"""
Test helper functions and base classes.
"""
import inspect
import json
import unittest
import functools
import operator
import pprint
import requests
import os
import urlparse
from contextlib import contextmanager
from datetime import datetime
from path import path
from bok_choy.javascript import js_defined
from bok_choy.web_app_test import WebAppTest
from bok_choy.promise import EmptyPromise, Promise
from opaque_keys.edx.locator import CourseLocator
from pymongo import MongoClient, ASCENDING
from openedx.core.lib.tests.assertions.events import assert_event_matches, is_matching_event, EventMatchTolerates
from xmodule.partitions.partitions import UserPartition
from xmodule.partitions.tests.test_partitions import MockUserPartitionScheme
from selenium.webdriver.support.select import Select
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from unittest import TestCase


from ..pages.common import BASE_URL


MAX_EVENTS_IN_FAILURE_OUTPUT = 20


def skip_if_browser(browser):
    """
    Method decorator that skips a test if browser is `browser`

    Args:
        browser (str): name of internet browser

    Returns:
        Decorated function

    """
    def decorator(test_function):
        @functools.wraps(test_function)
        def wrapper(self, *args, **kwargs):
            if self.browser.name == browser:
                raise unittest.SkipTest('Skipping as this test will not work with {}'.format(browser))
            test_function(self, *args, **kwargs)
        return wrapper
    return decorator


def is_youtube_available():
    """
    Check if the required youtube urls are available.

    If a URL in `youtube_api_urls` is not reachable then subsequent URLs will not be checked.

    Returns:
        bool:

    """

    youtube_api_urls = {
        'main': 'https://www.youtube.com/',
        'player': 'https://www.youtube.com/iframe_api',
        # For transcripts, you need to check an actual video, so we will
        # just specify our default video and see if that one is available.
        'transcript': 'http://video.google.com/timedtext?lang=en&v=3_yD_cEKoCk',
    }

    for url in youtube_api_urls.itervalues():
        try:
            response = requests.get(url, allow_redirects=False)
        except requests.exceptions.ConnectionError:
            return False

        if response.status_code >= 300:
            return False

    return True


def load_data_str(rel_path):
    """
    Load a file from the "data" directory as a string.
    `rel_path` is the path relative to the data directory.
    """
    full_path = path(__file__).abspath().dirname() / "data" / rel_path  # pylint: disable=no-value-for-parameter
    with open(full_path) as data_file:
        return data_file.read()


def remove_file(filename):
    """
    Remove a file if it exists
    """
    if os.path.exists(filename):
        os.remove(filename)


def disable_animations(page):
    """
    Disable jQuery and CSS3 animations.
    """
    disable_jquery_animations(page)
    disable_css_animations(page)


def enable_animations(page):
    """
    Enable jQuery and CSS3 animations.
    """
    enable_jquery_animations(page)
    enable_css_animations(page)


@js_defined('window.jQuery')
def disable_jquery_animations(page):
    """
    Disable jQuery animations.
    """
    page.browser.execute_script("jQuery.fx.off = true;")


@js_defined('window.jQuery')
def enable_jquery_animations(page):
    """
    Enable jQuery animations.
    """
    page.browser.execute_script("jQuery.fx.off = false;")


def disable_css_animations(page):
    """
    Disable CSS3 animations, transitions, transforms.
    """
    page.browser.execute_script("""
        var id = 'no-transitions';

