'''
common.py - this file is part of S3QL.

Copyright © 2008 Nikolaus Rath <Nikolaus@rath.org>

This work can be distributed under the terms of the GNU GPLv3.


This module contains common functions used by multiple unit tests.
'''

from contextlib import contextmanager
from functools import wraps
import re
import time
import os
import subprocess
import stat
import random
import configparser
import logging
import pytest
import functools

def get_clock_granularity():
    resolution = float('inf')
    for i in range(50):
        stamp1 = time.time()
        stamp2 = stamp1
        while stamp1 == stamp2:
            stamp2 = time.time()
        resolution = min(resolution, stamp2 - stamp1)
        time.sleep(0.01)
    return resolution
CLOCK_GRANULARITY = get_clock_granularity()

# When testing, we want to make sure that we don't sleep for too short a time
# (cause it may cause spurious test failures), and that the sleep interval
# covers at least one timer update. We have to monkeypatch because we especially
# want functions like s3ql.backends.common.retry to use the "safe" sleep
# version.
@functools.wraps(time.sleep)
def safe_sleep(secs, _sleep_real=time.sleep):
    '''Like time.sleep(), but sleep for at least *secs*

    `time.sleep` may sleep less than the given period if a signal is
    received. This function ensures that we sleep for at least the
    desired time.
    '''

    now = time.time()
    end = now + secs
    while now < end:
        _sleep_real(max(end - now, CLOCK_GRANULARITY))
        now = time.time()

@pytest.fixture(autouse=True, scope='session')
def install_safe_sleep():
    time.sleep = safe_sleep

class CountMessagesHandler(logging.Handler):
    def __init__(self, level=logging.NOTSET):
        super().__init__(level)
        self.count = 0

    def emit(self, record):
        self.count += 1

@contextmanager
def assert_logs(pattern, level=logging.WARNING, count=None):
    '''Assert that suite emits specified log message

    *pattern* is matched against the *unformatted* log message, i.e. before any
    arguments are merged.

    If *count* is not None, raise an exception unless exactly *count* matching
    messages are caught.

    Matched log records will also be flagged so that the caplog fixture
    does not generate exceptions for them (no matter their severity).
    '''

    def filter(record):
        if (record.levelno == level and
            re.search(pattern, record.msg)):
            record.caplog_ignore = True
            return True
        return False

    handler = CountMessagesHandler()
    handler.setLevel(level)
    handler.addFilter(filter)
    logger = logging.getLogger()
    logger.addHandler(handler)
    try:
        yield

    finally:
        logger.removeHandler(handler)

        if count is not None and handler.count != count:
            raise AssertionError('Expected to catch %d %r messages, but got only %d'
                                 % (count, pattern, handler.count))

def retry(timeout, fn, *a, **kw):
    """Wait for fn(*a, **kw) to return True.

    If the return value of fn() returns something True, this value
    is returned. Otherwise, the function is called repeatedly for
    `timeout` seconds. If the timeout is reached, `RetryTimeoutError` is
    raised.
    """

    step = 0.2
    waited = 0
    while waited < timeout:
        ret = fn(*a, **kw)
        if ret:
            return ret
        time.sleep(step)
        waited += step
        if step < waited / 30:
            step *= 2

    raise RetryTimeoutError()

class RetryTimeoutError(Exception):
    '''Raised by `retry()` when a timeout is reached.'''

    pass

def skip_if_no_fusermount():
    '''Raise SkipTest if fusermount is not available'''

    with subprocess.Popen(['which', 'fusermount'], stdout=subprocess.PIPE,
                          universal_newlines=True) as which:
        fusermount_path = which.communicate()[0].strip()

    if not fusermount_path or which.returncode != 0:
        pytest.skip("Can't find fusermount executable")

    if not os.path.exists('/dev/fuse'):
        pytest.skip("FUSE kernel module does not seem to be loaded")

    if os.getuid() == 0:
        return

    mode = os.stat(fusermount_path).st_mode
    if mode & stat.S_ISUID == 0:
        pytest.skip('fusermount executable not setuid, and we are not root.')

    try:
        fd = os.open('/dev/fuse', os.O_RDWR)
    except OSError as exc:
        pytest.skip('Unable to open /dev/fuse: %s' % exc.strerror)
    else:
        os.close(fd)

def skip_without_rsync():
    try:
        with open('/dev/null', 'wb') as null:
            subprocess.call(['rsync', '--version'], stdout=null,
                            stderr=subprocess.STDOUT,)
    except FileNotFoundError:
        pytest.skip('rsync not installed')

def populate_dir(path, entries=1000, size=20*1024*1024,
                 pooldir='/usr/bin', seed=None):
    '''Populate directory with random data

    *entries* specifies the total number of directory entries that are created
    in the tree. *size* specifies the size occupied by all files together. The
    files in *pooldir* are used as a source of directory names and file
    contents.

