taskbuffer/readme.md

# @push.rocks/taskbuffer 🚀

> **Modern TypeScript task orchestration with smart buffering, scheduling, labels, and real-time event streaming**

[![npm version](https://img.shields.io/npm/v/@push.rocks/taskbuffer.svg)](https://www.npmjs.com/package/@push.rocks/taskbuffer)
[![TypeScript](https://img.shields.io/badge/TypeScript-5.x-blue.svg)](https://www.typescriptlang.org/)
[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)

## Issue Reporting and Security

For reporting bugs, issues, or security vulnerabilities, please visit [community.foss.global/](https://community.foss.global/). This is the central community hub for all issue reporting. Developers who sign and comply with our contribution agreement and go through identification can also get a [code.foss.global/](https://code.foss.global/) account to submit Pull Requests directly.

## 🌟 Features

- **🎯 Type-Safe Task Management** — Full TypeScript support with generics and type inference
- **📊 Real-Time Progress Tracking** — Step-based progress with percentage weights
- **⚡ Smart Buffering** — Intelligent request debouncing and batching
- **⏰ Cron Scheduling** — Schedule tasks with cron expressions
- **🔗 Task Chains & Parallel Execution** — Sequential and parallel task orchestration
- **🏷️ Labels** — Attach arbitrary `Record<string, string>` metadata (userId, tenantId, etc.) for multi-tenant filtering
- **📡 Push-Based Events** — rxjs `Subject<ITaskEvent>` on every Task and TaskManager for real-time state change notifications
- **🛡️ Error Handling** — Configurable error propagation with `catchErrors`, error tracking, and clear error state
- **🎨 Web Component Dashboard** — Built-in Lit-based dashboard for real-time task visualization
- **🌐 Distributed Coordination** — Abstract coordinator for multi-instance task deduplication

## 📦 Installation

```bash
pnpm add @push.rocks/taskbuffer
# or
npm install @push.rocks/taskbuffer
```

## 🚀 Quick Start

### Basic Task

```typescript
import { Task } from '@push.rocks/taskbuffer';

const greetTask = new Task({
  name: 'Greet',
  taskFunction: async (name) => {
    return `Hello, ${name}!`;
  },
});

const result = await greetTask.trigger('World');
console.log(result); // "Hello, World!"
```

### Task with Steps & Progress 📊

```typescript
const deployTask = new Task({
  name: 'Deploy',
  steps: [
    { name: 'build', description: 'Building app', percentage: 30 },
    { name: 'test', description: 'Running tests', percentage: 20 },
    { name: 'deploy', description: 'Deploying to server', percentage: 40 },
    { name: 'verify', description: 'Verifying deployment', percentage: 10 },
  ] as const,
  taskFunction: async () => {
    deployTask.notifyStep('build');
    await buildApp();

    deployTask.notifyStep('test');
    await runTests();

    deployTask.notifyStep('deploy');
    await deployToServer();

    deployTask.notifyStep('verify');
    await verifyDeployment();

    return 'Deployment successful!';
  },
});

await deployTask.trigger();
console.log(deployTask.getProgress()); // 100
console.log(deployTask.getStepsMetadata()); // Step details with status
```

> **Note:** `notifyStep()` is fully type-safe — TypeScript only accepts step names you declared in the `steps` array when you use `as const`.

## 🎯 Core Concepts

### Task Buffering — Intelligent Request Management

Prevent overwhelming your system with rapid-fire requests:

```typescript
const apiTask = new Task({
  name: 'APIRequest',
  buffered: true,
  bufferMax: 5, // Maximum 5 concurrent executions
  execDelay: 100, // Minimum 100ms between executions
  taskFunction: async (endpoint) => {
    return await fetch(endpoint).then((r) => r.json());
  },
});

// Rapid fire 100 calls — only bufferMax execute concurrently
for (let i = 0; i < 100; i++) {
  apiTask.trigger(`/api/data/${i}`);
}
```

