Input Prompt: Implement left and right arrow

1 files changed, 30 insertions, 8 deletions

diff --git a/lib/input_prompt.ml b/lib/input_prompt.ml
index aec6021..a407741 100644
--- a/lib/input_prompt.ml
+++ b/lib/input_prompt.ml
@@ -3,22 +3,27 @@ module Common = Common
 open Notty
 
 type state =
-  { user_input : string
+  { (* Pre = before the cursor, post = after the cursor *)
+    user_input_pre : string
+  ; user_input_post : string
   ; on_enter : string -> unit
   ; on_cancel : unit -> unit
   ; prompt : string
   ; screen : I.t
   }
 
-let rec render t ({ user_input; on_enter; on_cancel; prompt; screen } as state) =
+let rec render
+  t
+  ({ user_input_pre; user_input_post; on_enter; on_cancel; prompt; screen } as state)
+  =
   let size_x, size_y = Common.Term.size t in
   Common.Term.cursor
     t
-    (Some (String.length user_input + String.length prompt + 3, size_y));
+    (Some (String.length user_input_pre + String.length prompt + 3, size_y));
   let img =
     let open I in
     I.strf " %s " ~attr:(A.st A.reverse) prompt
-    <|> I.strf " %s%s" user_input (String.make size_x ' ')
+    <|> I.strf " %s%s%s" user_input_pre user_input_post (String.make size_x ' ')
     |> I.pad ~l:0 ~t:(size_y - 1)
     </> screen
   in
@@ -26,19 +31,36 @@ let rec render t ({ user_input; on_enter; on_cancel; prompt; screen } as state)
   match Common.Term.event t with
   | `End | `Key (`Escape, []) | `Key (`ASCII 'G', [ `Ctrl ]) | `Key (`ASCII 'C', [ `Ctrl ])
     -> on_cancel ()
-  | `Key (`Enter, []) -> on_enter user_input
+  | `Key (`Enter, []) -> on_enter (user_input_pre ^ user_input_post)
   | `Key (`Backspace, []) ->
-    if String.equal "" user_input
+    if String.equal "" (user_input_pre ^ user_input_post)
     then on_cancel ()
     else (
       let state =
         { state with
-          user_input = String.sub user_input 0 (max (String.length user_input - 1) 0)
+          user_input_pre =
+            String.sub user_input_pre 0 (max (String.length user_input_pre - 1) 0)
         }
       in
       render t state)
   | `Resize _ -> render t state
+  | `Key (`Arrow `Left, []) ->
+    if user_input_pre = ""
+    then render t state
+    else (
+      let char_to_move = Str.last_chars user_input_pre 1
+      and new_pre = Str.string_before user_input_pre (String.length user_input_pre - 1) in
+      let new_post = char_to_move ^ user_input_post in
+      render t { state with user_input_pre = new_pre; user_input_post = new_post })
+  | `Key (`Arrow `Right, []) ->
+    if user_input_post = ""
+    then render t state
+    else (
+      let char_to_move = Str.first_chars user_input_post 1
+      and new_post = Str.string_after user_input_post 1 in
+      let new_pre = user_input_pre ^ char_to_move in
+      render t { state with user_input_pre = new_pre; user_input_post = new_post })
   | `Key (`ASCII c, []) ->
-    let state = { state with user_input = user_input ^ String.make 1 c } in
+    let state = { state with user_input_pre = user_input_pre ^ String.make 1 c } in
     render t state
   | _ -> render t state