WIP: Allow different amounts per month for categories

api/build.gradle

@@ -27,6 +27,10 @@ jar {
     description = "twigs-server"
 }
 
+test {
+    useJUnitPlatform()
+}
+
 mainClassName = "com.wbrawner.budgetserver.BudgetServerApplication"
 
 sourceCompatibility = 14

api/src/main/java/com/wbrawner/budgetserver/category/Category.java

@@ -3,6 +3,9 @@ package com.wbrawner.budgetserver.category;
 import com.wbrawner.budgetserver.budget.Budget;
 
 import javax.persistence.*;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.Set;
 
 @Entity
 public class Category implements Comparable<Category> {
@@ -11,26 +14,21 @@ public class Category implements Comparable<Category> {
     private final Long id = null;
     private String title;
     private String description;
-    private long amount;
+    @JoinColumn(nullable = false)
+    @OneToMany(mappedBy = "category", fetch = FetchType.EAGER)
+    private final Set<CategoryAmount> amounts = new HashSet<>();
     @JoinColumn(nullable = false)
     @ManyToOne
     private Budget budget;
     private boolean expense;
 
     public Category() {
-        this(null, null, 0L, null, true);
+        this(null, null, null, true);
     }
 
-    public Category(
-            String title,
-            String description,
-            Long amount,
-            Budget budget,
-            boolean expense
-    ) {
+    public Category(String title, String description, Budget budget, boolean expense) {
         this.title = title;
         this.description = description;
-        this.amount = amount;
         this.budget = budget;
         this.expense = expense;
     }
@@ -60,12 +58,51 @@ public class Category implements Comparable<Category> {
         this.description = description;
     }
 
-    public long getAmount() {
-        return amount;
+    /**
+     * Returns the effective amount for the given year and month.
+     *
+     * Category amounts are stored via the {@link CategoryAmount} object, where the month is the first month where
+     * the given amount is active and the year is the first year the given amount is active. So if you created a
+     * category in January of 2020 and then queried the amount for April of 2020, the amount would be returned from
+     * January. If in May the amount is updated, then that amount would be returned for all the months following May
+     * until the next update.
+     * @param month the maximum month to search
+     * @param year the maximum year to search
+     * @return the amount value from the {@link CategoryAmount} that corresponds to the given month and year, or 0 if
+     * no current or previous amounts can be found.
+     */
+    public long getAmount(int month, int year) {
+        return this.amounts.stream()
+                .filter(categoryAmount -> categoryAmount.getMonth() <= month && categoryAmount.getYear() <= year)
+                .max(Comparator.comparingInt(CategoryAmount::getYear).thenComparingInt(CategoryAmount::getMonth))
+                .orElse(new CategoryAmount(this, 0L, month, year))
+                .getAmount();
     }
 
-    public void setAmount(long amount) {
-        this.amount = amount;
+    public long getMostRecentAmount() {
+        return this.amounts.stream()
+                .sorted()
+                .findFirst()
+                .orElse(new CategoryAmount(this, 0L, 0, 0))
+                .getAmount();
+    }
+
+    public void setAmount(long amount, int month, int year) {
+        CategoryAmount categoryAmount = this.amounts.stream()
+                .filter(ca -> ca.getMonth() == month && ca.getYear() == year)
+                .findAny()
+                .orElse(null);
+        if (categoryAmount == null) {
+            categoryAmount = new CategoryAmount();
+            this.amounts.add(categoryAmount);
+        }
+        categoryAmount.setAmount(amount);
+        categoryAmount.setMonth(month);
+        categoryAmount.setYear(year);
+    }
+
+    public void setAmount(CategoryAmountRequest amount) {
+        setAmount(amount.getAmount(), amount.getMonth(), amount.getYear());
     }
 
     public Budget getBudget() {

api/src/main/java/com/wbrawner/budgetserver/category/CategoryAmount.java

@@ -0,0 +1,74 @@
+package com.wbrawner.budgetserver.category;
+
+import javax.persistence.*;
+import javax.validation.constraints.NotNull;
+import java.util.Comparator;
+
+@Entity
+public class CategoryAmount implements Comparable<CategoryAmount> {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+    @ManyToOne
+    private Category category;
+    private long amount;
+    private int month;
+    private int year;
+
+    public CategoryAmount(Category category, long amount, int month, int year) {
+        this.category = category;
+        this.amount = amount;
+        if (month < 0 || month > 11) throw new IllegalArgumentException("Invalid month");
+        this.month = month;
+        this.year = year;
+    }
+
+    public CategoryAmount() {
+        // required empty constructor for Hibernate
+        this(null, 0L, 0, 0);
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public Category getCategory() {
+        return category;
+    }
+
+    public long getAmount() {
+        return amount;
+    }
+
+    public int getMonth() {
+        return month;
+    }
+
+    public int getYear() {
+        return year;
+    }
+
+    public void setCategory(Category category) {
+        this.category = category;
+    }
+
+    public void setAmount(long amount) {
+        this.amount = amount;
+    }
+
+    public void setMonth(int month) {
+        this.month = month;
+    }
+
+    public void setYear(int year) {
+        this.year = year;
+    }
+
+    @Override
+    public int compareTo(@NotNull CategoryAmount o) {
+        int yearComparison = Integer.compare(o.getYear(), getYear());
+        if (yearComparison != 0) return yearComparison;
+        return Integer.compare(o.getMonth(), getMonth());
+    }
+}

