//! WASM-compatible cryptographic implementations

use bip39::Mnemonic;
use ed25519_dalek::{SigningKey, SECRET_KEY_LENGTH};
use chacha20poly1305::{aead::{Aead, KeyInit}, XChaCha20Poly1305, Key, XNonce};
use hkdf::Hkdf;
use sha2::Sha256;

use crate::domain::entities::*;
use crate::domain::error::DomainError;
use crate::domain::traits::*;
use crate::infrastructure::rng;
use crate::infrastructure::time;
use super::shared::*;

#[derive(Clone)]
pub struct Bip39MnemonicGenerator;

impl MnemonicGenerator for Bip39MnemonicGenerator {
    type Error = DomainError;

    fn generate(&self) -> Result<RecoveryPhrase, Self::Error> {
        let mut entropy = [0u8; 32];
        let mut rng = rng::new_rng();
        rng.fill_bytes(&mut entropy)?;

        let mnemonic = Mnemonic::from_entropy(&entropy)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to generate mnemonic: {}", e)))?;

        let words: Vec<String> = mnemonic.words().into_iter().map(|s| s.to_string()).collect();
        Ok(RecoveryPhrase::new(words))
    }

    fn validate(&self, words: &[String]) -> Result<(), Self::Error> {
        let phrase = words.join(" ");
        Mnemonic::parse(&phrase)
            .map_err(|e| DomainError::InvalidMnemonic(format!("Invalid mnemonic: {}", e)))?;
        Ok(())
    }
}

#[derive(Clone)]
pub struct Ed25519KeyDeriver;

impl KeyDeriver for Ed25519KeyDeriver {
    type Error = DomainError;

    fn derive_from_seed(&self, seed: &Seed) -> Result<(PublicKey, PrivateKey), Self::Error> {
        validate_seed_length(seed.as_bytes())?;

        let signing_key = SigningKey::from_bytes(&seed.as_bytes()[..SECRET_KEY_LENGTH].try_into()
            .map_err(|_| DomainError::CryptographicError("Invalid seed length".to_string()))?);

        let verifying_key = signing_key.verifying_key();

        Ok((
            PublicKey(verifying_key.to_bytes().to_vec()),
            PrivateKey(signing_key.to_bytes().to_vec()),
        ))
    }

    fn derive_from_mnemonic(&self, mnemonic: &RecoveryPhrase, univ_id: &str) -> Result<Seed, Self::Error> {
        let phrase = mnemonic.words().join(" ");
        let bip39_mnemonic = Mnemonic::parse(&phrase)
            .map_err(|e| DomainError::InvalidMnemonic(format!("Invalid mnemonic: {}", e)))?;

        // Use univ_id as passphrase to bind seed to universe
        let bip39_seed = bip39_mnemonic.to_seed(univ_id);

        // BIP39 produces 64-byte seed, but we only need 32 bytes for Ed25519
        // Use the first 32 bytes of the BIP39 seed
        let ed25519_seed: [u8; 32] = bip39_seed[..32]
            .try_into()
            .map_err(|_| DomainError::CryptographicError("Failed to extract 32-byte seed from BIP39 seed".to_string()))?;

        Ok(Seed::new(ed25519_seed.to_vec()))
    }
}

#[derive(Clone)]
pub struct XChaCha20FileEncryptor;

impl FileEncryptor for XChaCha20FileEncryptor {
    type Error = DomainError;

    fn encrypt(
        &self,
        seed: &Seed,
        password: &str,
        public_key: &PublicKey,
        did: &Did,
        univ_id: &str,
        user_profiles: &[UserProfile],
        date_of_birth: &Option<DateOfBirth>,
        default_user_profile_id: &Option<String>,
    ) -> Result<PassportFile, Self::Error> {
        // Generate salt and nonce using WASM-compatible RNG
        let mut salt = [0u8; SALT_LENGTH];
        let mut nonce_bytes = [0u8; NONCE_LENGTH];
        let mut rng = rng::new_rng();
        rng.fill_bytes(&mut salt)?;
        rng.fill_bytes(&mut nonce_bytes)?;

        // Derive KEK from password using HKDF
        let hk = Hkdf::<Sha256>::new(Some(&salt), password.as_bytes());
        let mut kek = [0u8; 32];
        hk.expand(KDF_INFO, &mut kek)
            .map_err(|e| DomainError::CryptographicError(format!("HKDF failed: {}", e)))?;

        // Encrypt seed
        let cipher = XChaCha20Poly1305::new(&Key::from(kek));
        let nonce = XNonce::from_slice(&nonce_bytes);
        let enc_seed = cipher
            .encrypt(&nonce, seed.as_bytes())
            .map_err(|e| DomainError::CryptographicError(format!("Encryption failed: {}", e)))?;