**Buffer Behavior:**

- First `bufferMax` calls execute immediately
- Additional calls are queued
- When buffer is full, new calls overwrite the last queued item
- Perfect for real-time data streams where only recent data matters

### Task Chains — Sequential Workflows 🔗

Build complex workflows with automatic data flow between tasks:

```typescript
import { Taskchain } from '@push.rocks/taskbuffer';

const fetchTask = new Task({
  name: 'Fetch',
  taskFunction: async () => {
    const res = await fetch('/api/data');
    return res.json();
  },
});

const transformTask = new Task({
  name: 'Transform',
  taskFunction: async (data) => {
    return data.map((item) => ({ ...item, transformed: true }));
  },
});

const saveTask = new Task({
  name: 'Save',
  taskFunction: async (transformedData) => {
    await database.save(transformedData);
    return transformedData.length;
  },
});

const pipeline = new Taskchain({
  name: 'DataPipeline',
  taskArray: [fetchTask, transformTask, saveTask],
});

const savedCount = await pipeline.trigger();
console.log(`Saved ${savedCount} items`);
```

Taskchain also supports dynamic mutation:

```typescript
pipeline.addTask(newTask); // Append to chain
pipeline.removeTask(oldTask); // Remove by reference (returns boolean)
pipeline.shiftTask(); // Remove & return first task
```

Error context is rich — a chain failure includes the chain name, failing task name, task index, and preserves the original error as `.cause`.

### Parallel Execution — Concurrent Processing ⚡

Execute multiple tasks simultaneously:

```typescript
import { Taskparallel } from '@push.rocks/taskbuffer';

const parallel = new Taskparallel({
  taskArray: [emailTask, smsTask, pushNotificationTask, webhookTask],
});

await parallel.trigger(notificationData);
```

### Debounced Tasks — Smart Trigger Coalescing 🕐

Coalesce rapid triggers into a single execution after a quiet period:

```typescript
import { TaskDebounced } from '@push.rocks/taskbuffer';

const searchTask = new TaskDebounced({
  name: 'Search',
  debounceTimeInMillis: 300,
  taskFunction: async (query) => {
    return await searchAPI(query);
  },
});

// Rapid calls — only the last triggers after 300ms of quiet
searchTask.trigger('h');
searchTask.trigger('he');
searchTask.trigger('hel');
searchTask.trigger('hello'); // ← this one fires
```

### TaskOnce — Single-Execution Guard

Ensure a task only runs once, regardless of how many times it's triggered:

```typescript
import { TaskOnce } from '@push.rocks/taskbuffer';

const initTask = new TaskOnce({
  name: 'Init',
  taskFunction: async () => {
    await setupDatabase();
    console.log('Initialized!');
  },
});

await initTask.trigger(); // Runs
await initTask.trigger(); // No-op
await initTask.trigger(); // No-op
console.log(initTask.hasTriggered); // true
```

### TaskRunner — Managed Queue with Concurrency Control

Process a queue of tasks with a configurable parallelism limit:

```typescript
import { TaskRunner } from '@push.rocks/taskbuffer';

const runner = new TaskRunner();
runner.setMaxParallelJobs(3); // Run up to 3 tasks concurrently

await runner.start();

runner.addTask(taskA);
runner.addTask(taskB);
runner.addTask(taskC);
runner.addTask(taskD); // Queued until a slot opens

// When done:
await runner.stop();
```

## 🏷️ Labels — Multi-Tenant Task Filtering

Attach arbitrary key-value labels to any task for filtering, grouping, or multi-tenant isolation:

```typescript
const task = new Task({
  name: 'ProcessOrder',
  labels: { userId: 'u-42', tenantId: 'acme-corp', priority: 'high' },
  taskFunction: async (order) => {
    /* ... */
  },
});

// Manipulate labels at runtime
task.setLabel('region', 'eu-west');
task.getLabel('userId'); // 'u-42'
task.hasLabel('tenantId', 'acme-corp'); // true
task.removeLabel('priority'); // true

// Labels are included in metadata snapshots
const meta = task.getMetadata();
console.log(meta.labels); // { userId: 'u-42', tenantId: 'acme-corp', region: 'eu-west' }
```

