<?php
/**
 * EsSearch —— 轻量 ElasticSearch REST 封装（零新增依赖，复用项目已引入的 GuzzleHttp）
 *
 * 设计原则（对应路线 C3「ES 全文检索替代 LIKE」）：
 *   - 薄封装：ES 仅负责「按关键词返回匹配的 id 列表」，命中后由调用方 `whereIn('id', $ids)` 回表取完整行 + 关联，
 *     最大限度复用现有视图与模型关联，降低改造面。
 *   - 可降级：本类方法在 ES 不可用时抛出异常，由上层 SearchService 捕获并回退到原生 LIKE。
 *   - 中文分词：依赖 ES 服务端 IK 分词插件（index 创建时指定 analyzer）；若未装，ES 默认 standard 仍可按词/字匹配。
 *
 * 依赖：项目根 composer.json 已间接引入 guzzlehttp/guzzle（经 yansongda/pay）。
 */
declare(strict_types=1);

namespace ywxapp\library\Search;

use GuzzleHttp\Client;
use GuzzleHttp\Exception\TransferException;

class EsSearch
{
    /** @var Client|null 懒加载的 HTTP 客户端 */
    protected static ?Client $client = null;

    /**
     * 获取 HTTP 客户端
     */
    protected static function client(): Client
    {
        if (self::$client === null) {
            self::$client = new Client(['timeout' => 3.0, 'connect_timeout' => 2.0]);
        }
        return self::$client;
    }

    /**
     * 拼接 ES 端点 URL
     */
    protected static function url(string $host, string $path): string
    {
        return rtrim($host, '/') . $path;
    }

    /**
     * 确保索引存在（带中文 IK 分词器映射，缺失则创建）
     * @throws \RuntimeException
     */
    public static function ensureIndex(string $host, string $index, array $fields): void
    {
        $url = self::url($host, '/' . $index);
        try {
            $resp = self::client()->request('HEAD', $url);
            if ($resp->getStatusCode() === 200) {
                return; // 已存在
            }
        } catch (TransferException $e) {
            throw new \RuntimeException('ES 连接失败：' . $e->getMessage());
        }

        // 创建索引，默认用 ik_max_word（若有 IK 插件），否则 standard
        $properties = [];
        foreach ($fields as $f) {
            $properties[$f] = ['type' => 'text', 'analyzer' => 'ik_max_word'];
        }
        $body = json_encode([
            'settings' => ['number_of_shards' => 1, 'number_of_replicas' => 0],
            'mappings' => ['properties' => $properties],
        ], JSON_UNESCAPED_UNICODE);
        try {
            self::client()->request('PUT', $url, ['body' => $body, 'headers' => ['Content-Type' => 'application/json']]);
        } catch (TransferException $e) {
            // IK 分词器不存在时降级为 standard
            $properties = [];
            foreach ($fields as $f) {
                $properties[$f] = ['type' => 'text'];
            }
            $body = json_encode([
                'settings' => ['number_of_shards' => 1, 'number_of_replicas' => 0],
                'mappings' => ['properties' => $properties],
            ], JSON_UNESCAPED_UNICODE);
            self::client()->request('PUT', $url, ['body' => $body, 'headers' => ['Content-Type' => 'application/json']]);
        }
    }

    /**
     * 索引单条文档
     * @throws \RuntimeException
     */
    public static function indexDoc(string $host, string $index, int $id, array $body): void
    {
        try {
            self::client()->request(
                'PUT',
                self::url($host, '/' . $index . '/_doc/' . $id),
                ['body' => json_encode($body, JSON_UNESCAPED_UNICODE), 'headers' => ['Content-Type' => 'application/json']]
            );
        } catch (TransferException $e) {
            throw new \RuntimeException('ES 写入失败：' . $e->getMessage());
        }
    }

