//! Connection handling and send/receive queues

pub mod handshake;
mod packet;
pub mod socket;

use ::std::{sync::Arc, vec::Vec};

pub use crate::connection::{
    handshake::Handshake,
    packet::{ConnectionID as ID, Packet, PacketData},
};

use crate::enc::{
    hkdf::HkdfSha3,
    sym::{CipherKind, CipherRecv, CipherSend},
};

/// strong typedef for receiving connection id
#[derive(Debug, Copy, Clone)]
pub struct IDRecv(pub ID);
/// strong typedef for sending connection id
#[derive(Debug, Copy, Clone)]
pub struct IDSend(pub ID);

/// Version of the fenrir protocol in use
#[derive(::num_derive::FromPrimitive, Debug, Copy, Clone)]
#[repr(u8)]
pub enum ProtocolVersion {
    /// First Fenrir Protocol Version
    V0 = 0,
}
impl ProtocolVersion {
    /// actual length of the protocol version field
    pub const fn len() -> usize {
        1
    }
    /// Serialize into raw bytes
    pub fn serialize(&self, out: &mut u8) {
        *out = *self as u8;
    }
}

/// A single connection and its data
#[derive(Debug)]
pub struct Connection {
    /// Receiving Connection ID
    pub id_recv: IDRecv,
    /// Sending Connection ID
    pub id_send: IDSend,
    /// The main hkdf used for all secrets in this connection
    pub hkdf: HkdfSha3,
    /// Cipher for decrypting data
    pub cipher_recv: CipherRecv,
    /// Cipher for encrypting data
    pub cipher_send: CipherSend,
}

/// Role: used to set the correct secrets
/// * Server: Connection is Incoming
/// * Client: Connection is Outgoing
#[derive(Debug, Copy, Clone)]
#[repr(u8)]
pub enum Role {
    /// Server: we receive the connection
    Server = 0,
    /// Client: we initate the connection
    Client,
}

impl Connection {
    pub(crate) fn new(
        hkdf: HkdfSha3,
        cipher: CipherKind,
        role: Role,
        rand: &::ring::rand::SystemRandom,
    ) -> Self {
        let (secret_recv, secret_send) = match role {
            Role::Server => {
                (hkdf.get_secret(b"to_server"), hkdf.get_secret(b"to_client"))
            }
            Role::Client => {
                (hkdf.get_secret(b"to_client"), hkdf.get_secret(b"to_server"))
            }
        };
        let mut cipher_recv = CipherRecv::new(cipher, secret_recv);
        let mut cipher_send = CipherSend::new(cipher, secret_send, rand);

        Self {
            id_recv: IDRecv(ID::Handshake),
            id_send: IDSend(ID::Handshake),
            hkdf,
            cipher_recv,
            cipher_send,
        }
    }
}

// PERF: Arc<RwLock<ConnList>> loks a bit too much, need to find
// faster ways to do this
pub(crate) struct ConnList {
    connections: Vec<Option<Arc<Connection>>>,
    /// Bitmap to track which connection ids are used or free
    ids_used: Vec<::bitmaps::Bitmap<1024>>,
}

impl ConnList {
    pub(crate) fn new() -> Self {
        let mut bitmap_id = ::bitmaps::Bitmap::<1024>::new();
        bitmap_id.set(0, true); // ID(0) == handshake
        Self {
            connections: Vec::with_capacity(128),
            ids_used: vec![bitmap_id],
        }
    }
    pub(crate) fn reserve_first(
        &mut self,
        mut conn: Connection,
    ) -> Arc<Connection> {
        // uhm... bad things are going on here:
        // * id must be initialized, but only because:
        // * rust does not understand that after the `!found` id is always
        //   initialized
        // * `ID::new_u64` is really safe only with >0, but here it always is
        // ...we should probably rewrite it in better, safer rust
        let mut id: u64 = 0;
        let mut found = false;
        for (i, b) in self.ids_used.iter_mut().enumerate() {
            match b.first_false_index() {
                Some(idx) => {
                    b.set(idx, true);
                    id = ((i as u64) * 1024) + (idx as u64);
                    found = true;
                    break;
                }
                None => {}
            }
        }
        if !found {
            let mut new_bitmap = ::bitmaps::Bitmap::<1024>::new();
            new_bitmap.set(0, true);
            id = (self.ids_used.len() as u64) * 1024;
            self.ids_used.push(new_bitmap);
        }
        let new_id = IDRecv(ID::new_u64(id));
        conn.id_recv = new_id;
        let conn = Arc::new(conn);
        if (self.connections.len() as u64) < id {
            self.connections.push(Some(conn.clone()));
        } else {
            // very probably redundant
            self.connections[id as usize] = Some(conn.clone());
        }
        conn
    }
}