        // if styles were already added, just do nothing.
        if (document.getElementById(id)) {
            return;
        }

        var css = [
                '* {',
                    '-webkit-transition: none !important;',
                    '-moz-transition: none !important;',
                    '-o-transition: none !important;',
                    '-ms-transition: none !important;',
                    'transition: none !important;',
                    '-webkit-transition-property: none !important;',
                    '-moz-transition-property: none !important;',
                    '-o-transition-property: none !important;',
                    '-ms-transition-property: none !important;',
                    'transition-property: none !important;',
                    '-webkit-transform: none !important;',
                    '-moz-transform: none !important;',
                    '-o-transform: none !important;',
                    '-ms-transform: none !important;',
                    'transform: none !important;',
                    '-webkit-animation: none !important;',
                    '-moz-animation: none !important;',
                    '-o-animation: none !important;',
                    '-ms-animation: none !important;',
                    'animation: none !important;',
                '}'
            ].join(''),
            head = document.head || document.getElementsByTagName('head')[0],
            styles = document.createElement('style');

        styles.id = id;
        styles.type = 'text/css';
        if (styles.styleSheet){
          styles.styleSheet.cssText = css;
        } else {
          styles.appendChild(document.createTextNode(css));
        }

        head.appendChild(styles);
    """)


def enable_css_animations(page):
    """
    Enable CSS3 animations, transitions, transforms.
    """
    page.browser.execute_script("""
        var styles = document.getElementById('no-transitions'),
            head = document.head || document.getElementsByTagName('head')[0];

        head.removeChild(styles)
    """)


def select_option_by_text(select_browser_query, option_text):
    """
    Chooses an option within a select by text (helper method for Select's select_by_visible_text method).
    """
    select = Select(select_browser_query.first.results[0])
    select.select_by_visible_text(option_text)


def get_selected_option_text(select_browser_query):
    """
    Returns the text value for the first selected option within a select.
    """
    select = Select(select_browser_query.first.results[0])
    return select.first_selected_option.text


def get_options(select_browser_query):
    """
    Returns all the options for the given select.
    """
    return Select(select_browser_query.first.results[0]).options


def generate_course_key(org, number, run):
    """
    Makes a CourseLocator from org, number and run
    """
    default_store = os.environ.get('DEFAULT_STORE', 'draft')
    return CourseLocator(org, number, run, deprecated=(default_store == 'draft'))


def select_option_by_value(browser_query, value):
    """
    Selects a html select element by matching value attribute
    """
    select = Select(browser_query.first.results[0])
    select.select_by_value(value)

    def options_selected():
        """
        Returns True if all options in select element where value attribute
        matches `value`. if any option is not selected then returns False
        and select it. if value is not an option choice then it returns False.
        """
        all_options_selected = True
        has_option = False
        for opt in select.options:
            if opt.get_attribute('value') == value:
                has_option = True
                if not opt.is_selected():
                    all_options_selected = False
                    opt.click()
        # if value is not an option choice then it should return false
        if all_options_selected and not has_option:
            all_options_selected = False
        return all_options_selected

    # Make sure specified option is actually selected
    EmptyPromise(options_selected, "Option is selected").fulfill()


def is_option_value_selected(browser_query, value):
    """
    return true if given value is selected in html select element, else return false.
    """
    select = Select(browser_query.first.results[0])
    ddl_selected_value = select.first_selected_option.get_attribute('value')
    return ddl_selected_value == value


def element_has_text(page, css_selector, text):
    """
    Return true if the given text is present in the list.
    """
    text_present = False
    text_list = page.q(css=css_selector).text

    if len(text_list) > 0 and (text in text_list):
        text_present = True

    return text_present


def get_modal_alert(browser):
    """
    Returns instance of modal alert box shown in browser after waiting
    for 6 seconds
    """
    WebDriverWait(browser, 6).until(EC.alert_is_present())
    return browser.switch_to.alert


class EventsTestMixin(TestCase):
    """
    Helpers and setup for running tests that evaluate events emitted
    """
    def setUp(self):
        super(EventsTestMixin, self).setUp()
        self.event_collection = MongoClient()["test"]["events"]
        self.reset_event_tracking()

    def reset_event_tracking(self):
        """Drop any events that have been collected thus far and start collecting again from scratch."""
        self.event_collection.drop()
        self.start_time = datetime.now()

    @contextmanager
    def capture_events(self, event_filter=None, number_of_matches=1, captured_events=None):
        """
        Context manager that captures all events emitted while executing a particular block.