    /**
     * 删除文档
     */
    public static function deleteDoc(string $host, string $index, int $id): void
    {
        try {
            self::client()->request('DELETE', self::url($host, '/' . $index . '/_doc/' . $id));
        } catch (TransferException $e) {
            // 索引不存在或文档已删，忽略
        }
    }

    /**
     * 全文检索，返回匹配的 id 列表（按相关度排序）
     * @param array $fields 检索字段，如 ['title','content']
     * @return int[] 命中文档 id（相关度降序）
     * @throws \RuntimeException
     */
    public static function search(string $host, string $index, string $keyword, array $fields, int $limit = 50, int $from = 0): array
    {
        if (trim($keyword) === '') {
            return [];
        }
        $should = [];
        foreach ($fields as $f) {
            $should[] = ['match' => [$f => ['query' => $keyword, 'boost' => 1.0]]];
        }
        $body = json_encode([
            'from'  => $from,
            'size'  => $limit,
            'query' => ['bool' => ['should' => $should, 'minimum_should_match' => 1]],
            '_source' => false,
        ], JSON_UNESCAPED_UNICODE);
        try {
            $resp = self::client()->request(
                'POST',
                self::url($host, '/' . $index . '/_search'),
                ['body' => $body, 'headers' => ['Content-Type' => 'application/json']]
            );
        } catch (TransferException $e) {
            throw new \RuntimeException('ES 检索失败：' . $e->getMessage());
        }
        $data = json_decode((string) $resp->getBody(), true);
        $ids = [];
        foreach (($data['hits']['hits'] ?? []) as $hit) {
            $ids[] = (int) ($hit['_id'] ?? 0);
        }
        return $ids;
    }

    /**
     * 相关推荐（基于 ES more_like_this，按内容相似度返回相似文档 id）
     * @param array $fields 参与相似的字段，如 ['title','content']
     * @param string $likeText 源文档文本（title + content 拼接）
     * @return int[] 相似文档 id（相关度降序，不含自身）
     * @throws \RuntimeException
     */
    public static function moreLikeThis(string $host, string $index, string $likeText, array $fields, int $excludeId, int $limit = 6): array
    {
        $likeText = trim($likeText);
        if ($likeText === '') {
            return [];
        }
        $body = json_encode([
            'size'  => $limit + 1,
            'query' => [
                'more_like_this' => [
                    'fields'           => $fields,
                    'like'             => $likeText,
                    'min_term_freq'    => 1,
                    'min_doc_freq'     => 1,
                    'minimum_should_match' => '20%',
                ],
            ],
            '_source' => false,
        ], JSON_UNESCAPED_UNICODE);
        try {
            $resp = self::client()->request(
                'POST',
                self::url($host, '/' . $index . '/_search'),
                ['body' => $body, 'headers' => ['Content-Type' => 'application/json']]
            );
        } catch (TransferException $e) {
            throw new \RuntimeException('ES 相关推荐失败：' . $e->getMessage());
        }
        $data = json_decode((string) $resp->getBody(), true);
        $ids = [];
        foreach (($data['hits']['hits'] ?? []) as $hit) {
            $id = (int) ($hit['_id'] ?? 0);
            if ($id !== $excludeId) {
                $ids[] = $id;
            }
        }
        return array_slice($ids, 0, $limit);
    }

    /**
     * 全量重建索引（清空后批量写入）
     * @param callable $each 迭代器回调：function(int $page, int $size): array 返回 [id=>body] 映射
     */
    public static function rebuild(string $host, string $index, array $fields, callable $each, int $size = 200): void
    {
        // 删除旧索引重建
        try {
            self::client()->request('DELETE', self::url($host, '/' . $index));
        } catch (TransferException $e) {
        }
        self::ensureIndex($host, $index, $fields);

        $page = 1;
        while (true) {
            $batch = $each($page, $size);
            if (empty($batch)) {
                break;
            }
            foreach ($batch as $id => $doc) {
                self::indexDoc($host, $index, (int) $id, $doc);
            }
            if (count($batch) < $size) {
                break;
            }
            $page++;
        }
    }
}