package org.ngbw.pise.commandrenderer;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;

import org.apache.log4j.Logger;


public class PerlEval
{
    private static final Logger logger = Logger.getLogger(PerlEval.class);
    
    Process worker = null;
    BufferedReader stdout = null;
    BufferedReader stderr = null;
    PrintStream stdin = null;


    public static void main ( String[] args ) throws Exception
    {
        String[] perlStatements = {
            "print \"hi there\"\n",
            "print \"two\\nlines\\n\"\n",
            "(! 1 )? print \" -endgaps\": print \"\"\n",
            "((\"-align\" =~ /align/ ))? print \"true\" : print \"false\";\n",
            "print  <<\"EOT\"\n<commands>set Increase = no;</commands>\\n\nEOT\n",
            "print  <<\"EOT\"\n<commands>set Increase = no;</commands>\\nsecond line\n\n\nEOT\n",
            "print"
        };

        PerlEval perlEval = null;
        try {
            String result;
            perlEval = new PerlEval();
            perlEval.initialize();
            for (int i = 0; i < perlStatements.length; i++) {
                logger.debug("Statement: " + perlStatements[i]);
                result = perlEval.evaluateStatement(perlStatements[i]);
                logger.debug("Evaluates to: " + result);
            }
            perlEval.terminate();
        }
        catch ( Exception e ) {
            logger.error("", e);
            perlEval.cleanup();
        }
    }


    public PerlEval ()
    {}


    public void initialize () throws Exception
    {
        String[] command = new String[1];

        try {
            command[0] = "piseEval";
            logger.info("initialize()::Running piseEval ...");
            worker = Runtime.getRuntime().exec(command);
            stdout = new BufferedReader(new InputStreamReader(worker.getInputStream()));
            stderr = new BufferedReader(new InputStreamReader(worker.getErrorStream()));
            stdin = new PrintStream(new BufferedOutputStream(worker.getOutputStream(), 8192));
        }
        catch ( Exception e ) {
            logger.error("Runtime exec of piseEval failed.  Make sure piseEval script is in the path and executable.", e);
            throw e;
        }
    }


    public void terminate () throws Exception
    {
        logger.debug("BEGIN: terminate()::void");
        try {
            stdin.close();
            stdin = null;
            // todo: need to read stdout and stderr?
            final int exitCode = worker.waitFor();
            if (exitCode != 0) {
                throw new RuntimeException("Exit value was not 0 but " + exitCode);
            }
        }
        finally {
            cleanup();
        }
        logger.debug("END: terminate()::void");
    }


    public void cleanup ()
    {
        logger.debug("BEGIN: cleanup()::void");
        try {
            if (stdin != null) {
                stdin.close();
                stdin = null;
            }
            if (stdout != null) {
                stdout.close();
                stdout = null;
            }
            if (stderr != null) {
                stderr.close();
                stderr = null;
            }
        }
        catch ( Exception e ) {
            logger.error("Caught exception:" + e.getMessage());
        }
        logger.debug("END: cleanup()::void");
    }


    public String evaluateStatement ( String statement ) throws Exception
    {
        String response;
        String error = null;
        String result = "";

        //log.debug("Sending:" + statement);
        if (!statement.endsWith("\n")) {
            statement += "\n";
        }
        stdin.print(statement);
        stdin.print("piseEnd\n");
        stdin.flush();

        while ((response = stdout.readLine()) != null) {
            //log.debug("Read:" + response);
            if (response.equals("PiseEval:")) {
                break;
            }
            else if (response.startsWith("PiseEvalError=")) {
                logger.error("Starting error message: " + error);
                error = response + "\n";
            }
            else if (error != null) {
                logger.error("Adding to error message: " + error);
                error += (response + "\n");
            }
            else {
                //log.debug("Adding to result: " + result);
                result += (response + "\n");
            }
        }
        if (response == null) {
            throw new Exception("Unexepected EOF from piseEval");
        }
        if (error != null) {
            logger.error(error);
            throw new Exception("piseEval error");
        }
        return result.trim();
    }

}