        All captured events are stored in the list referenced by `captured_events`. Note that this list is appended to
        *in place*. The events will be appended to the list in the order they are emitted.

        The `event_filter` is expected to be a callable that allows you to filter the event stream and select particular
        events of interest. A dictionary `event_filter` is also supported, which simply indicates that the event should
        match that provided expectation.

        `number_of_matches` tells this context manager when enough events have been found and it can move on. The
        context manager will not exit until this many events have passed the filter. If not enough events are found
        before a timeout expires, then this will raise a `BrokenPromise` error. Note that this simply states that
        *at least* this many events have been emitted, so `number_of_matches` is simply a lower bound for the size of
        `captured_events`.
        """
        start_time = datetime.utcnow()

        yield

        events = self.wait_for_events(
            start_time=start_time, event_filter=event_filter, number_of_matches=number_of_matches)

        if captured_events is not None and hasattr(captured_events, 'append') and callable(captured_events.append):
            for event in events:
                captured_events.append(event)

    @contextmanager
    def assert_events_match_during(self, event_filter=None, expected_events=None):
        """
        Context manager that ensures that events matching the `event_filter` and `expected_events` are emitted.

        This context manager will filter out the event stream using the `event_filter` and wait for
        `len(expected_events)` to match the filter.

        It will then compare the events in order with their counterpart in `expected_events` to ensure they match the
        more detailed assertion.

        Typically `event_filter` will be an `event_type` filter and the `expected_events` list will contain more
        detailed assertions.
        """
        captured_events = []
        with self.capture_events(event_filter, len(expected_events), captured_events):
            yield

        self.assert_events_match(expected_events, captured_events)

    def wait_for_events(self, start_time=None, event_filter=None, number_of_matches=1, timeout=None):
        """
        Wait for `number_of_matches` events to pass the `event_filter`.

        By default, this will look at all events that have been emitted since the beginning of the setup of this mixin.
        A custom `start_time` can be specified which will limit the events searched to only those emitted after that
        time.

        The `event_filter` is expected to be a callable that allows you to filter the event stream and select particular
        events of interest. A dictionary `event_filter` is also supported, which simply indicates that the event should
        match that provided expectation.

        `number_of_matches` lets us know when enough events have been found and it can move on. The function will not
        return until this many events have passed the filter. If not enough events are found before a timeout expires,
        then this will raise a `BrokenPromise` error. Note that this simply states that *at least* this many events have
        been emitted, so `number_of_matches` is simply a lower bound for the size of `captured_events`.

        Specifying a custom `timeout` can allow you to extend the default 30 second timeout if necessary.
        """
        if start_time is None:
            start_time = self.start_time

        if timeout is None:
            timeout = 30

        def check_for_matching_events():
            """Gather any events that have been emitted since `start_time`"""
            return self.matching_events_were_emitted(
                start_time=start_time,
                event_filter=event_filter,
                number_of_matches=number_of_matches
            )

        return Promise(
            check_for_matching_events,
            # This is a bit of a hack, Promise calls str(description), so I set the description to an object with a
            # custom __str__ and have it do some intelligent stuff to generate a helpful error message.
            CollectedEventsDescription(
                'Waiting for {number_of_matches} events to match the filter:\n{event_filter}'.format(
                    number_of_matches=number_of_matches,
                    event_filter=self.event_filter_to_descriptive_string(event_filter),
                ),
                functools.partial(self.get_matching_events_from_time, start_time=start_time, event_filter={})
            ),
            timeout=timeout
        ).fulfill()

    def matching_events_were_emitted(self, start_time=None, event_filter=None, number_of_matches=1):
        """Return True if enough events have been emitted that pass the `event_filter` since `start_time`."""
        matching_events = self.get_matching_events_from_time(start_time=start_time, event_filter=event_filter)
        return len(matching_events) >= number_of_matches, matching_events

    def get_matching_events_from_time(self, start_time=None, event_filter=None):
        """
        Return a list of events that pass the `event_filter` and were emitted after `start_time`.

