<?php

namespace app\service\Search;

use OpenSearch\Client;

class OpenSearchChunkIndex
{
    public function __construct(private readonly ?Client $client = null)
    {
    }

    public function ensureExists(): void
    {
        $client = $this->client();
        $index = $this->indexName();

        if ($client->indices()->exists(['index' => $index])) {
            $this->ensureProperties($client, $index);
            return;
        }

        $client->indices()->create([
            'index' => $index,
            'body' => $this->mapping(),
        ]);
    }

    public function bulkIndex(array $documents): array
    {
        if ($documents === []) {
            return ['items' => [], 'errors' => false];
        }

        $body = [];
        foreach ($documents as $document) {
            $body[] = [
                'index' => [
                    '_index' => $this->indexName(),
                    '_id' => $document['chunk_uid'],
                ],
            ];
            $body[] = $document;
        }

        return $this->client()->bulk([
            'refresh' => config('opensearch.bulk.refresh', 'false'),
            'body' => $body,
        ]);
    }

    public function mapping(): array
    {
        return [
            'settings' => [
                'index' => [
                    'knn' => true,
                ],
            ],
            'mappings' => [
                'properties' => [
                    'chunk_uid' => ['type' => 'keyword'],
                    'archive_uid' => ['type' => 'keyword'],
                    'chunk_index' => ['type' => 'integer'],
                    'page_start' => ['type' => 'integer'],
                    'page_end' => ['type' => 'integer'],
                    'title' => $this->textWithKeyword(),
                    'summary' => ['type' => 'text'],
                    'source' => $this->textWithKeyword(),
                    'author' => $this->textWithKeyword(),
                    'year' => ['type' => 'integer'],
                    'series' => $this->textWithKeyword(),
                    'tags' => ['type' => 'keyword'],
                    'text' => ['type' => 'text'],
                    'embedding' => [
                        'type' => 'knn_vector',
                        'dimension' => (int) config('opensearch.vector.dimensions', 2048),
                        'method' => [
                            'name' => 'hnsw',
                            'space_type' => config('opensearch.vector.space_type', 'cosinesimil'),
                            'engine' => config('opensearch.vector.engine', 'lucene'),
                        ],
                    ],
                    'embedding_model' => ['type' => 'keyword'],
                    'embedding_dimensions' => ['type' => 'integer'],
                    'created_time' => ['type' => 'date'],
                    'updated_time' => ['type' => 'date'],
                ],
            ],
        ];
    }

    private function client(): Client
    {
        return $this->client ?? (new OpenSearchClientFactory())->make();
    }

    private function ensureProperties(Client $client, string $index): void
    {
        $mapping = $client->indices()->getMapping(['index' => $index]);
        $existing = $mapping[$index]['mappings']['properties'] ?? [];
        $desired = $this->mapping()['mappings']['properties'] ?? [];
        $missing = [];

        foreach ($desired as $field => $definition) {
            if (!array_key_exists($field, $existing)) {
                $missing[$field] = $definition;
            }
        }

        if ($missing === []) {
            return;
        }

        $client->indices()->putMapping([
            'index' => $index,
            'body' => [
                'properties' => $missing,
            ],
        ]);
    }

    private function indexName(): string
    {
        return config('opensearch.indices.chunks', 'proofdb_chunks');
    }

    private function textWithKeyword(): array
    {
        return [
            'type' => 'text',
            'fields' => [
                'keyword' => [
                    'type' => 'keyword',
                    'ignore_above' => 512,
                ],
            ],
        ];
    }
}