### Filtering Tasks by Label in TaskManager

```typescript
const manager = new TaskManager();
manager.addTask(orderTask1); // labels: { tenantId: 'acme' }
manager.addTask(orderTask2); // labels: { tenantId: 'globex' }
manager.addTask(orderTask3); // labels: { tenantId: 'acme' }

const acmeTasks = manager.getTasksByLabel('tenantId', 'acme');
// → [orderTask1, orderTask3]

const acmeMetadata = manager.getTasksMetadataByLabel('tenantId', 'acme');
// → [ITaskMetadata, ITaskMetadata]
```

## 📡 Push-Based Events — Real-Time Task Lifecycle

Every `Task` exposes an rxjs `Subject<ITaskEvent>` that emits events as the task progresses through its lifecycle:

```typescript
import type { ITaskEvent } from '@push.rocks/taskbuffer';

const task = new Task({
  name: 'DataSync',
  steps: [
    { name: 'fetch', description: 'Fetching data', percentage: 50 },
    { name: 'save', description: 'Saving data', percentage: 50 },
  ] as const,
  taskFunction: async () => {
    task.notifyStep('fetch');
    const data = await fetchData();
    task.notifyStep('save');
    await saveData(data);
  },
});

// Subscribe to individual task events
task.eventSubject.subscribe((event: ITaskEvent) => {
  console.log(`[${event.type}] ${event.task.name} @ ${new Date(event.timestamp).toISOString()}`);
  if (event.type === 'step') console.log(`  Step: ${event.stepName}`);
  if (event.type === 'failed') console.log(`  Error: ${event.error}`);
});

await task.trigger();
// [started] DataSync @ 2025-01-26T...
// [step] DataSync @ 2025-01-26T...
//   Step: fetch
// [step] DataSync @ 2025-01-26T...
//   Step: save
// [completed] DataSync @ 2025-01-26T...
```

### Event Types

| Type | When | Extra Fields |
| --- | --- | --- |
| `'started'` | Task begins execution | — |
| `'step'` | `notifyStep()` is called | `stepName` |
| `'completed'` | Task finishes successfully | — |
| `'failed'` | Task throws an error | `error` (message string) |

Every event includes a full `ITaskMetadata` snapshot (including labels) at the time of emission.

### Aggregated Events on TaskManager

`TaskManager` automatically aggregates events from all added tasks into a single `taskSubject`:

```typescript
const manager = new TaskManager();
manager.addTask(syncTask);
manager.addTask(reportTask);
manager.addTask(cleanupTask);

// Single subscription for ALL task events
manager.taskSubject.subscribe((event) => {
  sendToMonitoringDashboard(event);
});

// Events stop flowing for a task after removal
manager.removeTask(syncTask);
```

`manager.stop()` automatically cleans up all event subscriptions.

## 🛡️ Error Handling

By default, `trigger()` **rejects** when the task function throws — errors propagate naturally:

```typescript
const task = new Task({
  name: 'RiskyOp',
  taskFunction: async () => {
    throw new Error('something broke');
  },
});

try {
  await task.trigger();
} catch (err) {
  console.error(err.message); // "something broke"
}
```

### Swallowing Errors with `catchErrors`

Set `catchErrors: true` to swallow errors and return `undefined` instead of rejecting:

```typescript
const task = new Task({
  name: 'BestEffort',
  catchErrors: true,
  taskFunction: async () => {
    throw new Error('non-critical');
  },
});

const result = await task.trigger(); // undefined (no throw)
```

### Error State Tracking

Regardless of `catchErrors`, the task tracks errors:

```typescript
console.log(task.lastError); // Error object (or undefined)
console.log(task.errorCount); // Number of failures across all runs
console.log(task.getMetadata().status); // 'failed'

task.clearError(); // Resets lastError to undefined (errorCount stays)
```

On a subsequent successful run, `lastError` is automatically cleared.

