support colour reinsert after resets, switch to intrinsics by default

lib/processing.ml

@@ -1,15 +1,6 @@
 open Types
 open Array
 
-let ansi_filter s =
-  s |> function
-  | Ansi a ->
-      Types.Ansi
-        (List.filter
-           (function Fg _ | Bg _ -> false | _ -> true)
-           a)
-  | n -> n
-
 (* TODO: implement this so cli can use a dsl to specify colourising patterns *)
 type culr = { colours : colour array; sz : int; mutable current : int }
 
@@ -31,6 +22,8 @@ module Culriser = struct
     in
     { colours; sz = length colours; current = 0 }
 
+  let current t = t.colours.(t.current)
+
   let next t =
     let ret = t.current and nv = t.current + 1 in
     if nv >= t.sz then t.current <- 0 else t.current <- nv;
@@ -47,3 +40,26 @@ module Culriser = struct
     | _ -> ());
     Emitter.serialise serialiser chunk
 end
+
+let ansi_filter t s =
+  s |> function
+  | Ansi a -> (
+      let open List in
+      let ol = length a
+      and result =
+        a
+        |> filter (function Fg _ | Bg _ -> false | _ -> true)
+        |> fold_left
+             (fun acc el ->
+               if el = Reset then acc @ [ el; Fg (Culriser.current t) ]
+               else acc @ [ el ])
+             []
+      in
+      let rl = length result in
+      match (rl, ol) with
+      (* empty ansi code is equivalent to a reset *)
+      | 0, 0 -> Ansi [ Reset; Fg (Culriser.current t) ]
+      (* if we filtered everything out of it produce no tokens *)
+      | 0, _ -> Empty
+      | _, _ -> Ansi result)
+  | n -> n