From 3a07eae54ff7ffee98f134e5721cbad7b322a847 Mon Sep 17 00:00:00 2001
From: mehbark <terezi@pyrope.net>
Date: Sat, 4 Oct 2025 15:23:49 -0400
Subject: [PATCH] finish huffman

---
 src/huffman.rs | 82 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 61 insertions(+), 21 deletions(-)

diff --git a/src/huffman.rs b/src/huffman.rs
index 62070b0..061fc42 100644
--- a/src/huffman.rs
+++ b/src/huffman.rs
@@ -21,12 +21,22 @@ impl CompressionScheme for Huffman {
 
         let tree = Node::build(&counts)?;
 
+        for &byte in src {
+            tree.encode_byte(byte, buf);
+        }
+
         Some(tree)
     }
 
-    fn decode(src: &BitSlice, header: &Self::Header, buf: &mut Vec<u8>) {
-        if let Some(node) = header {
-            todo!()
+    fn decode(mut src: &BitSlice, header: &Self::Header, buf: &mut Vec<u8>) {
+        let Some(header) = header else {
+            // no header means an empty source
+            return;
+        };
+
+        while let Some((byte, rest)) = header.decode_byte(src) {
+            buf.push(byte);
+            src = rest;
         }
     }
 
@@ -38,7 +48,7 @@ impl CompressionScheme for Huffman {
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum Node {
     Leaf { byte: u8 },
-    Branch { left: Box<Self>, right: Box<Self> },
+    Branch { path0: Box<Self>, path1: Box<Self> },
 }
 
 impl Node {
@@ -52,18 +62,48 @@ impl Node {
     /// Panics if called with a byte that was not passed to [`build`].
     fn encode_byte(&self, byte: u8, buf: &mut BitVec) {
         let mut current = self;
-        todo!()
+        loop {
+            match current {
+                Node::Leaf { byte: _ } => break,
+                Node::Branch { path0, path1 } => {
+                    // TODO: this contains check is wasteful. be less dumb?
+                    if path0.contains(byte) {
+                        buf.push(false);
+                        current = path0;
+                    } else {
+                        buf.push(true);
+                        current = path1;
+                    }
+                }
+            }
+        }
     }
 
-    /// Return the next encoded byte in the stream of bits.
-    fn decode_byte(src: &BitSlice) -> Option<u8> {
-        todo!()
+    /// Return the next encoded byte in a stream of bits and the rest of the bits.
+    fn decode_byte<'a>(&self, src: &'a BitSlice) -> Option<(u8, &'a BitSlice)> {
+        match self {
+            Node::Leaf { byte } => Some((*byte, src)),
+            Node::Branch { path0, path1 } => {
+                if *src.first()? {
+                    path1.decode_byte(&src[1..])
+                } else {
+                    path0.decode_byte(&src[1..])
+                }
+            }
+        }
+    }
+
+    fn contains(&self, byte: u8) -> bool {
+        match self {
+            Node::Leaf { byte: b } => *b == byte,
+            Node::Branch { path0, path1 } => path0.contains(byte) || path1.contains(byte),
+        }
     }
 
     fn byte_size(&self) -> usize {
         match self {
             Node::Leaf { .. } => 1,
-            Node::Branch { left, right, .. } => 1 + left.byte_size() + right.byte_size(),
+            Node::Branch { path0, path1, .. } => 1 + path0.byte_size() + path1.byte_size(),
         }
     }
 
@@ -73,10 +113,10 @@ impl Node {
         }
         match self {
             Node::Leaf { byte } => writeln!(f, "| {:?}", *byte as char),
-            Node::Branch { left, right } => {
+            Node::Branch { path0, path1 } => {
                 writeln!(f, "{depth}+")?;
-                left.write_depth(f, depth + 1)?;
-                right.write_depth(f, depth + 1)
+                path0.write_depth(f, depth + 1)?;
+                path1.write_depth(f, depth + 1)
             }
         }
     }
@@ -96,8 +136,8 @@ enum WeightedNode {
     },
     Branch {
         count: u32,
-        left: Box<Self>,
-        right: Box<Self>,
+        path0: Box<Self>,
+        path1: Box<Self>,
     },
 }
 
@@ -126,20 +166,20 @@ impl WeightedNode {
         }
     }
 
-    fn join(left: Self, right: Self) -> Self {
+    fn join(path0: Self, path1: Self) -> Self {
         Self::Branch {
-            count: left.count() + right.count(),
-            left: Box::new(left),
-            right: Box::new(right),
+            count: path0.count() + path1.count(),
+            path0: Box::new(path0),
+            path1: Box::new(path1),
         }
     }
 
     fn unburden(self) -> Node {
         match self {
             WeightedNode::Leaf { byte, .. } => Node::Leaf { byte },
-            WeightedNode::Branch { left, right, .. } => Node::Branch {
-                left: Box::new(left.unburden()),
-                right: Box::new(right.unburden()),
+            WeightedNode::Branch { path0, path1, .. } => Node::Branch {
+                path0: Box::new(path0.unburden()),
+                path1: Box::new(path1.unburden()),
             },
         }
     }