GraphTest.php

<?php

declare (strict_types=1);
namespace Drupal\Tests\Component\Graph;

use Drupal\Component\Graph\Graph;
use PHPUnit\Framework\TestCase;

/**
 * @coversDefaultClass \Drupal\Component\Graph\Graph
 * @group Graph
 */
class GraphTest extends TestCase {
    
    /**
     * Tests depth-first-search features.
     */
    public function testDepthFirstSearch() : void {
        // The sample graph used is:
        // @code
        // 1 --> 2 --> 3     5 ---> 6
        //       |     ^     ^
        //       |     |     |
        //       |     |     |
        //       +---> 4 <-- 7      8 ---> 9
        // @endcode
        $graph = $this->normalizeGraph([
            1 => [
                2,
            ],
            2 => [
                3,
                4,
            ],
            3 => [],
            4 => [
                3,
            ],
            5 => [
                6,
            ],
            7 => [
                4,
                5,
            ],
            8 => [
                9,
            ],
            9 => [],
        ]);
        $graph_object = new Graph($graph);
        $graph = $graph_object->searchAndSort();
        $expected_paths = [
            1 => [
                2,
                3,
                4,
            ],
            2 => [
                3,
                4,
            ],
            3 => [],
            4 => [
                3,
            ],
            5 => [
                6,
            ],
            7 => [
                4,
                3,
                5,
                6,
            ],
            8 => [
                9,
            ],
            9 => [],
        ];
        $this->assertPaths($graph, $expected_paths);
        $expected_reverse_paths = [
            1 => [],
            2 => [
                1,
            ],
            3 => [
                2,
                1,
                4,
                7,
            ],
            4 => [
                2,
                1,
                7,
            ],
            5 => [
                7,
            ],
            7 => [],
            8 => [],
            9 => [
                8,
            ],
        ];
        $this->assertReversePaths($graph, $expected_reverse_paths);
        // Assert that DFS didn't created "missing" vertexes automatically.
        $this->assertFalse(isset($graph[6]), 'Vertex 6 has not been created');
        $expected_components = [
            [
                1,
                2,
                3,
                4,
                5,
                7,
            ],
            [
                8,
                9,
            ],
        ];
        $this->assertComponents($graph, $expected_components);
        $expected_weights = [
            [
                1,
                2,
                3,
            ],
            [
                2,
                4,
                3,
            ],
            [
                7,
                4,
                3,
            ],
            [
                7,
                5,
            ],
            [
                8,
                9,
            ],
        ];
        $this->assertWeights($graph, $expected_weights);
    }
    
    /**
     * Normalizes a graph.
     *
     * @param $graph
     *   A graph array processed by \Drupal\Component\Graph\Graph::searchAndSort()
     *
     * @return array
     *   The normalized version of a graph.
     */
    protected function normalizeGraph($graph) : array {
        $normalized_graph = [];
        foreach ($graph as $vertex => $edges) {
            // Create vertex even if it hasn't any edges.
            $normalized_graph[$vertex] = [];
            foreach ($edges as $edge) {
                $normalized_graph[$vertex]['edges'][$edge] = TRUE;
            }
        }
        return $normalized_graph;
    }
    
    /**
     * Verify expected paths in a graph.
     *
     * @param array $graph
     *   A graph array processed by \Drupal\Component\Graph\Graph::searchAndSort()
     * @param array $expected_paths
     *   An associative array containing vertices with their expected paths.
     *
     * @internal
     */
    protected function assertPaths(array $graph, array $expected_paths) : void {
        foreach ($expected_paths as $vertex => $paths) {
            // Build an array with keys = $paths and values = TRUE.
            $expected = array_fill_keys($paths, TRUE);
            $result = $graph[$vertex]['paths'] ?? [];
            $this->assertEquals($expected, $result, sprintf('Expected paths for vertex %s: %s, got %s', $vertex, $this->displayArray($expected, TRUE), $this->displayArray($result, TRUE)));
        }
    }
    
    /**
     * Verify expected reverse paths in a graph.
     *
     * @param array $graph
     *   A graph array processed by \Drupal\Component\Graph\Graph::searchAndSort()
     * @param array $expected_reverse_paths
     *   An associative array containing vertices with their expected reverse
     *   paths.
     *
     * @internal
     */
    protected function assertReversePaths(array $graph, array $expected_reverse_paths) : void {
        foreach ($expected_reverse_paths as $vertex => $paths) {
            // Build an array with keys = $paths and values = TRUE.
            $expected = array_fill_keys($paths, TRUE);
            $result = $graph[$vertex]['reverse_paths'] ?? [];
            $this->assertEquals($expected, $result, sprintf('Expected reverse paths for vertex %s: %s, got %s', $vertex, $this->displayArray($expected, TRUE), $this->displayArray($result, TRUE)));
        }
    }
    
    /**
     * Verify expected components in a graph.
     *
     * @param array $graph
     *   A graph array processed by \Drupal\Component\Graph\Graph::searchAndSort().
     * @param array $expected_components
     *   An array containing of components defined as a list of their vertices.
     *
     * @internal
     */
    protected function assertComponents(array $graph, array $expected_components) : void {
        $unassigned_vertices = array_fill_keys(array_keys($graph), TRUE);
        foreach ($expected_components as $component) {
            $result_components = [];
            foreach ($component as $vertex) {
                $result_components[] = $graph[$vertex]['component'];
                unset($unassigned_vertices[$vertex]);
            }
            $this->assertCount(1, array_unique($result_components), sprintf('Expected one unique component for vertices %s, got %s', $this->displayArray($component), $this->displayArray($result_components)));
        }
        $this->assertEquals([], $unassigned_vertices, sprintf('Vertices not assigned to a component: %s', $this->displayArray($unassigned_vertices, TRUE)));
    }
    
    /**
     * Verify expected order in a graph.
     *
     * @param array $graph
     *   A graph array processed by \Drupal\Component\Graph\Graph::searchAndSort()
     * @param array $expected_orders
     *   An array containing lists of vertices in their expected order.
     *
     * @internal
     */
    protected function assertWeights(array $graph, array $expected_orders) : void {
        foreach ($expected_orders as $order) {
            $previous_vertex = array_shift($order);
            foreach ($order as $vertex) {
                $this->assertLessThan($graph[$vertex]['weight'], $graph[$previous_vertex]['weight'], sprintf("Weight of vertex %s should be less than vertex %s.", $previous_vertex, $vertex));
            }
        }
    }
    
    /**
     * Helper function to output vertices as comma-separated list.
     *
     * @param $paths
     *   An array containing a list of vertices.
     * @param $keys
     *   (optional) Whether to output the keys of $paths instead of the values.
     */
    protected function displayArray($paths, $keys = FALSE) : string {
        if (!empty($paths)) {
            return implode(', ', $keys ? array_keys($paths) : $paths);
        }
        else {
            return '(empty)';
        }
    }

}