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use crate::{Address, Node, Topic, Nodes};
use serde::{Deserialize, Serialize};
use std::collections::HashSet;

#[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum Selection {
    Topic { topic: Topic },
    Any,
}

pub struct ViewBuilder {
    event_origin: Option<Address>,

    selection: Selection,

    view: HashSet<Address>,
}

impl ViewBuilder {
    pub fn new(selection: Selection) -> Self {
        Self {
            event_origin: None,
            selection,
            view: HashSet::new(),
        }
    }

    pub fn with_origin(&mut self, origin: Address) -> &Self {
        self.event_origin = Some(origin);
        self
    }

    pub fn origin(&self) -> Option<&Address> {
        self.event_origin.as_ref()
    }

    pub fn selection(&self) -> &Selection {
        &self.selection
    }

    pub fn add(&mut self, node: &mut Node) {
        if let Selection::Topic { topic } = self.selection() {
            node.logs_mut().use_of(*topic);
        }

        self.view.insert(node.address().clone());
    }

    pub(crate) fn build(self, nodes: &mut Nodes) -> Vec<Address> {
        let mut result = Vec::with_capacity(self.view.len());

        for address in self.view {
            // this is necessary to refresh the LRU cache
            let _ = nodes.get(&address);
            result.push(address);
        }

        result
    }
}