async-backplane 0.1.1

use crate::{DeviceID, Line};

pub type Drain<'a, T> = std::vec::Drain<'a, T>;

#[derive(Clone, Debug, Eq, PartialEq)]
pub(crate) enum LineOp {
    Attach(Line),
    Detach(DeviceID),
}

#[derive(Debug)]
pub(crate) struct LineMap {
    inner: Inner,
}

#[derive(Debug)]
enum Inner {
    Small(Small),
    // Large,
}

#[derive(Debug, Default)]
struct Small {
    inner: Vec<(DeviceID, Option<Line>)>,
}

impl LineMap {

    pub fn new() -> Self { LineMap{ inner: Inner::Small(Small::default()) } }

    pub fn apply(&mut self, op: LineOp) {
        match op {
            LineOp::Attach(line) => { self.attach(line); }
            LineOp::Detach(did) => { self.detach(did); }
        }
    }

    /// Returns whether the line was found and overwritten.
    pub fn attach(&mut self, line: Line) -> bool {
        match self.inner {
            Inner::Small(ref mut small) => small.attach(line),
        }
    }

    /// Returns whether the item was found and deleted.
    pub fn detach(&mut self, did: DeviceID) -> bool {
        match self.inner {
            Inner::Small(ref mut small) => small.detach(did),
        }
    }

    pub fn drain(&mut self) -> Drain<(DeviceID, Option<Line>)> {
        match self.inner {
            Inner::Small(ref mut small) => small.inner.drain(..),
        }
    }

}

impl Small {

    fn attach(&mut self, line: Line) -> bool {
        let line_did = line.device_id();
        let mut last_free: Option<usize> = None;
        for (idx, (did, ref mut loon)) in self.inner.iter_mut().enumerate() {
            if *did == line_did {
                *loon = Some(line);
                return true;
            } else if loon.is_none() {
                last_free = Some(idx);
                continue;
            }
        }
        if let Some(free) = last_free {
            self.inner[free] = (line_did, Some(line));
        } else {
            self.inner.push((line_did, Some(line)));
        }
        false
    }

    fn detach(&mut self, did: DeviceID) -> bool {
        let count = self.inner.len();
        for (idx, (did2, ref mut loon)) in self.inner.iter_mut().enumerate() {
            if did == *did2 {
                if idx == (count - 1) {
                    self.inner.pop();
                } else {
                    *loon = None;
                }
                return true;
            }
        }
        false
    }
}