## 📋 TaskManager — Centralized Orchestration

```typescript
const manager = new TaskManager();

// Add tasks
manager.addTask(dataProcessor);
manager.addTask(deployTask);

// Schedule with cron expressions
manager.addAndScheduleTask(backupTask, '0 2 * * *'); // Daily at 2 AM
manager.addAndScheduleTask(healthCheck, '*/5 * * * *'); // Every 5 minutes

// Query metadata
const meta = manager.getTaskMetadata('Deploy');
console.log(meta);
// {
//   name: 'Deploy',
//   status: 'completed',
//   steps: [...],
//   currentProgress: 100,
//   runCount: 3,
//   labels: { env: 'production' },
//   lastError: undefined,
//   errorCount: 0,
//   ...
// }

// All tasks at once
const allMeta = manager.getAllTasksMetadata();

// Scheduled task info
const scheduled = manager.getScheduledTasks();
const nextRuns = manager.getNextScheduledRuns(5);

// Trigger by name
await manager.triggerTaskByName('Deploy');

// One-shot: add, execute, collect report, remove
const report = await manager.addExecuteRemoveTask(temporaryTask);
console.log(report);
// {
//   taskName: 'TempTask',
//   startTime: 1706284800000,
//   endTime: 1706284801523,
//   duration: 1523,
//   steps: [...],
//   stepsCompleted: ['step1', 'step2'],
//   progress: 100,
//   result: any
// }

// Lifecycle
await manager.start(); // Starts cron scheduling + distributed coordinator
await manager.stop(); // Stops scheduling, cleans up event subscriptions
```

### Remove Tasks

```typescript
manager.removeTask(task); // Removes from map and unsubscribes event forwarding
manager.descheduleTaskByName('Deploy'); // Remove cron schedule only
```

## 🎨 Web Component Dashboard

Visualize your tasks in real-time with the included Lit-based web component:

```html
<script type="module">
  import { TaskManager } from '@push.rocks/taskbuffer';
  import '@push.rocks/taskbuffer/dist_ts_web/taskbuffer-dashboard.js';

  const manager = new TaskManager();
  // ... add and schedule tasks ...

  const dashboard = document.querySelector('taskbuffer-dashboard');
  dashboard.taskManager = manager;
  dashboard.refreshInterval = 500; // Poll every 500ms
</script>

<taskbuffer-dashboard></taskbuffer-dashboard>
```

The dashboard provides:

- 📊 Real-time progress bars with step indicators
- 📈 Task execution history and metadata
- ⏰ Scheduled task information with next-run times
- 🌓 Light/dark theme support

## 🌐 Distributed Coordination

For multi-instance deployments, extend `AbstractDistributedCoordinator` to prevent duplicate task execution:

```typescript
import { TaskManager, distributedCoordination } from '@push.rocks/taskbuffer';

class RedisCoordinator extends distributedCoordination.AbstractDistributedCoordinator {
  async fireDistributedTaskRequest(request) {
    // Implement leader election / distributed lock via Redis
    return { shouldTrigger: true, considered: true, rank: 1, reason: 'elected', ...request };
  }
  async updateDistributedTaskRequest(request) {
    /* update status */
  }
  async start() {
    /* connect */
  }
  async stop() {
    /* disconnect */
  }
}

const manager = new TaskManager({
  distributedCoordinator: new RedisCoordinator(),
});
```

When a distributed coordinator is configured, scheduled tasks consult it before executing — only the elected instance runs the task.

