#!/usr/bin/env python

import random   # Random number generator
import os       # Crossplatform OS rutines
import sys      # interpreter tools


legal_chars = "abcdefghijklmnopqrstuvwxyz"+\
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"+"0123456789_"


def random_string(length=6, prefix="", legal_chars=legal_chars):
    """
Create a random string of text.

Parameters
----------
length : int
    Length of the string (minus the prefix part).
prefix : string
    Prefix the string with some text.
legal_chars : string
    A string of charracter that are allowed to be used in the
    output.

Returns
-------
rnd_str : str
    A string of random charracters.
    """
    # Insert user code here



def generate_tree(target, dirs=3, rec_depth=2, verbose=False):
    """
Genereate a random folder structure with random names.

Parameters
----------
target : str
    Path to the root where folders are to be created.
dirs : int
    Maximum number of directories to be created per directory.
rec_depth : int
    Maximum directory depth.
verbose : bool
    Be loud about what to do.
    """
    # Insert user code here



def populate_tree(target, files=5, size=800, start_time=1388534400,
        end_time=1406851201000, verbose=False):
    """
Generate random files with random content.

Parameters
----------
target : str
    Path to the file tree where the files are being created.
files : int
    Maximum number of directories to be created.
size : int
    Maximum size in kilobyte for each file.
start_time : int
    Lower bound for access time (atime) and modified time (mtime)
    allowed in each file.
    Denoted in Unix time format.
end_time : int
    Same as start_time, but for upper bound.
verbose : bool
    Be loud about what to do.
    """

    def walk_function(arg, dirname, fnames):
        """
Function used in os.path.walk

Following the logic of Python scoping, this is a local function,
only visible inside of populate_tree.
This function should be passed to os.path.walk.

Parameters
----------
arg : obj
    Arbitrary argument specified at initialization.
dirname : str
    Name of a directory in file tree (changes with each call.
fnames : list
    List of filenames in file tree.
        """
        # Fill in code for walk function

    os.path.walk(target, walk_function, None)




# If-test to ensure code only executed if ran as stand-alone app.
if __name__ == "__main__":

    l = len(sys.argv)

    if l < 4:
        print "Not enough arguments included."
        print "usage: %s target dirs files " % sys.argv[0] +\
            "[size rec_depth start end seed verbose]"
        sys.exit(0)

    target = sys.argv[1]
    dirs = int(sys.argv[2])
    files = int(sys.argv[3])

    # And-or trick to use argv only if argv is long enough.
    size = l<5 and 1000 or int(sys.argv[4])
    rec_depth = l<6 and 2 or int(sys.argv[5])
    start = l<7 and 1388534400 or int(sys.argv[6])
    end = l<8 and 1406851200 or int(sys.argv[7])
    seed = [l<9 and "0" or sys.argv[8]][0]
    verbose = [l<10 and "0" or sys.argv[9]][0]

    # Fix the random seed (if not None):
    random.seed(int(seed) or None)

    generate_tree(target, dirs, rec_depth, verbose)
    populate_tree(target, files, size, start, end, verbose)