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use super::*;
use crypto::encryption::EncryptionKeypair;

use sodiumoxide;

trait Export<I, O> {
    fn export(&self, id: &I) -> SdaClientResult<Option<O>>;
}

pub trait SignExport<I, O>
    where O: Clone + ::std::fmt::Debug + PartialEq + ::serde::Serialize + ::serde::Deserialize
{
    fn sign_export(&self, signer: &Agent, id: &I) -> SdaClientResult<Option<Signed<O>>>;
}

pub trait SignatureVerification<O> {
    fn signature_is_valid(&self, object: &O) -> SdaClientResult<bool>;
}

/// Description of a signature keypair.
#[derive(Debug, Serialize, Deserialize)]
pub struct SignatureKeypair {
    pub vk: VerificationKey,
    pub sk: SigningKey,
}


impl KeyGeneration<VerificationKeyId> for CryptoModule {
    fn new_key(&self) -> SdaClientResult<VerificationKeyId> {
        // generate
        let (vk, sk) = sodiumoxide::crypto::sign::gen_keypair();
        let wrapped_vk = VerificationKey::Sodium(vk.0.into());
        let wrapped_sk = SigningKey::Sodium(sk.0.into());

        // save
        let keypair = SignatureKeypair { vk: wrapped_vk, sk: wrapped_sk };
        let id = VerificationKeyId::random();
        self.keystore.put(&id, &keypair)?;

        Ok(id)
    }
}


impl KeyGeneration<Labelled<VerificationKeyId, VerificationKey>> for CryptoModule {
    fn new_key(&self) -> SdaClientResult<Labelled<VerificationKeyId, VerificationKey>> {
        // generate key
        let key_id: VerificationKeyId = self.new_key()?;

        // export public part, assuming that it is there since we just created it and haven't failed
        let key: VerificationKey = self.export(&key_id)?.expect("Recently created key not found");

        Ok(Labelled {
            id: key_id,
            body: key,
        })
    }
}


impl Export<VerificationKeyId, VerificationKey> for CryptoModule {
    fn export(&self, id: &VerificationKeyId) -> SdaClientResult<Option<VerificationKey>> {
        let keypair: Option<SignatureKeypair> = self.keystore.get(id)?;
        match keypair {
            None => Ok(None),
            Some(keypair) => Ok(Some(keypair.vk))
        }
    }
}


impl SignExport<EncryptionKeyId, Labelled<EncryptionKeyId, EncryptionKey>> for CryptoModule {
    fn sign_export(&self, signer: &Agent, id: &EncryptionKeyId) -> SdaClientResult<Option<Signed<Labelled<EncryptionKeyId, EncryptionKey>>>> {
        // message
        let encryption_keypair: Option<EncryptionKeypair> = self.keystore.get(id)?;
        let message_to_be_signed = match encryption_keypair {
            None => { return Ok(None) },
            Some(encryption_keypair) => {
                Labelled {
                    id: id.clone(),
                    body: encryption_keypair.ek,
                }
            }
        };
        // signature
        let signature_keypair: Option<SignatureKeypair> = self.keystore.get(&signer.verification_key.id)?;
        let signature = match signature_keypair {
            None => { return Ok(None) },
            Some(SignatureKeypair{ sk: SigningKey::Sodium(raw_sk), .. }) => {
                let sk = sodiumoxide::crypto::sign::SecretKey(*raw_sk);
                let msg = &message_to_be_signed.canonical()?;
                let signature = sodiumoxide::crypto::sign::sign_detached(msg, &sk);
                Signature::Sodium(signature.0.into())
            }
        };
        // wrapper
        Ok(Some(Signed {
            signature: signature,
            signer: signer.id().clone(),
            body: message_to_be_signed,
        }))
    }
}


impl<M> SignatureVerification<Signed<M>> for Agent
    where M: Clone + ::std::fmt::Debug + PartialEq + ::serde::Serialize + ::serde::Deserialize
{
    fn signature_is_valid(&self, signed: &Signed<M>) -> SdaClientResult<bool> {

        // FIXME remember result to avoid running verification more than once

        if signed.signer != self.id {
            Err("Agent differs from claimed signer")?
        }

        let wrapped_sig = &signed.signature;
        let wrapped_vk = &self.verification_key.body;

        match (wrapped_vk, wrapped_sig) {

            (&VerificationKey::Sodium(raw_vk), &Signature::Sodium(raw_sig)) => {
                let sig = sodiumoxide::crypto::sign::Signature(*raw_sig);
                let vk = sodiumoxide::crypto::sign::PublicKey(*raw_vk);
                let msg = signed.body.canonical()?;
                let is_valid = sodiumoxide::crypto::sign::verify_detached(&sig, &*msg, &vk);
                Ok(is_valid)
            }

        }
    }
}