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use crate::dht::Did;

use super::payload::MessageRelay;
use super::payload::MessageRelayMethod;
use super::types::Message;

// A -> B -> C
// B handle_find_success relay with SEND contains
// {
//     from_path: [A]
//     to_path: [B]
// }
// if find successor on B, then return relay with REPORT
// then A get relay contains
// {
//     from_path: [B],
//     to_path: [A]
// }
// otherwise, send to C with relay with SEND contains
// {
//    from_path: [A, B]
//    to_path: [B, C]
// }
// if find successor on C, than return relay with REPORT
// then B get relay contains
// {
//    from_path: [B, C]
//    to_path: [A, B]
// }
pub trait MessageSessionRelayProtocol {
    fn find_prev(&self) -> Option<Did>;
    fn push_prev(&mut self, current: Did, prev: Did);
    fn next_hop(&mut self, current: Did, next: Did);
    fn add_to_path(&mut self, node: Did);
    fn add_from_path(&mut self, node: Did);
    fn remove_to_path(&mut self) -> Option<Did>;
    fn remove_from_path(&mut self) -> Option<Did>;
}

impl MessageSessionRelayProtocol for MessageRelay<Message> {
    #[inline]
    fn find_prev(&self) -> Option<Did> {
        match self.method {
            MessageRelayMethod::SEND => {
                if !self.from_path.is_empty() {
                    self.from_path.back().cloned()
                } else {
                    None
                }
            }
            MessageRelayMethod::REPORT => {
                if !self.to_path.is_empty() {
                    self.to_path.back().cloned()
                } else {
                    None
                }
            }
            _ => unreachable!(),
        }
    }

    #[inline]
    fn push_prev(&mut self, current: Did, prev: Did) {
        match self.method {
            MessageRelayMethod::SEND => {
                self.from_path.push_back(prev);
            }
            MessageRelayMethod::REPORT => {
                assert_eq!(self.to_path.pop_back(), Some(current));
                self.from_path.push_back(prev);
            }
            _ => unreachable!(),
        }
    }

    #[inline]
    fn next_hop(&mut self, current: Did, next: Did) {
        match self.method {
            MessageRelayMethod::SEND => {
                self.to_path.push_back(next);
                self.from_path.push_back(current);
            }
            MessageRelayMethod::REPORT => unimplemented!(),
            _ => unreachable!(),
        };
    }

    #[inline]
    fn add_to_path(&mut self, node: Did) {
        self.to_path.push_back(node);
    }

    #[inline]
    fn add_from_path(&mut self, node: Did) {
        self.from_path.push_back(node);
    }

    #[inline]
    fn remove_to_path(&mut self) -> Option<Did> {
        if !self.to_path.is_empty() {
            self.to_path.pop_back()
        } else {
            None
        }
    }

    #[inline]
    fn remove_from_path(&mut self) -> Option<Did> {
        if !self.from_path.is_empty() {
            self.from_path.pop_back()
        } else {
            None
        }
    }
}