FUNCTION {{p}}farrier_fee
  IMPORTING
    iv_horses TYPE i
    iv_km TYPE decfloat34
    iv_new_shoes TYPE abap_bool
    iv_contract TYPE abap_bool
  EXPORTING
    ev_fee TYPE decfloat34
    ev_weeks TYPE i
    ev_reject TYPE abap_bool
  EXCEPTIONS
    invalid_horses.

  CONSTANTS c_shoeing_rate TYPE decfloat34 VALUE '45'.
  CONSTANTS c_bulk_rate TYPE decfloat34 VALUE '40'.
  CONSTANTS c_bulk_from TYPE i VALUE 5.
  CONSTANTS c_new_shoes_rate TYPE decfloat34 VALUE '30'.
  CONSTANTS c_km_rate TYPE decfloat34 VALUE '0.6'.
  CONSTANTS c_travel_minimum TYPE decfloat34 VALUE '10'.
  CONSTANTS c_contract_percent TYPE decfloat34 VALUE '88'.
  CONSTANTS c_full_percent TYPE decfloat34 VALUE '100'.
  CONSTANTS c_weeks_standard TYPE i VALUE 6.
  CONSTANTS c_weeks_contract TYPE i VALUE 4.

  IF iv_horses < 0.
    RAISE invalid_horses.
  ENDIF.

  IF iv_horses = 0.
    ev_reject = abap_true.
    ev_fee = 0.
    ev_weeks = 0.
    RETURN.
  ENDIF.

  ev_reject = abap_false.

* Next visit: every six weeks, contract stables every four weeks.
  ev_weeks = c_weeks_standard.
  IF iv_contract = abap_true.
    ev_weeks = c_weeks_contract.
  ENDIF.

* Shoeing fee: the first four horses cost the standard rate, every further
* horse costs the bulk rate.
  DATA(lv_bulk_horses) = iv_horses - c_bulk_from + 1.
  IF lv_bulk_horses < 0.
    lv_bulk_horses = 0.
  ENDIF.
  DATA(lv_standard_horses) = iv_horses - lv_bulk_horses.
  ev_fee = lv_standard_horses * c_shoeing_rate + lv_bulk_horses * c_bulk_rate.

* New shoes are charged for every horse.
  IF iv_new_shoes = abap_true.
    ev_fee = ev_fee + iv_horses * c_new_shoes_rate.
  ENDIF.

* Travel: a rate per kilometre, at least the minimum, rounded up to a whole
* euro.
  DATA(lv_travel) = iv_km * c_km_rate.
  IF lv_travel < c_travel_minimum.
    lv_travel = c_travel_minimum.
  ENDIF.
  ev_fee = ev_fee + ceil( lv_travel ).

* Contract stables get a discount on the whole visit.
  IF iv_contract = abap_true.
    ev_fee = ev_fee * c_contract_percent / c_full_percent.
  ENDIF.

ENDFUNCTION.