add ability to protect sheets and lock/unlock cells

example.exs

@@ -136,6 +136,16 @@ sheet6 =
   # nest further
   |> Sheet.group_cols("C", "D")
 
+# Sheets can be protected. Cells are locked by default but can be set to be unlocked
+# Here, A1 is editable while the sheet is protected, but B1 is not
+sheet7 =
+  %Sheet{
+    name: "Protected",
+    protected: true
+  }
+  |> Sheet.set_cell("A1", "Can be edited", locked: false)
+  |> Sheet.set_cell("B1", "Cannot be edited")
+
 Workbook.append_sheet(workbook, sheet4)
 |> Workbook.append_sheet(sheet5)
 |> Workbook.append_sheet(sheet6)

lib/elixlsx/sheet.ex

@@ -25,7 +25,8 @@ defmodule Elixlsx.Sheet do
             group_rows: [],
             merge_cells: [],
             pane_freeze: nil,
-            show_grid_lines: true
+            show_grid_lines: true,
+            protected: false
 
   @type t :: %Sheet{
           name: String.t(),
@@ -36,7 +37,8 @@ defmodule Elixlsx.Sheet do
           group_rows: list(rowcol_group),
           merge_cells: [{String.t(), String.t()}],
           pane_freeze: {number, number} | nil,
-          show_grid_lines: boolean()
+          show_grid_lines: boolean(),
+          protected: boolean()
         }
   @type rowcol_group :: Range.t() | {Range.t(), opts :: keyword}
 

lib/elixlsx/style/cell_style.ex

@@ -4,23 +4,26 @@ defmodule Elixlsx.Style.CellStyle do
   alias Elixlsx.Style.Font
   alias Elixlsx.Style.Fill
   alias Elixlsx.Style.BorderStyle
+  alias Elixlsx.Style.Protection
 
-  defstruct font: nil, fill: nil, numfmt: nil, border: nil
+  defstruct font: nil, fill: nil, numfmt: nil, border: nil, protection: nil
 
   @type t :: %CellStyle{
           font: Font.t(),
           fill: Fill.t(),
           numfmt: NumFmt.t(),
-          border: BorderStyle.t()
+          border: BorderStyle.t(),
+          protection: Protection.t()
         }
 
   def from_props(props) do
     font = Font.from_props(props)
     fill = Fill.from_props(props)
     numfmt = NumFmt.from_props(props)
     border = BorderStyle.from_props(props[:border])
+    protection = Protection.from_props(props)
 
-    %CellStyle{font: font, fill: fill, numfmt: numfmt, border: border}
+    %CellStyle{font: font, fill: fill, numfmt: numfmt, border: border, protection: protection}
   end
 
   def is_date?(cellstyle) do

lib/elixlsx/style/protection.ex

@@ -0,0 +1,25 @@
+defmodule Elixlsx.Style.Protection do
+  @moduledoc ~S"""
+  Protection properties.
+
+  Supported formatting properties are:
+
+  - locked: boolean
+  """
+  alias __MODULE__
+
+  defstruct locked: nil
+
+  @type t :: %Protection{
+          locked: boolean
+        }
+
+  @doc ~S"""
+  Create a Protection object from a property list.
+  """
+  def from_props(props) do
+    ft = %Protection{locked: props[:locked]}
+
+    if ft == %Protection{}, do: nil, else: ft
+  end
+end

lib/elixlsx/xml_templates.ex

@@ -12,6 +12,7 @@ defmodule Elixlsx.XMLTemplates do
   alias Elixlsx.Style.Font
   alias Elixlsx.Style.Fill
   alias Elixlsx.Style.BorderStyle
+  alias Elixlsx.Style.Protection
   alias Elixlsx.Sheet
 
   # TODO: the xml_text_exape functions belong into Elixlsx.Util,
@@ -291,6 +292,12 @@ defmodule Elixlsx.XMLTemplates do
     """
   end
 
+  defp xl_sheet_protection(%Sheet{protected: true}) do
+    "<sheetProtection sheet=\"1\" objects=\"1\" scenarios=\"1\"/>"
+  end
+
+  defp xl_sheet_protection(_), do: ""
+
   defp xl_sheet_rows(data, row_heights, grouping_info, wci) do
     rows =
       Enum.zip(data, 1..length(data))
@@ -459,6 +466,7 @@ defmodule Elixlsx.XMLTemplates do
       </sheetData>
       """ <>
       xl_merge_cells(sheet.merge_cells) <>
+      xl_sheet_protection(sheet) <>
       """
       <pageMargins left="0.75" right="0.75" top="1" bottom="1.0" header="0.5" footer="0.5"/>
       </worksheet>
@@ -583,15 +591,25 @@ defmodule Elixlsx.XMLTemplates do
             alignment ->
               {"applyAlignment=\"1\"", alignment}
           end
-      end
+        end
+
+    {apply_protection, protection_tag} =
+      case style.protection do
+        nil ->
+          {"", ""}
+
+        protection ->
+          {"applyProtection=\"1\"", "<protection #{protection_attrs(protection)}/>"}
+        end
 
     """
     <xf borderId="#{borderid}"
            fillId="#{fillid}"
            fontId="#{fontid}"
            numFmtId="#{numfmtid}"
-           xfId="0" #{apply_alignment}>
+           xfId="0" #{apply_alignment} #{apply_protection}>
       #{wrap_text_tag}
+      #{protection_tag}
     </xf>
     """
   end
@@ -646,6 +664,11 @@ defmodule Elixlsx.XMLTemplates do
     end
   end
 
+  @spec protection_attrs(Protection.t()) :: String.t()
+  defp protection_attrs(%Protection{locked: true}), do: "locked=\"1\" "
+  defp protection_attrs(%Protection{locked: false}), do: "locked=\"0\" "
+  defp protection_attrs(_), do: ""
+
   # Returns the inner content of the <CellXfs> block.
   @spec make_cellxfs(list(CellStyle.t()), WorkbookCompInfo.t()) :: String.t()
   defp make_cellxfs(ordered_style_list, wci) do