"""
This module creates a sysadmin dashboard for managing and viewing
courses.
"""


import json
import logging
import os
from six import StringIO
import subprocess

import mongoengine
import unicodecsv as csv
from django.conf import settings
from django.contrib.auth.decorators import login_required
from django.contrib.auth.models import User
from django.core.paginator import EmptyPage, PageNotAnInteger, Paginator
from django.db import IntegrityError
from django.http import Http404, HttpResponse
from django.utils.decorators import method_decorator
from django.utils.html import escape
from django.utils.translation import ugettext as _
from django.views.decorators.cache import cache_control
from django.views.decorators.csrf import ensure_csrf_cookie
from django.views.decorators.http import condition
from django.views.generic.base import TemplateView
from opaque_keys.edx.keys import CourseKey
from path import Path as path
from six import text_type

import dashboard.git_import as git_import
import track.views
from lms.djangoapps.courseware.courses import get_course_by_id
from dashboard.git_import import GitImportError
from dashboard.models import CourseImportLog
from edxmako.shortcuts import render_to_response
from openedx.core.djangolib.markup import HTML
from student.models import CourseEnrollment, Registration, UserProfile
from student.roles import CourseInstructorRole, CourseStaffRole
from xmodule.modulestore.django import modulestore

log = logging.getLogger(__name__)


class SysadminDashboardView(TemplateView):
    """Base class for sysadmin dashboard views with common methods"""

    template_name = 'sysadmin_dashboard.html'

    def __init__(self, **kwargs):
        """
        Initialize base sysadmin dashboard class with modulestore,
        modulestore_type and return msg
        """

        self.def_ms = modulestore()
        self.msg = u''
        self.datatable = []
        super(SysadminDashboardView, self).__init__(**kwargs)

    @method_decorator(ensure_csrf_cookie)
    @method_decorator(login_required)
    @method_decorator(cache_control(no_cache=True, no_store=True,
                                    must_revalidate=True))
    @method_decorator(condition(etag_func=None))
    def dispatch(self, *args, **kwargs):
        return super(SysadminDashboardView, self).dispatch(*args, **kwargs)

    def get_courses(self):
        """ Get an iterable list of courses."""

        return self.def_ms.get_courses()

    def return_csv(self, filename, header, data):
        """
        Convenient function for handling the http response of a csv.
        data should be iterable and is used to stream object over http
        """

        csv_file = StringIO()
        writer = csv.writer(csv_file, dialect='excel', quotechar='"',
                            quoting=csv.QUOTE_ALL)

        writer.writerow(header)

        # Setup streaming of the data
        def read_and_flush():
            """Read and clear buffer for optimization"""
            csv_file.seek(0)
            csv_data = csv_file.read()
            csv_file.seek(0)
            csv_file.truncate()
            return csv_data

        def csv_data():
            """Generator for handling potentially large CSVs"""
            for row in data:
                writer.writerow(row)
            csv_data = read_and_flush()
            yield csv_data
        response = HttpResponse(csv_data(), content_type='text/csv')
        response['Content-Disposition'] = u'attachment; filename={0}'.format(
            filename)
        return response


class Users(SysadminDashboardView):
    """
    The status view provides Web based user management, a listing of
    courses loaded, and user statistics
    """

    def create_user(self, uname, name, password=None):
        """ Creates a user """

        if not uname:
            return _('Must provide username')
        if not name:
            return _('Must provide full name')

        msg = u''
        if not password:
            return _('Password must be supplied')

        email = uname

        if '@' not in email:
            msg += _('email address required (not username)')
            return msg
        new_password = password

        user = User(username=uname, email=email, is_active=True)
        user.set_password(new_password)
        try:
            user.save()
        except IntegrityError:
            msg += _(u'Oops, failed to create user {user}, {error}').format(
                user=user,
                error="IntegrityError"
            )
            return msg

        reg = Registration()
        reg.register(user)

        profile = UserProfile(user=user)
        profile.name = name
        profile.save()

        msg += _(u'User {user} created successfully!').format(user=user)
        return msg

    def delete_user(self, uname):
        """Deletes a user from django auth"""

