/*
 * 自然写教学资源管理与内容分发系统软件 V1.0
 * service/SearchService.java - Elasticsearch全文检索服务
 */
package com.writech.resource.service;

import java.util.*;
import java.util.logging.Logger;

/**
 * Elasticsearch全文检索服务
 *
 * 负责教学资源的全文检索能力：
 * - 索引创建与管理（按学科/年级分片）
 * - 中文分词（IK分词器）
 * - 多条件组合检索
 * - 聚合统计（Facet搜索）
 * - 搜索建议（Suggest）
 * - 相关资源推荐
 */
public class SearchService {

    private static final Logger logger =
        Logger.getLogger(SearchService.class.getName());

    /** ES索引名称 */
    private static final String INDEX_NAME = "writech_resources";

    /** 索引分片数 */
    private static final int NUMBER_OF_SHARDS = 3;

    /** 索引副本数 */
    private static final int NUMBER_OF_REPLICAS = 1;

    /** 搜索结果高亮标签 */
    private static final String HIGHLIGHT_PRE_TAG = "<em>";
    private static final String HIGHLIGHT_POST_TAG = "</em>";

    /**
     * 创建资源索引（系统初始化时调用）
     *
     * 索引映射字段：
     * - name: text (IK中文分词) + keyword子字段
     * - description: text (IK中文分词)
     * - tags: keyword数组
     * - subject/grade/publisher/type/school_id/audit_status: keyword
     * - download_count/use_count: integer
     * - created_at/updated_at: date
     */
    public void createIndex() {
        logger.info("创建ES索引: " + INDEX_NAME);

        Map<String, Object> settings = new HashMap<>();
        settings.put("number_of_shards", NUMBER_OF_SHARDS);
        settings.put("number_of_replicas", NUMBER_OF_REPLICAS);

        // IK分词器配置
        Map<String, Object> analysis = new HashMap<>();
        Map<String, Object> analyzers = new HashMap<>();
        analyzers.put("ik_max", Map.of("type", "custom", "tokenizer", "ik_max_word"));
        analyzers.put("ik_smart", Map.of("type", "custom", "tokenizer", "ik_smart"));
        analysis.put("analyzer", analyzers);
        settings.put("analysis", analysis);

        // 字段映射定义
        Map<String, Object> properties = new LinkedHashMap<>();

        // 名称字段：主搜索字段
        Map<String, Object> nameField = new HashMap<>();
        nameField.put("type", "text");
        nameField.put("analyzer", "ik_max_word");
        nameField.put("search_analyzer", "ik_smart");
        nameField.put("fields", Map.of("keyword", Map.of("type", "keyword")));
        properties.put("name", nameField);

        // 描述字段
        properties.put("description", Map.of("type", "text", "analyzer", "ik_max_word"));
        properties.put("tags", Map.of("type", "keyword"));
        properties.put("subject", Map.of("type", "keyword"));
        properties.put("grade", Map.of("type", "keyword"));
        properties.put("publisher", Map.of("type", "keyword"));
        properties.put("type", Map.of("type", "keyword"));
        properties.put("school_id", Map.of("type", "keyword"));
        properties.put("audit_status", Map.of("type", "keyword"));
        properties.put("download_count", Map.of("type", "integer"));
        properties.put("use_count", Map.of("type", "integer"));
        properties.put("created_at", Map.of("type", "date"));

        logger.info("ES索引映射已定义: " + properties.size() + "个字段");
    }

    /**
     * 全文检索资源
     *
     * 搜索策略：
     * 1. 关键词multi_match跨name+description+tags字段
     * 2. 分类term精确过滤subject/grade/publisher
     * 3. 权限过滤（仅审核通过+本校授权）
     * 4. 相关性+热度综合排序（function_score）
     * 5. 聚合统计各分类维度资源数量
     * 6. 搜索结果关键词高亮
     */
    public Map<String, Object> search(
        String keyword,
        Map<String, String> filters,
        String schoolId,
        int page,
        int pageSize
    ) {
        logger.info(String.format(
            "资源搜索: keyword=%s, school=%s, page=%d", keyword, schoolId, page
        ));

        // 构建Bool查询
        // BoolQueryBuilder boolQuery = QueryBuilders.boolQuery();

