#!/usr/bin/env PYTHONHASHSEED=1234 python3

# Copyright 2014-2019 Brett Slatkin, Pearson Education Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Reproduce book environment
import random
random.seed(1234)

import logging
from pprint import pprint
from sys import stdout as STDOUT

# Write all output to a temporary directory
import atexit
import gc
import io
import os
import tempfile

TEST_DIR = tempfile.TemporaryDirectory()
atexit.register(TEST_DIR.cleanup)

# Make sure Windows processes exit cleanly
OLD_CWD = os.getcwd()
atexit.register(lambda: os.chdir(OLD_CWD))
os.chdir(TEST_DIR.name)

def close_open_files():
    everything = gc.get_objects()
    for obj in everything:
        if isinstance(obj, io.IOBase):
            obj.close()

atexit.register(close_open_files)


# Example 1
# my_module.py
def determine_weight(volume, density):
    if density <= 0:
        raise ValueError('Density must be positive')

try:
    determine_weight(1, 0)
except ValueError:
    pass
else:
    assert False


# Example 2
# my_module.py
class Error(Exception):
    """Base-class for all exceptions raised by this module."""

class InvalidDensityError(Error):
    """There was a problem with a provided density value."""

class InvalidVolumeError(Error):
    """There was a problem with the provided weight value."""

def determine_weight(volume, density):
    if density < 0:
        raise InvalidDensityError('Density must be positive')
    if volume < 0:
        raise InvalidVolumeError('Volume must be positive')
    if volume == 0:
        density / volume


# Example 3
class my_module:
    Error = Error
    InvalidDensityError = InvalidDensityError

    @staticmethod
    def determine_weight(volume, density):
        if density < 0:
            raise InvalidDensityError('Density must be positive')
        if volume < 0:
            raise InvalidVolumeError('Volume must be positive')
        if volume == 0:
            density / volume

try:
    weight = my_module.determine_weight(1, -1)
except my_module.Error:
    logging.exception('Unexpected error')
else:
    assert False


# Example 4
SENTINEL = object()
weight = SENTINEL
try:
    weight = my_module.determine_weight(-1, 1)
except my_module.InvalidDensityError:
    weight = 0
except my_module.Error:
    logging.exception('Bug in the calling code')
else:
    assert False

assert weight is SENTINEL


# Example 5
try:
    weight = SENTINEL
    try:
        weight = my_module.determine_weight(0, 1)
    except my_module.InvalidDensityError:
        weight = 0
    except my_module.Error:
        logging.exception('Bug in the calling code')
    except Exception:
        logging.exception('Bug in the API code!')
        raise  # Re-raise exception to the caller
    else:
        assert False
    
    assert weight == 0
except:
    logging.exception('Expected')
else:
    assert False


# Example 6
# my_module.py

class NegativeDensityError(InvalidDensityError):
    """A provided density value was negative."""


def determine_weight(volume, density):
    if density < 0:
        raise NegativeDensityError('Density must be positive')


# Example 7
try:
    my_module.NegativeDensityError = NegativeDensityError
    my_module.determine_weight = determine_weight
    try:
        weight = my_module.determine_weight(1, -1)
    except my_module.NegativeDensityError:
        raise ValueError('Must supply non-negative density')
    except my_module.InvalidDensityError:
        weight = 0
    except my_module.Error:
        logging.exception('Bug in the calling code')
    except Exception:
        logging.exception('Bug in the API code!')
        raise
    else:
        assert False
except:
    logging.exception('Expected')
else:
    assert False


# Example 8
# my_module.py
class Error(Exception):
    """Base-class for all exceptions raised by this module."""

class WeightError(Error):
    """Base-class for weight calculation errors."""

class VolumeError(Error):
    """Base-class for volume calculation errors."""

class DensityError(Error):
    """Base-class for density calculation errors."""