        if not uname:
            return _('Must provide username')
        if '@' in uname:
            try:
                user = User.objects.get(email=uname)
            except User.DoesNotExist as err:
                msg = _(u'Cannot find user with email address {email_addr}').format(email_addr=uname)
                return msg
        else:
            try:
                user = User.objects.get(username=uname)
            except User.DoesNotExist as err:
                msg = _(u'Cannot find user with username {username} - {error}').format(
                    username=uname,
                    error=str(err)
                )
                return msg
        user.delete()
        return _(u'Deleted user {username}').format(username=uname)

    def make_datatable(self):
        """
        Build the datatable for this view
        """
        datatable = {
            'header': [
                _('Statistic'),
                _('Value'),
            ],
            'title': _('Site statistics'),
            'data': [
                [
                    _('Total number of users'),
                    User.objects.all().count(),
                ],
            ],
        }
        return datatable

    def get(self, request):
        if not request.user.is_staff:
            raise Http404
        context = {
            'datatable': self.make_datatable(),
            'msg': self.msg,
            'djangopid': os.getpid(),
            'modeflag': {'users': 'active-section'},
        }
        return render_to_response(self.template_name, context)

    def post(self, request):
        """Handle various actions available on page"""

        if not request.user.is_staff:
            raise Http404
        action = request.POST.get('action', '')
        track.views.server_track(request, action, {}, page='user_sysdashboard')

        if action == 'download_users':
            header = [_('username'), _('email'), ]
            data = ([u.username, u.email] for u in
                    (User.objects.all().iterator()))
            return self.return_csv('users_{0}.csv'.format(
                request.META['SERVER_NAME']), header, data)
        elif action == 'create_user':
            uname = request.POST.get('student_uname', '').strip()
            name = request.POST.get('student_fullname', '').strip()
            password = request.POST.get('student_password', '').strip()
            self.msg = HTML(u'<h4>{0}</h4><p>{1}</p><hr />{2}').format(
                _('Create User Results'),
                self.create_user(uname, name, password), self.msg)
        elif action == 'del_user':
            uname = request.POST.get('student_uname', '').strip()
            self.msg = HTML(u'<h4>{0}</h4><p>{1}</p><hr />{2}').format(
                _('Delete User Results'), self.delete_user(uname), self.msg)
        context = {
            'datatable': self.make_datatable(),
            'msg': self.msg,
            'djangopid': os.getpid(),
            'modeflag': {'users': 'active-section'},
        }
        return render_to_response(self.template_name, context)


class Courses(SysadminDashboardView):
    """
    This manages adding/updating courses from git, deleting courses, and
    provides course listing information.
    """

    def git_info_for_course(self, cdir):
        """This pulls out some git info like the last commit"""

        cmd = ''
        gdir = settings.DATA_DIR / cdir
        info = ['', '', '']

        # Try the data dir, then try to find it in the git import dir
        if not gdir.exists():
            git_repo_dir = getattr(settings, 'GIT_REPO_DIR', git_import.DEFAULT_GIT_REPO_DIR)
            gdir = path(git_repo_dir) / cdir
            if not gdir.exists():
                return info

        cmd = ['git', 'log', '-1',
               u'--format=format:{ "commit": "%H", "author": "%an %ae", "date": "%ad"}', ]
        try:
            output_json = json.loads(subprocess.check_output(cmd, cwd=gdir).decode('utf-8'))
            info = [output_json['commit'],
                    output_json['date'],
                    output_json['author'], ]
        except OSError as error:
            log.warning(text_type(u"Error fetching git data: %s - %s"), text_type(cdir), text_type(error))
        except (ValueError, subprocess.CalledProcessError):
            pass

        return info

    def get_course_from_git(self, gitloc, branch):
        """This downloads and runs the checks for importing a course in git"""

        if not (gitloc.endswith('.git') or gitloc.startswith('http:') or
                gitloc.startswith('https:') or gitloc.startswith('git:')):
            return _("The git repo location should end with '.git', "
                     "and be a valid url")

        return self.import_mongo_course(gitloc, branch)

    def import_mongo_course(self, gitloc, branch):
        """
        Imports course using management command and captures logging output
        at debug level for display in template
        """

        msg = u''

        log.debug(u'Adding course using git repo %s', gitloc)

