use std::io::Read;

use bytes::Bytes;
use p256::EncodedPoint;
use p256::ecdsa::{
    Signature, SigningKey, VerifyingKey,
    signature::{Signer, Verifier},
};
use rand_core::OsRng;
use sha2::{Digest, Sha256};

///
/// contains the ecdsa private key, the ecdsa public key and the username
///
///
pub struct CryptographicSignature {
    priv_key: SigningKey,
    pub pub_key: VerifyingKey,
    pub username: String,
}

impl CryptographicSignature {
    ///
    /// creates a CryptographicSignature
    ///
    pub fn new(username: String) -> CryptographicSignature {
        // generate a private key
        let priv_key = SigningKey::random(&mut OsRng);
        // extract the public key from the private key
        let pub_key = VerifyingKey::from(&priv_key);
        // return the new struct
        CryptographicSignature {
            priv_key: priv_key,
            pub_key: pub_key,
            username: username,
        }
    }
}

///
/// returns a string representing the pub_key as a String
///
pub fn formatPubKey(crypto_pair: CryptographicSignature) -> String {
    let encoded_point = crypto_pair.pub_key.to_encoded_point(false);
    let pubkey_bytes = encoded_point.as_bytes();
    hex::encode(pubkey_bytes)
}

pub async fn get_peer_key(username: &String) -> Result<VerifyingKey, reqwest::Error> {
    let client = reqwest::Client::new();
    let uri = format!("https://jch.irif.fr:8443/peers/{}/key", username);
    let res = client.get(uri).send().await?;
    if res.status().is_success() {
        println!("Successfully retreived the peers key.");
    } else {
        eprintln!(
            "Failed to get the peers key from the server. Status: {}",
            res.status()
        );
    }
    let body: Bytes = res.bytes().await?;
    let slice: &[u8] = body.as_ref();
    let body_bytes: &[u8; 64] = slice.try_into().expect("size error");
    let received_key = convert_verifyingkey(body_bytes);
    Ok(received_key)
}

fn convert_verifyingkey(raw_xy: &[u8; 64]) -> VerifyingKey {
    let mut sec1 = [0u8; 65];
    sec1[0] = 0x04;
    sec1[1..].copy_from_slice(raw_xy);

    let ep = EncodedPoint::from_bytes(&sec1).expect("invalid point bytes");
    let pk = VerifyingKey::from_encoded_point(&ep).expect("invalid encoded point");
    VerifyingKey::from(pk)
}

pub fn verify_signature(pubkey: VerifyingKey, message: &Vec<u8>) -> bool {
    let length_bytes: [u8; 2] = message[5..7].try_into().expect("Taille incorrecte");
    let length = u16::from_be_bytes(length_bytes);
    println!("message length: {}", length);
    let msg_to_hash = &message[..length as usize + 7];
    let signature_bytes = &message[length as usize + 7..length as usize + 7 + 64];
    println!("conversion start");
    let sig = match Signature::from_bytes(signature_bytes.try_into().expect("conversion error")) {
        Ok(s) => s,
        Err(_) => return false,
    };
    println!("conversion done");
    match pubkey.verify(&msg_to_hash, &sig) {
        Ok(()) => true,
        Err(_) => false,
    }
}

///
/// takes a serialized message and adds the signature using the private key
///
pub fn sign_message(crypto_pair: &CryptographicSignature, message: &Vec<u8>) -> Vec<u8> {
    let length_bytes: [u8; 2] = message[5..7]
        .try_into()
        .expect("slice with incorrect length");
    let msg_length = u16::from_be_bytes(length_bytes);
    println!(
        "message to serialize: {:?}",
        &message[..7 + msg_length as usize]
    );
    let digest = Sha256::digest(&message[..7 + msg_length as usize]);
    let signature = crypto_pair.priv_key.sign_prehash_recoverable(&digest);

    let message_length = 7 + msg_length as usize + 64;
    let mut signed_message = Vec::with_capacity(message_length);
    println!("{}", message_length);
    signed_message.extend_from_slice(&message[..7 + msg_length as usize]);
    println!("signed_tmp:{:?}", signed_message);
    match signature {
        Ok(signature) => {
            let r = signature.0.r();
            let s = signature.0.s();

            let r_bytes = r.to_bytes(); // Returns a GenericArray/bytes object
            let s_bytes = s.to_bytes();
            signed_message.extend_from_slice(&r_bytes[..32]);
            signed_message.extend_from_slice(&s_bytes[..32]);
            println!("signed:{:?}, len: {}", signed_message, signed_message.len());
            signed_message
        }
        Err(e) => {
            panic!("error");
        }
    }
}

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

    ///
    /// creates a cryptographic signature
    ///
    #[test]
    fn creating_cryptographic_signature() {
        let username = String::from("gamixtreize");
        let crypto_pair = CryptographicSignature::new(username);
        let formatted_pubkey = formatPubKey(crypto_pair);
        println!("pubkey : {}", formatted_pubkey);
    }

    /*#[test]
    fn signing_message() {
        let username = String::from("gamixtreize");
        let crypto_pair = CryptographicSignature::new(username.clone());
        let handshake = HandshakeMessage::hello(0, 12, username);
        let ser = handshake.serialize();
        let signed_message = sign_message(&crypto_pair, &ser);
        println!("unsigned_message: {:?}", ser);
        println!("signed_message: {:?}", signed_message);
    }*/
}