task-stream/libs/api/tracker/application/src/lib/workflows.service.ts

import { Injectable } from '@nestjs/common';
import {
  DEFAULT_PROJECT_SETTINGS,
  IssueReadModel,
  ProjectWorkflow,
} from '@task-stream/api/tracker/domain';
import { FindProjectsRepository } from './ports/find-projects.repository';

/** How long a project's workflow is reused (a board asks once per ticket). */
const TTL_MS = 2_000;

/**
 * The workflow of each project, for presenting tickets (e.g. which statuses a
 * ticket can move to). Commands always load the aggregate instead.
 */
@Injectable()
export class WorkflowsService {
  private readonly cache = new Map<
    string,
    { at: number; workflow: Promise<ProjectWorkflow> }
  >();

  constructor(private readonly projects: FindProjectsRepository) {}

  of(projectId: string): Promise<ProjectWorkflow> {
    const now = Date.now();
    const hit = this.cache.get(projectId);
    if (hit && now - hit.at < TTL_MS) return hit.workflow;
    for (const [id, entry] of this.cache)
      if (now - entry.at >= TTL_MS) this.cache.delete(id);
    const workflow = this.projects
      .findById(projectId)
      .then(
        (project) =>
          new ProjectWorkflow(project?.settings ?? DEFAULT_PROJECT_SETTINGS),
      );
    this.cache.set(projectId, { at: now, workflow });
    return workflow;
  }

  /** Active statuses the ticket can move to next. */
  async allowedTransitions(issue: IssueReadModel): Promise<string[]> {
    return (await this.of(issue.projectId)).allowedFrom(issue.status);
  }
}