3 files changed, 38 insertions, 4 deletions
diff --git a/helix-core/src/lib.rs b/helix-core/src/lib.rs
index 6b93de78..4be3e71b 100644
--- a/helix-core/src/lib.rs
+++ b/helix-core/src/lib.rs
@@ -16,6 +16,7 @@ pub mod selection;
 mod state;
 pub mod syntax;
 mod transaction;
+pub mod words;
 
 pub(crate) fn find_first_non_whitespace_char2(line: RopeSlice) -> Option<usize> {
     // find first non-whitespace char
diff --git a/helix-core/src/movement.rs b/helix-core/src/movement.rs
index 297911ae..c5e2df4a 100644
--- a/helix-core/src/movement.rs
+++ b/helix-core/src/movement.rs
@@ -174,22 +174,22 @@ pub fn move_next_word_end(slice: RopeSlice, mut begin: usize, count: usize) -> O
 
 // used for by-word movement
 
-fn is_word(ch: char) -> bool {
+pub(crate) fn is_word(ch: char) -> bool {
     ch.is_alphanumeric() || ch == '_'
 }
 
-fn is_horiz_blank(ch: char) -> bool {
+pub(crate) fn is_horiz_blank(ch: char) -> bool {
     matches!(ch, ' ' | '\t')
 }
 
 #[derive(Debug, Eq, PartialEq)]
-enum Category {
+pub(crate) enum Category {
     Whitespace,
     Eol,
     Word,
     Punctuation,
 }
-fn categorize(ch: char) -> Category {
+pub(crate) fn categorize(ch: char) -> Category {
     if ch == '\n' {
         Category::Eol
     } else if ch.is_ascii_whitespace() {
diff --git a/helix-core/src/words.rs b/helix-core/src/words.rs
new file mode 100644
index 00000000..0099d56a
--- /dev/null
+++ b/helix-core/src/words.rs
@@ -0,0 +1,33 @@
+use crate::movement::{categorize, is_horiz_blank, is_word, skip_over_prev};
+use ropey::RopeSlice;
+
+#[must_use]
+pub fn nth_prev_word_boundary(slice: RopeSlice, mut char_idx: usize, count: usize) -> usize {
+    let mut with_end = false;
+
+    for _ in 0..count {
+        if char_idx == 0 {
+            break;
+        }
+
+        // return if not skip while?
+        skip_over_prev(slice, &mut char_idx, |ch| ch == '\n');
+
+        with_end = skip_over_prev(slice, &mut char_idx, is_horiz_blank);
+
+        // refetch
+        let ch = slice.char(char_idx);
+
+        if is_word(ch) {
+            with_end = skip_over_prev(slice, &mut char_idx, is_word);
+        } else if ch.is_ascii_punctuation() {
+            with_end = skip_over_prev(slice, &mut char_idx, |ch| ch.is_ascii_punctuation());
+        }
+    }
+
+    if with_end {
+        char_idx
+    } else {
+        char_idx + 1
+    }
+}