feat(task 2): add Statistics feature

src/main/java/lv/ctco/springboottemplate/errorhandling/ErrorMessages.java

@@ -0,0 +1,6 @@
+package lv.ctco.springboottemplate.errorhandling;
+
+public final class ErrorMessages {
+  public static final String TODO_STATS_DATE_RANGE_INVALID =
+      "Either from, to, or both can be provided. 'from' date must be before or equal to 'to' date";
+}

src/main/java/lv/ctco/springboottemplate/errorhandling/ExceptionHandler.java

@@ -0,0 +1,43 @@
+package lv.ctco.springboottemplate.errorhandling;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import org.springframework.context.support.DefaultMessageSourceResolvable;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.validation.BindException;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+
+@RestControllerAdvice
+public class ExceptionHandler {
+  @org.springframework.web.bind.annotation.ExceptionHandler({
+    MethodArgumentNotValidException.class,
+    BindException.class
+  })
+  public ResponseEntity<Map<String, Object>> handleValidationExceptions(Exception ex) {
+    List<String> errors = new ArrayList<>();
+
+    if (ex instanceof MethodArgumentNotValidException invalidArgumentException) {
+      errors =
+          invalidArgumentException.getBindingResult().getAllErrors().stream()
+              .map(DefaultMessageSourceResolvable::getDefaultMessage)
+              .toList();
+    } else if (ex instanceof BindException be) {
+      errors =
+          be.getBindingResult().getAllErrors().stream()
+              .map(DefaultMessageSourceResolvable::getDefaultMessage)
+              .toList();
+    }
+
+    return ResponseEntity.badRequest()
+        .body(Map.of("status", 400, "error", "Bad Request", "messages", errors));
+  }
+
+  @org.springframework.web.bind.annotation.ExceptionHandler(RuntimeException.class)
+  public ResponseEntity<Map<String, String>> handleServerError(RuntimeException ex) {
+    return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
+        .body(Map.of("error", "Internal server error", "details", ex.getMessage()));
+  }
+}

src/main/java/lv/ctco/springboottemplate/features/todo/Todo.java

@@ -32,4 +32,5 @@ public record Todo(
     String createdBy,
     String updatedBy,
     Instant createdAt,
-    Instant updatedAt) {}
+    Instant updatedAt,
+    Instant completedAt) {}

src/main/java/lv/ctco/springboottemplate/features/todo/TodoDataInitializer.java

@@ -22,43 +22,106 @@ CommandLineRunner initDatabase(TodoRepository todoRepository) {
       var todos =
           List.of(
               new Todo(
-                  null, "Buy groceries", "Milk, eggs, bread", false, "system", "system", now, now),
+                  null,
+                  "Buy groceries",
+                  "Milk, eggs, bread",
+                  false,
+                  "user3",
+                  "user3",
+                  now,
+                  null,
+                  null),
               new Todo(
                   null,
                   "Call dentist",
                   "Schedule annual checkup",
                   true,
+                  "user1",
                   "system",
-                  "system",
+                  now,
                   now,
                   now),
               new Todo(
                   null,
                   "Fix bug in production",
                   "High priority issue #123",
                   false,
-                  "system",
-                  "system",
+                  "user1",
+                  "user3",
                   now,
-                  now),
+                  null,
+                  null),
               new Todo(
                   null,
                   "Write documentation",
                   "Update API docs",
                   false,
-                  "system",
-                  "system",
+                  "user2",
+                  "user4",
                   now,
-                  now),
+                  null,
+                  null),
               new Todo(
                   null,
                   "Plan vacation",
                   "Research destinations",
                   true,
+                  "user2",
+                  "user5",
+                  now,
+                  now,
+                  now),
+              // 👇 new 5 todos
+              new Todo(
+                  null,
+                  "Clean workspace",
+                  "Organize desk and archive old files",
+                  false,
+                  "user2",
+                  "user1",
+                  now,
+                  null,
+                  null),
+              new Todo(
+                  null,
+                  "Submit expense report",
+                  "Expenses for August",
+                  true,
+                  "user3",
                   "system",
-                  "system",
                   now,
-                  now));
+                  now,
+                  now),
+              new Todo(
+                  null,
+                  "Prepare presentation",
+                  "Slides for Monday’s meeting",
+                  false,
+                  "user3",
+                  "user2",
+                  now,
+                  null,
+                  null),
+              new Todo(
+                  null,
+                  "Refactor authentication module",
+                  "Improve security and code quality",
+                  true,
+                  "user1",
+                  "user2",
+                  now,
+                  now,
+                  now),
+              new Todo(
+                  null,
+                  "Read new tech article",
+                  "Microservices best practices",
+                  false,
+                  "user2",
+                  "user3",
+                  now,
+                  null,
+                  null));
 
