fix&feature: fixxing some logical bogs and adding cursor pagination

src/modules/task-manager/providers/task.service.ts

@@ -11,6 +11,8 @@ import { TaskMessage, TaskPhaseMessage } from "../../../common/enums/message.enu
 import { TaskPhaseRepository } from "../repositories/task-phase.repository";
 import { TMTaskPhase } from "../entities/task-phase.entity";
 import { PermissionEnum } from "../../users/enums/permission.enum";
+import { encodeCursor } from "../../utils/providers/cursor-pagination.utils";
+import { CursorDirection, CursorPaginationDto } from "../../../common/DTO/cursor-pagination.dto";
 
 @Injectable()
 export class TaskService {
@@ -126,4 +128,61 @@ export class TaskService {
     const taskDetail = await this.taskRepository.getTaskDetail(taskId);
     return taskDetail;
   }
+
+  async findTasksByTaskPhase(
+    taskPhaseId: string,
+    pagination: CursorPaginationDto,
+  ): Promise<{
+    data: TMTask[];
+    nextCursor: string | null;
+    previousCursor: string | null;
+    hasNextPage: boolean;
+    hasPreviousPage: boolean;
+    cursorPaginate: true;
+  }> {
+    await this.findTaskPhaseOrFail(taskPhaseId);
+
+    const isBackward = pagination.direction === CursorDirection.PREV;
+    const { items, hasMore } = await this.taskRepository.findTasksByTaskPhase(taskPhaseId, pagination);
+
+    // paging backward always has more ahead (we came from there); paging forward relies on
+    // whether a cursor was even supplied to know whether anything precedes this page
+    const hasNextPage = items.length > 0 && (isBackward ? true : hasMore);
+    const hasPreviousPage = items.length > 0 && (isBackward ? hasMore : !!pagination.cursor);
+
+    const nextCursor = hasNextPage ? encodeCursor(items[items.length - 1]) : null;
+    const previousCursor = hasPreviousPage ? encodeCursor(items[0]) : null;
+
+    return { data: items, nextCursor, previousCursor, hasNextPage, hasPreviousPage, cursorPaginate: true };
+  }
+
+  async changePriority(srcTaskId: string, destTaskId: string): Promise<TMTask> {
+    const srcTask = await this.findOneOrFail(srcTaskId);
+    const desTask = await this.findOneOrFail(destTaskId);
+
+    if (srcTask.taskPhaseId !== desTask.taskPhaseId)
+      throw new BadRequestException(TaskMessage.TASKS_NOT_IN_THE_SAME_TASK_PHASE);
+
+    let movingUp: boolean = false;
+
+    if(srcTask.priority < desTask.priority) {
+      movingUp  = true;
+    } else if(srcTask.priority < desTask.priority) {
+      movingUp = false;
+    } else {
+      if(srcTask.createdAt > desTask.createdAt) {
+        movingUp = true;
+      }else {
+        movingUp = false;
+      }
+    }
+
+    const priorityChange: number = movingUp ? 1 : -1;
+
+    srcTask.priority = desTask.priority + priorityChange;
+
+    await this.taskRepository.save(srcTask);
+
+    return srcTask;
+  }
 }