#!/usr/bin/python
#                 /usr/local/bin/beats_per_minute
# http://crystalfaeries.net/posix/bin/beats_per_minute
# 2013-08-10 02:02:29+00:00 from: http://jorgenmodin.net/index_html/archive/2010/08/18/a-python-script-to-count-bpm-beats-per-minute-on-linux
DOC = ''' This program detects bpm for mp3 files. It relies on lame and soundstretch being
installed on your system. 


Usage: 

    %s <filename>
    
-or pipe filenames to it.

Example:

    find . -name "*.mp3"| %s\n''' % (__file__, __file__)

import os
import pipes
import select
import shutil
import subprocess
import sys
import tempfile
 
## Define the window for sane bpm values. This may depend on genre of music. ##
BPM_WINDOW_MAX = 240
# Do not change this one
BPM_WINDOW_MIN = BPM_WINDOW_MAX/2
###############################################################################

def _get_bpm_from_soundstretch(output):
    """Gets bpm value from soundstretch output"""
    
    output = output.split("\n")
    for line in output:
        if 'Detected BPM rate ' in line:
            bpm = line[18:]
            return float(bpm)
    return None # Could not parse output

def fit_bpm_in_window(bpm_suggestion):
    """Double or halve a bpm suggestion until it fits inside the bpm window"""
    
    if bpm_suggestion is not None:
        while bpm_suggestion < (BPM_WINDOW_MIN):
            bpm_suggestion = bpm_suggestion * 2
        while bpm_suggestion > (BPM_WINDOW_MAX):
            bpm_suggestion = bpm_suggestion / 2
    return bpm_suggestion
    
def analyze_mp3(mp3filespec):
    """Uses lame and soundstretch to analyze an mp3 file for its bpm rate"""
    
    # Make a temporary working directory for storing the wav file
    # that soundstretch should analyze
    workingdir = tempfile.mkdtemp()
    wavfilespec = workingdir + "/tempwavfile.wav"
    
    # Use lame to make a wav representation of the mp3 file to be analyzed
    wav_command = 'lame --decode %s %s' % (mp3filespec, wavfilespec)
    subprocess.call([wav_command], shell=True, stderr=open(os.devnull, 'w'))
    
    # Call soundstretch to analyze the wav file
    bpm_command = 'soundstretch %s -bpm' % wavfilespec
    p = subprocess.Popen([bpm_command], shell=True,stdout=subprocess.PIPE)
    output = p.communicate()[0]
    
    # Delete temporary working directory and its contents
    shutil.rmtree(workingdir)

    bpm_suggestion =  _get_bpm_from_soundstretch(output)

    return fit_bpm_in_window(bpm_suggestion)

def process_input(mp3filespec):
    bpm_suggestion = analyze_mp3(pipes.quote(mp3filespec))
    if bpm_suggestion is None:
        print "Unable to detect bpm for file %s" % mp3filespec
    else:
        print "BPM rate for %s is estimated to be %s" % (mp3filespec, bpm_suggestion)
    
if __name__ == "__main__":
    argv = sys.argv[1:]
    if select.select([sys.stdin], [], [], 0) == ([sys.stdin], [], []): # input is piped to program
        mp3filespecs = sys.stdin.readlines()
        for mp3filespec in mp3filespecs:
            process_input(mp3filespec.rstrip('\n'))
    elif len(argv) < 1: # No pipe and no input file, print help text and exit
        print DOC
        sys.exit()
    else: # Input file present
        mp3filespec = os.path.abspath(argv[0])
        process_input(mp3filespec)