# Two questions video.sh cannot ask of a picture that moves.
#
# Grid scrolls a pixel a frame, so nothing can be asked about a particular pixel: whether
# pixel 4 is a grid line depends on which frame this is. Both questions below are true of the
# picture whatever the fine scroll offset happens to be.
#
#   grid   - is this a grid of one repeated tile? Periodic every eight pixels across, and
#            not all one colour.
#   bands  - does the attribute nibble recolour each cell row? The colours found in one band
#            of eight rows differ from those in the next, whatever the ground is doing.
import sys

data = open(sys.argv[1], "rb").read()
fields = data.split(b"\n", 3)
width = int(fields[1].split()[0])
body = fields[3]


def pixel(x, y):
    at = (y * width + x) * 3
    return tuple(body[at:at + 3])


if sys.argv[2] == "grid":
    # ---- The WHOLE scanline, not the first few cells ----
    #
    # This looked at 32 pixels, which is four cells at the left edge, and so could not see a
    # program that had filled part of the map and scrolled off the end of what it filled. The
    # gap was on the right and nothing was looking there. A gap anywhere breaks periodicity at
    # its two edges, so the full width finds it wherever it is.
    row = [pixel(x, 4) for x in range(width)]
    bad = [x for x in range(width - 8) if row[x] != row[x + 8]]
    varied = len(set(row)) > 1
    print("yes" if not bad and varied else
          "breaks at column %d" % bad[0] if bad else "all one colour")
else:
    # A band is eight rows, which is one cell row wherever the boundary has slid to. The
    # ground is the same under every scheme, so what tells them apart is the line colour -
    # and looking at the whole band finds it without knowing where in the band it is.
    first = set(pixel(0, y) for y in range(8))
    second = set(pixel(0, y) for y in range(8, 16))
    print("yes" if first != second else "the same in both: %s" % sorted(first))