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//! # 网络层
//!
//! 网络层(net)规定了数据包格式(Packet)，负责维护路由表

mod history;
pub mod packet;
mod route;

use crate::id::*;
use crate::link::Link;
use crate::protocol;
use core::sync::atomic::{AtomicU8, Ordering};
use heapless::Vec;
use log::{info, warn};
use packet::{Field, Packet};
use route::Routes;
use spin::RwLock;

lazy_static! {
    static ref SN: AtomicU8 = AtomicU8::new({
        let mut data: [u8; 1] = [0; 1];
        getrandom::getrandom(&mut data).unwrap();
        data[0]
    });
    static ref CFG: RwLock<Config> = RwLock::new(Config {
        id: Id::default(),
        relay: false,
    });
    /// 路由表
    static ref ROUTES: RwLock<Routes> = RwLock::new(Routes::new());
}

/// 配置
struct Config {
    /// 本设备ID
    id: Id,
    /// 转发开关
    relay: bool,
}

/// 设置本机ID
pub fn set_id(id: Id) {
    CFG.write().id = id;
}
/// 读取本机ID
pub fn get_id() -> Id {
    return CFG.read().id.clone();
}
/// 设置中继开关
pub fn set_relay(relay: bool) {
    CFG.write().relay = relay;
}
/// 通用发送函数
fn send_common(
    packet: &mut Packet,
    dst: Option<&Id>,
    dst_link: Option<Link>,
    origin: Option<Link>,
) {
    let id: &Id = if let Some(id) = dst {
        let buf: Vec<_, _> = id.into();
        packet.set_var(Field::Dst, &buf);
        id
    } else {
        &packet.dst
    };
    if let None = dst_link {
        history::add(&packet);
        let buf = packet.to_buf();
        if let Ok(_) = ROUTES.write().sendto(id, &buf, origin) {
            return;
        }
        if let Err(_) = ROUTES.write().sendto(&ID_PARENT, &buf, origin) {
            warn!("unmp can't find router.");
        }
    } else {
        let link = dst_link.unwrap();
        if let Some(origin) = origin {
            if origin == link {
                return;
            }
        }
        history::add(&packet);
        let err = link.send(&packet.to_buf());
        if let Err(_) = err {
            ROUTES.write().remove(id, link);
        }
    }
}
/// 发送数据包到指定设备
pub fn send(protocol: u8, data: &[u8], id: Option<&Id>, link: Option<Link>) {
    let mut packet = Packet::new();
    packet.sn = SN.fetch_add(1, Ordering::Relaxed);
    packet.set_var(Field::Protocol, &[protocol]);
    packet.set_var(Field::Data, data);
    let id_buf: Vec<_, _> = (&CFG.read().id).into();
    packet.set_var(Field::Src, &id_buf);
    packet.set_var(Field::Ttl, &[8]);
    send_common(&mut packet, id, link, None);
}
/// 发送数据包到所有链路
pub fn broadcast(protocol: u8, data: &[u8]) {
    let mut packet = Packet::new();
    packet.sn = SN.fetch_add(1, Ordering::Relaxed);
    packet.set_var(Field::Protocol, &[protocol]);
    packet.set_var(Field::Data, data);
    let id_buf: Vec<_, _> = (&CFG.read().id).into();
    packet.set_var(Field::Src, &id_buf);
    let id_buf: Vec<_, _> = (&ID_CHILD).into();
    packet.set_var(Field::Dst, &id_buf);
    packet.set_var(Field::Ttl, &[0]);
    let buf = packet.to_buf();
    Link::broadcast(&buf);
}
/// 收到了数据包
pub fn when_recv(link: Link, buf: &[u8]) {
    info!("{} recv:{:02X?}.", link, buf);
    let packet = Packet::try_from_buf(buf);
    let mut packet = if let Ok(packet) = packet {
        packet
    } else {
        return;
    };

    if history::has(&packet) {
        return;
    }

    if packet.src != ID_PARENT && packet.src != ID_CHILD {
        connect(&packet.src, link);
    }

    if packet.dst == CFG.read().id || packet.dst == ID_PARENT || packet.dst == ID_CHILD {
        protocol::distribute(packet.protocol, &packet.src, &packet.data);
    } else if CFG.read().relay {
        if packet.ttl > 0 {
            packet.set_var(Field::Ttl, &[packet.ttl - 1]);
            send_common(&mut packet, None, None, Some(link));
        } else {
            info!("unmp TTL is 0.");
        }
    }
}
/// 更新路由
pub fn connect(id: &Id, link: Link) {
    ROUTES.write().add(id, link);
}