"""
Test to analyze file.seek positional errors.
Feel free to play with different file formats, just pass it as a file object to the functions.
"""


# Pass in file object from external file
def seekread(file, size, back):
    f = open(file, 'rb')
    # Read entire file
    f.read(size)
    posread = f.tell()
    # Seek backwards
    seek_back = back
    f.seek(-seek_back, 1)
    pos2 = f.tell()
    f.close()
    # Print results
    print '\n--Result of read--\n'
    print 'File position:\t\t\t%4d' % posread
    print 'Amount to seek back:\t\t%4d' % -back
    print 'New position:\t\t\t%4d' % pos2
    # Calculate and print
    if pos2 == posread - seek_back:
        print 'Correct position!\n\n'
    else:
        print 'Wrong position\n\n'


def seekreadline(file, size, back):
    # Now for processing readline()
    f = open(file, 'rb')
    f.readline(size)
    posline = f.tell()
    seek_back = back
    f.seek(-seek_back, 1)
    pos2 = f.tell()
    f.close()
    print '--- Result of readline() ---\n'
    print 'File position:\t\t\t%4d' % posline
    print 'Amount to seek back:\t\t%4d' % -seek_back
    print 'New position in file:\t\t%4d' % pos2
    if pos2 == posline - seek_back:
        print 'Correct position\n\n'
    else:
        print 'Wrong position\n\n'


def seekboth(file, size, back):
    # Now for processing readline()
    f = open(file, 'rb')
    f.read(size)
    posread = f.tell()
    f.readline()
    posline = f.tell()
    seek_back = back
    f.seek(-seek_back, 1)
    pos2 = f.tell()
    # Print result
    print '--- Result of both() ---\n'
    print 'File position from read():\t\t%4d' % posread
    print 'File position from readline():\t\t%4d' % posline
    print 'Amount to seek back:\t\t\t%4d' % -seek_back
    print 'New position in file:\t\t\t%4d' % pos2
    # Calculate
    if pos2 == posline - seek_back:
        print 'Correct position\n\n'
    else:
        print 'Wrong position\n\n'


def seekboth_reversed(file, size, back):
    # Now for processing readline()
    f = open(file, 'rb')
    f.readline()
    posline = f.tell()
    f.read(size)
    posread = f.tell()
    seek_back = back
    f.seek(-seek_back, 1)
    pos2 = f.tell()
    f.close()
    print '--- Result of both_reversed() ---\n'
    print 'File position from readline():\t\t%4d' % posline
    print 'File position from read():\t\t%4d' % posread
    print 'Amount to seek back:\t\t\t%4d' % -seek_back
    print 'New position in file:\t\t\t%4d' % pos2
    if pos2 == posread - seek_back:
        print 'Correct position\n\n'
    else:
        print 'Wrong position\n\n'


# generate file
file = open("test.log", "wb")
file.write("." * 100 + "\n" + "." * 4100 + "\n" + "." * 100)
file.close()

# Run tests
seekread('test.log', 1024, 200)  # pass
seekreadline('test.log', 1024, 100)  # Fail
seekboth('test.log', 1024, 100)  # Pass
seekboth_reversed('test.log', 1024, 100)