api/src/main/java/com/wbrawner/budgetserver/category/CategoryAmountRequest.java

@@ -0,0 +1,31 @@
+package com.wbrawner.budgetserver.category;
+
+import java.util.Calendar;
+
+public class CategoryAmountRequest {
+    private final Long amount;
+    private final Integer month;
+    private final Integer year;
+
+    public CategoryAmountRequest() {
+        this(null, null, null);
+    }
+
+    public CategoryAmountRequest(Long amount, Integer month, Integer year) {
+        this.amount = amount;
+        this.month = month;
+        this.year = year;
+    }
+
+    public long getAmount() {
+        return amount != null ? amount : 0L;
+    }
+
+    public int getMonth() {
+        return month != null ? month : Calendar.getInstance().get(Calendar.MONTH);
+    }
+
+    public int getYear() {
+        return year != null ? year : Calendar.getInstance().get(Calendar.YEAR);
+    }
+}

api/src/main/java/com/wbrawner/budgetserver/category/CategoryController.java

@@ -41,14 +41,21 @@ class CategoryController {
 
     @GetMapping(path = "", produces = {MediaType.APPLICATION_JSON_VALUE})
     @ApiOperation(value = "getCategories", nickname = "getCategories", tags = {"Categories"})
-    ResponseEntity<List<CategoryResponse>> getCategories(
+    ResponseEntity<Object> getCategories(
             @RequestParam(name = "budgetIds", required = false) List<Long> budgetIds,
             @RequestParam(name = "isExpense", required = false) Boolean isExpense,
+            @RequestParam(name = "month", required = false) Integer month,
+            @RequestParam(name = "year", required = false) Integer year,
             @RequestParam(name = "count", required = false) Integer count,
             @RequestParam(name = "page", required = false) Integer page,
             @RequestParam(name = "false", required = false) String sortBy,
             @RequestParam(name = "sortOrder", required = false) Sort.Direction sortOrder
     ) {
+        if ((month == null && year != null) || (month != null && year == null)) {
+            return ResponseEntity.badRequest()
+                    .body(new ErrorResponse("month and year must be provided together or not at all."));
+        }
+
         List<UserPermission> userPermissions;
         if (budgetIds != null && !budgetIds.isEmpty()) {
             userPermissions = userPermissionsRepository.findAllByUserAndBudget_IdIn(
@@ -69,6 +76,7 @@ class CategoryController {
                 sortOrder != null ? sortOrder : Sort.Direction.ASC,
                 sortBy != null ? sortBy : "title"
         );
+
         List<Category> categories;
         if (isExpense == null) {
             categories = categoryRepository.findAllByBudgetIn(budgets, pageRequest);
@@ -78,7 +86,13 @@ class CategoryController {
 
         return ResponseEntity.ok(
                 categories.stream()
-                        .map(CategoryResponse::new)
+                        .map(category -> {
+                            if (month != null) {
+                                return new CategoryResponse(category, month, year);
+                            } else {
+                                return new CategoryResponse(category);
+                            }
+                        })
                         .collect(Collectors.toList())
         );
     }
@@ -122,13 +136,14 @@ class CategoryController {
             return ResponseEntity.status(HttpStatus.FORBIDDEN).build();
         }
         var budget = userResponse.getBudget();
-        return ResponseEntity.ok(new CategoryResponse(categoryRepository.save(new Category(
+        var category = new Category(
                 request.getTitle(),
                 request.getDescription(),
-                request.getAmount(),
                 budget,
                 request.getExpense()
-        ))));
+        );
+        category.setAmount(request.getAmount());
+        return ResponseEntity.ok(new CategoryResponse(categoryRepository.save(category)));
     }
 
     @PutMapping(path = "/{id}", consumes = {MediaType.APPLICATION_JSON_VALUE}, produces = {MediaType.APPLICATION_JSON_VALUE})

api/src/main/java/com/wbrawner/budgetserver/category/CategoryResponse.java

@@ -10,12 +10,23 @@ public class CategoryResponse {
     private final long budgetId;
     private final boolean expense;
 
