diff --git a/day7/Cargo.toml b/day7/Cargo.toml
new file mode 100644
index 0000000..3812153
--- /dev/null
+++ b/day7/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "day7"
+version = "0.1.0"
+authors = ["Avril <flanchan@cumallover.me>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+generational-arena = "0.2.8"
diff --git a/day7/src/bag.rs b/day7/src/bag.rs
new file mode 100644
index 0000000..3ce43fc
--- /dev/null
+++ b/day7/src/bag.rs
@@ -0,0 +1,103 @@
+use std::{
+    mem,
+    ops,
+    hash::{Hash, Hasher,},
+};
+use generational_arena::{
+    Arena,
+    Index,
+};
+
+#[derive(Debug, Clone, Eq)]
+pub struct Bag
+{
+    name: String,
+    contains: Vec<Index>,
+}
+
+impl Hash for Bag {
+    #[inline] fn hash<H: Hasher>(&self, state: &mut H) {
+	self.as_ref().hash(state)
+    }
+}
+
+impl<T> PartialEq<T> for Bag
+where T: AsRef<BagRef>
+{
+    fn eq(&self, other: &T) -> bool
+    {
+	self.as_ref() == other.as_ref()
+    }
+}
+
+impl Bag
+{
+    pub fn new(name: String) -> Self
+    {
+	Self {
+	    name,
+	    contains: Vec::new(),
+	}
+    }
+    pub fn push_contents(&mut self, idx: Index)
+    {
+	self.contains.push(idx)
+    }
+    pub fn bags_in<'a>(&'a self, w: &'a Arena<Bag>) -> impl Iterator<Item = &'a BagRef> + 'a
+    {
+	self.contains.iter().filter_map(move |x| w.get(x.clone())).map(Self::as_ref)
+    }
+    pub fn contains_in(&self, w: &Arena<Bag>,  bag: impl AsRef<BagRef>) -> bool
+    {
+	for x in self.bags_in(w)
+	{
+	    if x == bag.as_ref() {
+		return true;
+	    }
+	}
+	false
+    }
+    
+}
+
+impl AsRef<BagRef> for Bag
+{
+    #[inline] fn as_ref(&self) -> &BagRef
+    {
+	BagRef::new_unchecked(&self.name[..])
+    }
+}
+
+impl ops::Deref for Bag
+{
+    type Target = BagRef;
+    #[inline] fn deref(&self) -> &Self::Target {
+	self.as_ref()
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Hash)]
+#[repr(transparent)]
+pub struct BagRef
+{
+    name: str
+}
+
+impl AsRef<BagRef> for BagRef
+{
+    #[inline] fn as_ref(&self) -> &BagRef
+    {
+	self
+    }
+}
+
+
+impl BagRef
+{
+    #[inline] fn new_unchecked<'a>(from: &'a str) -> &'a BagRef
+    {
+	unsafe {
+	    mem::transmute(from)
+	}
+    }
+}
diff --git a/day7/src/main.rs b/day7/src/main.rs
new file mode 100644
index 0000000..1c0436f
--- /dev/null
+++ b/day7/src/main.rs
@@ -0,0 +1,10 @@
+#![feature(str_split_once)]
+
+#![allow(dead_code)]
+
+mod parse;
+mod bag;
+
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/day7/src/parse.rs b/day7/src/parse.rs
new file mode 100644
index 0000000..4d7ac98
--- /dev/null
+++ b/day7/src/parse.rs
@@ -0,0 +1,109 @@
+use std::{
+    io::{
+	self, BufRead,
+    },
+    sync::{
+	mpsc,
+    },
+    thread,
+    marker::*,
+    collections::{HashMap, HashSet,},
+};
+use generational_arena::{
+    Arena, Index,
+};
+use super::bag;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+struct Rule
+{
+    contents: Vec<(usize, String)>,
+}
+
+fn parse_rest(from: mpsc::Receiver<String>) -> HashMap<String, Rule>
+{
+    let mut out = HashMap::new();
+    while let Ok(line) = from.recv() {
+	
+    }
+    out
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+struct UnlinkedBag<'a>
+{
+    name: &'a str,
+    cont: Rule,
+}
+
+enum MaybeLinked<'a>
+{
+    Unlinked(UnlinkedBag<'a>),
+    Linked(bag::Bag),
+}
+
+pub fn parse<R: BufRead>(from: R) -> Result<Arena<bag::Bag>, io::Error>
+{
+    let mut all_possible = HashSet::<String>::new();
+    let (tx, rx) = mpsc::channel();
+    let w = thread::spawn(move || parse_rest(rx));
+    
+    macro_rules! unwrap {
+	(? $opt:expr) => {
+	    match $opt {
+		Some(v) => v,
+		_ => continue,
+	    }
+	};
+	($res:expr) => {
+	    unwrap!(? $res.ok())
+	}
+    }
+    for line in from.lines()
+    {
+	let mut line = line?;
+
+	let irest = {
+	    const SPLIT: &str = "bags contain";
+	    let bn = {
+		let idx = unwrap!(? line.find(SPLIT));
+		&line[..idx]
+	    };
+	    all_possible.insert(bn.trim().to_owned());
+	};
+	unwrap!(tx.send(line));
+    }
+    let (mut unlinked, nref) = {
+	let mut ulinks = w.join().unwrap();
+	let mut unlinked = Arena::with_capacity(all_possible.len());
+	let mut nref = HashMap::new();
+	for name in all_possible.iter()
+	{
+	    let urule = ulinks.remove(name).unwrap();
+	    let idx = unlinked.insert(MaybeLinked::Unlinked(UnlinkedBag{name, cont: urule}));
+	    nref.insert(name, idx);
+	}
+	(unlinked, nref)
+    };
+
+    let indecies: Vec<_> = unlinked.iter().map(|(i, _)| i).collect();
+    for idx in indecies.into_iter()
+    {
+	let current = unlinked.get_mut(idx).unwrap();
+	let linked = match current {
+	    MaybeLinked::Unlinked(UnlinkedBag{name, cont: rule}) => {
+		let mut linking = bag::Bag::new(name.to_owned());
+		for (_, cont) in rule.contents.iter() {
+		    linking.push_contents(*nref.get(cont).unwrap());
+		}
+		linking
+	    },
+	    _=> continue,
+	};
+	*current = MaybeLinked::Linked(linked);
+    }
+
+    //TODO: how tf can we convert from Arena<MaybeLinked<_>> into Arena<_>?????
+    
+    todo!()
+}