Get appending at the end of the rope to work

editor-challenge/Cargo.toml

@@ -15,5 +15,5 @@ tui         = { version = "0.19", default-features = false, features = [ "crosst
 
 [[bin]]
 name = "bench"
-main = "bin/bench.rs"
-features = [ "bench" ]
+# main = "bin/bench.rs"
+# features = [ "bench" ]

editor-challenge/src/doc_rope.rs

@@ -0,0 +1,269 @@
+use std::{mem, ops::Deref};
+
+const CHUNK_SIZE: usize = 10;
+
+#[derive(Clone, Copy, Debug)]
+struct NodeId(usize);
+
+impl Deref for NodeId {
+    type Target = usize;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+#[derive(Debug)]
+enum Node {
+    Interior {
+        // the number of characters to the left of this node
+        // the number of lines to the left of this node
+        char_count: usize,
+
+        left: Option<NodeId>,
+        right: Option<NodeId>,
+    },
+    Leaf(LeafNode),
+}
+
+impl Node {
+    fn len(&self) -> usize {
+        match self {
+            Node::Interior { char_count, .. } => 0,
+            Node::Leaf(ln) => ln.len(),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct LeafNode(String);
+
+impl LeafNode {
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    fn take(&mut self) -> String {
+        let content = mem::replace(&mut self.0, "".to_owned());
+        content
+    }
+
+    fn as_str(&self) -> &str {
+        &self.0
+    }
+}
+
+impl From<String> for LeafNode {
+    fn from(s: String) -> Self {
+        Self(s)
+    }
+}
+
+/// A Rope is a regular tree which adds on some extra behavior for dealing with a continuous data
+/// structure. In this case, the nodes all contain strings, and the rope is arranged such that a
+/// depth-first traversal will yield the entire contents of the rope in proper order.
+#[derive(Debug)]
+pub struct Rope {
+    node_count: usize,
+    contents: Vec<Option<Node>>,
+}
+
+impl Rope {
+    /// Insert text at an index within the document. loc is the number of characters from the
+    /// beginning.
+    pub fn insert_at(&mut self, loc: usize, text: String) {
+        match self.find_insertion_node_id(loc) {
+            None => {
+                let node = Node::Leaf(LeafNode::from(text));
+                self.node_count += 1;
+                self.contents.push(Some(node));
+            }
+            Some(id) => {
+                self.insert_at_node(id, text);
+            }
+        }
+    }
+
+    /// Append text to the end of the document.
+    pub fn append(&mut self, text: String) {
+        self.insert_at(self.len(), text);
+    }
+
+    /// Convert the entire rope back to a continuous String.
+    pub fn to_string(&self) -> String {
+        if self.contents.is_empty() {
+            return "".to_owned();
+        }
+
+        let mut r = String::new();
+        let mut stack = vec![NodeId(0)];
+
+        while let Some(current_id) = stack.pop() {
+            let node = &self.contents[*current_id];
+            match node {
+                Some(Node::Interior { left, right, .. }) => {
+                    if let Some(right_id) = *right {
+                        stack.push(right_id);
+                    }
+                    if let Some(left_id) = *left {
+                        stack.push(left_id);
+                    }
+                }
+                Some(Node::Leaf(ln)) => r.push_str(ln.as_str()),
+                None => panic!("Should never leave an empty space in the node list"),
+            }
+        }
+
+        r
+    }
+
+    /// Calculate the length of the stored string.
+    pub fn len(&self) -> usize {
+        // This can be optimized later. Do a traversal of each right node. We already have
+        // character counts of each left tree. Only count the length of the final right leaf.
+        self.contents.iter().fold(0, |acc, node| {
+            if let Some(Node::Leaf(s)) = node {
+                acc + s.len()
+            } else {
+                acc
+            }
+        })
+    }
+
+    #[cfg(test)]
+    fn max_depth(&self) -> usize {
+        unimplemented!();
+    }
+
+    #[cfg(test)]
+    fn node_count(&self) -> usize {
+        self.node_count
+    }
+
+    // Find the node ID of the insertion point. This is not fully implemented, in that this
+    // function ignores the offset from the beginning. Because of that, it is also always inserting
+    // onto the right side, and never traversing down the left.
+    fn find_insertion_node_id(&self, _loc: usize) -> Option<NodeId> {
+        let mut current_id = NodeId(0);
+        loop {
+            match self.contents.get(*current_id) {
+                Some(Some(Node::Interior { ref right, .. })) => match right {
+                    Some(id) => current_id = *id,
+                    None => return Some(current_id),
+                },
+                Some(Some(Node::Leaf(_))) => return Some(current_id),
+                Some(None) => panic!("There should never be an empty node in the tree"),
+                // This only happens when the list is empty. Otherwise, we're detecting the None in
+                // advance.
+                None => return None,
+            }
+        }
+    }
+
+    // Insert text at a particular node location.
+    //
+    // This is not a self-balancing operation (yet). Once we know where text needs to be inserted,
+    // based on the offset from the beginning, we can grab that node and either replace it (if it
+    // is a Leaf node) or update it (if it is an Interior node).
+    //
+    // This function is currently naive, in that it will always assume that text needs to be added
+    // to the right side, which may not be correct.
+    fn insert_at_node(&mut self, id: NodeId, text: String) {
+        match self.contents[*id] {
+            Some(Node::Interior { ref mut right, .. }) => {
+                let new_node = Node::Leaf(LeafNode::from(text));
+                let new_node_id = NodeId(self.node_count + 1);
+
+                *right = Some(new_node_id);
+                self.contents.push(Some(new_node));
+
+                self.node_count += 1;
+            }
+            Some(Node::Leaf(_)) => {
+                let Some(Node::Leaf(mut ln)) = mem::replace(&mut self.contents[*id], None) else {
+                    panic!("Should never leave an empty space in the node list")
+                };
+                let contents = ln.take();
+
+                let lnode = Node::Leaf(LeafNode::from(contents));
+                let rnode = Node::Leaf(LeafNode::from(text));
+
+                let lnode_id = self.node_count;
+                let rnode_id = self.node_count + 1;
+
+                let interior_node = Node::Interior {
+                    char_count: lnode.len(),
+                    left: Some(NodeId(lnode_id)),
+                    right: Some(NodeId(rnode_id)),
+                };
+
+                let _ = mem::replace(&mut self.contents[*id], Some(interior_node));
+
+                self.node_count += 2;
+                self.contents.push(Some(lnode));
+                self.contents.push(Some(rnode));
+
+            }
+            None => panic!("Should never leave an empty space in the node list"),
+        }
+    }
+}
+
+impl Default for Rope {
+    fn default() -> Self {
+        Self {
+            node_count: 0,
+            contents: vec![],
+        }
+    }
+}
+
+// Populate the initial rope. The simplest way is to split along lines and turn each line into its
+// own leaf node.
+impl From<String> for Rope {
+    fn from(s: String) -> Self {
+        let mut rope = Rope::default();
+        #[allow(unused_assignments)]
+        let mut first = s.as_str();
+        let mut lst = s.as_str();
+
+        while lst.len() > CHUNK_SIZE {
+            (first, lst) = lst.split_at(CHUNK_SIZE);
+            rope.append(first.to_owned());
+        }
+        rope.append(lst.to_owned());
+        rope
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    struct TestCase {
+        content: String,
+    }
+
+    #[test]
+    fn it_creates_a_rope_from_a_string() {
+        let test_cases = vec![
+            TestCase{ content: "".to_owned() },
+            TestCase{ content: "This".to_owned() },
+            TestCase{ content: "This is some basic".to_owned() },
+            TestCase{ content: "This is some basic context which is much smaller".to_owned() },
+            TestCase{ content:
+            "This is some basic context which is much smaller than the rope is designed for."
+                .to_owned()
+            },
+        ];
+
+        for case in test_cases {
+            let rope = Rope::from(case.content.clone());
+
+            for (idx, node) in rope.contents.iter().enumerate() {
+            }
+
+            assert_eq!(rope.len(), case.content.len(), "{}", case.content);
+            assert_eq!(rope.to_string(), case.content, "{:?}", case.content);
+        }
+    }
+}