+    public CategoryResponse(Category category, int month, int year) {
+        this(
+                Objects.requireNonNull(category.getId()),
+                category.getTitle(),
+                category.getDescription(),
+                category.getAmount(month, year),
+                Objects.requireNonNull(category.getBudget()).getId(),
+                category.isExpense()
+        );
+    }
+
     public CategoryResponse(Category category) {
         this(
                 Objects.requireNonNull(category.getId()),
                 category.getTitle(),
                 category.getDescription(),
-                category.getAmount(),
+                category.getMostRecentAmount(),
                 Objects.requireNonNull(category.getBudget()).getId(),
                 category.isExpense()
         );

api/src/main/java/com/wbrawner/budgetserver/category/NewCategoryRequest.java

@@ -3,7 +3,7 @@ package com.wbrawner.budgetserver.category;
 public class NewCategoryRequest {
     private final String title;
     private final String description;
-    private final Long amount;
+    private final CategoryAmountRequest amount;
     private final Long budgetId;
     private final Boolean expense;
 
@@ -11,7 +11,11 @@ public class NewCategoryRequest {
         this(null, null, null, null, null);
     }
 
-    public NewCategoryRequest(String title, String description, Long amount, Long budgetId, Boolean expense) {
+    public NewCategoryRequest(String title,
+                              String description,
+                              CategoryAmountRequest amount,
+                              Long budgetId,
+                              Boolean expense) {
         this.title = title;
         this.description = description;
         this.amount = amount;
@@ -27,7 +31,7 @@ public class NewCategoryRequest {
         return description;
     }
 
-    public Long getAmount() {
+    public CategoryAmountRequest getAmount() {
         return amount;
     }
 

api/src/main/java/com/wbrawner/budgetserver/category/UpdateCategoryRequest.java

@@ -3,14 +3,19 @@ package com.wbrawner.budgetserver.category;
 public class UpdateCategoryRequest {
     private final String title;
     private final String description;
-    private final Long amount;
+    private final CategoryAmountRequest amount;
     private final Boolean expense;
 
     public UpdateCategoryRequest() {
         this(null, null, null, null);
     }
 
-    public UpdateCategoryRequest(String title, String description, Long amount, Boolean expense) {
+    public UpdateCategoryRequest(
+            String title,
+            String description,
+            CategoryAmountRequest amount,
+            Boolean expense
+    ) {
         this.title = title;
         this.description = description;
         this.amount = amount;
@@ -25,7 +30,7 @@ public class UpdateCategoryRequest {
         return description;
     }
 
-    public Long getAmount() {
+    public CategoryAmountRequest getAmount() {
         return amount;
     }
 

api/src/test/java/com/wbrawner/budgetserver/category/CategoryAmountTest.java

@@ -0,0 +1,28 @@
+package com.wbrawner.budgetserver.category;
+
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class CategoryAmountTest {
+
+    @Test
+    public void sortTest() {
+        var first = new CategoryAmount(null, 0L, 4, 2020);
+        var second = new CategoryAmount(null, 0L, 2, 2020);
+        var third = new CategoryAmount(null, 0L, 2, 2019);
+        var categoryAmounts = Arrays.asList(
+                third,
+                first,
+                second
+        );
+        Collections.sort(categoryAmounts);
+        assertEquals(first, categoryAmounts.get(0));
+        assertEquals(second, categoryAmounts.get(1));
+        assertEquals(third, categoryAmounts.get(2));
+    }
+}

api/src/test/java/com/wbrawner/budgetserver/category/CategoryTest.java

@@ -0,0 +1,52 @@
+package com.wbrawner.budgetserver.category;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.params.provider.Arguments.arguments;
+
+class CategoryTest {
+    private final Category category = new Category("Test Category", null, null, false);
+
+    @BeforeEach
+    public void setup() {
+        category.setAmount(815L, 8, 2015);
+        category.setAmount(310L, 3, 2010);
+        category.setAmount(920L, 9, 2020);
+        category.setAmount(1117L, 11, 2017);
+        category.setAmount(217L, 2, 2017);
+        category.setAmount(412L, 4, 2012);
+    }
+
+    @ParameterizedTest(name = "{index} amount: {0} month: {1}, year: {2}")
+    @ArgumentsSource(AmountArgumentsSource.class)
+    void getAmount(long expected, int month, int year) {
+        assertEquals(expected, category.getAmount(month, year));
+    }
+
+    @Test
+    void getMostRecentAmount() {
+        assertEquals(920L, category.getMostRecentAmount());
+    }
+
+    public static class AmountArgumentsSource implements ArgumentsProvider {
+
+        @Override
+        public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+            return Stream.of(
+                    arguments(0L, 1, 2014),
+                    arguments(412L, 5, 2013),
+                    arguments(310L, 3, 2010),
+                    arguments(920L, 10, 2021)
+            );
+        }
+    }
+}