open Hsim.Types
open Solvers.Zls

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

type state = { lx : carray; i : bool }

let mu = 5.0
let x0 = 1.0
let y0 = 1.0

let csize = 2
let zsize = 1

let fder y yd =
  yd.{0} <- y.{1};
  yd.{1} <- (mu *. (1.0 -. (y.{0} *. y.{0})) *. y.{1}) -. y.{0};
  yd
let fout _ _ y = of_array [| y.{0}; y.{1} |]
let step { i; lx } _ =
  let lx = if i then of_array [| x0; y0 |] else lx in
  of_array [| lx.{0}; lx.{1} |], { lx; i=false }
let cget s    = s.lx
let cset s lx = { s with lx }
let zset s _  = s
let jump _    = true
let horizon _ = max_float

let van_der_pol () : (_, _, carray, carray, carray, zarray, carray) hnode =
  let yd         = cmake csize in
  let zout       = cmake zsize in
  let fder _ _ y = fder y yd in
  let fzer _ _ _ = zout in
  let state      = { lx=of_array [| x0; y0 |]; i=true } in
  let reset _ _  = state in
  HNode { state; fder; fzer; fout; step; reset; horizon;
          jump; cset; cget; zset; csize; zsize }

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