Add support for Unicode input

note: a better approach is here https://github.com/quantonganh/snippets-ls
ref: https://github.com/helix-editor/helix/issues/1438
ref: https://github.com/helix-editor/helix/pull/2852

Co-authored-by: Linden Krouse <ztaticnull@gmail.com>

3 files changed, 442 insertions, 0 deletions

diff --git a/helix-view/src/digraph.rs b/helix-view/src/digraph.rs
new file mode 100644
index 00000000..257bd7c5
--- /dev/null
+++ b/helix-view/src/digraph.rs
@@ -0,0 +1,437 @@
+use anyhow::Result;
+use serde::{ser::SerializeMap, Deserialize, Serialize};
+use std::collections::HashMap;
+
+// Errors
+#[derive(PartialEq, Eq, Debug, Clone)]
+pub enum Error {
+    EmptyInput(String),
+    DuplicateEntry {
+        seq: String,
+        current: String,
+        existing: String,
+    },
+    Custom(String),
+}
+
+impl serde::de::Error for Error {
+    fn custom<T>(msg: T) -> Self
+    where
+        T: std::fmt::Display,
+    {
+        Error::Custom(msg.to_string())
+    }
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Error::EmptyInput(s) => {
+                f.write_str(&format!("No symbols were given for key sequence {}", s))
+            }
+            Error::DuplicateEntry {
+                seq,
+                current,
+                existing,
+            } => f.write_str(&format!(
+                "Attempted to bind {} to symbols ({}) when already bound to ({})",
+                seq, current, existing
+            )),
+            Error::Custom(s) => f.write_str(s),
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+
+/// Trie implementation for storing and searching input
+/// strings -> unicode characters defined by the user.
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+pub struct DigraphStore {
+    head: DigraphNode,
+}
+
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+struct DigraphNode {
+    output: Option<FullDigraphEntry>,
+    children: Option<HashMap<char, DigraphNode>>,
+}
+
+#[derive(Default, Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct DigraphEntry {
+    pub symbols: String,
+    pub description: Option<String>,
+}
+
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+pub struct FullDigraphEntry {
+    pub sequence: String,
+    pub symbols: String,
+    pub description: Option<String>,
+}
+
+impl<'de> Deserialize<'de> for DigraphStore {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        #[serde(untagged)]
+        enum EntryDef {
+            Full(DigraphEntry),
+            Symbols(String),
+        }
+
+        let mut store = Self::default();
+        HashMap::<String, EntryDef>::deserialize(deserializer)?
+            .into_iter()
+            .map(|(k, d)| match d {
+                EntryDef::Symbols(symbols) => (
+                    k,
+                    DigraphEntry {
+                        symbols,
+                        description: None,
+                    },
+                ),
+                EntryDef::Full(entry) => (k, entry),
+            })
+            .try_for_each(|(k, v)| store.insert(&k, v))
+            .map_err(serde::de::Error::custom)?;
+
+        Ok(store)
+    }
+}
+
+impl Serialize for DigraphStore {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        let mut m = serializer.serialize_map(None)?;
+
+        self.search("").try_for_each(|entry| {
+            m.serialize_entry(
+                &entry.sequence,
+                &DigraphEntry {
+                    symbols: entry.symbols.clone(),
+                    description: entry.description.clone(),
+                },
+            )
+        })?;
+        m.end()
+    }
+}
+
+/// A Store of input -> unicode strings that can be quickly looked up and
+/// searched.
+impl DigraphStore {
+    /// Inserts a new unicode string into the store
+    pub fn insert(&mut self, input_seq: &str, entry: DigraphEntry) -> Result<(), Error> {
+        if input_seq.is_empty() {
+            return Err(Error::EmptyInput(input_seq.to_string()));
+        }
+
+        self.head.insert(
+            input_seq,
+            FullDigraphEntry {
+                sequence: input_seq.to_string(),
+                symbols: entry.symbols,
+                description: entry.description,
+            },
+        )
+    }
+
+    /// Attempts to retrieve a stored unicode string if it exists
+    pub fn get(&self, exact_seq: &str) -> Option<&FullDigraphEntry> {