        # Grab logging output for debugging imports
        output = StringIO()
        import_log_handler = logging.StreamHandler(output)
        import_log_handler.setLevel(logging.DEBUG)

        logger_names = ['xmodule.modulestore.xml_importer',
                        'dashboard.git_import',
                        'xmodule.modulestore.xml',
                        'xmodule.seq_module', ]
        loggers = []

        for logger_name in logger_names:
            logger = logging.getLogger(logger_name)
            logger.setLevel(logging.DEBUG)
            logger.addHandler(import_log_handler)
            loggers.append(logger)

        error_msg = ''
        try:
            git_import.add_repo(gitloc, None, branch)
        except GitImportError as ex:
            error_msg = str(ex)
        ret = output.getvalue()

        # Remove handler hijacks
        for logger in loggers:
            logger.setLevel(logging.NOTSET)
            logger.removeHandler(import_log_handler)

        if error_msg:
            msg_header = error_msg
            color = 'red'
        else:
            msg_header = _('Added Course')
            color = 'blue'

        msg = HTML(u"<h4 style='color:{0}'>{1}</h4>").format(color, msg_header)
        msg += HTML(u"<pre>{0}</pre>").format(escape(ret))
        return msg

    def make_datatable(self, courses=None):
        """Creates course information datatable"""

        data = []
        courses = courses or self.get_courses()
        for course in courses:
            gdir = course.id.course
            data.append([course.display_name, text_type(course.id)]
                        + self.git_info_for_course(gdir))

        return dict(header=[_('Course Name'),
                            _('Directory/ID'),
                            # Translators: "Git Commit" is a computer command; see http://gitref.org/basic/#commit
                            _('Git Commit'),
                            _('Last Change'),
                            _('Last Editor')],
                    title=_('Information about all courses'),
                    data=data)

    def get(self, request):
        """Displays forms and course information"""

        if not request.user.is_staff:
            raise Http404

        context = {
            'datatable': self.make_datatable(),
            'msg': self.msg,
            'djangopid': os.getpid(),
            'modeflag': {'courses': 'active-section'},
        }
        return render_to_response(self.template_name, context)

    def post(self, request):
        """Handle all actions from courses view"""

        if not request.user.is_staff:
            raise Http404

        action = request.POST.get('action', '')
        track.views.server_track(request, action, {},
                                 page='courses_sysdashboard')

        courses = {course.id: course for course in self.get_courses()}
        if action == 'add_course':
            gitloc = request.POST.get('repo_location', '').strip().replace(' ', '').replace(';', '')
            branch = request.POST.get('repo_branch', '').strip().replace(' ', '').replace(';', '')
            self.msg += self.get_course_from_git(gitloc, branch)

        elif action == 'del_course':
            course_id = request.POST.get('course_id', '').strip()
            course_key = CourseKey.from_string(course_id)
            course_found = False
            if course_key in courses:
                course_found = True
                course = courses[course_key]
            else:
                try:
                    course = get_course_by_id(course_key)
                    course_found = True
                except Exception as err:   # pylint: disable=broad-except
                    self.msg += _(
                        HTML(u'Error - cannot get course with ID {0}<br/><pre>{1}</pre>')
                    ).format(
                        course_key,
                        escape(str(err))
                    )

            if course_found:
                # delete course that is stored with mongodb backend
                self.def_ms.delete_course(course.id, request.user.id)
                # don't delete user permission groups, though
                self.msg += \
                    HTML(u"<font color='red'>{0} {1} = {2} ({3})</font>").format(
                        _('Deleted'), text_type(course.location), text_type(course.id), course.display_name)

        context = {
            'datatable': self.make_datatable(list(courses.values())),
            'msg': self.msg,
            'djangopid': os.getpid(),
            'modeflag': {'courses': 'active-section'},
        }
        return render_to_response(self.template_name, context)


class Staffing(SysadminDashboardView):
    """
    The status view provides a view of staffing and enrollment in
    courses that include an option to download the data as a csv.
    """

    def get(self, request):
        """Displays course Enrollment and staffing course statistics"""

        if not request.user.is_staff:
            raise Http404
        data = []

