#!/usr/bin/python -u
"""Create sparse files for testing with various patterns."""
import datetime
import pathlib
import os
import string
import sys

PAGE_SIZE = 4096
PAGE_HEADER = "<<<Start Of Page>>>\n"
PAGE_FOOTER = "\n<<<End Of Page>>>\n"

line = string.ascii_letters + string.digits + "\n"
data_len = PAGE_SIZE - len(PAGE_HEADER + PAGE_FOOTER)
(n_lines, n_chars) = divmod(data_len, len(line))
page_data = PAGE_HEADER + (line * n_lines) + line[:n_chars] + PAGE_FOOTER
PAGE_DATA = page_data.encode()

FILE_BASE = pathlib.Path(sys.argv[1])
FILE_SIZE = int(sys.argv[2])
FILE_SIZE_BYTES = FILE_SIZE * 1024 * 1024
FILE_N_PAGES = FILE_SIZE_BYTES // PAGE_SIZE


def allocate_testfile(name: str, n_pages: int, hole: bool) -> None:
    """Allocate a single test file."""
    file = FILE_BASE / f"{FILE_SIZE}M-{name}"
    if file.exists():
        return
    print(f"Allocating file: {file.stem} ...", end="")
    start = datetime.datetime.now()
    with open(file, 'wb') as f:
        f.truncate(FILE_SIZE_BYTES)
        for chunk in range(FILE_N_PAGES // n_pages):
            if hole:
                f.seek(PAGE_SIZE * n_pages, os.SEEK_CUR)
            else:
                f.write(PAGE_DATA * n_pages)
            hole = not hole
        os.fsync(f)
    tdelta = datetime.datetime.now() - start
    time = float(f"{tdelta.seconds}.{tdelta.microseconds}")
    print(f" [Done: {round(time, 2):.2f}s]")


allocate_testfile("data", FILE_N_PAGES, False)
allocate_testfile("hole", FILE_N_PAGES, True)
for chunk in [int(c) for c in sys.argv[3].split(",")]:
    allocate_testfile(f"mixed-{chunk}d", chunk, False)
    allocate_testfile(f"mixed-{chunk}h", chunk, True)