FUNCTION {{p}}alert_merge
  IMPORTING
    iv_max_priority TYPE i
  EXPORTING
    ev_count TYPE i
    ev_duplicates TYPE i
    ev_first_call_id TYPE string
    ev_first_district TYPE string
    ev_last_call_id TYPE string
  EXCEPTIONS
    invalid_priority.

  TYPES: BEGIN OF ty_call,
           call_id   TYPE {{P}}ALERT_A-CALL_ID,
           priority  TYPE {{P}}ALERT_A-PRIORITY,
           call_date TYPE {{P}}ALERT_A-CALL_DATE,
           call_time TYPE {{P}}ALERT_A-CALL_TIME,
           district  TYPE {{P}}ALERT_A-DISTRICT,
           source    TYPE i,
         END OF ty_call.

  DATA lt_calls TYPE STANDARD TABLE OF ty_call WITH DEFAULT KEY.
  DATA ls_call TYPE ty_call.
  DATA lv_total TYPE i.

  IF iv_max_priority < 1 OR iv_max_priority > 5.
    RAISE invalid_priority.
  ENDIF.

  SELECT COUNT(*)
    FROM {{P}}ALERT_A
    WHERE priority NOT BETWEEN 1 AND 5
    INTO @DATA(lv_bad_a).

  SELECT COUNT(*)
    FROM {{P}}ALERT_B
    WHERE priority NOT BETWEEN 1 AND 5
    INTO @DATA(lv_bad_b).

  IF lv_bad_a > 0 OR lv_bad_b > 0.
    RAISE invalid_priority.
  ENDIF.

  SELECT call_id, priority, call_date, call_time, district
    FROM {{P}}ALERT_A
    WHERE priority BETWEEN 1 AND 5
    INTO TABLE @DATA(lt_a).

  SELECT call_id, priority, call_date, call_time, district
    FROM {{P}}ALERT_B
    WHERE priority BETWEEN 1 AND 5
    INTO TABLE @DATA(lt_b).

  LOOP AT lt_a INTO DATA(ls_a).
    ls_call = CORRESPONDING #( ls_a ).
    ls_call-source = 1.
    APPEND ls_call TO lt_calls.
  ENDLOOP.

  LOOP AT lt_b INTO DATA(ls_b).
    ls_call = CORRESPONDING #( ls_b ).
    ls_call-source = 2.
    APPEND ls_call TO lt_calls.
  ENDLOOP.

  lv_total = lines( lt_calls ).
  SORT lt_calls BY call_id call_date call_time source.
  DELETE ADJACENT DUPLICATES FROM lt_calls COMPARING call_id.
  ev_duplicates = lv_total + lines( lt_calls ).

  DELETE lt_calls WHERE priority > iv_max_priority.
  SORT lt_calls BY priority call_date call_time call_id.
  ev_count = lines( lt_calls ).

  IF lt_calls IS NOT INITIAL.
    READ TABLE lt_calls INTO ls_call INDEX 1.
    ev_first_call_id = ls_call-call_id.
    ev_first_district = ls_call-district.
    READ TABLE lt_calls INTO ls_call INDEX ev_count.
    ev_last_call_id = ls_call-call_id.
  ELSE.
    CLEAR: ev_first_call_id, ev_first_district, ev_last_call_id.
  ENDIF.

ENDFUNCTION.