        This function is used internally by most of the other assertions and convenience methods in this class.

        The `event_filter` is expected to be a callable that allows you to filter the event stream and select particular
        events of interest. A dictionary `event_filter` is also supported, which simply indicates that the event should
        match that provided expectation.
        """
        if start_time is None:
            start_time = self.start_time

        if isinstance(event_filter, dict):
            event_filter = functools.partial(is_matching_event, event_filter)
        elif not callable(event_filter):
            raise ValueError(
                'event_filter must either be a dict or a callable function with as single "event" parameter that '
                'returns a boolean value.'
            )

        matching_events = []
        cursor = self.event_collection.find(
            {
                "time": {
                    "$gte": start_time
                }
            }
        ).sort("time", ASCENDING)
        for event in cursor:
            matches = False
            try:
                # Mongo automatically assigns an _id to all events inserted into it. We strip it out here, since
                # we don't care about it.
                del event['_id']
                if event_filter is not None:
                    # Typically we will be grabbing all events of a particular type, however, you can use arbitrary
                    # logic to identify the events that are of interest.
                    matches = event_filter(event)
            except AssertionError:
                # allow the filters to use "assert" to filter out events
                continue
            else:
                if matches is None or matches:
                    matching_events.append(event)
        return matching_events

    def assert_matching_events_were_emitted(self, start_time=None, event_filter=None, number_of_matches=1):
        """Assert that at least `number_of_matches` events have passed the filter since `start_time`."""
        description = CollectedEventsDescription(
            'Not enough events match the filter:\n' + self.event_filter_to_descriptive_string(event_filter),
            functools.partial(self.get_matching_events_from_time, start_time=start_time, event_filter={})
        )

        self.assertTrue(
            self.matching_events_were_emitted(
                start_time=start_time, event_filter=event_filter, number_of_matches=number_of_matches
            ),
            description
        )

    def assert_no_matching_events_were_emitted(self, event_filter, start_time=None):
        """Assert that no events have passed the filter since `start_time`."""
        matching_events = self.get_matching_events_from_time(start_time=start_time, event_filter=event_filter)

        description = CollectedEventsDescription(
            'Events unexpected matched the filter:\n' + self.event_filter_to_descriptive_string(event_filter),
            lambda: matching_events
        )

        self.assertEquals(len(matching_events), 0, description)

    def assert_events_match(self, expected_events, actual_events):
        """
        Assert that each item in the expected events sequence matches its counterpart at the same index in the actual
        events sequence.
        """
        for expected_event, actual_event in zip(expected_events, actual_events):
            assert_event_matches(
                expected_event,
                actual_event,
                tolerate=EventMatchTolerates.lenient()
            )

    def relative_path_to_absolute_uri(self, relative_path):
        """Return an aboslute URI given a relative path taking into account the test context."""
        return urlparse.urljoin(BASE_URL, relative_path)

    def event_filter_to_descriptive_string(self, event_filter):
        """Find the source code of the callable or pretty-print the dictionary"""
        message = ''
        if callable(event_filter):
            file_name = '(unknown)'
            try:
                file_name = inspect.getsourcefile(event_filter)
            except TypeError:
                pass

            try:
                list_of_source_lines, line_no = inspect.getsourcelines(event_filter)
            except IOError:
                pass
            else:
                message = '{file_name}:{line_no}\n{hr}\n{event_filter}\n{hr}'.format(
                    event_filter=''.join(list_of_source_lines).rstrip(),
                    file_name=file_name,
                    line_no=line_no,
                    hr='-' * 20,
                )

        if not message:
            message = '{hr}\n{event_filter}\n{hr}'.format(
                event_filter=pprint.pformat(event_filter),
                hr='-' * 20,
            )

        return message


class CollectedEventsDescription(object):
    """
    Produce a clear error message when tests fail.

