Stirling-PDF/src/main/java/stirling/software/SPDF/utils/ProcessExecutor.java

package stirling.software.SPDF.utils;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Semaphore;

public class ProcessExecutor {

    public enum Processes {
        LIBRE_OFFICE,
        OCR_MY_PDF,
        PYTHON_OPENCV,
        GHOSTSCRIPT,
        WEASYPRINT
    }

    private static final Map<Processes, ProcessExecutor> instances = new ConcurrentHashMap<>();

    public static ProcessExecutor getInstance(Processes processType) {
        return instances.computeIfAbsent(
                processType,
                key -> {
                    int semaphoreLimit =
                            switch (key) {
                                case LIBRE_OFFICE -> 1;
                                case OCR_MY_PDF -> 2;
                                case PYTHON_OPENCV -> 8;
                                case GHOSTSCRIPT -> 16;
                                case WEASYPRINT -> 16;
                            };
                    return new ProcessExecutor(semaphoreLimit);
                });
    }

    private final Semaphore semaphore;

    private ProcessExecutor(int semaphoreLimit) {
        this.semaphore = new Semaphore(semaphoreLimit);
    }

    public ProcessExecutorResult runCommandWithOutputHandling(List<String> command)
            throws IOException, InterruptedException {
        return runCommandWithOutputHandling(command, null);
    }

    public ProcessExecutorResult runCommandWithOutputHandling(
            List<String> command, File workingDirectory) throws IOException, InterruptedException {
        int exitCode = 1;
        String messages = "";
        semaphore.acquire();
        try {

            System.out.print("Running command: " + String.join(" ", command));
            ProcessBuilder processBuilder = new ProcessBuilder(command);

            // Use the working directory if it's set
            if (workingDirectory != null) {
                processBuilder.directory(workingDirectory);
            }
            Process process = processBuilder.start();

            // Read the error stream and standard output stream concurrently
            List<String> errorLines = new ArrayList<>();
            List<String> outputLines = new ArrayList<>();

            Thread errorReaderThread =
                    new Thread(
                            () -> {
                                try (BufferedReader errorReader =
                                        new BufferedReader(
                                                new InputStreamReader(
                                                        process.getErrorStream(),
                                                        StandardCharsets.UTF_8))) {
                                    String line;
                                    while ((line = errorReader.readLine()) != null) {
                                        errorLines.add(line);
                                    }
                                } catch (IOException e) {
                                    e.printStackTrace();
                                }
                            });

            Thread outputReaderThread =
                    new Thread(
                            () -> {
                                try (BufferedReader outputReader =
                                        new BufferedReader(
                                                new InputStreamReader(
                                                        process.getInputStream(),
                                                        StandardCharsets.UTF_8))) {
                                    String line;
                                    while ((line = outputReader.readLine()) != null) {
                                        outputLines.add(line);
                                    }
                                } catch (IOException e) {
                                    e.printStackTrace();
                                }
                            });

            errorReaderThread.start();
            outputReaderThread.start();

            // Wait for the conversion process to complete
            exitCode = process.waitFor();

            // Wait for the reader threads to finish
            errorReaderThread.join();
            outputReaderThread.join();

            if (outputLines.size() > 0) {
                String outputMessage = String.join("\n", outputLines);
                messages += outputMessage;
                System.out.println("Command output:\n" + outputMessage);
            }

            if (errorLines.size() > 0) {
                String errorMessage = String.join("\n", errorLines);
                messages += errorMessage;
                System.out.println("Command error output:\n" + errorMessage);
                if (exitCode != 0) {
                    throw new IOException(
                            "Command process failed with exit code "
                                    + exitCode
                                    + ". Error message: "
                                    + errorMessage);
                }
            }
        } finally {
            semaphore.release();
        }
        return new ProcessExecutorResult(exitCode, messages);
    }

    public class ProcessExecutorResult {
        int rc;
        String messages;

        public ProcessExecutorResult(int rc, String messages) {
            this.rc = rc;
            this.messages = messages;
        }

        public int getRc() {
            return rc;
        }

        public void setRc(int rc) {
            this.rc = rc;
        }

        public String getMessages() {
            return messages;
        }

        public void setMessages(String messages) {
            this.messages = messages;
        }
    }
}