(* Example due to JB. Jeannin - zero-crossing detection *)
(* the signal x(t) is expected to have a zero-crossing at [t = 0.3] *)

(* to draw: ./main.exe -s sin_1_x -stop 2 -sample 10000 | feedgnuplot --stream --domain --lines *)

open Hsim.Types
open Solvers.Zls

(* let hybrid sin_1_x() =
     let der t = 1.0 init 0.0 in
     let t = t -. 0.3 in
     let v = sin(1/t) in
     let o = t *. (v *. v) in [that is: t *. (sin(1/t)^2]
     present up(o) -> 1.0 else 0.0, o *)

let of_array a = Bigarray.Array1.of_array Bigarray.Float64 Bigarray.c_layout a

type ('a, 'b) state = { s_x: 'a; zin: 'b }

let csize = 1
let zsize = 1

let fder _ _ yd = yd.{0} <- 1.0

let fzer _ y zout =
  let t = y.{0} in
  let t = t -. 0.3 in
  let v = sin(1.0 /. t) in
  let o = t *. (v *. v) in
  zout.{0} <- o

let fout s y =
  let z = if s.zin.{0} = 1l then 1.0 else 0.0 in
  let t = y.{0} in
  let t = t -. 0.3 in
  let v = sin(1.0 /. t) in
  let o = t *. (v *. v) in
  of_array [| z; o |]

let step ({ s_x; zin } as s) zfalse =
  let z = if zin.{0} = 1l then 1.0 else 0.0 in
  let t = s_x.{0} in
  let t = t -. 0.3 in
  let v = sin(1.0 /. t) in
  let o = t *. (v *. v) in
  of_array [| z; o |], { s with zin = zfalse }

let reset _ s = s

let cget { s_x; _ } = s_x
let cset s l_x = { s with s_x = l_x }
let zset s zin = { s with zin }
let jump _ = true
let horizon _ = max_float

let sin_1_x () =
  let zfalse = zmake 1 in
  let yd     = cmake 1 in
  let zout   = cmake 1 in
  let fder _ _ y = fder 0.0 y yd; yd in
  let fzer _ _ y = fzer 0.0 y zout; zout in
  let fout s _ y = fout s y in
  let step s _ = step s zfalse in
  let state = { s_x = of_array [| 0.0 |]; zin = zfalse } in
  { state; fder; fzer; fout; step; reset; horizon;
    cset; cget; zset; csize; zsize; jump }

let errmsg = "Too many arguments for the model (needed: 0)"
let init = function
  | [] -> HNode (sin_1_x ())
  | _  -> raise (Invalid_argument errmsg)