Task Graph Solver

The Task Graph Solver Package is a PHP library that provides a mechanism for resolving dependencies between tasks represented as a directed acyclic graph (DAG).

It helps you manage and execute tasks that are dependent on each other and ensures that the tasks are executed in the correct order to resolve their dependencies.

Installation

You can install this package using Composer:

composer require netlogix/task-graph-solver

Components

Task

You can use the simple Task implementation or create your own task based on the TaskInterface.

If you want to execute a task multiple times, you can implement the ResettableTaskInterface and reset the task to its initial state using the reset() method.

TaskPool

Tasks are managed by a TaskPool, you can use the bas TaskPool implementation or create your own TaskPool based on the TaskPoolInterface. The TaskPool is responsible for storing and providing access to your defined tasks.

TaskGraph

The TaskGraph class is used to resolve the task dependencies. It takes a TaskPool as input and can be iterated to get the tasks in the correct resolution order, considering their dependencies. It also checks for cyclic dependencies and prevents infinite loops.

Usage

use Netlogix\DependencyResolver\TaskGraph;

$taskGraph = new TaskGraph($taskPool);

foreach ($taskGraph as $resolutionBatch) {
        foreach ($resolutionBatch as $task) {
        // Execute the task or do any necessary operations.
        $task->resolve();
    }
}

Resetting Tasks

If your TaskPool implements the ResettableTaskPoolInterface, you can reset all tasks to their initial state for re-execution using the resetPool() method of the TaskGraph:

$taskGraph->resetPool();

Example

Here is a simple example that shows how to use the TaskGraph to resolve the dependencies between tasks and generate a mermaid state diagram.

<?php

require_once __DIR__ . '/vendor/autoload.php';

use Netlogix\DependencyResolver\Task;
use Netlogix\DependencyResolver\TaskPool;
use Netlogix\DependencyResolver\TaskGraph;

$graph = new TaskGraph(
    new TaskPool([
        new Task('TaskA'),
        new Task('TaskB', ['TaskA']),
        new Task('TaskC', ['TaskA']),
        new Task('TaskD', ['TaskB', 'TaskC']),
        new Task('TaskE'),
    ])
);

$first=true;
$lines = ['stateDiagram'];
$lastTasks = [];
foreach ($graph->getIterator() as $tasks) {
    foreach ($tasks as $name => $task) {
        $lastTasks = array_filter($lastTasks, fn($t) => !in_array($t, $task->getDependencies()));
        array_push($lines, ...$first ? ["  [*] --> $name"]
            : array_map(fn($t) => "  $t --> $name", $task->getDependencies()));
        $lastTasks[$name] = $name;
        $task->resolve();
    }
    $first=false;
}
foreach ($lastTasks as $lastTask) {
    $lines[] = "  $lastTask --> [*]";
}

echo implode("\n", $lines) . "\n";

Result:

stateDiagram
    [*] --> TaskA
    [*] --> TaskE
    TaskA --> TaskB
    TaskA --> TaskC
    TaskB --> TaskD
    TaskC --> TaskD
    TaskE --> [*]
    TaskD --> [*]

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