from subprocess import Popen, PIPE
import re
import os
import sys
import shutil
import tempfile

def get_process_output(command):
    """
    Run subprocess and return stdout
    """
    p = Popen(command, shell=True, stdout=PIPE)
    return p.communicate()[0].strip()

def run_process(command):
    """
    Run subprocess and return "return code"
    """
    p = Popen(command, shell=True)
    return os.waitpid(p.pid, 0)[1]

def get_mime_type(file_path):
    """
    Attempts to get the mime type but will return prematurely if the process
    takes longer than 5 seconds. Note that this function should only be called 
    for files which do not have a mp3/ogg/flac extension.
    """

    return get_process_output("timeout 5 file -b --mime-type %s" % file_path)

def duplicate_file(file_path):
    """
    Makes a duplicate of the file and returns the path of this duplicate file.
    """
    fsrc = open(file_path, 'r')
    fdst = tempfile.NamedTemporaryFile(delete=False)

    print "Copying %s to %s" % (file_path, fdst.name)

    shutil.copyfileobj(fsrc, fdst)

    fsrc.close()
    fdst.close()

    return fdst.name

def calculate_replay_gain(file_path):
    """
    This function accepts files of type mp3/ogg/flac and returns a calculated ReplayGain value in dB.
    If the value cannot be calculated for some reason, then we default to 0 (Unity Gain).
       
    http://wiki.hydrogenaudio.org/index.php?title=ReplayGain_1.0_specification
    """

    try:
        """
        Making a duplicate is required because the ReplayGain extraction utilities we use
        make unwanted modifications to the file. 
        """

        search = None
        temp_file_path = duplicate_file(file_path)

        if re.search(r'mp3$', temp_file_path, re.IGNORECASE) or get_mime_type(temp_file_path) == "audio/mpeg":
            if run_process("which mp3gain > /dev/null") == 0:
                out = get_process_output('mp3gain -q "%s" 2> /dev/null' % temp_file_path)
                search = re.search(r'Recommended "Track" dB change: (.*)', out)
            else:
                print "mp3gain not found"
                #Log warning
        elif re.search(r'ogg$', temp_file_path, re.IGNORECASE) or get_mime_type(temp_file_path) == "application/ogg":
            if run_process("which vorbisgain > /dev/null  && which ogginfo > /dev/null") == 0:
                run_process('vorbisgain -q -f "%s" 2>/dev/null >/dev/null' % temp_file_path)
                out = get_process_output('ogginfo "%s"' % temp_file_path)
                search = re.search(r'REPLAYGAIN_TRACK_GAIN=(.*) dB', out)
            else:
                print "vorbisgain/ogginfo not found"
                #Log warning
        elif re.search(r'flac$', temp_file_path, re.IGNORECASE) or get_mime_type(temp_file_path) == "audio/x-flac":
            if run_process("which metaflac > /dev/null") == 0:
                out = get_process_output('metaflac --show-tag=REPLAYGAIN_TRACK_GAIN "%s"' % temp_file_path)
                search = re.search(r'REPLAYGAIN_TRACK_GAIN=(.*) dB', out)
            else:
                print "metaflac not found"
                #Log warning
        else:
            pass
            #Log unknown file type.

        #no longer need the temp, file simply remove it.
        os.remove(temp_file_path)
    except Exception, e:
        print e

    replay_gain = 0
    if search:
        matches = search.groups()
        if len(matches) == 1:
            replay_gain = matches[0]

    return replay_gain


# Example of running from command line:
# python replay_gain.py /path/to/filename.mp3
if __name__ == "__main__":
    print calculate_replay_gain(sys.argv[1])