import os

from settings import repoconfig, repohelp


def reverse_readline(filename, buf_size=8192):
    # https://stackoverflow.com/a/23646049
    """a generator that returns the lines of a file in reverse order"""
    with open(filename) as fh:
        segment = None
        offset = 0
        fh.seek(0, os.SEEK_END)
        file_size = remaining_size = fh.tell()
        while remaining_size > 0:
            offset = min(file_size, offset + buf_size)
            fh.seek(file_size - offset)
            buffer = fh.read(min(remaining_size, buf_size))
            remaining_size -= buf_size
            lines = buffer.split('\n')
            # the first line of the buffer is probably not a complete line so
            # we'll save it and append it to the last line of the next buffer
            # we read
            if segment is not None:
                # if the previous chunk starts right from the beginning of line
                # do not concact the segment to the last line of new chunk
                # instead, yield the segment first 
                if buffer[-1] != '\n':
                    lines[-1] += segment
                else:
                    yield segment
            segment = lines[0]
            for index in range(len(lines) - 1, 0, -1):
                if len(lines[index]):
                    yield lines[index]
        # Don't yield None if the file was empty
        if segment is not None:
            yield segment


def sizeof_fmt(num, suffix='B'):
    # https://stackoverflow.com/a/1094933
    for unit in ['', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi']:
        if abs(num) < 1024.0:
            return "%3.2f%s%s" % (num, unit, suffix)
        num /= 1024.0
    return "%.2f%s%s" % (num, 'Yi', suffix)


def isint(val):
    try: 
        int(val)
        return True
    except ValueError:
        return False


def mirror_config():
    return {r: {**repoconfig[r], 'details': repohelp.get(r, '')} for r in sorted(repoconfig.keys())}
