<?php

namespace GermanAirlinesVa\Graphql\Classes;

use Cache;
use Nuwave\Lighthouse\Schema\Source\SchemaSourceProvider as LighthouseSchemaSourceProvider;
use GraphQL\Language\Parser;
use GraphQL\Error\Error;
use Cms\Classes\ComponentManager;
use Cms\Classes\ComponentPartial;

class SchemaSourceProvider implements LighthouseSchemaSourceProvider
{
  protected $fieldGraphMapCacheKey = 'graphql-schema-field-graph-map';

  /**
   * @var Schema
   */
  public $template;

  /**
   * @var string
   */
  protected $rootSchemaPath;

  /**
   * @var array
   * Collects graphs and their parsed schema
   */
  protected $graphMap;

  /**
   * @var array
   * Maps field names to graphs
   */
  protected $fieldGraphMap;

  /**
   * SchemaSource constructor.
   *
   * @param string|null $template
   */
  public function __construct($template = null)
  {
    $this->template = Schema::load(is_string($template) ? $template : 'graphql');
    $this->rootSchemaPath = $this->template->getPath();
  }

  /**
   * Set schema root path.
   *
   * @param string $path
   *
   * @return SchemaSourceProvider
   */
  public function setRootPath(string $path): self
  {
    $this->rootSchemaPath = $path;

    return $this;
  }

  /**
   * Stitch together schema documents and return the result as a string.
   *
   * @return string
   */
  public function getSchemaString(): string
  {
    // root types
    $schema = '
        type Query {
          dummy: Boolean
        }
        
        type Mutation {
          dummy: Boolean
        }
        ';
    // schema
    $schema .= collect($this->getGraphMap())->implode('schema', '');
    return $schema;
  }

  public function findGraph($fieldName, $findOrFail = false)
  {
    if (!isset($this->getFieldGraphMap()[$fieldName])) {
      if ($findOrFail) {
        throw new Error("Could not find graph of field '{$fieldName}'.");
      }

      return null;
    }

    $name = $this->getFieldGraphMap()[$fieldName];

    if (isset($this->graphMap[$name])) {
      // if available, use already instantiated graph objects in memory
      return $this->graphMap[$name]['graph'];
    }

    return Graph::loadCached($this->template, $name);
  }

  public function getFieldGraphMap()
  {
    if (!is_null($this->fieldGraphMap)) {
      return $this->fieldGraphMap;
    }

    // restore from cache

    $cacheable = true;

    if ($cacheable) {
      $map = Cache::get($this->fieldGraphMapCacheKey, false);
      if ($map && ($map = @unserialize(@base64_decode($map))) && is_array($map)) {
        $this->fieldGraphMap = $map;
        return $this->fieldGraphMap;
      }
    }

    // rebuild mapping

    $this->fieldGraphMap = [];

    foreach ($this->getGraphMap() as $key => $element) {
      if (empty(trim($element['schema']))) {
        continue;
      }

      // parse the AST to collect fields mapping
      $ast = Parser::parse($element['schema'], ['noLocation' => true]);
      $fields = collect($ast->definitions)
        ->filter(function ($node) {
          // we only consider the root types since their fields are unique
          return $node->name->value == 'Query' || $node->name->value == 'Mutation';
        })
        ->flatMap(function ($node) {
          // collect field names
          return collect($node->fields)->map(function ($field) {
            return $field->name->value;
          });
        });

      // map as [$field_name => $graph_filename]
      $this->fieldGraphMap = array_merge($this->fieldGraphMap, array_fill_keys($fields->toArray(), $key));
    }

    // cache mapping

    if ($cacheable) {
      Cache::put($this->fieldGraphMapCacheKey, base64_encode(serialize($this->fieldGraphMap)), 10);
    }

    return $this->fieldGraphMap;
  }

  public function getGraphMap()
  {
    if (!is_null($this->graphMap)) {
      return $this->graphMap;
    }

    $this->graphMap = [];
    $component_re = '/{%\s*component\s+["|\'](.*)["|\']\s*%}/m';
    $component_str = [$this, 'getComponentSchemaString'];
    foreach ($this->template->listGraphs() as $graph) {
      /* @var $graph \GermanAirlinesVa\Graphql\Classes\Graph */
      $markup = $graph->markup;

      $schema = preg_replace_callback(
        $component_re,
        function (array $matches) use ($graph, $component_str) {
          $matched_alias = $matches[1];
          foreach ($graph->settings['components'] as $component => $properties) {
            // find component by alias
            [$name, $alias] = strpos($component, ' ') ? explode(' ', $component) : [$component, $component];
            if ($alias == $matched_alias) {
              // resolve component schema
              return $component_str($name, $alias);
            }
          }
          // if not found, remove
          return '';
        },
        $markup
      );

      $this->graphMap[$graph->getFileName()] = [
        'graph' => $graph,
        'schema' => $schema,
      ];
    }

    return $this->graphMap;
  }

  public function getComponentSchemaString($componentName, $alias)
  {
    $manager = ComponentManager::instance();
    $componentObj = $manager->makeComponent($componentName);
    if ($partial = ComponentPartial::load($componentObj, 'schema.graphqls')) {
      $content = $partial->getContent();
      $content = str_replace('__SELF__', $alias, $content);

      return $content;
    } else {
      return "# {$componentName} does not provide a default schema definition";
    }
  }

  public function clearCache()
  {
    Cache::forget($this->fieldGraphMapCacheKey);
  }
}