<?php

namespace App\Services\Graph;

use Illuminate\Support\Facades\Log;

class AssignmentFetcher
{
    public function __construct(
        private readonly MicrosoftGraphClient $graphClient,
        private readonly GraphContractRegistry $contracts,
    ) {}

    /**
     * Fetch policy assignments with fallback strategy.
     *
     * Primary: GET {assignments_list_path}
     * Fallback: GET {resource}?$expand=assignments&$filter=id eq '{id}'
     *
     * @return array Returns assignment array or empty array on failure
     */
    public function fetch(string $policyType, string $tenantId, string $policyId, array $options = []): array
    {
        try {
            $contract = $this->contracts->get($policyType);
            $listPathTemplate = $contract['assignments_list_path'] ?? null;
            $resource = $contract['resource'] ?? null;
            $requestOptions = array_merge($options, ['tenant' => $tenantId]);

            // Try primary endpoint
            $assignments = $this->fetchPrimary($listPathTemplate, $policyId, $requestOptions);

            if (! empty($assignments)) {
                Log::debug('Fetched assignments via primary endpoint', [
                    'tenant_id' => $tenantId,
                    'policy_type' => $policyType,
                    'policy_id' => $policyId,
                    'count' => count($assignments),
                ]);

                return $assignments;
            }

            // Try fallback with $expand
            Log::debug('Primary endpoint returned empty, trying fallback', [
                'tenant_id' => $tenantId,
                'policy_type' => $policyType,
                'policy_id' => $policyId,
            ]);

            if (! is_string($resource) || $resource === '') {
                Log::debug('Assignments resource not configured for policy type', [
                    'tenant_id' => $tenantId,
                    'policy_type' => $policyType,
                    'policy_id' => $policyId,
                ]);

                return [];
            }

            $assignments = $this->fetchWithExpand($resource, $policyId, $requestOptions);

            if (! empty($assignments)) {
                Log::debug('Fetched assignments via fallback endpoint', [
                    'tenant_id' => $tenantId,
                    'policy_type' => $policyType,
                    'policy_id' => $policyId,
                    'count' => count($assignments),
                ]);

                return $assignments;
            }

            // Both methods returned empty
            Log::debug('No assignments found for policy', [
                'tenant_id' => $tenantId,
                'policy_type' => $policyType,
                'policy_id' => $policyId,
            ]);

            return [];
        } catch (GraphException $e) {
            Log::warning('Failed to fetch assignments', [
                'tenant_id' => $tenantId,
                'policy_type' => $policyType,
                'policy_id' => $policyId,
                'error' => $e->getMessage(),
                'context' => $e->context,
            ]);

            return [];
        }
    }

    /**
     * Fetch assignments using primary endpoint.
     */
    private function fetchPrimary(?string $listPathTemplate, string $policyId, array $options): array
    {
        if (! is_string($listPathTemplate) || $listPathTemplate === '') {
            return [];
        }

        $path = $this->resolvePath($listPathTemplate, $policyId);

        if ($path === null) {
            return [];
        }

        $response = $this->graphClient->request('GET', $path, $options);

        return $response->data['value'] ?? [];
    }

    /**
     * Fetch assignments using $expand fallback.
     */
    private function fetchWithExpand(string $resource, string $policyId, array $options): array
    {
        $path = $resource;
        $params = [
            '$expand' => 'assignments',
            '$filter' => "id eq '{$policyId}'",
        ];

        $response = $this->graphClient->request('GET', $path, array_merge($options, [
            'query' => $params,
        ]));

        $policies = $response->data['value'] ?? [];

        if (empty($policies)) {
            return [];
        }

        return $policies[0]['assignments'] ?? [];
    }

    private function resolvePath(string $template, string $policyId): ?string
    {
        if ($template === '') {
            return null;
        }

        return str_replace('{id}', urlencode($policyId), $template);
    }
}