+        self.head.get(exact_seq).and_then(|n| n.output.as_ref())
+    }
+
+    /// Returns an iterator of closest matches to the input string
+    pub fn search(&self, input_seq: &str) -> impl Iterator<Item = &FullDigraphEntry> {
+        self.head.get(input_seq).into_iter().flat_map(|x| x.iter())
+    }
+}
+
+impl DigraphNode {
+    fn insert(&mut self, input_seq: &str, entry: FullDigraphEntry) -> Result<(), Error> {
+        // see if we found the spot to insert our unicode
+        if input_seq.is_empty() {
+            if let Some(existing) = &self.output {
+                return Err(Error::DuplicateEntry {
+                    seq: entry.sequence,
+                    existing: existing.symbols.clone(),
+                    current: entry.symbols,
+                });
+            } else {
+                self.output = Some(entry);
+                return Ok(());
+            }
+        }
+
+        // continue searching
+        let node = self
+            .children
+            .get_or_insert(Default::default())
+            .entry(input_seq.chars().next().unwrap())
+            .or_default();
+
+        node.insert(&input_seq[1..], entry)
+    }
+
+    fn get(&self, exact_seq: &str) -> Option<&Self> {
+        if exact_seq.is_empty() {
+            return Some(self);
+        }
+
+        self.children
+            .as_ref()
+            .and_then(|cm| cm.get(&exact_seq.chars().next().unwrap()))
+            .and_then(|node| node.get(&exact_seq[1..]))
+    }
+
+    fn iter(&self) -> impl Iterator<Item = &FullDigraphEntry> {
+        DigraphIter::new(self)
+    }
+}
+
+pub struct DigraphIter<'a, 'b>
+where
+    'a: 'b,
+{
+    element_iter: Box<dyn Iterator<Item = &'a FullDigraphEntry> + 'b>,
+    node_iter: Box<dyn Iterator<Item = &'a DigraphNode> + 'b>,
+}
+
+impl<'a, 'b> DigraphIter<'a, 'b>
+where
+    'a: 'b,
+{
+    fn new(node: &'a DigraphNode) -> Self {
+        // do a lazy breadth-first search by keeping track of the next 'rung' of
+        // elements to produce, and the next 'rung' of nodes to refill the element
+        // iterator when empty
+        Self {
+            element_iter: Box::new(node.output.iter().chain(Self::get_child_elements(node))),
+            node_iter: Box::new(Self::get_child_nodes(node)),
+        }
+    }
+
+    fn get_child_elements(
+        node: &'a DigraphNode,
+    ) -> impl Iterator<Item = &'a FullDigraphEntry> + 'b {
+        node.children
+            .iter()
+            .flat_map(|hm| hm.iter())
+            .flat_map(|(_, node)| node.output.as_ref())
+    }
+
+    fn get_child_nodes(node: &'a DigraphNode) -> impl Iterator<Item = &'a DigraphNode> + 'b {
+        node.children
+            .iter()
+            .flat_map(|x| x.iter().map(|(_, node)| node))
+    }
+}
+impl<'a, 'b> Iterator for DigraphIter<'a, 'b>
+where
+    'a: 'b,
+{
+    type Item = &'a FullDigraphEntry;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if let Some(e) = self.element_iter.next() {
+                return Some(e);
+            }
+
+            // We ran out of elements, fetch more by traversing the next rung of nodes
+            match self.node_iter.next() {
+                Some(node) => {
+                    // todo: figure out a better way to update self's nodes
+                    let mut new_nodes: Box<dyn Iterator<Item = &DigraphNode>> =
+                        Box::new(std::iter::empty());
+                    std::mem::swap(&mut new_nodes, &mut self.node_iter);
+                    let mut new_nodes: Box<dyn Iterator<Item = &DigraphNode>> =
+                        Box::new(new_nodes.chain(Self::get_child_nodes(node)));
+                    std::mem::swap(&mut new_nodes, &mut self.node_iter);
+
+                    self.element_iter = Box::new(Self::get_child_elements(node));
+                }
+                None => return None,
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn digraph_insert() {
+        let mut dg = DigraphStore::default();
+        dg.insert(
+            "abc",
+            DigraphEntry {
+                symbols: "testbug".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        dg.insert(
+            "abd",
+            DigraphEntry {
+                symbols: "deadbeef".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        assert_eq!(
+            dg.head
+                .children
+                .as_ref()
+                .unwrap()
