#!/bin/sh
"""": # -*-python-*-
bup_python="$(dirname "$0")/../cmd/bup-python" || exit $?
exec "$bup_python" "$0" ${1+"$@"}
"""

from __future__ import absolute_import, print_function
from random import randint
from sys import stderr, stdout
import sys

from bup.io import byte_stream

def smaller_region(max_offset):
    start = randint(0, max_offset)
    return (start, min(max_offset, randint(start + 1, start + 5)))


def possibly_larger_region(max_offset, min_sparse_len):
    start = randint(0, max_offset)
    return (start, min(max_offset, randint(start + 1,
                                           start + 3 * min_sparse_len)))


def initial_region(max_offset, min_sparse_len):
    start = 0
    return (start, min(max_offset, randint(start + 1,
                                           start + 3 * min_sparse_len)))


def final_region(max_offset, min_sparse_len):
    start = max(0, randint(max_offset - 3 * min_sparse_len,
                           max_offset - 1))
    return (start, max_offset)


def region_around_min_len(max_offset, min_sparse_len):
    start = randint(0, max_offset)
    return (start, min(max_offset, randint(start + min_sparse_len - 5,
                                           start + min_sparse_len + 5)))


generators = []

def random_region():
    global generators
    return generators[randint(0, len(generators) - 1)]()

if len(sys.argv) == 0:
    stdout.flush()
    out = byte_stream(stdout)
if len(sys.argv) == 2:
    out = open(sys.argv[1], 'wb')
else:
    print('Usage: sparse-test-data [FILE]', file=stderr)
    sys.exit(2)

bup_read_size = 2 ** 16
bup_min_sparse_len = 512
out_size = randint(0, bup_read_size * 10)

generators = (lambda : smaller_region(out_size),
              lambda : possibly_larger_region(out_size, bup_min_sparse_len),
              lambda : initial_region(out_size, bup_min_sparse_len),
              lambda : final_region(out_size, bup_min_sparse_len),
              lambda : region_around_min_len(out_size, bup_min_sparse_len))

sparse = []
sparse.append(random_region())
sparse.append(random_region())

# Handle overlaps
if sparse[1][0] < sparse[0][0]:
    sparse[0], sparse[1] = sparse[1], sparse[0]

sparse_offsets = []
sparse_offsets.append(sparse[0][0])
if sparse[1][0] <= sparse[0][1]:
    sparse_offsets.append(max(sparse[0][1], sparse[1][1]))
else:
    sparse_offsets.extend((sparse[0][1], sparse[1][0], sparse[1][1]))

if sparse[1][1] != out_size:
    sparse_offsets.append(out_size)

# Now sparse_offsets indicates where to start/stop zero runs
data = b'x'
pos = 0
print('offsets:', sparse_offsets, file=stderr)
for offset in sparse_offsets:
    count = offset - pos
    print('write:', 'x' if data == 'x' else '0', count, file=stderr)
    out.write(data * (offset - pos))
    pos += count
    data = b'\0' if data == b'x' else b'x'

out.close()