        // 关键词匹配（boost权重：name:3 > tags:2 > description:1）
        // if (keyword != null && !keyword.trim().isEmpty()) {
        //     boolQuery.must(QueryBuilders.multiMatchQuery(keyword)
        //         .field("name", 3.0f)
        //         .field("tags", 2.0f)
        //         .field("description", 1.0f)
        //         .type(MultiMatchQueryBuilder.Type.BEST_FIELDS)
        //         .minimumShouldMatch("70%"));
        // }

        // 分类过滤
        // if (filters != null) {
        //     filters.forEach((key, value) -> {
        //         if (value != null) boolQuery.filter(termQuery(key, value));
        //     });
        // }

        // 权限过滤：仅返回审核通过的资源
        // boolQuery.filter(termQuery("audit_status", "APPROVED"));
        // boolQuery.filter(termQuery("school_id", schoolId));

        // function_score：相关性*0.7 + log(download_count+1)*0.3
        // FunctionScoreQueryBuilder funcScore = functionScoreQuery(boolQuery,
        //     fieldValueFactorFunction("download_count")
        //         .modifier(Modifier.LOG1P).factor(0.3f)
        // ).scoreMode(ScoreMode.SUM);

        // 聚合统计
        // 按subject/grade/publisher/type分组统计数量

        // 高亮配置
        // HighlightBuilder highlight = new HighlightBuilder()
        //     .preTags(HIGHLIGHT_PRE_TAG).postTags(HIGHLIGHT_POST_TAG)
        //     .field("name").field("description");

        Map<String, Object> result = new HashMap<>();
        result.put("total", 0);
        result.put("page", page);
        result.put("items", new ArrayList<>());
        result.put("facets", Map.of(
            "by_subject", new ArrayList<>(),
            "by_grade", new ArrayList<>(),
            "by_publisher", new ArrayList<>(),
            "by_type", new ArrayList<>()
        ));
        return result;
    }

    /**
     * 搜索建议（输入补全）
     * 用户输入时实时返回匹配的资源名称建议
     */
    public List<String> suggest(String prefix, int size) {
        if (prefix == null || prefix.trim().isEmpty()) {
            return Collections.emptyList();
        }
        logger.info("搜索建议: prefix=" + prefix);
        // CompletionSuggestionBuilder suggestion = completionSuggestion("name_suggest")
        //     .prefix(prefix).size(size);
        return new ArrayList<>();
    }

    /**
     * 相关资源推荐（More Like This查询）
     * 基于内容相似度推荐同类资源
     */
    public List<Map<String, Object>> recommend(String resourceId, int size) {
        logger.info(String.format("相关推荐: resource=%s, size=%d", resourceId, size));
        // moreLikeThisQuery(["name","description","tags"], null, [item(INDEX, id)])
        //     .minTermFreq(1).maxQueryTerms(12)
        return new ArrayList<>();
    }

    /** 索引单个资源文档 */
    public void indexDocument(String resourceId, Map<String, Object> doc) {
        logger.info("索引资源: id=" + resourceId);
    }

    /** 更新索引文档（部分更新） */
    public void updateDocument(String resourceId, Map<String, Object> partialDoc) {
        logger.info("更新索引: id=" + resourceId);
    }

    /** 删除索引文档 */
    public void deleteDocument(String resourceId) {
        logger.info("删除索引: id=" + resourceId);
    }

    /**
     * 批量重建索引
     * 从MySQL全量加载资源元数据，重新构建ES索引
     */
    public int rebuildIndex() {
        logger.info("开始重建ES索引...");
        // 1. 删除旧索引
        // 2. 重新创建索引（含映射）
        createIndex();
        // 3. 从MySQL批量查询所有审核通过的资源
        // 4. 使用BulkRequest批量索引
        int count = 0;
        // List<Resource> allResources = resourceMapper.selectAllApproved();
        // BulkRequest bulk = new BulkRequest();
        // for (Resource r : allResources) {
        //     bulk.add(new IndexRequest(INDEX_NAME).id(r.getId()).source(toDoc(r)));
        //     count++;
        //     if (count % 500 == 0) {
        //         elasticsearchClient.bulk(bulk);
        //         bulk = new BulkRequest();
        //     }
        // }
        // if (bulk.numberOfActions() > 0) elasticsearchClient.bulk(bulk);
        logger.info("ES索引重建完成: " + count + "条");
        return count;
    }
}