package ru.ulstu.paper.service;

import org.springframework.stereotype.Service;
import ru.ulstu.file.service.FileService;
import ru.ulstu.paper.model.PaperDto;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.file.Files;

@Service
public class LatexService {
    private final String pdfLatexError = "Errors occurred while executing pdfLaTeX.";
    private final String bibtexError = "Errors occurred while executing bibtex.";
    private String errorMessage;
    private File pdfFile;
    private FileService fileService;

    public LatexService(FileService fileService) {
        this.fileService = fileService;
    }

    public byte[] generatePdfFromLatexFile(PaperDto paper) throws IOException, InterruptedException {
        fileService.createLatexAttachs(paper);
        File tex = fileService.createLatexFile(paper);

        if (!generate(paper.getTitle(), tex.getParentFile())) {
            throw new IOException(errorMessage);
        }

        return Files.readAllBytes(pdfFile.toPath());
    }

    private int startProcess(String[] args, File dir, String message) throws IOException, InterruptedException {
        ProcessBuilder processBuilder = new ProcessBuilder(args);
        processBuilder.redirectErrorStream(true);
        processBuilder.directory(dir);

        Process process = processBuilder.start();
        InputStreamReader inputStreamReader = new InputStreamReader(process.getInputStream());

        try (BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {
            String line = bufferedReader.readLine();
            while (line != null) {
                line = bufferedReader.readLine();
            }
        }

        int exitCode = process.waitFor();
        if (exitCode != 0) {
            errorMessage = message + " Exit value of the process: " + exitCode;
        }
        return exitCode;
    }

    private boolean generate(String filename, File dir) throws IOException, InterruptedException {
        startProcess(new String[]{"pdflatex", filename, "--interaction=nonstopmode"}, dir, pdfLatexError);
        startProcess(new String[]{"bibtex", filename}, dir, bibtexError);
        if (startProcess(new String[]{"pdflatex", filename, "--interaction=nonstopmode"}, dir, pdfLatexError) != 0) {
            return false;
        }
        return checkPdf(filename, dir);
    }

    private boolean checkPdf(String filename, File dir) {
        pdfFile = new File(dir.getAbsolutePath() + File.separator + filename + ".pdf");

        if (pdfFile.isFile()) {
            return true;
        } else {
            errorMessage = "The pdf file could not be created.";
            return false;
        }
    }
}