<?php

declare(strict_types=1);

namespace GitContributionGraph\Service\Provider;

use Psr\Log\LoggerInterface;
use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;
use Symfony\Contracts\HttpClient\HttpClientInterface;
use Symfony\Contracts\HttpClient\ResponseInterface;

/**
 * Fetches the last 365 days of contributions from the GitHub GraphQL API.
 *
 * Required token scopes: read:user
 */
final class GitHubProvider implements ProviderInterface
{
    use ProbeTrait;

    private const GRAPHQL_URL = 'https://api.github.com/graphql';

    public function __construct(
        private readonly HttpClientInterface $client,
        private readonly string $username,
        private readonly string $token,
        private readonly LoggerInterface $logger,
    ) {}

    public function getName(): string
    {
        return 'github';
    }

    public function isConfigured(): bool
    {
        return $this->username !== '' && $this->token !== '';
    }

    public function ping(): void
    {
        $this->client->request('GET', 'https://api.github.com/user', [
            'headers' => ['Authorization' => "Bearer {$this->token}"],
        ])->getContent();
    }

    /** Fires the GraphQL contributionsCollection query bounded by $since/$until. */
    public function startFetch(?\DateTimeImmutable $since = null, ?\DateTimeImmutable $until = null): ResponseInterface
    {
        $this->logger->debug('GitHubProvider: fetching contributions', ['user' => $this->username]);

        $from = ($since ?? new \DateTimeImmutable('-365 days'))->format('Y-m-d\T00:00:00\Z');
        $to   = ($until ?? new \DateTimeImmutable())->format('Y-m-d\T23:59:59\Z');

        $query = sprintf(
            'query { user(login: %s) { contributionsCollection(from: %s, to: %s) { contributionCalendar { weeks { contributionDays { date contributionCount } } } } } }',
            json_encode($this->username),
            json_encode($from),
            json_encode($to),
        );

        // GitHub's GraphQL API requires application/json.
        // request() doesn't block; the response is read in resolveFetch() so
        // multiple providers' requests can be in flight at once.
        return $this->client->request('POST', self::GRAPHQL_URL, [
            'headers' => [
                'Authorization' => "Bearer {$this->token}",
                'Content-Type'  => 'application/json',
            ],
            'json' => ['query' => $query],
        ]);
    }

    /**
     * Parses the GraphQL response into a per-day count map, skipping zero-count days.
     *
     * @param  ResponseInterface $handle the response returned by startFetch()
     * @return array<string, int> date (Y-m-d) => contribution count
     */
    public function resolveFetch(mixed $handle): array
    {
        /** @var ResponseInterface $handle */
        $data = $handle->toArray();

        if (isset($data['errors'])) {
            throw new ServiceUnavailableHttpException(null, 'GitHub GraphQL error: ' . json_encode($data['errors']));
        }

        $result = [];
        $weeks  = $data['data']['user']['contributionsCollection']['contributionCalendar']['weeks'] ?? [];

        foreach ($weeks as $week) {
            foreach ($week['contributionDays'] as $day) {
                if ($day['contributionCount'] > 0) {
                    $result[$day['date']] = $day['contributionCount'];
                }
            }
        }

        $this->logger->info('GitHubProvider: fetched contributions', [
            'user'  => $this->username,
            'days'  => count($result),
            'total' => array_sum($result),
        ]);

        return $result;
    }
}