+                .get(&'a')
+                .unwrap()
+                .children
+                .as_ref()
+                .unwrap()
+                .get(&'b')
+                .unwrap()
+                .children
+                .as_ref()
+                .unwrap()
+                .get(&'c')
+                .unwrap()
+                .output
+                .clone()
+                .unwrap()
+                .symbols
+                .clone(),
+            "testbug".to_string()
+        );
+    }
+
+    #[test]
+    fn digraph_insert_and_get() {
+        let mut dg = DigraphStore::default();
+        dg.insert(
+            "abc",
+            DigraphEntry {
+                symbols: "testbug".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        dg.insert(
+            "abd",
+            DigraphEntry {
+                symbols: "deadbeef".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        assert_eq!(
+            dg.get("abc").map(|x| x.symbols.clone()),
+            Some("testbug".to_string())
+        );
+        assert_eq!(
+            dg.get("abd").map(|x| x.symbols.clone()),
+            Some("deadbeef".to_string())
+        );
+        assert_eq!(dg.get("abe").map(|x| x.symbols.clone()), None);
+    }
+
+    #[test]
+    fn digraph_node_iter() {
+        let mut dg = DigraphStore::default();
+        dg.insert(
+            "abc",
+            DigraphEntry {
+                symbols: "testbug".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        dg.insert(
+            "abd",
+            DigraphEntry {
+                symbols: "deadbeef".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        assert_eq!(dg.head.iter().count(), 2);
+    }
+
+    #[test]
+    fn digraph_search() {
+        let mut dg = DigraphStore::default();
+        dg.insert(
+            "abc",
+            DigraphEntry {
+                symbols: "testbug".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        dg.insert(
+            "abd",
+            DigraphEntry {
+                symbols: "deadbeef".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+        dg.insert(
+            "azz",
+            DigraphEntry {
+                symbols: "qwerty".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        assert_eq!(dg.search("ab").count(), 2);
+        assert_eq!(dg.search("az").next().unwrap().symbols, "qwerty");
+    }
+
+    #[test]
+    fn digraph_search_breadth() {
+        let mut dg = DigraphStore::default();
+        dg.insert(
+            "abccccc",
+            DigraphEntry {
+                symbols: "testbug".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        dg.insert(
+            "abd",
+            DigraphEntry {
+                symbols: "deadbeef".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+        dg.insert(
+            "abee",
+            DigraphEntry {
+                symbols: "qwerty".into(),
+                ..Default::default()
+            },
+        )
+        .unwrap();
+
+        assert_eq!(dg.search("ab").count(), 3);
+        assert_eq!(dg.search("ab").next().unwrap().symbols, "deadbeef");
+    }
+}
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index a9014fe7..a38a3760 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -1,5 +1,6 @@
 use crate::{
     align_view,
+    digraph::DigraphStore,
     document::{DocumentSavedEventFuture, DocumentSavedEventResult, Mode, SavePoint},
     graphics::{CursorKind, Rect},
     info::Info,
@@ -321,6 +322,8 @@ pub struct Config {
     pub insert_final_newline: bool,
     /// Enables smart tab
     pub smart_tab: Option<SmartTabConfig>,
+    /// User supplied digraphs for use with the `insert_diagraphs` command
+    pub digraphs: DigraphStore,
 }
 
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize, Eq, PartialOrd, Ord)]
@@ -889,6 +892,7 @@ impl Default for Config {
             default_line_ending: LineEndingConfig::default(),
             insert_final_newline: true,
             smart_tab: Some(SmartTabConfig::default()),
+            digraphs: Default::default(),
         }
     }
 }
diff --git a/helix-view/src/lib.rs b/helix-view/src/lib.rs
index 6a68e7d6..250edc4c 100644
--- a/helix-view/src/lib.rs
+++ b/helix-view/src/lib.rs
@@ -12,6 +12,7 @@ pub mod handlers {
     pub mod lsp;
 }
 pub mod base64;
+pub mod digraph;
 pub mod info;
 pub mod input;
 pub mod keyboard;