CLASS {{p}}prescription_check DEFINITION PUBLIC FINAL CREATE PUBLIC.
  PUBLIC SECTION.
    TYPES ty_drug_id TYPE c LENGTH 10.

    TYPES:
      BEGIN OF ty_item,
        drug_id    TYPE ty_drug_id,
        quantity   TYPE i,
        daily_dose TYPE i,
      END OF ty_item,
      tt_item TYPE STANDARD TABLE OF ty_item WITH EMPTY KEY.

    METHODS constructor.

    METHODS validate
      IMPORTING iv_issue_date TYPE d
                iv_valid_days TYPE i
                iv_as_of_date TYPE d
                it_item       TYPE tt_item
      RAISING   {{p}}cx_presc_error.

  PRIVATE SECTION.
    DATA mo_drug_master TYPE REF TO {{p}}drug_master.

    METHODS expiry_date
      IMPORTING iv_issue_date TYPE d
                iv_valid_days TYPE i
      RETURNING VALUE(rv_expiry) TYPE d.

    METHODS check_items
      IMPORTING it_item TYPE tt_item
      RAISING   {{p}}cx_presc_error.

    METHODS check_item
      IMPORTING is_item TYPE ty_item
      RAISING   {{p}}cx_presc_error.

    METHODS check_duplicates
      IMPORTING it_item TYPE tt_item
      RAISING   {{p}}cx_presc_error.
ENDCLASS.


CLASS {{p}}prescription_check IMPLEMENTATION.
  METHOD constructor.
    mo_drug_master = NEW {{p}}drug_master( ).
  ENDMETHOD.

  METHOD validate.
    IF it_item IS INITIAL.
      RAISE EXCEPTION TYPE {{p}}cx_presc_error
        EXPORTING iv_reason = {{p}}cx_presc_error=>c_reason-empty.
    ENDIF.

    IF iv_as_of_date > expiry_date( iv_issue_date = iv_issue_date
                                    iv_valid_days = iv_valid_days ).
      RAISE EXCEPTION TYPE {{p}}cx_presc_error
        EXPORTING iv_reason = {{p}}cx_presc_error=>c_reason-expired.
    ENDIF.

    check_items( it_item ).
    check_duplicates( it_item ).
  ENDMETHOD.

  METHOD expiry_date.
    rv_expiry = iv_issue_date + iv_valid_days.
  ENDMETHOD.

  METHOD check_items.
    LOOP AT it_item INTO DATA(ls_item).
      check_item( ls_item ).
    ENDLOOP.
  ENDMETHOD.

  METHOD check_item.
    IF is_item-quantity < 1.
      RAISE EXCEPTION TYPE {{p}}cx_presc_error
        EXPORTING iv_reason = {{p}}cx_presc_error=>c_reason-quantity.
    ENDIF.

    DATA(ls_drug) = mo_drug_master->get_drug( is_item-drug_id ).
    IF ls_drug IS INITIAL.
      RAISE EXCEPTION TYPE {{p}}cx_presc_error
        EXPORTING iv_reason = {{p}}cx_presc_error=>c_reason-unknown.
    ENDIF.

    IF is_item-daily_dose < 1 OR is_item-daily_dose > ls_drug-max_daily_dose.
      RAISE EXCEPTION TYPE {{p}}cx_presc_error
        EXPORTING iv_reason = {{p}}cx_presc_error=>c_reason-dose.
    ENDIF.
  ENDMETHOD.

  METHOD check_duplicates.
    DATA lt_seen TYPE HASHED TABLE OF ty_item WITH UNIQUE KEY drug_id.
    LOOP AT it_item INTO DATA(ls_item).
      INSERT ls_item INTO TABLE lt_seen.
      IF sy-subrc <> 0.
        RAISE EXCEPTION TYPE {{p}}cx_presc_error
          EXPORTING iv_reason = {{p}}cx_presc_error=>c_reason-duplicate.
      ENDIF.
    ENDLOOP.
  ENDMETHOD.
ENDCLASS.