/*
 * Copyright (C) 2025 - 2026, Stephan Mueller <smueller@chronox.de>
 *
 * License: see LICENSE file in root directory
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

use crate::error::KemError;
use crate::ffi::leancrypto;
use std::ptr;
use std::sync::atomic;

#[derive(Debug, Copy, Clone)]
pub enum lcr_kyber_type {
    lcr_kyber_512,
    lcr_kyber_768,
    lcr_kyber_1024,
}

/// Leancrypto wrapper for lc_kyber
pub struct lcr_kyber {
    // Context
    //kyber_ctx: *mut leancrypto::lc_kyber_ctx,
    /// Kyber shared secret
    ss: leancrypto::lc_kyber_ss,

    /// Kyber public key
    pk: leancrypto::lc_kyber_pk,

    /// Kyber secret key
    sk: leancrypto::lc_kyber_sk,

    /// Kyber cipher text
    ct: leancrypto::lc_kyber_ct,

    pk_set: bool,
    sk_set: bool,
    ct_set: bool,
    ss_set: bool,
}

#[allow(dead_code)]
impl lcr_kyber {
    pub fn new() -> Self {
        lcr_kyber {
            //kyber_ctx: ptr::null_mut(),
            pk: unsafe { std::mem::zeroed() },
            sk: unsafe { std::mem::zeroed() },
            ct: unsafe { std::mem::zeroed() },
            ss: unsafe { std::mem::zeroed() },
            pk_set: false,
            sk_set: false,
            ct_set: false,
            ss_set: false,
        }
    }

    /// Load secret key for using with leancrypto
    ///
    /// # Arguments
    ///
    /// * `sk_buf` buffer with raw secret key
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn sk_load(
        &mut self,
        sk_buf: &[u8],
    ) -> Result<(), KemError> {
        // No check for self.sk_set == false as we allow overwriting
        // of existing key.

        let result = unsafe {
            leancrypto::lc_kyber_sk_load(
                &mut self.sk,
                sk_buf.as_ptr(),
                sk_buf.len(),
            )
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.sk_set = true;

        Ok(())
    }

    /// Load secret key seed for using with leancrypto
    ///
    /// # Arguments
    ///
    /// * `sk_seed_buf` buffer with raw secret key seed
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or SignatureError on error
    pub fn sk_seed_load(
        &mut self,
        sk_seed_buf: &[u8],
        kyber_type: lcr_kyber_type,
    ) -> Result<(), KemError> {
        // No check for self.sk_set == false as we allow overwriting
        // of existing key.

        let result = unsafe {
            leancrypto::lc_kyber_keypair_from_seed(
                &mut self.pk,
                &mut self.sk,
                sk_seed_buf.as_ptr(),
                sk_seed_buf.len(),
                Self::lcr_kyber_type_mapping(kyber_type),
            )
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.sk_set = true;
        self.pk_set = true;

        Ok(())
    }

    /// Load public key for using with leancrypto
    ///
    /// # Arguments
    ///
    /// * `pk_buf` buffer with raw public key
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn pk_load(
        &mut self,
        pk_buf: &[u8],
    ) -> Result<(), KemError> {
        // No check for self.pk_set == false as we allow overwriting
        // of existing key.

        let result = unsafe {
            leancrypto::lc_kyber_pk_load(
                &mut self.pk,
                pk_buf.as_ptr(),
                pk_buf.len(),
            )
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.pk_set = true;

        Ok(())
    }

    /// Load ML-KEM ciphertext using with leancrypto
    ///
    /// # Arguments
    ///
    /// * `ct_buf` buffer with raw ML-KEM ciphertext
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn ct_load(
        &mut self,
        ct_buf: &[u8],
    ) -> Result<(), KemError> {
        // No check for self.ct_set == false as we allow overwriting
        // of existing key.

        let result = unsafe {
            leancrypto::lc_kyber_ct_load(
                &mut self.ct,
                ct_buf.as_ptr(),
                ct_buf.len(),
            )
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.ct_set = true;

        Ok(())
    }

    /// Load ML-KEM shared secret using with leancrypto
    ///
    /// # Arguments
    ///
    /// * `ss_buf` buffer with raw ML-KEM shared secret
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn ss_load(
        &mut self,
        ss_buf: &[u8],
    ) -> Result<(), KemError> {
        // No check for self.ss_set == false as we allow overwriting
        // of existing key.

        let result = unsafe {
            leancrypto::lc_kyber_ss_load(
                &mut self.ss,
                ss_buf.as_ptr(),
                ss_buf.len(),
            )
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.ss_set = true;

        Ok(())
    }

    /// Mapping of lcr_kyber_type to leancrypto ML-KEM implementation type
    ///
    /// # Returns
    ///
    /// * Returns leancrypto ML-KEM implementation type
    fn lcr_kyber_type_mapping(kyber_type: lcr_kyber_type) -> u32 {
        match kyber_type {
            lcr_kyber_type::lcr_kyber_512 => {
                leancrypto::lc_kyber_type_LC_KYBER_512
            }
            lcr_kyber_type::lcr_kyber_768 => {
                leancrypto::lc_kyber_type_LC_KYBER_768
            }
            lcr_kyber_type::lcr_kyber_1024 => {
                leancrypto::lc_kyber_type_LC_KYBER_1024
            }
        }
    }

