package com.lingyue.parse.service;

import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.Data;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

/**
 * 文档索引服务
 * 负责生成和管理文档的位置索引
 * 
 * @author lingyue
 * @since 2026-01-20
 */
@Slf4j
@Service
@RequiredArgsConstructor
public class DocumentIndexService {
    
    private final ObjectMapper objectMapper;
    
    /**
     * 分页符字符（Form Feed）
     */
    private static final char FORM_FEED = '\f';
    
    /**
     * 为纯文本生成行索引（Word/Excel等文档）
     * 如果文本中包含分页符(\f)，则根据分页符生成页面索引
     * 
     * @param text 文本内容
     * @param documentId 文档ID
     * @param indexOutputPath 索引输出路径
     * @return 文档索引
     */
    public DocumentIndex generateLineIndex(String text, String documentId, String indexOutputPath) {
        if (text == null || text.isEmpty()) {
            return createEmptyIndex(documentId);
        }
        
        // 检查是否包含分页符
        boolean hasPageBreaks = text.indexOf(FORM_FEED) >= 0;
        
        if (hasPageBreaks) {
            log.info("检测到分页符，生成分页索引: documentId={}", documentId);
            return generateIndexWithPageBreaks(text, documentId, indexOutputPath);
        } else {
            log.debug("无分页符，生成单页索引: documentId={}", documentId);
            return generateSinglePageIndex(text, documentId, indexOutputPath);
        }
    }
    
    /**
     * 根据分页符生成多页索引
     */
    private DocumentIndex generateIndexWithPageBreaks(String text, String documentId, String indexOutputPath) {
        List<PageIndex> pageIndices = new ArrayList<>();
        List<LineIndex> lineIndices = new ArrayList<>();
        
        int charPos = 0;
        int lineNum = 1;
        int pageNum = 1;
        int pageCharStart = 0;
        int pageLineStart = 1;
        
        String[] lines = text.split("\n", -1);
        
        for (String line : lines) {
            // 检查这一行是否包含分页符
            int ffIndex = line.indexOf(FORM_FEED);
            
            if (ffIndex >= 0) {
                // 处理分页符之前的内容
                if (ffIndex > 0) {
                    LineIndex lineIndex = new LineIndex();
                    lineIndex.setLine(lineNum);
                    lineIndex.setCharStart(charPos);
                    lineIndex.setCharEnd(charPos + ffIndex);
                    lineIndices.add(lineIndex);
                }
                
                // 结束当前页
                PageIndex pageIndex = new PageIndex();
                pageIndex.setPage(pageNum);
                pageIndex.setCharStart(pageCharStart);
                pageIndex.setCharEnd(charPos + ffIndex);
                pageIndex.setLineStart(pageLineStart);
                pageIndex.setLineEnd(lineNum);
                pageIndices.add(pageIndex);
                
                // 开始新页
                pageNum++;
                pageCharStart = charPos + ffIndex + 1; // +1 跳过分页符
                pageLineStart = lineNum + 1;
                
                // 处理分页符之后的内容（如果有）
                if (ffIndex + 1 < line.length()) {
                    lineNum++;
                    LineIndex afterLineIndex = new LineIndex();
                    afterLineIndex.setLine(lineNum);
                    afterLineIndex.setCharStart(charPos + ffIndex + 1);
                    afterLineIndex.setCharEnd(charPos + line.length());
                    lineIndices.add(afterLineIndex);
                }
            } else {
                // 普通行
                LineIndex lineIndex = new LineIndex();
                lineIndex.setLine(lineNum);
                lineIndex.setCharStart(charPos);
                lineIndex.setCharEnd(charPos + line.length());
                lineIndices.add(lineIndex);
            }
            
            charPos += line.length() + 1; // +1 for \n
            lineNum++;
        }
        
        // 添加最后一页
        if (pageCharStart < text.length()) {
            PageIndex lastPage = new PageIndex();
            lastPage.setPage(pageNum);
            lastPage.setCharStart(pageCharStart);
            lastPage.setCharEnd(text.length());
            lastPage.setLineStart(pageLineStart);
            lastPage.setLineEnd(lineNum - 1);
            pageIndices.add(lastPage);
        }
        
        // 创建文档索引
        DocumentIndex index = new DocumentIndex();
        index.setDocumentId(documentId);
        index.setTotalChars(text.length());
        index.setTotalLines(lineNum - 1);
        index.setTotalPages(pageIndices.size());
        index.setPages(pageIndices);
        index.setLines(lineIndices);
        
        log.info("分页索引生成完成: documentId={}, pages={}, lines={}", 
                documentId, pageIndices.size(), lineIndices.size());
        
