Add FS tree zipper

lib/fs.ml

@@ -0,0 +1,33 @@
+type tree =
+  | File of string
+  | Dir of string * tree array
+
+let file_name = function
+  | File path -> path
+  | Dir (path, _) -> path
+
+type cursor = 
+  {
+     pos: int;
+     files: tree array;
+  }
+
+type zipper =
+   {
+     parents: cursor list;
+     current: cursor;
+   }
+
+let go_down zipper = 
+  let cursor = zipper.current in
+  let len = Array.length cursor.files in
+  let new_pos = (cursor.pos + 1) mod len in
+  let new_cursor = { cursor with pos = new_pos } in
+  { zipper with current = new_cursor }
+
+let go_up zipper = 
+  let cursor = zipper.current in
+  let len = Array.length cursor.files in
+  let new_pos = (cursor.pos + len - 1) mod len in
+  let new_cursor = { cursor with pos = new_pos } in
+  { zipper with current = new_cursor }

lib/tui/model.ml

@@ -1,7 +1,6 @@
 type code_tab =
   {
-    pos: int ;
-    files: string list ;
+    fs: Fs.zipper ;
   }
 
 type tab = 
@@ -20,7 +19,17 @@ let initial_model repo: t =
      repo ;
      current_tab = Code;
      code_tab = {
-      pos = 0;
-      files = [ "src/"; "lib/"; "README.md" ]
+      fs = 
+        {
+          parents = [];
+          current = {
+            pos = 0;
+            files = 
+              [| Dir ("src/", [||]);
+                 Dir ("lib/", [||]);
+                 File "README.md";
+              |]
+          }
+        }
      };
   }

lib/tui/update.ml

@@ -2,18 +2,14 @@ open Minttea
 
 let move_up (model: Model.t) = match model.current_tab with
   | Code ->
-    let files_num = List.length model.code_tab.files in
-    let new_pos = (model.code_tab.pos + files_num - 1) mod files_num in
-    let code_tab = { model.code_tab with pos = new_pos } in
-    { model with code_tab }
+    let fs = Fs.go_up model.code_tab.fs in
+    { model with code_tab = { fs } }
   | Issues | PullRequests -> model
 
 let move_down (model: Model.t) = match model.current_tab with
   | Code ->
-    let files_num = List.length model.code_tab.files in
-    let new_pos = (model.code_tab.pos + 1) mod files_num in
-    let code_tab = { model.code_tab with pos = new_pos } in
-    { model with code_tab }
+    let fs = Fs.go_down model.code_tab.fs in
+    { model with code_tab = { fs } }
   | Issues | PullRequests -> model
 
 let move_left model = model

lib/tui/view.ml

@@ -48,6 +48,7 @@ let file_widget ~max_name_len ~selected files =
   in
   let hi_pos = 2 * selected + 1 in
   files
+  |> Array.to_list
   |> List.map fmt_line
   |> List_extra.in_between ~sep:mid
   |> (fun lines -> [top] @ lines @ [bot])
@@ -59,8 +60,13 @@ let file_widget ~max_name_len ~selected files =
   |> String_extra.unlines
 
 let code_section (code_tab: Model.code_tab) =
-  let max_name_len = code_tab.files |> List.map String_extra.graphemes_len |> List.fold_left max 0 in
-  file_widget ~max_name_len ~selected:code_tab.pos code_tab.files
+  let cursor = code_tab.fs.current in
+  let files = Array.map Fs.file_name cursor.files in
+  let max_name_len = 
+    files 
+    |> Array.map String_extra.graphemes_len
+    |> Array.fold_left max 0 in
+  file_widget ~max_name_len ~selected:cursor.pos files
 
 let tab_content_section (model: Model.t) =
   match model.current_tab with