        // Serialize and encrypt user profiles
        let user_profiles_vec: Vec<UserProfile> = user_profiles.to_vec();
        let user_profiles_bytes = serde_cbor::to_vec(&user_profiles_vec)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to serialize user profiles: {}", e)))?;
        let enc_user_profiles = cipher
            .encrypt(&nonce, &*user_profiles_bytes)
            .map_err(|e| DomainError::CryptographicError(format!("User profiles encryption failed: {}", e)))?;

        // Serialize and encrypt date of birth
        let date_of_birth_bytes = serde_cbor::to_vec(&date_of_birth)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to serialize date of birth: {}", e)))?;
        let enc_date_of_birth = cipher
            .encrypt(&nonce, &*date_of_birth_bytes)
            .map_err(|e| DomainError::CryptographicError(format!("Date of birth encryption failed: {}", e)))?;

        // Serialize and encrypt default user profile ID
        let default_user_profile_id_bytes = serde_cbor::to_vec(&default_user_profile_id)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to serialize default user profile ID: {}", e)))?;
        let enc_default_user_profile_id = cipher
            .encrypt(&nonce, &*default_user_profile_id_bytes)
            .map_err(|e| DomainError::CryptographicError(format!("Default user profile ID encryption failed: {}", e)))?;

        // Get current timestamp using WASM-compatible time
        let created_at = time::now_seconds()?;

        Ok(PassportFile {
            enc_seed,
            kdf: KDF_HKDF_SHA256.to_string(),
            cipher: CIPHER_XCHACHA20_POLY1305.to_string(),
            salt: salt.to_vec(),
            nonce: nonce_bytes.to_vec(),
            public_key: public_key.0.clone(),
            did: did.0.clone(),
            univ_id: univ_id.to_string(),
            created_at,
            version: "1.0.0".to_string(),
            enc_user_profiles,
            enc_date_of_birth,
            enc_default_user_profile_id,
        })
    }

    fn decrypt(
        &self,
        file: &PassportFile,
        password: &str,
    ) -> Result<(Seed, PublicKey, PrivateKey, Vec<UserProfile>, Option<DateOfBirth>, Option<String>), Self::Error> {
        // Validate file format
        validate_file_format(&file.kdf, &file.cipher)?;

        // Derive KEK from password
        let hk = Hkdf::<Sha256>::new(Some(&file.salt), password.as_bytes());
        let mut kek = [0u8; 32];
        hk.expand(KDF_INFO, &mut kek)
            .map_err(|e| DomainError::CryptographicError(format!("HKDF failed: {}", e)))?;

        // Decrypt seed
        let cipher = XChaCha20Poly1305::new(&Key::from(kek));
        let nonce = XNonce::from_slice(&file.nonce);
        let seed_bytes = cipher
            .decrypt(&nonce, &*file.enc_seed)
            .map_err(|e| DomainError::CryptographicError(format!("Decryption failed: {}", e)))?;

        let seed = Seed::new(seed_bytes);

        // Re-derive keys from seed to verify
        let key_deriver = Ed25519KeyDeriver;
        let (public_key, private_key) = key_deriver.derive_from_seed(&seed)?;

        // Verify public key matches
        if public_key.0 != file.public_key {
            return Err(DomainError::CryptographicError(
                "Public key mismatch - wrong password?".to_string(),
            ));
        }

        // Decrypt user profiles
        let user_profiles_bytes = cipher
            .decrypt(&nonce, &*file.enc_user_profiles)
            .map_err(|e| DomainError::CryptographicError(format!("User profiles decryption failed: {}", e)))?;
        let user_profiles: Vec<UserProfile> = serde_cbor::from_slice(&user_profiles_bytes)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to deserialize user profiles: {}", e)))?;

        // Decrypt date of birth
        let date_of_birth_bytes = cipher
            .decrypt(&nonce, &*file.enc_date_of_birth)
            .map_err(|e| DomainError::CryptographicError(format!("Date of birth decryption failed: {}", e)))?;
        let date_of_birth: Option<DateOfBirth> = serde_cbor::from_slice(&date_of_birth_bytes)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to deserialize date of birth: {}", e)))?;

        // Decrypt default user profile ID
        let default_user_profile_id_bytes = cipher
            .decrypt(&nonce, &*file.enc_default_user_profile_id)
            .map_err(|e| DomainError::CryptographicError(format!("Default user profile ID decryption failed: {}", e)))?;
        let default_user_profile_id: Option<String> = serde_cbor::from_slice(&default_user_profile_id_bytes)
            .map_err(|e| DomainError::CryptographicError(format!("Failed to deserialize default user profile ID: {}", e)))?;

        // Note: univ_id is stored in the PassportFile and will be used when creating the Passport
        Ok((seed, public_key, private_key, user_profiles, date_of_birth, default_user_profile_id))
    }
}