    *seed* is used to initalize the random number generator and can be used to
    make the created structure reproducible (provided that the contents of
    *pooldir* don't change).
    '''

    poolnames = os.listdir(pooldir)
    if seed is None:
        # We want tests to be reproducible on a given system, so users
        # can report meaningful bugs
        seed = len(poolnames)
    random.seed(seed)

    # Entries in percentages
    subdir_cnt = random.randint(5, 10)
    file_cnt = random.randint(60, 70)
    fifo_cnt = random.randint(5, 10)
    symlink_cnt = random.randint(10, 20)
    hardlink_cnt = random.randint(5, 15)

    # Normalize to desired entry count
    scale = entries / sum((subdir_cnt, file_cnt, fifo_cnt, symlink_cnt, hardlink_cnt))
    subdir_cnt = int(scale * subdir_cnt)
    file_cnt = int(scale * file_cnt)
    fifo_cnt = int(scale * fifo_cnt)
    symlink_cnt = int(scale * symlink_cnt)
    hardlink_cnt = int(scale * hardlink_cnt)

    # Sizes, make sure there is at least one big file
    file_sizes = [ random.randint(0, 100) for _ in range(file_cnt-1) ]
    scale = 0.5 * size / sum(file_sizes)
    file_sizes = [ int(scale * x) for x in file_sizes ]
    file_sizes.append(int(0.5 * size))

    # Special characters for use in filenames
    special_chars = [ chr(x) for x in range(128)
                      if x not in (0, ord('/')) ]

    def random_name(path):
        '''Get random, non-existing file name underneath *path*

        Returns a fully qualified path with a filename chosen from *poolnames*.
        '''
        while True:
            name = poolnames[random.randrange(len(poolnames))]

            # Special characters
            len_ = random.randrange(4)
            if len_ > 0:
                pos = random.choice((-1,0,1)) # Prefix, Middle, Suffix
                s = ''.join(special_chars[random.randrange(len(special_chars))]
                            for _ in range(len_))
                if pos == -1:
                    name = s + name
                elif pos == 1:
                    name += s
                else:
                    name += s + poolnames[random.randrange(len(poolnames))]

            fullname = os.path.join(path, name)
            if not os.path.lexists(fullname):
                break
        return fullname


    #
    # Step 1: create directory tree
    #
    dirs = [ path ]
    for _ in range(subdir_cnt):
        idx = random.randrange(len(dirs))
        name = random_name(dirs[idx])
        os.mkdir(name)
        dirs.append(name)


    #
    # Step 2: populate the tree with files
    #
    files = []
    for size in file_sizes:
        idx = random.randrange(len(dirs))
        name = random_name(dirs[idx])
        with open(name, 'wb') as dst:
            while size > 0:
                idx = random.randrange(len(poolnames))
                srcname = os.path.join(pooldir, poolnames[idx])
                if not os.path.isfile(srcname):
                    continue
                with open(srcname, 'rb') as src:
                    buf = src.read(size)
                    dst.write(buf)
                size -= len(buf)
        files.append(name)

    #
    # Step 3: Special files
    #
    for _ in range(fifo_cnt):
        name = random_name(dirs[random.randrange(len(dirs))])
        os.mkfifo(name)
        files.append(name)

    #
    # Step 4: populate tree with symlinks
    #
    for _ in range(symlink_cnt):
        relative = random.choice((True, False))
        existing = random.choice((True, False))
        idx = random.randrange(len(dirs))
        dir_ = dirs[idx]
        name = random_name(dir_)

        if existing:
            directory = random.choice((True, False))
            if directory:
                target = dirs[random.randrange(len(dirs))]
            else:
                target = files[random.randrange(len(files))]
        else:
            target = random_name(dirs[random.randrange(len(dirs))])

        if relative:
            target = os.path.relpath(target, dir_)
        else:
            target = os.path.abspath(target)

        os.symlink(target, name)

    #
    # Step 5: Create some hardlinks
    #
    for _ in range(hardlink_cnt):
        samedir = random.choice((True, False))

        target = files[random.randrange(len(files))]
        if samedir:
            dir_ = os.path.dirname(target)
        else:
            dir_ = dirs[random.randrange(len(dirs))]
        name = random_name(dir_)
        os.link(target, name)
        files.append(name)


class NoTestSection(Exception):
    '''
    Raised by get_remote_test_info if no matching test
    section was found.
    '''

    def __init__(self, reason):
        self.reason = reason

def get_remote_test_info(name):
        authfile = os.path.expanduser('~/.s3ql/authinfo2')
        if not os.path.exists(authfile):
            raise NoTestSection('No authentication file found.')

        mode = os.stat(authfile).st_mode
        if mode & (stat.S_IRGRP | stat.S_IROTH):
            raise NoTestSection("Authentication file has insecure permissions")

        config = configparser.ConfigParser()
        config.read(authfile)

        try:
            fs_name = config.get(name, 'test-fs')
            backend_login = config.get(name, 'backend-login')
            backend_password = config.get(name, 'backend-password')
        except (configparser.NoOptionError, configparser.NoSectionError):
            raise NoTestSection("Authentication file does not have %s section" % name)

        # Append prefix to make sure that we're starting with an empty bucket
        if fs_name[-1] != '/':
            fs_name += '/'
        fs_name += 's3ql_test_%d/' % time.time()

        return (backend_login, backend_password, fs_name)