       todoRepository.saveAll(todos);
       log.info("Initialized database with {} todo items", todos.size());

src/main/java/lv/ctco/springboottemplate/features/todo/TodoService.java

@@ -50,7 +50,17 @@ public List<Todo> searchTodos(String title) {
 
   public Todo createTodo(String title, String description, boolean completed, String createdBy) {
     var now = Instant.now();
-    var todo = new Todo(null, title, description, completed, createdBy, createdBy, now, now);
+    var todo =
+        new Todo(
+            null,
+            title,
+            description,
+            completed,
+            createdBy,
+            createdBy,
+            now,
+            now,
+            completed ? Instant.now() : null);
     return todoRepository.save(todo);
   }
 
@@ -69,7 +79,8 @@ public Optional<Todo> updateTodo(
                       existingTodo.createdBy(),
                       updatedBy,
                       existingTodo.createdAt(),
-                      Instant.now());
+                      Instant.now(),
+                      completed ? Instant.now() : existingTodo.completedAt());
               return todoRepository.save(updatedTodo);
             });
   }

src/main/java/lv/ctco/springboottemplate/features/todo_statistics/TodoStatisticsController.java

@@ -0,0 +1,33 @@
+package lv.ctco.springboottemplate.features.todo_statistics;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import jakarta.validation.Valid;
+import lv.ctco.springboottemplate.features.todo.Todo;
+import lv.ctco.springboottemplate.features.todo_statistics.dto.TodoStatistics;
+import lv.ctco.springboottemplate.features.todo_statistics.dto.TodoStatisticsRequest;
+import org.springdoc.core.annotations.ParameterObject;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+/** REST controller for getting statistics for {@link Todo} items. */
+@RestController
+@RequestMapping("/api/statistics")
+@Tag(name = "Statistics Controller", description = "Provides statistics for Todo items")
+public class TodoStatisticsController {
+  private final TodoStatisticsService statisticsService;
+
+  public TodoStatisticsController(TodoStatisticsService statisticsService) {
+    this.statisticsService = statisticsService;
+  }
+
+  @GetMapping
+  @Operation(summary = "Get todo items statistics")
+  public ResponseEntity<TodoStatistics> getStatistics(
+      @Valid @ParameterObject @ModelAttribute TodoStatisticsRequest request) {
+
+    TodoStatistics stats = statisticsService.makeStatistics(request);
+
+    return ResponseEntity.ok(stats);
+  }
+}

src/main/java/lv/ctco/springboottemplate/features/todo_statistics/TodoStatisticsFormatEnum.java

@@ -0,0 +1,31 @@
+package lv.ctco.springboottemplate.features.todo_statistics;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+public enum TodoStatisticsFormatEnum {
+  SUMMARY("summary"),
+  DETAILED("detailed");
+
+  private final String value;
+
+  TodoStatisticsFormatEnum(String value) {
+    this.value = value;
+  }
+
+  @JsonValue
+  public String getValue() {
+    return value;
+  }
+
+  @JsonCreator
+  public static TodoStatisticsFormatEnum fromString(String value) {
+    for (TodoStatisticsFormatEnum format : TodoStatisticsFormatEnum.values()) {
+      if (format.value.equalsIgnoreCase(value)) {
+        return format;
+      }
+    }
+    throw new IllegalArgumentException(
+        "Unknown format: " + value + "must be summary, detailed or empty");
+  }
+}

src/main/java/lv/ctco/springboottemplate/features/todo_statistics/TodoStatisticsFormatEnumConverter.java

@@ -0,0 +1,17 @@
+package lv.ctco.springboottemplate.features.todo_statistics;
+
+import com.mongodb.lang.Nullable;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.stereotype.Component;
+
+@Component
+public class TodoStatisticsFormatEnumConverter
+    implements Converter<String, TodoStatisticsFormatEnum> {
+  @Override
+  public TodoStatisticsFormatEnum convert(@Nullable String source) {
+    if (source == null || source.isBlank()) {
+      return TodoStatisticsFormatEnum.SUMMARY;
+    }
+    return TodoStatisticsFormatEnum.fromString(source);
+  }
+}