#!/usr/bin/env python

"""
Author   : flo
date     : 2017.10.17
Purpose  : pull random sample data from a large dataset.
         : 
Comments : you might need to know the size of your csv file first.
         : if its a csv text file, you can do this in linux, `cat data.csv | wc -l`
         : if your file is not of text base and not one line per record, then idk, man.
         :
example  : python randDataSet.py maxDataSize sampleSize fullPathToDataInput fullPathToSampleOutput
example  : python randDataSet.py 1000000 1000 /home/username/data.csv /var/tmp/output.txt
"""

import random as rand
import sys
import os

def chkSanity(tmp):

    ssize, msize, fin, fout = 0,0,"",""

    if len(tmp) == 4:
        # Max data size
        if tmp[0].isdigit():
            msize = int(tmp[0])
            if msize <= 0:
                print "Value can not be less than or equal to zero."
                sys.exit()            
        else:
            print "Value entered was not numeric."
            sys.exit()

        # Sample data size 
        if tmp[1].isdigit():
            ssize = int(tmp[1])
            if ssize <= 0:
                print "Value can not be less than or equal to zero."
                sys.exit()

            if ssize >= msize:
                print "Value can not be equal or larger than the number of Max Data size."
                sys.exit()
        else:
            print "Value entered was not numeric."
            sys.exit()

        #  file Input
        if os.path.exists(os.path.dirname(tmp[2])):
            fin = tmp[2]
        else:
            print "File system path does not exists."
            sys.exit()

        # file Output
        if os.path.exists(os.path.dirname(tmp[3])):
            fout = tmp[3]
        else:
            print "File system path does not exists."
            sys.exit()


        randdataset(msize,ssize,fin,fout)

    else:
        print "Not enough Parameters."
        sys.exit()
   

def randdataset(m,s,fi,fo):

    rand.seed(rand.weibullvariate(1, rand.randint(1,m)))

    f_i = open(fi, "r+")
    f_o = open(fo, "w+")
    w,y =[],[]
    
    for i in f_i:
        w.append(i)

    x = rand.sample(w, s)

    for i in x:
        y.append(i)
        f_o.write(i)

    f_i.close()
    f_o.close()


def main():
    s = sys.argv[1:]
    chkSanity(s)
   
# main
if __name__ == "__main__":
    main()