package cn.edu.bjut.textmining.chapter5.support;

import java.io.InputStream;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import cn.edu.bjut.textmining.chapter5.KMeansEngine;

/** 将原始记录、特征矩阵行与聚类结果连接起来，不改变特征或聚类计算。 */
public final class DocumentRegistry {
    public static final String SMALL_CONFIG = "ch5-char12-rawtf-smoothidf-l2-v1";
    public static final String LARGE_CONFIG = "ch5-char23-filter-df2-60pct-top5000-rawtf-smoothidf-l2-v1";

    private DocumentRegistry() {}

    /** clusterByInput 使用算法内部的零基簇号；-1 表示零向量未进入聚类。 */
    public static void write(String prefix, List<TNewsCorpusLoader.NewsRecord> records,
            TextFeatures.Result features, int[] clusterByInput, String config) {
        if (records.size() != features.vectors.length || records.size() != clusterByInput.length) {
            throw new IllegalArgumentException("原始记录、向量行和聚类状态必须一一对应");
        }
        Path source = ProjectPaths.data("tnews_public/train.json");
        List<TNewsCorpusLoader.NewsRecord> original = TNewsCorpusLoader.readAll(source);
        String sourceHash = sha256(source);
        List<String> rows = new ArrayList<String>();
        rows.add("local_id\tsource_id\tsource_physical_line\tsource_file\tsource_file_sha256"
                + "\ttext_sha256\ttext\tpreprocess_version\tvector_row_0based\tfeature_dimension"
                + "\tstatus\tcluster_id\treference_label");
        for (int i = 0; i < records.size(); i++) {
            TNewsCorpusLoader.NewsRecord record = records.get(i);
            int line = record.getSourceLine();
            if (line < 1 || line > original.size()
                    || !record.getTitle().equals(original.get(line - 1).getTitle())
                    || !record.getLabel().equals(original.get(line - 1).getLabel())) {
                throw new IllegalStateException("清单与原始文件不符：source_line=" + line);
            }
            boolean zero = KMeansEngine.squaredNorm(features.vectors[i]) == 0.0;
            if ((clusterByInput[i] < 0) != zero) {
                throw new IllegalArgumentException("只有零向量可以没有聚类结果，向量行=" + i);
            }
            String sourceId = String.format(Locale.ROOT, "tnews-train-%06d", line);
            String localId = ("news_sample".equals(prefix) ? "N" : "selection-") + (i + 1);
            rows.add(localId + "\t" + sourceId + "\t" + line
                    + "\tdata/chapter5/tnews_public/train.json\t" + sourceHash
                    + "\t" + sha256(record.getTitle().getBytes(StandardCharsets.UTF_8))
                    + "\t" + tsv(record.getTitle()) + "\t" + config + "\t" + i
                    + "\t" + features.vocabulary.size() + "\t" + (zero ? "zero_vector" : "clustered")
                    + "\t" + (zero ? "" : Integer.toString(clusterByInput[i] + 1))
                    + "\t" + record.getLabel());
        }
        ResultWriter.lines(prefix + "_document_registry.tsv", rows);
    }

    private static String tsv(String value) {
        // JSON 风格反斜杠转义，避免原文制表符/换行破坏列结构。
        return value.replace("\\", "\\\\").replace("\t", "\\t")
                .replace("\r", "\\r").replace("\n", "\\n");
    }

    private static MessageDigest digest() {
        try {
            return MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException("JDK 缺少 SHA-256", e);
        }
    }

    public static String sha256(Path path) {
        MessageDigest digest = digest();
        try (InputStream in = Files.newInputStream(path)) {
            byte[] buffer = new byte[8192];
            int count;
            while ((count = in.read(buffer)) != -1) {
                digest.update(buffer, 0, count);
            }
            return hex(digest.digest());
        } catch (IOException e) {
            throw new UncheckedIOException("无法校验来源文件：" + path, e);
        }
    }

    private static String sha256(byte[] bytes) { return hex(digest().digest(bytes)); }

    private static String hex(byte[] bytes) {
        StringBuilder result = new StringBuilder();
        for (byte b : bytes) result.append(String.format(Locale.ROOT, "%02x", b & 0xff));
        return result.toString();
    }
}