# 1. Goal
Show the milk deliveries of each farm in an ALV list. The cooperative uses the
list to compare the farms of a region for a period.

# 2. Open questions
None.

# 3. Context
- Table {{P}}FARM exists in package $TMP. It contains data.
  Fields: FARM_ID (CHAR 10, key), FARM_NAME (CHAR 40), REGION (CHAR 4).
- Table {{P}}MILK exists in package $TMP. It contains data.
  Fields: DELIV_ID (INT4, key), FARM_ID (CHAR 10), DELIV_DATE (DATS),
  LITRES (DEC 13,2).

# 4. Contract
- Create the executable program {{P}}MILK_SUM in package $TMP.
- Selection screen:
  - Parameter P_FROM, type DATS, mandatory: the first delivery date to include.
  - Parameter P_TO, type DATS, mandatory: the last delivery date to include.
  - Select-option S_REG for the region.
- Show the result with CL_SALV_TABLE. The output table has these columns, with
  these names: FARM_ID, FARM_NAME, REGION, LITRES, DELIVERIES.

# 5. Business rules
1. Include a delivery only if DELIV_DATE is on or after P_FROM and on or before
   P_TO. Both limits are included.
2. Include a farm only if REGION is in S_REG. An empty S_REG includes every
   region. A line with sign E in S_REG excludes its region.
3. Show one line for each included farm. A farm without an included delivery also
   gets a line.
4. LITRES is the sum of the litres of the included deliveries of the farm. LITRES
   is 0 if the farm has no included delivery.
5. DELIVERIES is the number of included deliveries of the farm. DELIVERIES is 0
   if the farm has no included delivery.
6. Sort the lines by LITRES, the highest value first. If two lines have the same
   LITRES, sort them by FARM_ID, the lowest value first.
7. FARM_NAME and REGION are the values of the farm.

# 6. Constraints
- Release target: 7.58.
- Coding standards: Clean ABAP. Read each table with one database access.
- Out of scope: do not change {{P}}FARM and {{P}}MILK.

# 7. Acceptance
- The program is active and has no syntax error.
- The hidden tests pass.
- Write ABAP Unit tests as local test classes in the program.