## 🧩 Advanced Patterns

### Pre-Task & After-Task Hooks

Run setup/teardown tasks automatically:

```typescript
const mainTask = new Task({
  name: 'MainWork',
  preTask: new Task({
    name: 'Setup',
    taskFunction: async () => {
      console.log('Setting up...');
    },
  }),
  afterTask: new Task({
    name: 'Cleanup',
    taskFunction: async () => {
      console.log('Cleaning up...');
    },
  }),
  taskFunction: async () => {
    console.log('Doing work...');
    return 'done';
  },
});

await mainTask.trigger();
// Setting up... → Doing work... → Cleaning up...
```

### One-Time Setup Functions

Run an expensive initialization exactly once, before the first execution:

```typescript
const task = new Task({
  name: 'DBQuery',
  taskSetup: async () => {
    const pool = await createConnectionPool();
    return pool; // This becomes `setupValue`
  },
  taskFunction: async (input, pool) => {
    return await pool.query(input);
  },
});

await task.trigger('SELECT * FROM users'); // Setup runs here
await task.trigger('SELECT * FROM orders'); // Setup skipped, pool reused
```

### Blocking Tasks

Make one task wait for another to finish before executing:

```typescript
const initTask = new Task({
  name: 'Init',
  taskFunction: async () => {
    await initializeSystem();
  },
});

const workerTask = new Task({
  name: 'Worker',
  taskFunction: async () => {
    await doWork();
  },
});

workerTask.blockingTasks.push(initTask);

// Triggering worker will automatically wait for init to complete
initTask.trigger();
workerTask.trigger(); // Waits until initTask.finished resolves
```

### Database Migration Pipeline

```typescript
const migration = new Taskchain({
  name: 'DatabaseMigration',
  taskArray: [backupTask, validateSchemaTask, runMigrationsTask, verifyIntegrityTask],
});

try {
  await migration.trigger();
  console.log('Migration successful!');
} catch (error) {
  // error includes chain name, failing task name, index, and original cause
  console.error(error.message);
  await rollbackTask.trigger();
}
```

### Multi-Tenant SaaS Monitoring

Combine labels + events for a real-time multi-tenant dashboard:

```typescript
const manager = new TaskManager();

// Create tenant-scoped tasks
function createTenantTask(tenantId: string, taskName: string, fn: () => Promise<any>) {
  const task = new Task({
    name: `${tenantId}:${taskName}`,
    labels: { tenantId },
    taskFunction: fn,
  });
  manager.addTask(task);
  return task;
}

createTenantTask('acme', 'sync', async () => syncData('acme'));
createTenantTask('globex', 'sync', async () => syncData('globex'));

// Stream events to tenant-specific WebSocket channels
manager.taskSubject.subscribe((event) => {
  const tenantId = event.task.labels?.tenantId;
  if (tenantId) {
    wss.broadcast(tenantId, JSON.stringify(event));
  }
});

// Query tasks for a specific tenant
const acmeTasks = manager.getTasksMetadataByLabel('tenantId', 'acme');
```

## 📚 API Reference

### Classes

| Class | Description |
| --- | --- |
| `Task<T, TSteps>` | Core task unit with optional step tracking, labels, and event streaming |
| `TaskManager` | Centralized orchestrator with scheduling, label queries, and aggregated events |
| `Taskchain` | Sequential task executor with data flow between tasks |
| `Taskparallel` | Concurrent task executor via `Promise.all()` |
| `TaskOnce` | Single-execution guard |
| `TaskDebounced` | Debounced task using rxjs |
| `TaskRunner` | Sequential queue with configurable parallelism |
| `TaskStep` | Step tracking unit (internal, exposed via metadata) |

### Task Methods

| Method | Returns | Description |
| --- | --- | --- |
| `trigger(input?)` | `Promise<any>` | Execute the task |
| `notifyStep(name)` | `void` | Advance to named step (type-safe) |
| `getProgress()` | `number` | Current progress 0–100 |
| `getStepsMetadata()` | `ITaskStep[]` | Step details with status |
| `getMetadata()` | `ITaskMetadata` | Full task metadata snapshot |
| `setLabel(key, value)` | `void` | Set a label |
| `getLabel(key)` | `string \| undefined` | Get a label value |
| `removeLabel(key)` | `boolean` | Remove a label |
| `hasLabel(key, value?)` | `boolean` | Check label existence / value |
| `clearError()` | `void` | Reset `lastError` to undefined |

