<?php

declare(strict_types = 1);

namespace Fgm\Drupal\Composer;

use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;
use Symfony\Component\Yaml\Yaml;

/**
 * Merge params.local.yml into dist.params.local.yml.
 *
 * The former overrides the latter.
 *
 * @package Fgm\Drupal\Composer
 */
class MergeParamsCommand extends BaseBuilderCommand {

  const DEFAULT_SITE = '_default';

  /**
   * The event triggering this command.
   *
   * @var string
   */
  protected $eventName;

  /**
   * Configures the current command.
   */
  public function configure() {
    parent::configure();
    $this->eventName = $this->getName();
    $this
      ->setName('build:merge_params')
      ->setDescription('Step 1: merges the params.local.yml with dist.params.local.yml.')
      ->setDefinition([])
      ->setHelp(
        <<<EOT
Step 1 of a build, the build:merge_params command combines shared and per-environment
parameters and generates merged.params.local.yml containing the merged result.

EOT
      );
  }

  /**
   * Perform merging.
   *
   * @param array $dist
   *   Distribution parameters (default).
   * @param array $local
   *   Local parameters (overrides).
   *
   * @return array
   *   The merge result.
   */
  protected function merge(array $dist, array $local): array {
    if (empty($local)) {
      return $dist;
    }

    // Merge local into defaults.
    $merged = static::mergeDeepArray([$dist, $local]);

    // Generate per-site data from settings/_default.
    $default = $merged['sites'][static::DEFAULT_SITE] ?? [];
    $sites = array_diff_key($merged['sites'], [static::DEFAULT_SITE => NULL]);
    $merged['sites'] = [];
    foreach ($sites as $name => $params) {
      $merged['sites'][$name] = static::mergeDeepArray([$default, $params]);
    }
    return $merged;
  }

  /**
   * Executes the current command.
   *
   * {@inheritDoc}
   */
  public function execute(InputInterface $input, OutputInterface $output) {
    $settingsPath = $this->getSettingsPath();
    $yaml = new Yaml();

    // Load defaults.
    $defaultsPath = "${settingsPath}/dist.params.local.yml";
    $realDefaultsPath = realpath($defaultsPath);
    if (empty($realDefaultsPath)) {
      $output->writeln("Failed to open $defaultsPath");
      return 1;
    }
    $defaults = $yaml->parseFile($realDefaultsPath);

    // Load local.
    $localPath = "${settingsPath}/params.local.yml";
    $realLocalPath = realpath($localPath);
    if (empty($realLocalPath)) {
      if ($output->isVerbose()) {
        $output->writeln("File $localPath not found, using only defaults");
      }
      $local = [];
    }
    else {
      $local = $yaml->parseFile($realLocalPath);
    }

    // Merge.
    $merged = $this->merge($defaults, $local);

    // Write.
    $ok = file_put_contents("${settingsPath}/merged.params.local.yml",
      $yaml->dump($merged, 10, 2));
    if (!$ok) {
      $output->writeln("Failed to write merged params.");
      return 2;
    }

    return 0;
  }

  /**
   * Merges multiple arrays, recursively, and returns the merged array.
   *
   * Only keyed arrays are merged recursively, indexed arrays are not merged :
   * the deepest array replace the less deep array. This is unlike the original
   * function introduced in Drupal 8.x, from which this derives.
   *
   * @param array $arrays
   *   An arrays of arrays to merge.
   *
   * @return array
   *   The merged array.
   *
   * @see \Fgm\Drupal\Composer\MergeParamsCommandTest::testMergeDeepArray()
   */
  public static function mergeDeepArray(array $arrays) {

    $result = [];
    foreach ($arrays as $array) {
      foreach ($array as $key => $value) {
        // Remove keys having NULL value to allow deletion of key previously
        // defined.
        if ($value === NULL) {
          unset($result[$key]);
          continue;
        }
        // Renumber integer keys as array_merge_recursive() does. Note that
        // PHP automatically converts array keys that are integer strings
        // (e.g., '1') to integers.
        if (is_int($key)) {
          // When an indexed array is overrided, the new values replace
          // all overrided values (no merge).
          if ($key === 0) {
            $result = [];
          }
          $result[] = $value;
        }
        // Recurse when both values are arrays.
        elseif (isset($result[$key]) && is_array($result[$key]) && is_array($value)) {
          $result[$key] = static::mergeDeepArray([$result[$key], $value]);
        }
        // Otherwise, use the latter value, overriding any previous value.
        else {
          $result[$key] = $value;
        }
      }
    }
    return $result;
  }

}