Add scroller

README.md

@@ -13,6 +13,14 @@ A TUI interface to GitHub.
 > `github-tui` is in _alpha_ stage of development!
 > Expect missing features and horrible bugs.
 
+## Prerequisites
+
+To use `github-tui`, you need to have the following installed:
+
+1. OCaml toolchain: to build the project
+1. `bat` version ⩾ 0.19.0
+1. [Hack Mono Nerd Font](https://www.nerdfonts.com/)
+
 ## Development
 
 Initialise the project when building for the first time:

lib/fs.ml

@@ -1,5 +1,10 @@
+type file_contents = {
+  lines : Pretty.doc array;
+  offset : int;
+}
+
 type tree =
-  | File of string * string lazy_t
+  | File of string * file_contents lazy_t
   | Dir of string * tree array
 
 let file_name = function
@@ -26,10 +31,18 @@ let rec sort_tree = function
 (* Reads file contents using 'bat' to have pretty syntax highlighting *)
 let read_file_contents path =
   let cmd =
-    "bat --plain --color=always --italic-text=always --paging=never \
-     --terminal-width=80 " ^ path
+    "bat --style=numbers,changes --color=always --italic-text=always \
+     --paging=never --terminal-width=80 " ^ path
   in
-  Shell.proc_stdout cmd
+  let contents = Shell.proc_stdout cmd in
+  let lines =
+    contents
+    |> String.split_on_char '\n'
+    |> List.map Pretty.str
+    |> Array.of_list
+  in
+  let offset = 0 in
+  { lines; offset }
 
 let rec to_tree path =
   if Sys.is_directory path then

lib/fs.mli

@@ -1,6 +1,12 @@
+(** File contents as an array of lines, where each line is wrapped into a document (for rendering efficiency) *)
+type file_contents = {
+  lines : Pretty.doc array;
+  offset : int;
+}
+
 (** A definition of a file tree. *)
 type tree =
-  | File of string * string lazy_t
+  | File of string * file_contents lazy_t
   | Dir of string * tree array
 
 (** Return the name of a given tree node. *)

lib/list_extra.ml

@@ -7,13 +7,11 @@ let in_between ~sep list =
   | [] | [ _ ] -> list
   | x :: xs -> x :: loop xs
 
-let generate n f =
-  let rec loop i = if i = n then [] else f i :: loop (i + 1) in
+let of_sub_array ~offset ~len arr =
+  let len =
+    if offset + len > Array.length arr then Array.length arr - offset else len
+  in
+  let rec loop i = if i >= len then [] else arr.(offset + i) :: loop (i + 1) in
   loop 0
 
-let rec take n = function
-  | _ when n <= 0 -> []
-  | [] -> []
-  | x :: xs -> x :: take (n - 1) xs
-
 let max_on f list = List.fold_left (fun acc x -> max acc (f x)) 0 list

lib/scroll.ml

@@ -0,0 +1,21 @@
+type t = {
+  height : int;
+  span : int;
+  lines : int;
+  offset : int;
+}
+
+type sections = {
+  before : int;
+  scroll : int;
+  after : int;
+}
+
+let make ~height ~span ~lines ~offset =
+  if lines <= height then None else Some { height; span; lines; offset }
+
+let to_sections { height; span; lines; offset } =
+  let before = offset * height / lines in
+  let scroll = span * height / lines in
+  let after = (lines - span - offset) * height / lines in
+  { before; scroll; after }

lib/scroll.mli

@@ -0,0 +1,10 @@
+type t
+
+type sections = {
+  before : int;
+  scroll : int;
+  after : int;
+}
+
+val make : height:int -> span:int -> lines:int -> offset:int -> t option
+val to_sections : t -> sections

lib/tui/widget.ml

@@ -41,6 +41,19 @@ let pull_requests_tab ~is_selected =
       "┴───────────────┴";
     ] [@@ocamlformat "disable"]
 
+let scroll ~lines ~span ~offset =
+  let height = 40 in
+  let scroll = Scroll.make ~height ~span ~lines ~offset in
+  match scroll with
+  | None -> Pretty.str " "
+  | Some scroll ->
+      let sections = Scroll.to_sections scroll in
+      let before = List.init sections.before (fun _ -> Pretty.str "░") in
+      let scroll = List.init sections.scroll (fun _ -> Pretty.str "█") in
+      let after = List.init sections.after (fun _ -> Pretty.str "░") in
+      let scroll_bar = before @ scroll @ after in
+      Pretty.vertical scroll_bar
+
 let pwd_char = "\u{e5fd}"
 let dir_char = "\u{f4d4}"
 let empty_dir_char = "\u{f413}"
@@ -55,16 +68,20 @@ let pwd root_dir_path parents =
   let full_path = pwd_char ^ " " ^ Filename.concat root_dir_name pwd_path in
   Pretty.fmt style_directory full_path
 
-let file_contents_to_doc ~file_name:_ ~file_contents =
-  let file_contents_preview =
-    file_contents
-    |> Lazy.force
-    |> String.split_on_char '\n'
-    |> List_extra.take 30
-    |> List.map Pretty.str
-    |> Pretty.vertical
+let file_contents_to_doc ~file_contents =
+  let (file_contents : Fs.file_contents) = Lazy.force file_contents in
+
+  let lines = Array.length file_contents.lines in
+  let span = 40 in
+  let offset = file_contents.offset in
+
+  let contents_span =
+    List_extra.of_sub_array ~offset ~len:span file_contents.lines
   in
-  Pretty.(horizontal [ str " "; file_contents_preview ])
+
+  let scroll_doc = scroll ~lines ~span ~offset in
+  let contents_doc = Pretty.vertical contents_span in
+  Pretty.(horizontal [ scroll_doc; str " "; contents_doc ])
 
 (* Extra padding for:
 
@@ -132,7 +149,7 @@ let children_to_doc ~prev_total ~pos children =
   let prev_rows_count = (2 * prev_total) + 1 in
   let connect_pos = (2 * pos) + 1 in
   let connector_doc =
-    List_extra.generate prev_rows_count (fun i ->
+    List.init prev_rows_count (fun i ->
         let is_current_pos = i = connect_pos in
         if is_current_pos then str "─" else str " ")
     |> vertical
@@ -159,9 +176,7 @@ let children_to_doc ~prev_total ~pos children =
     |> List_extra.in_between ~sep:mid
     |> (fun lines -> [ top ] @ lines @ [ bot ])
     |> (fun lines ->
-         let pad_before =
-           List_extra.generate (max (connect_pos - 1) 0) (fun _ -> "")
-         in
+         let pad_before = List.init (max (connect_pos - 1) 0) (fun _ -> "") in
          pad_before @ lines)
     |> List.map str
     |> vertical
@@ -182,8 +197,8 @@ let next_level_to_doc ~prev_total ~pos (selected_file : Fs.tree) =
   (* Get the next level files *)
   match selected_file with
   (* No children of a file *)
-  | File (file_name, file_contents) ->
-      File_contents (file_contents_to_doc ~file_name ~file_contents)
+  | File (_file_name, file_contents) ->
+      File_contents (file_contents_to_doc ~file_contents)
   (* No children of a directory without children *)
   | Dir (_, [||]) -> Empty_directory
   (* Non-empty array of children *)