editor-challenge/src/lib.rs

@@ -1,3 +1,4 @@
+pub mod doc_rope;
 pub mod ui;
 pub mod state;
 pub mod types;

editor-challenge/src/types.rs

@@ -14,6 +14,10 @@ impl Document {
         Self { rows: contents }
     }
 
+    pub fn line(&self, id: usize) -> Option<&str> {
+        self.rows.get(id).map(|x| x.as_str())
+    }
+
     pub fn contents(&self) -> String {
         self.rows.join("\n")
     }
@@ -117,7 +121,7 @@ mod test_utils {
         time::{Duration, Instant},
     };
 
-    pub fn with_file<F>(test: F)
+    pub fn with_moby_dick<F>(test: F)
     where
         F: FnOnce(Document),
     {
@@ -163,12 +167,18 @@ mod test {
 
     #[test]
     fn it_inserts_a_line() {
-        with_file(|mut doc| {
+        with_moby_dick(|mut doc| {
             let mut cursor = Cursor::default();
 
             let num_lines = doc.row_count();
+            assert_eq!(
+                doc.line(num_lines - 3),
+                Some("subscribe to our email newsletter to hear about new eBooks.")
+            );
+
             doc.new_line(&mut cursor);
             assert_eq!(doc.row_count(), num_lines + 1);
+            assert_eq!(doc.line(0), Some(""));
         });
     }
 }
@@ -177,7 +187,7 @@ pub mod bench {
     use super::{test_utils::*, *};
 
     pub fn bench_insert_lines() {
-        with_file(|doc| {
+        with_moby_dick(|doc| {
             let performance = benchmark(
                 1000,
                 || doc.clone(),