FUNCTION {{P}}DON_SUM
  IMPORTING
    iv_donations TYPE string
  EXPORTING
    ev_donor_count TYPE i
  CHANGING
    cv_totals TYPE string
  EXCEPTIONS
    invalid_units.

  TYPES:
    BEGIN OF ty_total,
      donor_id    TYPE string,
      group_code  TYPE string,
      total_units TYPE i,
    END OF ty_total.

  DATA lt_lines     TYPE STANDARD TABLE OF string WITH EMPTY KEY.
  DATA lt_totals    TYPE SORTED TABLE OF ty_total
                      WITH UNIQUE KEY donor_id group_code.
  DATA lv_line      TYPE string.
  DATA lv_donor     TYPE string.
  DATA lv_group     TYPE string.
  DATA lv_units     TYPE string.
  DATA lv_units_int TYPE i.
  DATA lv_result    TYPE string.
  DATA lv_prev      TYPE string.

  IF iv_donations IS NOT INITIAL.
    SPLIT iv_donations AT cl_abap_char_utilities=>newline INTO TABLE lt_lines.
  ENDIF.

  LOOP AT lt_lines INTO lv_line.
    SPLIT lv_line AT ';' INTO lv_donor lv_group lv_units.

    lv_units_int = lv_units.
    IF lv_units_int < 1.
      RAISE invalid_units.
    ENDIF.

    lv_group = to_upper( lv_group ).

    READ TABLE lt_totals ASSIGNING FIELD-SYMBOL(<ls_total>)
         WITH TABLE KEY donor_id = lv_donor group_code = lv_group.
    IF sy-subrc <> 0.
      INSERT VALUE #( donor_id    = lv_donor
                      group_code  = lv_group
                      total_units = 0 )
             INTO TABLE lt_totals ASSIGNING <ls_total>.
    ENDIF.
    <ls_total>-total_units = <ls_total>-total_units + lv_units_int.
  ENDLOOP.

  LOOP AT lt_totals INTO DATA(ls_total).
    IF ls_total-donor_id <> lv_prev.
      ev_donor_count = ev_donor_count + 1.
      lv_prev = ls_total-donor_id.
    ENDIF.

    DATA(lv_out) = |{ ls_total-donor_id };{ ls_total-group_code };{ ls_total-total_units }|.
    IF lv_result IS INITIAL.
      lv_result = lv_out.
    ELSE.
      lv_result = lv_result && cl_abap_char_utilities=>newline && lv_out.
    ENDIF.
  ENDLOOP.

  cv_totals = lv_result.

ENDFUNCTION.