    /// Generate ML-KEM key pair
    ///
    /// # Arguments
    ///
    /// * `kyber_type` ML-KEM type to generate key pair for
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn keypair(
        &mut self,
        kyber_type: lcr_kyber_type,
    ) -> Result<(), KemError> {
        let result = unsafe {
            leancrypto::lc_kyber_keypair(
                &mut self.pk,
                &mut self.sk,
                leancrypto::lc_seeded_rng,
                Self::lcr_kyber_type_mapping(kyber_type),
            )
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.sk_set = true;
        self.pk_set = true;

        Ok(())
    }

    /// Decapsulate message
    ///
    /// The ciphertext and the secret key must be already loaded. Upon
    /// success, the shared secret is present and can be retrieved.
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn decapsulate(&mut self) -> Result<(), KemError> {
        if self.sk_set == false || self.ct_set == false {
            return Err(KemError::UninitializedContext);
        }

        let result = unsafe {
            leancrypto::lc_kyber_dec(&mut self.ss, &self.ct, &self.sk)
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.ss_set = true;

        Ok(())
    }

    /// Encapsulate message
    ///
    /// The publick key must be already loaded. Upon success, the shared
    /// secret and the ciphertext are present and can be retrieved.
    ///
    /// # Returns
    ///
    /// * Returns Ok() on success or KemError on error
    pub fn encapsulate(&mut self) -> Result<(), KemError> {
        if self.pk_set == false {
            return Err(KemError::UninitializedContext);
        }

        let result = unsafe {
            leancrypto::lc_kyber_enc(&mut self.ct, &mut self.ss, &self.pk)
        };
        if result < 0 {
            return Err(KemError::ProcessingError);
        }

        self.ct_set = true;
        self.ss_set = true;

        Ok(())
    }

    /// Method for safe immutable access to ML-KEM ciphertext buffer
    ///
    /// # Returns
    ///
    /// * Returns Ok() with the ciphertext on success or KemError on error
    pub fn get_ct(&mut self) -> Result<&[u8], KemError> {
        if self.ct_set == false {
            return Err(KemError::UninitializedContext);
        }

        let mut ptr: *mut u8 = ptr::null_mut();
        let mut len: usize = 0;

        let result = unsafe {
            leancrypto::lc_kyber_ct_ptr(&mut ptr, &mut len, &mut self.ct)
        };
        if result < 0 || ptr == ptr::null_mut() {
            return Err(KemError::ProcessingError);
        }

        let slice = unsafe { std::slice::from_raw_parts(ptr, len) };

        Ok(&slice)
    }

    /// Method for safe immutable access to ML-KEM secret key
    ///
    /// # Returns
    ///
    /// * Returns Ok() with the secret key on success or KemError on error
    pub fn get_sk(&mut self) -> Result<&[u8], KemError> {
        if self.sk_set == false {
            return Err(KemError::UninitializedContext);
        }

        let mut ptr: *mut u8 = ptr::null_mut();
        let mut len: usize = 0;

        let result = unsafe {
            leancrypto::lc_kyber_sk_ptr(&mut ptr, &mut len, &mut self.sk)
        };
        if result < 0 || ptr == ptr::null_mut() {
            return Err(KemError::ProcessingError);
        }

        let slice = unsafe { std::slice::from_raw_parts(ptr, len) };

        Ok(&slice)
    }

    /// Method for safe immutable access to ML-KEM public key
    ///
    /// # Returns
    ///
    /// * Returns Ok() with the public key on success or KemError on error
    pub fn get_pk(&mut self) -> Result<&[u8], KemError> {
        if self.pk_set == false {
            return Err(KemError::UninitializedContext);
        }

        let mut ptr: *mut u8 = ptr::null_mut();
        let mut len: usize = 0;

        let result = unsafe {
            leancrypto::lc_kyber_pk_ptr(&mut ptr, &mut len, &mut self.pk)
        };
        if result < 0 || ptr == ptr::null_mut() {
            return Err(KemError::ProcessingError);
        }

        let slice = unsafe { std::slice::from_raw_parts(ptr, len) };

        Ok(&slice)
    }

    /// Method for safe immutable access to ML-KEM shared secret
    ///
    /// # Returns
    ///
    /// * Returns Ok() with the shared secret on success or KemError on error
    pub fn get_ss(&mut self) -> Result<&[u8], KemError> {
        if self.ss_set == false {
            return Err(KemError::UninitializedContext);
        }

        let mut ptr: *mut u8 = ptr::null_mut();
        let mut len: usize = 0;

        let result = unsafe {
            leancrypto::lc_kyber_ss_ptr(&mut ptr, &mut len, &mut self.ss)
        };
        if result < 0 || ptr == ptr::null_mut() {
            return Err(KemError::ProcessingError);
        }

        let slice = unsafe { std::slice::from_raw_parts(ptr, len) };

        Ok(&slice)
    }
}

/// This ensures the sensitive buffers are always zeroized
/// regardless of when it goes out of scope
impl Drop for lcr_kyber {
    fn drop(&mut self) {
        let sk: leancrypto::lc_kyber_sk = unsafe { std::mem::zeroed() };

        unsafe { std::ptr::write_volatile(&mut self.sk, sk) };
        atomic::compiler_fence(atomic::Ordering::SeqCst);

        let ct: leancrypto::lc_kyber_ct = unsafe { std::mem::zeroed() };

        unsafe { std::ptr::write_volatile(&mut self.ct, ct) };
        atomic::compiler_fence(atomic::Ordering::SeqCst);

        let ss: leancrypto::lc_kyber_ss = unsafe { std::mem::zeroed() };

        unsafe { std::ptr::write_volatile(&mut self.ss, ss) };
        atomic::compiler_fence(atomic::Ordering::SeqCst);
    }
}
