1 files changed, 66 insertions, 0 deletions
diff --git a/runtime/lua/core/motion.lua b/runtime/lua/core/motion.lua
new file mode 100644
index 0000000..a6bcb80
--- /dev/null
+++ b/runtime/lua/core/motion.lua
@@ -0,0 +1,66 @@
+local M = {}
+
+local function is_word_char(ch)
+  if ch == "" then
+    return false
+  end
+  local byte = string.byte(ch)
+  if not byte then
+    return false
+  end
+
+  if byte >= string.byte("a") and byte <= string.byte("z") then
+    return true
+  end
+  if byte >= string.byte("A") and byte <= string.byte("Z") then
+    return true
+  end
+  if byte >= string.byte("0") and byte <= string.byte("9") then
+    return true
+  end
+  return ch == "_"
+end
+
+function M.forward_word()
+  local len = editor.buffer_length()
+  local point = editor.point()
+  if point >= len then
+    return
+  end
+
+  local ch = editor.char_at(point)
+  if is_word_char(ch) then
+    while point < len and is_word_char(editor.char_at(point)) do
+      point = point + 1
+    end
+  else
+    while point < len and not is_word_char(editor.char_at(point)) do
+      point = point + 1
+    end
+    while point < len and is_word_char(editor.char_at(point)) do
+      point = point + 1
+    end
+  end
+
+  editor.set_point(point)
+end
+
+function M.backward_word()
+  local point = editor.point()
+  if point <= 0 then
+    return
+  end
+
+  point = point - 1
+  while point >= 0 and not is_word_char(editor.char_at(point)) do
+    point = point - 1
+  end
+
+  while point >= 0 and is_word_char(editor.char_at(point)) do
+    point = point - 1
+  end
+
+  editor.set_point(point + 1)
+end
+
+return M