#![feature(return_position_impl_trait_in_trait)]
use std::{
    future::Future,
    sync::Arc,
    time::{SystemTime, UNIX_EPOCH},
};

use common::{
    msg::{MessageHeader, Output},
    msg_id::{gen_msg_id, MessageID},
    run_server, Handler,
};
use rand::{thread_rng, Rng};
use serde::{Deserialize, Serialize};

fn main() {
    run_server::<UniqueIdsHandler>()
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type")]
enum UniqueIdsBody {
    #[serde(rename = "generate")]
    Generate { msg_id: MessageID },

    #[serde(rename = "generate_ok")]
    GenerateOk {
        msg_id: MessageID,
        in_reply_to: MessageID,
        id: u128,
    },
}

struct UniqueIdsHandler {
    output: Output<UniqueIdsBody>,
}

impl Handler for UniqueIdsHandler {
    type Body = UniqueIdsBody;

    fn init(_node_id: String, _node_ids: Vec<String>, output: Output<Self::Body>) -> Self {
        Self { output }
    }

    fn handle<'a>(
        self: &'a Arc<Self>,
        header: MessageHeader,
        body: Self::Body,
    ) -> impl Future<Output = ()> + Send + 'a {
        async move {
            match body {
                UniqueIdsBody::Generate { msg_id } => {
                    let id = gen_id();
                    self.output
                        .send(
                            &header.src,
                            &UniqueIdsBody::GenerateOk {
                                msg_id: gen_msg_id(),
                                in_reply_to: msg_id,
                                id,
                            },
                        )
                        .await;
                }
                UniqueIdsBody::GenerateOk { .. } => (),
            };
        }
    }
}

fn gen_id() -> u128 {
    // Time since UNIX epoch in milliseconds
    let now = SystemTime::now();
    let time_millis: u128 = now.duration_since(UNIX_EPOCH).unwrap().as_millis();

    // 80 bits of randomness
    let rand1: u16 = thread_rng().gen();
    let rand2: u64 = thread_rng().gen();
    let rand: u128 = rand1 as u128 | ((rand2 as u128) << 64);

    (time_millis << 80) | rand
}