        for course in self.get_courses():
            datum = [course.display_name, course.id]
            datum += [CourseEnrollment.objects.filter(
                course_id=course.id).count()]
            datum += [CourseStaffRole(course.id).users_with_role().count()]
            datum += [','.join([x.username for x in CourseInstructorRole(
                course.id).users_with_role()])]
            data.append(datum)

        datatable = dict(header=[_('Course Name'), _('course_id'),
                                 _('# enrolled'), _('# staff'),
                                 _('instructors')],
                         title=_('Enrollment information for all courses'),
                         data=data)
        context = {
            'datatable': datatable,
            'msg': self.msg,
            'djangopid': os.getpid(),
            'modeflag': {'staffing': 'active-section'},
        }
        return render_to_response(self.template_name, context)

    def post(self, request):
        """Handle all actions from staffing and enrollment view"""

        action = request.POST.get('action', '')
        track.views.server_track(request, action, {},
                                 page='staffing_sysdashboard')

        if action == 'get_staff_csv':
            data = []
            roles = [CourseInstructorRole, CourseStaffRole, ]

            for course in self.get_courses():
                for role in roles:
                    for user in role(course.id).users_with_role():
                        datum = [course.id, role, user.username, user.email,
                                 user.profile.name.encode('utf-8')]
                        data.append(datum)
            header = [_('course_id'),
                      _('role'), _('username'),
                      _('email'), _('full_name'), ]
            return self.return_csv('staff_{0}.csv'.format(
                request.META['SERVER_NAME']), header, data)

        return self.get(request)


class GitLogs(TemplateView):
    """
    This provides a view into the import of courses from git repositories.
    It is convenient for allowing course teams to see what may be wrong with
    their xml
    """

    template_name = 'sysadmin_dashboard_gitlogs.html'

    @method_decorator(login_required)
    def get(self, request, *args, **kwargs):
        """Shows logs of imports that happened as a result of a git import"""

        course_id = kwargs.get('course_id')
        if course_id:
            course_id = CourseKey.from_string(course_id)

        page_size = 10

        # Set mongodb defaults even if it isn't defined in settings
        mongo_db = {
            'host': 'localhost',
            'user': '',
            'password': '',
            'db': 'xlog',
        }

        # Allow overrides
        if hasattr(settings, 'MONGODB_LOG'):
            for config_item in ['host', 'user', 'password', 'db', ]:
                mongo_db[config_item] = settings.MONGODB_LOG.get(
                    config_item, mongo_db[config_item])

        mongouri = 'mongodb://{user}:{password}@{host}/{db}'.format(**mongo_db)

        error_msg = ''

        try:
            if mongo_db['user'] and mongo_db['password']:
                mdb = mongoengine.connect(mongo_db['db'], host=mongouri)
            else:
                mdb = mongoengine.connect(mongo_db['db'], host=mongo_db['host'])
        except mongoengine.connection.ConnectionError:
            log.exception('Unable to connect to mongodb to save log, '
                          'please check MONGODB_LOG settings.')

        if course_id is None:
            # Require staff if not going to specific course
            if not request.user.is_staff:
                raise Http404
            cilset = CourseImportLog.objects.order_by('-created')
        else:
            # Allow only course team, instructors, and staff
            if not (request.user.is_staff or
                    CourseInstructorRole(course_id).has_user(request.user) or
                    CourseStaffRole(course_id).has_user(request.user)):
                raise Http404
            log.debug('course_id=%s', course_id)
            cilset = CourseImportLog.objects.filter(
                course_id=course_id
            ).order_by('-created')
            log.debug(u'cilset length=%s', len(cilset))

        # Paginate the query set
        paginator = Paginator(cilset, page_size)
        try:
            logs = paginator.page(request.GET.get('page'))
        except PageNotAnInteger:
            logs = paginator.page(1)
        except EmptyPage:
            # If the page is too high or low
            given_page = int(request.GET.get('page'))
            page = min(max(1, given_page), paginator.num_pages)
            logs = paginator.page(page)

        mdb.close()
        context = {
            'logs': logs,
            'course_id': text_type(course_id) if course_id else None,
            'error_msg': error_msg,
            'page_size': page_size
        }

        return render_to_response(self.template_name, context)