ct = "9029";
        let key = "603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4";
        let iv = "000102030405060708090a0b0c0d0e0f";

        cipher_test(super::Cipher::aes_256_cfb1(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes256_cfb128() {

        let pt = "6bc1bee22e409f96e93d7e117393172a";
        let ct = "dc7e84bfda79164b7ecd8486985d3860";
        let key = "603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4";
        let iv = "000102030405060708090a0b0c0d0e0f";

        cipher_test(super::Cipher::aes_256_cfb128(), pt, ct, key, iv);
    }

    #[test]
    fn test_aes256_cfb8() {

        let pt = "6bc1bee22e409f96e93d7e117393172aae2d";
        let ct = "dc1f1a8520a64db55fcc8ac554844e889700";
        let key = "603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4";
        let iv = "000102030405060708090a0b0c0d0e0f";

        cipher_test(super::Cipher::aes_256_cfb8(), pt, ct, key, iv);
    }

    #[test]
    fn test_des_cbc() {

        let pt = "54686973206973206120746573742e";
        let ct = "6f2867cfefda048a4046ef7e556c7132";
        let key = "7cb66337f3d3c0fe";
        let iv = "0001020304050607";

        cipher_test(super::Cipher::des_cbc(), pt, ct, key, iv);
    }

    #[test]
    fn test_des_ecb() {

        let pt = "54686973206973206120746573742e";
        let ct = "0050ab8aecec758843fe157b4dde938c";
        let key = "7cb66337f3d3c0fe";
        let iv = "0001020304050607";

        cipher_test(super::Cipher::des_ecb(), pt, ct, key, iv);
    }
}