<?php

declare(strict_types=1);

namespace App\Index;

final class IndexMetaManager
{
    private string $metaPath;
    private string $runtimePath;
    private IndexConfigurationProvider $provider;

    public function __construct(
        string $metaPath,
        string $runTimePath,
        IndexConfigurationProvider $provider
    ) {
        $this->metaPath = $metaPath;
        $this->provider = $provider;

        // runtime liegt im selben Verzeichnis
        $this->runtimePath = $runTimePath;
    }

    // =====================================================
    // META (Governance – unverändert lassen!)
    // =====================================================

    public function ensureExists(): void
    {
        if (!is_file($this->metaPath)) {
            $this->writeMeta(1);
        }
    }

    public function readMeta(): ?array
    {
        if (!is_file($this->metaPath)) {
            return null;
        }

        return json_decode(
            (string) file_get_contents($this->metaPath),
            true
        );
    }

    public function validateAgainstCurrent(): void
    {
        $meta = $this->readMeta();
        $current = $this->provider
            ->getConfiguration()
            ->toStructureArray();

        if ($meta === null) {
            return;
        }

        foreach ($current as $key => $value) {
            if (($meta[$key] ?? null) !== $value) {
                throw new \RuntimeException(
                    'Index structure changed. Global Reindex required.'
                );
            }
        }
    }

    public function writeMetaForGlobalReindex(): void
    {
        $current = $this->readMeta();
        $nextVersion = ($current['index_version'] ?? 0) + 1;

        $this->writeMeta($nextVersion);
    }

    public function writeMeta(int $indexVersion): void
    {
        $config = $this->provider->getConfiguration();

        $payload = array_merge(
            [
                'index_version' => $indexVersion,
                'created_at'    => (new \DateTimeImmutable())->format(DATE_ATOM),
            ],
            $config->toStructureArray()
        );

        $dir = dirname($this->metaPath);
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }

        file_put_contents(
            $this->metaPath,
            json_encode(
                $payload,
                JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES
            )
        );
    }

    // =====================================================
    // RUNTIME (Chunk Counter etc.)
    // =====================================================

    private function ensureRuntimeFileExists(): void
    {
        if (is_file($this->runtimePath)) {
            return;
        }

        $dir = dirname($this->runtimePath);
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }

        $payload = [
            'chunk_count' => 0,
            'last_rebuild_at' => null,
        ];

        file_put_contents(
            $this->runtimePath,
            json_encode($payload, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES)
        );
    }

    public function updateRuntimeStats(int $chunkCount): void
    {
        $this->ensureRuntimeFileExists();

        $payload = [
            'chunk_count' => $chunkCount,
            'last_rebuild_at' => (new \DateTimeImmutable())->format(DATE_ATOM),
        ];

        file_put_contents(
            $this->runtimePath,
            json_encode($payload, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES)
        );
    }

    public function getRuntimeChunkCount(): int
    {
        $this->ensureRuntimeFileExists();

        $data = json_decode(
            (string) file_get_contents($this->runtimePath),
            true
        );

        return (int)($data['chunk_count'] ?? 0);
    }
}