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/key.ml | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 lib/key.ml

(limited to 'lib/key.ml')

diff --git a/lib/key.ml b/lib/key.ml
new file mode 100644
index 0000000..85aa282
--- /dev/null
+++ b/lib/key.ml
@@ -0,0 +1,72 @@
+open Base
+
+type key =
+  | Arrow_down
+  | Arrow_left
+  | Arrow_right
+  | Arrow_up
+  | Backspace
+  | Ctrl of char
+  | Delete
+  | End
+  | Enter
+  | Esc
+  | Home
+  | Key of char
+  | Nul
+  | Page_down
+  | Page_up
+
+type t = key
+
+let ctrl c = Ctrl c
+let key c = Key c
+
+let of_char = function
+  | '\000' -> Nul
+  | '\013' -> Enter
+  | '\027' -> Esc
+  | '\127' -> Backspace
+  | c when Char.(c < ' ') -> Char.to_int c + 64 |> Char.of_int_exn |> ctrl
+  | c -> Key c
+
+let stream =
+  let step s c =
+    let open Sequence.Step in
+    let escaped = function
+      | 'A' -> Some Arrow_up
+      | 'B' -> Some Arrow_down
+      | 'C' -> Some Arrow_right
+      | 'D' -> Some Arrow_left
+      | 'F' -> Some End
+      | 'H' -> Some Home
+      | _ -> None
+    and tilda = function
+      | '1' -> Some Home
+      | '3' -> Some Delete
+      | '4' -> Some End
+      | '5' -> Some Page_up
+      | '6' -> Some Page_down
+      | '7' -> Some Home
+      | '8' -> Some End
+      | _ -> None
+    in
+    match (s, c) with
+    | `start, Some '\027' -> Skip { state = `esc }
+    | `esc, None -> Yield { value = Esc; state = `start }
+    | `esc, Some '[' | `escaped, Some 'O' -> Skip { state = `escaped }
+    | `escaped, Some i when Char.(i = '1' || ('3' <= i && i <= '8')) ->
+        Skip { state = `tilda i }
+    | `escaped, c -> (
+        match Option.(c >>= escaped) with
+        | None -> Skip { state = `state }
+        | Some c -> Yield { value = c; state = `start })
+    | `tilda i, Some '~' -> (
+        match tilda i with
+        | None -> Skip { state = `start }
+        | Some k -> Yield { value = k; state = `start })
+    | `esc, Some _ | `tilda _, _ -> Skip { state = `start }
+    | _, None -> Skip { state = `start }
+    | _, Some c -> Yield { value = of_char c; state = `start }
+  in
+  Sequence.unfold_with ~init:`start ~f:step Terminal.char_stream
-- 
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