#!/usr/bin/env python

def main ():
    """The main function."""

    import argparse
    import math
    import os
    import os.path
    import random
    import shutil
    import stat
    import sys
    import tempfile

    parser = argparse.ArgumentParser(description = """This script
randomly picks a chosen numer of files from a set of folders and
copies those files to a single destination folder. The files to be
considered can be filtered by suffix.""")

    parser.add_argument("DIR",
        help = "The directory to recursively consider",
        nargs = "+")

    parser.add_argument("-N",
        help = "Choose N files randomly",
        type = int,
        default = 10)

    parser.add_argument("--destination",
        metavar = "DIR",
        help = "Copy files to DIR")

    parser.add_argument("--delete-existing",
        help = """Delete existing files in the destionation folder
instead of moving those files to a new location.""",
        action = "store_true",
        default = False)

    parser.add_argument("--suffix",
        help = """Only consider files with this SUFFIX. The leading
'.' has to be included, i.e. jpeg files could be added as '.jpg'. By
default, all files are be considered. The suffix is case insensitive.""",
        action = "append",
        nargs = "+")

    parser.add_argument("--verbose",
        help = "Print a lot of stuff",
        action = "store_true",
        default = False)

    options = parser.parse_args()

    # Seed the random number generator.
    random.seed()

    if options.suffix != None:
        temp = []
        for i in options.suffix:
            temp.extend(i)
        options.suffix = temp

        for i in range(len(options.suffix)):
            options.suffix[i] = options.suffix[i].lower()

    photos = []
    for path in options.DIR:
        for root, dirs, files in os.walk(path):
            for i in files:
                if options.suffix != None:
                     ( basename, extension ) = os.path.splitext(i)
                     if not extension.lower() in options.suffix:
                        continue
                photos.append(os.path.join(root, i))

    if len(photos) == 0:
        print("could not find any files to select from")
        sys.exit(0)

    selectedPhotos = []
    if len(photos) >= options.N:
        N = options.N
    else:
        N = len(photos)

    for i in range(N):
        selectedPhotos.append(photos.pop(int(math.floor(random.random()*len(photos)))))

    if options.destination != None:
        try:
            os.mkdir(options.destination)
        except OSError as e:
            print("destination path already exists: %s" % (e))

            if options.delete_existing:
                print("deleting existing files")
                for root, dirs, files in os.walk(options.destination):
                    for i in files:
                        os.remove(os.path.join(root, i))
            else:
                backupfolder = tempfile.mkdtemp()
                print("moving old files to %s" % (backupfolder))
                for root, dirs, files in os.walk(options.destination):
                    for i in files:
                        shutil.move(os.path.join(root, i), backupfolder)

        # Set very permissible permissions on destination directory.
        os.chmod(options.destination,
                stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR |
                stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP |
                stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH)

    for i in selectedPhotos:
        if options.destination != None:
            if options.verbose:
                print("copying %s" % (i))
            shutil.copy(i, options.destination)
        else:
            print("skipping %s, no destination given" % (i))

if __name__ == "__main__":
    main()