<?php

namespace App\Service;

use Symfony\Contracts\HttpClient\HttpClientInterface;

/**
 * Fetches the last 365 days of contributions from the GitHub GraphQL API.
 *
 * Required token scopes: read:user
 */
class GitHubProvider
{
    private const GRAPHQL_URL = 'https://api.github.com/graphql';

    private const QUERY = <<<'GRAPHQL'
    query($username: String!, $from: DateTime!, $to: DateTime!) {
      user(login: $username) {
        contributionsCollection(from: $from, to: $to) {
          contributionCalendar {
            weeks {
              contributionDays {
                date
                contributionCount
              }
            }
          }
        }
      }
    }
    GRAPHQL;

    public function __construct(private readonly HttpClientInterface $client) {}

    /**
     * @return array<string, int>  date (Y-m-d) => contribution count
     */
    public function fetch(string $username, string $token): array
    {
        $from = (new \DateTimeImmutable('-365 days'))->format('Y-m-d\T00:00:00\Z');
        $to   = (new \DateTimeImmutable())->format('Y-m-d\T23:59:59\Z');

        $response = $this->client->request('POST', self::GRAPHQL_URL, [
            'headers' => [
                'Authorization' => "Bearer $token",
                'Content-Type'  => 'application/json',
            ],
            'json' => [
                'query'     => self::QUERY,
                'variables' => ['username' => $username, 'from' => $from, 'to' => $to],
            ],
        ]);

        $data = $response->toArray();

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

        return $result;
    }
}