package org.ooc.utils;

import java.io.File;
import java.io.StringWriter;
import java.util.Map;
import java.util.StringTokenizer;

import org.ubi.CompilationFailedError;

/**
 * Utilities for launching processes
 *  
 * @author Amos Wenger
 */
public class ShellUtils {

	public static File findExecutable(String executableName) {
		return findExecutable(executableName, false);
	}
	
	/**
	 * @return the path of an executable, if it can be found. It looks in the PATH
	 * environment variable.
	 */
	public static File findExecutable(String executableName, boolean crucial) {
		
		Map<String, String> env;
		try {
			env = System.getenv();
		} catch(Exception e) {
			e.printStackTrace();
			return null;
		}
		
		String pathVar = env.get("PATH");
		if(pathVar == null) {
			pathVar = env.get("Path");
			if(pathVar == null) {
				pathVar = env.get("path");
			}
		}
		
		if(pathVar == null) {
			env = ReadEnv.getEnv();
			pathVar = env.get("PATH");
			if(pathVar == null) {
				pathVar = env.get("Path");
				if(pathVar == null) {
					pathVar = env.get("path");
				}
			}
		}
		
		if(pathVar == null) {
			System.err.println("PATH environment variable not found!");
			return null;
		}
	
		StringTokenizer st = new StringTokenizer(pathVar, File.pathSeparator);
		while(st.hasMoreTokens()) {
			String path = st.nextToken();
			File file = new File(path, executableName);
			if(file.exists() && file.isFile()) {
				return file;
			}
		}
		
		if(crucial) {
			throw new CompilationFailedError(null, "Couldn't find '"+executableName+"' on your system. PATH = "+pathVar);
		}
		return null;
		
	}

	/**
	 * Run a command to get its output
	 * @param command
	 * @return the output of the command specified, once it has exited
	 */
	public static String getOutput(String... command) {
		
		String result = null;
		
		try {
			StringWriter writer = new StringWriter();
			Process p = new ProcessBuilder(command).start();
			ProcessUtils.redirectIO(p, writer);
			int exitCode = p.waitFor();
			if(exitCode == 0) {
				result = writer.toString();
			}
			writer.close();
		} catch (Exception e) {
			/* Exception? Will return null */
			e.printStackTrace();
		}
		
		return result;
		
	}
	
}