Endpoint for last motnhs graph was added

src/main/java/ntnu/idatt2016/v233/SmartMat/controller/group/WasteController.java

@@ -79,4 +79,17 @@ public class WasteController {
         return wasteService.getCakeDiagram(groupId).map(ResponseEntity::ok).orElseGet(()->ResponseEntity.notFound().build());
     }
 
+
+    /**
+     * Get the information of the last months of a specific group.
+     *
+     * @param groupId the id of the group to get the information for
+     * @return a ResponseEntity object containing an array of doubles representing the waste for each category
+     * in the last four months, or a not found response if the group does not exist or has no waste data
+     */
+    @GetMapping("/statistic/lastMonths/{groupId}")
+    public ResponseEntity<double[]> getInformationOfLastMoths(@PathVariable("groupId") long groupId){
+        return wasteService.getLastMonth(groupId).map(ResponseEntity::ok).orElseGet(()->ResponseEntity.notFound().build());
+    }
+
 }

src/main/java/ntnu/idatt2016/v233/SmartMat/service/group/WasteService.java

 package ntnu.idatt2016.v233.SmartMat.service.group;
 
+import java.nio.channels.FileChannel;
 import java.sql.Timestamp;
 import java.util.List;
 import lombok.AllArgsConstructor;
@@ -77,4 +78,15 @@ public class WasteService {
         return group.map(value -> StatisticUtil.getNumberOfWasteByCategoryName(wasteRepository.findByGroupId(value).get()));
     }
 
+    /**
+     * Retrieve an optional array of doubles representing the amount of waste produced in each of the last 4 months for a given group.
+     *
+     * @param groupId a long representing the id of the group whose waste production statistics are to be retrieved
+     * @return an optional array of doubles representing the amount of waste produced in each of the last 4 months for the given group,
+     *         or an empty optional if the group could not be found or no waste was produced in the last 4 months
+     */
+    public Optional<double[]>  getLastMonth(long groupId) {
+        Optional<Group> group = groupRepository.findByGroupId(groupId);
+        return group.map(value -> StatisticUtil.getNumberOfWasteByLastMonth(wasteRepository.findByGroupId(value).get()));
+    }
 }

src/main/java/ntnu/idatt2016/v233/SmartMat/util/StatisticUtil.java

@@ -3,6 +3,9 @@ package ntnu.idatt2016.v233.SmartMat.util;
 import ntnu.idatt2016.v233.SmartMat.entity.Waste;
 
 import java.sql.Date;
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 
 
@@ -47,4 +50,71 @@ public class StatisticUtil {
         }
         return numberOfWastes;
     }
+
+    /**
+     * Calculates the sum of waste for each of the four previous months.
+     * The amount of waste is converted to kilograms if the unit is in liters, grams, milliliters, centiliters, or deciliters.
+     *
+     * @param wastes the list of wastes to calculate the sum from
+     * @return an array of four doubles representing the sum of waste for each of the last four months,
+     *         in the same order as the months are counted backwards from the current month
+     */
+    public static double[] getNumberOfWasteByLastMonth(List<Waste> wastes){
+        double[] result = new double[4];
+        HashMap<Integer,List<Waste>> hashMap = new HashMap<>();
+
+        LocalDate localDate = LocalDate.now();
+        int currentMonth = localDate.getMonthValue();
+        int currentYear = localDate.getYear();
+        for(Waste waste : wastes){
+            LocalDate localDate1 = waste.getTimestamp().toLocalDateTime().toLocalDate();
+            if(currentMonth == localDate1.getMonthValue() && currentYear == localDate1.getYear()){
+                hashMap.computeIfAbsent(0, k -> new ArrayList<>());
+                hashMap.get(0).add(waste);
+            }
+            if(Math.abs((currentMonth-1) % 12) == localDate1.getMonthValue() && currentYear == localDate1.getYear()){
+                hashMap.computeIfAbsent(1, k -> new ArrayList<>());
+                hashMap.get(1).add(waste);
+            }
+            if(Math.abs((currentMonth-2) % 12) == localDate1.getMonthValue() && currentYear == localDate1.getYear()){
+                hashMap.computeIfAbsent(2, k -> new ArrayList<>());
+                hashMap.get(2).add(waste);
+            }
+            if(Math.abs((currentMonth-3) % 12) == localDate1.getMonthValue() && currentYear == localDate1.getYear()){
+                hashMap.computeIfAbsent(3, k -> new ArrayList<>());
+                hashMap.get(3).add(waste);
+            }
+        }
+        for(int i = 0; i < 4; i++){
+            result[i] = getSumOfWaste(hashMap.get(i));
+        }
+        return result;
+    }
+
+    /**
+     * Calculates the sum of waste for a list of wastes, and converts the amounts to kilograms if the unit is in liters,
+     * grams, milliliters, centiliters, or deciliters.
+     *
+     * @param wastes the list of wastes to calculate the sum from
+     * @return the sum of waste in kilograms
+     */
+    private static double getSumOfWaste(List<Waste> wastes){
+        double sum = 0.0;
+        if(wastes == null){
+            wastes = new ArrayList<>();
+        }
+        for(Waste waste: wastes){
+            switch (waste.getEan().getUnit()){
+                case "l" -> sum += waste.getAmount() * 0.998;
+                case "kg" -> sum += waste.getAmount();
+                case "g" -> sum += waste.getAmount() * 0.001;
+                case "ml" -> sum += waste.getAmount() * 0.000998;
+                case "cl" -> sum += waste.getAmount() * 0.00998;
+                case "dl" -> sum += waste.getAmount() * 0.0998;
+                default -> sum += 0.1;
+            }
+        }
+        return sum;
+    }
+
 }
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