From 055c743c55bde27f4475d3434c26d8383c0c3ea1 Mon Sep 17 00:00:00 2001
From: Federico Igne <undyamon@disroot.org>
Date: Thu, 11 Jan 2024 19:31:31 +0100
Subject: bulk: add PoC of vim-like modular editor

---
 lib/terminal.ml | 130 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 lib/terminal.ml

(limited to 'lib/terminal.ml')

diff --git a/lib/terminal.ml b/lib/terminal.ml
new file mode 100644
index 0000000..408f7a8
--- /dev/null
+++ b/lib/terminal.ml
@@ -0,0 +1,130 @@
+open Base
+open Unix
+open Util
+
+type terminal_size = int * int
+type state = { tio : terminal_io; size : terminal_size }
+
+let escape ?(prefix = "") ?(args = []) op =
+  let open Bytes in
+  let args = List.map ~f:Int.to_string args |> String.concat ~sep:";" in
+  let lenp = String.length prefix in
+  let lena = String.length args in
+  let lenb = 3 + lena + lenp in
+  let dst = Bytes.create lenb in
+  set dst 0 '\x1b';
+  set dst 1 '[';
+  From_string.blit ~src:prefix ~src_pos:0 ~dst ~dst_pos:2 ~len:lenp;
+  From_string.blit ~src:args ~src_pos:0 ~dst ~dst_pos:(2 + lenp) ~len:lena;
+  set dst (length dst - 1) op;
+  sequence_of_bytes dst
+
+let clear_screen = escape 'J' ~args:[ 2 ]
+let clear_to_eol = escape 'K'
+let move_cursor x y = escape 'H' ~args:[ x; y ]
+let move_down n = escape 'B' ~args:[ n ]
+let move_right n = escape 'C' ~args:[ n ]
+let query_cursor_pos = escape 'n' ~args:[ 6 ]
+let reset_cursor = move_cursor 1 1
+
+let show_cursor show =
+  let cmd = if show then 'h' else 'l' in
+  escape cmd ~prefix:"?" ~args:[ 25 ]
+
+let input_bytes = Bytes.create 1
+
+let get_char () =
+  let syscall () = read stdin input_bytes 0 1 in
+  match handle_unix_error syscall () with
+  | 0 -> None
+  | _ -> Some (Bytes.get input_bytes 0)
+
+let char_stream : char option Sequence.t =
+  Sequence.unfold ~init:() ~f:(fun s -> Some (get_char (), s))
+
+let write_seq =
+  let syscall s =
+    let buf = Sequence.to_list s |> Bytes.of_char_list in
+    single_write stdout buf 0 (Bytes.length buf) |> ignore
+  in
+  handle_unix_error syscall
+
+let write_lines (lines : char Sequence.t Sequence.t) =
+  let crnl = Sequence.of_list [ '\r'; '\n' ] in
+  let clear s = Sequence.append s clear_to_eol in
+  let syscall seq =
+    let buf =
+      Sequence.(map ~f:clear seq |> intersperse ~sep:crnl |> concat |> to_list)
+      |> Bytes.of_char_list
+    in
+    single_write stdout buf 0 (Bytes.length buf) |> ignore
+  in
+  handle_unix_error syscall lines
+
+let cmds_to_sequence l = Sequence.(of_list l |> concat)
+
+let restore_screen () =
+  cmds_to_sequence [ clear_screen; reset_cursor; show_cursor true ] |> write_seq
+
+let redraw screen (x, y) =
+  let pre = cmds_to_sequence [ show_cursor false; reset_cursor ]
+  and post = cmds_to_sequence [ move_cursor x y; show_cursor true ] in
+  write_seq pre;
+  write_lines screen;
+  write_seq post
+
+let get_state () = { tio = handle_unix_error tcgetattr stdin; size = (-1, -1) }
+
+let size =
+  let query () =
+    cmds_to_sequence [ move_right 999; move_down 999; query_cursor_pos ]
+    |> write_seq
+  and get_reply () =
+    Sequence.(
+      char_stream
+      |> take_while ~f:Option.is_some
+      |> Fn.flip drop_eagerly 2 (* Drop escape sequence '<esc>[' *)
+      |> map ~f:(Option.value ~default:'R')
+      |> take_while ~f:(fun c -> Char.(c <> 'R'))
+      |> to_list |> String.of_char_list |> Stdlib.Scanf.sscanf
+      |> fun scanner -> scanner "%d;%d" (fun a b -> (a, b)))
+  in
+  query &> get_reply
+
+let enable_raw_mode tio =
+  let syscall () =
+    tcsetattr stdin TCSAFLUSH
+      {
+        tio with
+        c_brkint = false;
+        c_csize = 8;
+        c_echo = false;
+        c_echonl = false;
+        c_icanon = false;
+        c_icrnl = false;
+        c_ignbrk = false;
+        c_igncr = false;
+        c_inlcr = false;
+        c_inpck = false;
+        c_isig = false;
+        c_istrip = false;
+        c_ixon = false;
+        c_opost = false;
+        c_parenb = false;
+        c_parmrk = false;
+        c_vmin = 0;
+        c_vtime = 1;
+      }
+  in
+  handle_unix_error syscall
+
+let restore_status tio =
+  let syscall () = tcsetattr stdin TCSAFLUSH tio in
+  handle_unix_error syscall
+
+let init () =
+  let state = get_state () in
+  enable_raw_mode state.tio ();
+  restore_status state.tio |> Stdlib.at_exit;
+  restore_screen |> Stdlib.at_exit;
+  { state with size = size () }
-- 
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