### Task Properties

| Property | Type | Description |
| --- | --- | --- |
| `name` | `string` | Task identifier |
| `running` | `boolean` | Whether the task is currently executing |
| `idle` | `boolean` | Inverse of `running` |
| `labels` | `Record<string, string>` | Attached labels |
| `eventSubject` | `Subject<ITaskEvent>` | rxjs Subject emitting lifecycle events |
| `lastError` | `Error \| undefined` | Last error encountered |
| `errorCount` | `number` | Total error count across all runs |
| `runCount` | `number` | Total execution count |
| `lastRun` | `Date \| undefined` | Timestamp of last execution |
| `blockingTasks` | `Task[]` | Tasks that must finish before this one starts |

### TaskManager Methods

| Method | Returns | Description |
| --- | --- | --- |
| `addTask(task)` | `void` | Register a task (wires event forwarding) |
| `removeTask(task)` | `void` | Remove task and unsubscribe events |
| `getTaskByName(name)` | `Task \| undefined` | Look up by name |
| `triggerTaskByName(name)` | `Promise<any>` | Trigger by name |
| `addAndScheduleTask(task, cron)` | `void` | Register + schedule |
| `scheduleTaskByName(name, cron)` | `void` | Schedule existing task |
| `descheduleTaskByName(name)` | `void` | Remove schedule |
| `getTaskMetadata(name)` | `ITaskMetadata \| null` | Single task metadata |
| `getAllTasksMetadata()` | `ITaskMetadata[]` | All tasks metadata |
| `getScheduledTasks()` | `IScheduledTaskInfo[]` | Scheduled task info |
| `getNextScheduledRuns(limit?)` | `Array<{...}>` | Upcoming scheduled runs |
| `getTasksByLabel(key, value)` | `Task[]` | Filter tasks by label |
| `getTasksMetadataByLabel(key, value)` | `ITaskMetadata[]` | Filter metadata by label |
| `addExecuteRemoveTask(task, opts?)` | `Promise<ITaskExecutionReport>` | One-shot execution with report |
| `start()` | `Promise<void>` | Start cron + coordinator |
| `stop()` | `Promise<void>` | Stop cron + clean up subscriptions |

### TaskManager Properties

| Property | Type | Description |
| --- | --- | --- |
| `taskSubject` | `Subject<ITaskEvent>` | Aggregated events from all added tasks |
| `taskMap` | `ObjectMap<Task>` | Internal task registry |

### Exported Types

```typescript
import type {
  ITaskMetadata,
  ITaskExecutionReport,
  IScheduledTaskInfo,
  ITaskEvent,
  TTaskEventType,
  ITaskStep,
  ITaskFunction,
  StepNames,
} from '@push.rocks/taskbuffer';
```

## License and Legal Information

This repository contains open-source code licensed under the MIT License. A copy of the license can be found in the [LICENSE](./LICENSE) file.

**Please note:** The MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as required for reasonable and customary use in describing the origin of the work and reproducing the content of the NOTICE file.

### Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH and any related products or services are trademarks of Task Venture Capital GmbH or third parties, and are not included within the scope of the MIT license granted herein.

Use of these trademarks must comply with Task Venture Capital GmbH's Trademark Guidelines or the guidelines of the respective third-party owners, and any usage must be approved in writing. Third-party trademarks used herein are the property of their respective owners and used only in a descriptive manner, e.g. for an implementation of an API or similar.

### Company Information

Task Venture Capital GmbH
Registered at District Court Bremen HRB 35230 HB, Germany

For any legal inquiries or further information, please contact us via email at hello@task.vc.

By using this repository, you acknowledge that you have read this section, agree to comply with its terms, and understand that the licensing of the code does not imply endorsement by Task Venture Capital GmbH of any derivative works.