<?php

declare(strict_types=1);

namespace GitContributionGraph\Service;

use GitContributionGraph\Service\Provider\ProviderInterface;
use Psr\Log\LoggerInterface;
use Symfony\Component\DependencyInjection\Attribute\AutowireIterator;

final class ContributionAggregator
{
    private const RENDER_WINDOW_DAYS = 371;
    private const OVERLAP_DAYS = 3;

    /** @param iterable<ProviderInterface> $providers */
    public function __construct(
        #[AutowireIterator('app.provider')]
        private readonly iterable $providers,
        private readonly ContributionStore $store,
        private readonly LoggerInterface $logger,
    ) {}

    /**
     * Incrementally fetches fresh contributions from each configured provider, merges them into
     * the store, and returns the rolling render window summed across providers.
     *
     * For each provider, only data since its last stored date (minus a trailing overlap) is
     * fetched; a provider with no stored history yet fetches its full default range. Fetches are
     * split into start/resolve phases so all providers' requests are in flight concurrently.
     * Failures are logged and the affected provider is skipped, not fatal to the others.
     *
     * @return array<string, int> date (Y-m-d) => contribution count, summed across all providers
     */
    public function aggregate(): array
    {
        $configured = [];

        /** @var ProviderInterface $provider */
        foreach ($this->providers as $provider) {
            if ($provider->isConfigured()) {
                $configured[] = $provider;
            }
        }

        $pending = [];

        foreach ($configured as $provider) {
            $latest = $this->store->latestDate($provider->getName());
            $since  = $latest !== null
                ? (new \DateTimeImmutable('@' . $latest))->modify('-' . self::OVERLAP_DAYS . ' days')
                : null;

            try {
                $pending[] = [$provider, $provider->startFetch($since)];
            } catch (\Throwable $e) {
                $this->logger->warning(sprintf('%s fetch failed: %s', $provider::class, $e->getMessage()), ['exception' => $e]);
            }
        }

        foreach ($pending as [$provider, $handle]) {
            try {
                $fresh = $provider->resolveFetch($handle);

                $dateCounts = [];
                foreach ($fresh as $date => $count) {
                    $dateCounts[(new \DateTimeImmutable($date))->getTimestamp()] = $count;
                }

                $this->store->merge($provider->getName(), $dateCounts);
            } catch (\Throwable $e) {
                $this->logger->warning(sprintf('%s fetch failed: %s', $provider::class, $e->getMessage()), ['exception' => $e]);
            }
        }

        $contributions = [];

        foreach ($configured as $provider) {
            foreach ($this->store->all($provider->getName(), sinceDays: self::RENDER_WINDOW_DAYS) as $contribution) {
                $date = (new \DateTimeImmutable('@' . $contribution->date))->format('Y-m-d');
                $contributions[$date] = ($contributions[$date] ?? 0) + $contribution->count;
            }
        }

        $this->store->prune();

        return $contributions;
    }
}