    This class calls the provided `get_events_func` when converted to a string, and pretty prints the returned events.
    """

    def __init__(self, description, get_events_func):
        self.description = description
        self.get_events_func = get_events_func

    def __str__(self):
        message_lines = [
            self.description,
            'Events:'
        ]
        events = self.get_events_func()
        events.sort(key=operator.itemgetter('time'), reverse=True)
        for event in events[:MAX_EVENTS_IN_FAILURE_OUTPUT]:
            message_lines.append(pprint.pformat(event))
        if len(events) > MAX_EVENTS_IN_FAILURE_OUTPUT:
            message_lines.append(
                'Too many events to display, the remaining events were omitted. Run locally to diagnose.')

        return '\n\n'.join(message_lines)


class UniqueCourseTest(WebAppTest):
    """
    Test that provides a unique course ID.
    """

    def __init__(self, *args, **kwargs):
        """
        Create a unique course ID.
        """
        super(UniqueCourseTest, self).__init__(*args, **kwargs)

    def setUp(self):
        super(UniqueCourseTest, self).setUp()

        self.course_info = {
            'org': 'test_org',
            'number': self.unique_id,
            'run': 'test_run',
            'display_name': 'Test Course' + self.unique_id
        }

    @property
    def course_id(self):
        """
        Returns the serialized course_key for the test
        """
        # TODO - is there a better way to make this agnostic to the underlying default module store?
        default_store = os.environ.get('DEFAULT_STORE', 'draft')
        course_key = CourseLocator(
            self.course_info['org'],
            self.course_info['number'],
            self.course_info['run'],
            deprecated=(default_store == 'draft')
        )
        return unicode(course_key)


class YouTubeConfigError(Exception):
    """
    Error occurred while configuring YouTube Stub Server.
    """
    pass


class YouTubeStubConfig(object):
    """
    Configure YouTube Stub Server.
    """

    PORT = 9080
    URL = 'http://127.0.0.1:{}/'.format(PORT)

    @classmethod
    def configure(cls, config):
        """
        Allow callers to configure the stub server using the /set_config URL.

        Arguments:
            config (dict): Configuration dictionary.

        Raises:
            YouTubeConfigError

        """
        youtube_stub_config_url = cls.URL + 'set_config'

        config_data = {param: json.dumps(value) for param, value in config.items()}
        response = requests.put(youtube_stub_config_url, data=config_data)

        if not response.ok:
            raise YouTubeConfigError(
                'YouTube Server Configuration Failed. URL {0}, Configuration Data: {1}, Status was {2}'.format(
                    youtube_stub_config_url, config, response.status_code))

    @classmethod
    def reset(cls):
        """
        Reset YouTube Stub Server Configurations using the /del_config URL.

        Raises:
            YouTubeConfigError

        """
        youtube_stub_config_url = cls.URL + 'del_config'

        response = requests.delete(youtube_stub_config_url)

        if not response.ok:
            raise YouTubeConfigError(
                'YouTube Server Configuration Failed. URL: {0} Status was {1}'.format(
                    youtube_stub_config_url, response.status_code))

    @classmethod
    def get_configuration(cls):
        """
        Allow callers to get current stub server configuration.

        Returns:
            dict

        """
        youtube_stub_config_url = cls.URL + 'get_config'

        response = requests.get(youtube_stub_config_url)

        if response.ok:
            return json.loads(response.content)
        else:
            return {}


def create_user_partition_json(partition_id, name, description, groups, scheme="random"):
    """
    Helper method to create user partition JSON. If scheme is not supplied, "random" is used.
    """
    return UserPartition(
        partition_id, name, description, groups, MockUserPartitionScheme(scheme)
    ).to_json()


class TestWithSearchIndexMixin(object):
    """ Mixin encapsulating search index creation """
    TEST_INDEX_FILENAME = "test_root/index_file.dat"

    def _create_search_index(self):
        """ Creates search index backing file """
        with open(self.TEST_INDEX_FILENAME, "w+") as index_file:
            json.dump({}, index_file)

    def _cleanup_index_file(self):
        """ Removes search index backing file """
        remove_file(self.TEST_INDEX_FILENAME)
