package net.gepafin.tendermanagement.util;

import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3URI;
import com.amazonaws.services.s3.model.S3Object;
import net.gepafin.tendermanagement.model.request.AttachmentRequest;
import org.apache.poi.xwpf.usermodel.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.*;
import java.net.URI;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.*;
import java.util.Base64;

public class S3DocxProcessor {

    private final AmazonS3 s3Client;

    public static final Logger log = LoggerFactory.getLogger(S3DocxProcessor.class);


    public S3DocxProcessor(AmazonS3 s3Client) {
        this.s3Client = s3Client;
    }

    /**
     * Fetches DOCX files from S3, replaces placeholders, and returns updated files
     * as AttachmentRequest objects (ready for PEC API).
     *
     * @param s3Urls List of S3 file URLs
     * @param replacements Map of placeholder -> value
     * @return Map of original file name -> AttachmentRequest
     * @throws IOException
     */
    public Map<String, AttachmentRequest> processFiles(List<String> s3Urls,
                                                       Map<String, String> replacements) throws IOException {
        Map<String, AttachmentRequest> processedFiles = new HashMap<>();

        for (String s3Url : s3Urls) {
            // Extract bucket & key from URL
            AmazonS3URI s3Uri = new AmazonS3URI(s3Url);
            String bucket = s3Uri.getBucket();
            String key = s3Uri.getKey();
            try (S3Object s3Object = s3Client.getObject(bucket, key);
                 InputStream originalStream = new BufferedInputStream(s3Object.getObjectContent())) {
                byte[] updatedBytes=null;
                if (isDocxFile(originalStream)) {
                    log.warn("Skipping non-DOCX file from S3: bucket={}, key={}", bucket, key);
                    updatedBytes = replacePlaceholders(originalStream, replacements);
                }else {
                    // non-DOCX → just copy raw stream
                    updatedBytes = originalStream.readAllBytes();
                    log.info("Skipped placeholder replacement, copied file as-is: {}", key);
                }

                // convert to base64
                String base64 = Base64.getEncoder().encodeToString(updatedBytes);
                String fileString = "data:application/octet-stream;base64," + base64;

                // create attachment request
                AttachmentRequest attachment = new AttachmentRequest();
                attachment.setName(extractFileName(key));
                attachment.setFile(fileString);

                processedFiles.put(key, attachment);
            }
        }

        return processedFiles;
    }


    private byte[] replacePlaceholders(InputStream docInputStream,
                                       Map<String, String> replacements) throws IOException {
        try (XWPFDocument document = new XWPFDocument(docInputStream);
             ByteArrayOutputStream out = new ByteArrayOutputStream()) {

            // replace in body paragraphs
            replaceInParagraphs(document.getParagraphs(), replacements);

            // replace inside tables
            for (XWPFTable table : document.getTables()) {
                for (XWPFTableRow row : table.getRows()) {
                    for (XWPFTableCell cell : row.getTableCells()) {
                        replaceInParagraphs(cell.getParagraphs(), replacements);
                    }
                }
            }

            document.write(out);
            return out.toByteArray();
        }
    }

    private void replaceInParagraphs(List<XWPFParagraph> paragraphs, Map<String, String> replacements) {
        for (XWPFParagraph paragraph : paragraphs) {
            String paragraphText = paragraph.getText();

            if (paragraphText != null && !paragraphText.isEmpty()) {
                // Apply all replacements
                for (Map.Entry<String, String> entry : replacements.entrySet()) {
                    paragraphText = paragraphText.replace(entry.getKey(), entry.getValue());
                }

                // Remove old runs
                int runCount = paragraph.getRuns().size();
                for (int i = runCount - 1; i >= 0; i--) {
                    paragraph.removeRun(i);
                }

                // Add one new run with replaced text
                XWPFRun newRun = paragraph.createRun();
                newRun.setText(paragraphText);
            }
        }
    }


    private String extractFileName(String key) {
        int lastSlash = key.lastIndexOf('/');
        if (lastSlash >= 0 && lastSlash < key.length() - 1) {
            return key.substring(lastSlash + 1);
        }
        return key;
    }

    private boolean isDocxFile(InputStream inputStream) throws IOException {
        inputStream.mark(4);
        byte[] header = new byte[2];
        int read = inputStream.read(header, 0, 2);
        inputStream.reset();

        // DOCX = ZIP = should start with PK (0x50 0x4B)
        return read == 2 && header[0] == 0x50 && header[1] == 0x4B;
    }
}