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(* Open Source License                                                       *)
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(* Copyright (c) 2022 Nomadic Labs. <contact@nomadic-labs.com>               *)
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module Numpy = struct
  let transpose x =
    let npy_transpose = Py.Module.get_function (Pyinit.numpy ()) "transpose" in
    npy_transpose [|x|]
end

module LinearModel = struct
  let assert_matrix_nontrivial (m : Scikit_matrix.t) =
    let l, c = Scikit_matrix.shape m in
    assert (l <> 0 && c <> 0)

  let ridge ~(alpha : float) ?(fit_intercept : bool = false)
      ~(input : Scikit_matrix.t) ~(output : Scikit_matrix.t) () =
    assert_matrix_nontrivial input ;
    assert_matrix_nontrivial output ;
    let input = Scikit_matrix.to_numpy input in
    let output = Scikit_matrix.to_numpy output in
    let ridge_object =
      Py.Module.get_function_with_keywords
        (Pyinit.linear_model ())
        "Ridge"
        [||]
        [
          ("alpha", Py.Float.of_float alpha);
          ("fit_intercept", Py.Bool.of_bool fit_intercept);
        ]
    in
    let _ =
      match Py.Object.get_attr_string ridge_object "fit" with
      | None -> Stdlib.failwith "Scikit.LinearModel.ridge: method fit not found"
      | Some meth -> Py.Callable.to_function meth [|input; output|]
    in
    match Py.Object.get_attr_string ridge_object "coef_" with
    | None ->
        Stdlib.failwith "Scikit.LinearModel.ridge: attribute coef_ not found"
    | Some coef -> Scikit_matrix.of_numpy (Numpy.transpose coef)

  let lasso ~(alpha : float) ?(fit_intercept : bool = false)
      ?(positive : bool = false) ~(input : Scikit_matrix.t)
      ~(output : Scikit_matrix.t) () =
    assert_matrix_nontrivial input ;
    assert_matrix_nontrivial output ;
    let input = Scikit_matrix.to_numpy input in
    let output = Scikit_matrix.to_numpy output in
    let lasso_object =
      Py.Module.get_function_with_keywords
        (Pyinit.linear_model ())
        "Lasso"
        [||]
        [
          ("alpha", Py.Float.of_float alpha);
          ("fit_intercept", Py.Bool.of_bool fit_intercept);
          ("positive", Py.Bool.of_bool positive);
        ]
    in
    let _ =
      match Py.Object.get_attr_string lasso_object "fit" with
      | None -> Stdlib.failwith "Scikit.LinearModel.lasso: method fit not found"
      | Some meth -> Py.Callable.to_function meth [|input; output|]
    in
    match Py.Object.get_attr_string lasso_object "coef_" with
    | None ->
        Stdlib.failwith "Scikit.LinearModel.lasso: attribute coef_ not found"
    | Some coef -> Scikit_matrix.of_numpy coef

  let nnls ~(input : Scikit_matrix.t) ~(output : Scikit_matrix.t) =
    assert_matrix_nontrivial input ;
    assert_matrix_nontrivial output ;
    let len = Scikit_matrix.dim1 output in
    let input = Scikit_matrix.to_numpy input in
    let output = Scikit_matrix.to_numpy output in
    let output =
      Py.Module.get_function
        (Pyinit.numpy ())
        "reshape"
        [|output; Py.Int.of_int len|]
    in
    let nnls_outcome =
      Py.Module.get_function (Pyinit.scipy_optimize ()) "nnls" [|input; output|]
    in
    let array = Py.Tuple.to_array nnls_outcome in
    if Array.length array <> 2 then
      Stdlib.failwith "Scikit.nnls: invalid outcome"
    else
      let res = array.(0) in
      Scikit_matrix.of_numpy res
end