feat: Outdent empty TODO lines on Enter press

lua/todoer/init.lua

@@ -140,17 +140,47 @@ local function setup_buffer_keymaps()
             return ""
 
         elseif details.is_todo and not has_content then
-            -- Case 2: Empty TODO line (e.g., "- [ ]")
-            -- TODO: Implement Step 3 logic (outdenting) here later.
-            -- For now, keep the old (potentially problematic) feedkeys behavior
-            -- or simply clear the line and let Neovim handle Enter.
-            -- Let's try clearing the line and returning <CR> for now.
-            vim.api.nvim_buf_set_lines(0, lnum - 1, lnum, false, { details.indent }) -- Replace with just indent
-            return vim.api.nvim_replace_termcodes("<CR>", true, false, true) -- Let Neovim handle newline
-
-            -- Old feedkeys behavior (kept for reference, but commented out):
-            -- vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<Esc>S<CR>", true, false, true), "n", false)
-            -- return "" -- Feedkeys handles it
+            -- Case 2: Empty TODO line (e.g., "- [ ]") - Implement Outdenting
+            local current_indent = details.indent
+            local current_indent_len = #current_indent
+            local sw = vim.bo.shiftwidth -- Get buffer's shiftwidth
+            local et = vim.bo.expandtab -- Get buffer's expandtab setting
+
+            if current_indent_len > 0 then
+                -- Line is indented, calculate new indentation
+                local new_indent = ""
+                if et then -- Using spaces
+                    local target_indent_len = math.max(0, current_indent_len - sw)
+                    new_indent = string.rep(" ", target_indent_len)
+                else -- Using tabs
+                    -- Remove the first tab character found
+                    new_indent = string.gsub(current_indent, "^\t", "", 1)
+                    -- Safety check: if gsub didn't change anything (e.g., indent was spaces),
+                    -- try removing spaces as a fallback, though this is less ideal with noexpandtab
+                    if new_indent == current_indent and current_indent_len > 0 then
+                       local target_indent_len = math.max(0, current_indent_len - sw)
+                       new_indent = string.rep(" ", target_indent_len)
+                    end
+                end
+
+                -- Replace the current line with the outdented version
+                local new_marker = details.marker or "-"
+                local new_line_content = new_indent .. new_marker .. " [ ] "
+                vim.api.nvim_buf_set_lines(0, lnum - 1, lnum, false, { new_line_content })
+
+                -- Move cursor after the "] " on the modified line
+                local cursor_col_bytes = #new_line_content
+                vim.api.nvim_win_set_cursor(0, { lnum, cursor_col_bytes })
+
+                -- Action handled
+                return ""
+            else
+                -- Line is not indented, terminate the list
+                -- Replace the line with an empty string
+                vim.api.nvim_buf_set_lines(0, lnum - 1, lnum, false, { "" })
+                -- Let Neovim handle inserting a newline below the now-empty line
+                return vim.api.nvim_replace_termcodes("<CR>", true, false, true)
+            end
 
         else
             -- Case 3: Not a TODO line