fix: check if file is text file before reading it

lua/chatgpt_nvim/context.lua

@@ -31,6 +31,20 @@ local function should_ignore_file(file, ignore_patterns)
   return false
 end
 
+local function is_text_file(file)
+  local fd = uv.fs_open(file, "r", 438)
+  if not fd then
+    return false
+  end
+  local chunk = uv.fs_read(fd, 1024, 0) or ""
+  uv.fs_close(fd)
+  -- Check for null bytes as a heuristic for binary files
+  if chunk:find("\0") then
+    return false
+  end
+  return true
+end
+
 local function scandir(dir, ignore_patterns, files)
   files = files or {}
   local fd = uv.fs_opendir(dir, nil, 50)
@@ -41,7 +55,7 @@ local function scandir(dir, ignore_patterns, files)
     for _, ent in ipairs(ents) do
       local fullpath = dir .. "/" .. ent.name
       if not should_ignore_file(fullpath, ignore_patterns) then
-        if ent.type == "file" then
+        if ent.type == "file" and is_text_file(fullpath) then
           table.insert(files, fullpath)
         elseif ent.type == "directory" and ent.name ~= ".git" then
           scandir(fullpath, ignore_patterns, files)