        // 保存索引文件
        if (indexOutputPath != null) {
            saveIndexFile(index, indexOutputPath);
        }
        
        return index;
    }
    
    /**
     * 生成单页索引（无分页符的文档）
     */
    private DocumentIndex generateSinglePageIndex(String text, String documentId, String indexOutputPath) {
        List<LineIndex> lineIndices = new ArrayList<>();
        int charPos = 0;
        int lineNum = 1;
        
        String[] lines = text.split("\n", -1);
        for (String line : lines) {
            LineIndex lineIndex = new LineIndex();
            lineIndex.setLine(lineNum);
            lineIndex.setCharStart(charPos);
            lineIndex.setCharEnd(charPos + line.length());
            lineIndices.add(lineIndex);
            
            charPos += line.length() + 1; // +1 for \n
            lineNum++;
        }
        
        // 创建文档索引（无分页，只有行索引）
        DocumentIndex index = new DocumentIndex();
        index.setDocumentId(documentId);
        index.setTotalChars(text.length());
        index.setTotalLines(lines.length);
        index.setTotalPages(1); // 非分页文档统一为1页
        index.setLines(lineIndices);
        
        // 创建虚拟的单页索引
        List<PageIndex> pages = new ArrayList<>();
        PageIndex singlePage = new PageIndex();
        singlePage.setPage(1);
        singlePage.setCharStart(0);
        singlePage.setCharEnd(text.length());
        singlePage.setLineStart(1);
        singlePage.setLineEnd(lines.length);
        pages.add(singlePage);
        index.setPages(pages);
        
        // 保存索引文件
        if (indexOutputPath != null) {
            saveIndexFile(index, indexOutputPath);
        }
        
        return index;
    }
    
    /**
     * 读取索引文件
     */
    public DocumentIndex loadIndex(String indexFilePath) {
        try {
            Path path = Paths.get(indexFilePath);
            if (!Files.exists(path)) {
                log.warn("索引文件不存在: {}", indexFilePath);
                return null;
            }
            String json = Files.readString(path);
            return objectMapper.readValue(json, DocumentIndex.class);
        } catch (Exception e) {
            log.error("读取索引文件失败: {}", indexFilePath, e);
            return null;
        }
    }
    
    /**
     * 根据字符位置查找页码和行号
     * 
     * @param index 文档索引
     * @param charPosition 字符位置
     * @return [页码, 行号] 或 null（未找到）
     */
    public int[] findPageAndLine(DocumentIndex index, int charPosition) {
        if (index == null || index.getPages() == null) {
            return null;
        }
        
        // 1. 找到所在页
        int page = 1;
        for (PageIndex pageIndex : index.getPages()) {
            if (charPosition >= pageIndex.getCharStart() && charPosition <= pageIndex.getCharEnd()) {
                page = pageIndex.getPage();
                break;
            }
        }
        
        // 2. 找到所在行
        int line = 1;
        if (index.getLines() != null) {
            for (LineIndex lineIndex : index.getLines()) {
                if (charPosition >= lineIndex.getCharStart() && charPosition <= lineIndex.getCharEnd()) {
                    line = lineIndex.getLine();
                    break;
                }
            }
        }
        
        return new int[]{page, line};
    }
    
    private DocumentIndex createEmptyIndex(String documentId) {
        DocumentIndex index = new DocumentIndex();
        index.setDocumentId(documentId);
        index.setTotalChars(0);
        index.setTotalLines(0);
        index.setTotalPages(0);
        index.setPages(new ArrayList<>());
        return index;
    }
    
    private void saveIndexFile(DocumentIndex index, String outputPath) {
        try {
            Path path = Paths.get(outputPath);
            Files.createDirectories(path.getParent());
            String json = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(index);
            Files.writeString(path, json);
            log.info("文档索引文件已保存: {}", outputPath);
        } catch (Exception e) {
            log.error("保存文档索引文件失败: {}", outputPath, e);
        }
    }
    
    /**
     * 文档索引
     */
    @Data
    public static class DocumentIndex {
        private String documentId;
        private List<PageIndex> pages;
        private List<LineIndex> lines;
        private int totalChars;
        private int totalLines;
        private int totalPages;
    }
    
    /**
     * 页面索引
     */
    @Data
    public static class PageIndex {
        private int page;
        private int charStart;
        private int charEnd;
        private int lineStart;
        private int lineEnd;
        private boolean ocrUsed;
    }
    
    /**
     * 行索引
     */
    @Data
    public static class LineIndex {
        private int line;
        private int charStart;
        private int charEnd;
    }
}