# -*- coding: utf-8 -*-
# Part of Odoo. See LICENSE file for full copyright and licensing details.
import ast
import itertools
import logging
from datetime import date, timedelta

from dateutil.relativedelta import relativedelta, MO
from markupsafe import Markup

from odoo import _, api, exceptions, fields, models
from odoo.http import SESSION_LIFETIME
from odoo.tools import ustr

_logger = logging.getLogger(__name__)

# display top 3 in ranking, could be db variable
MAX_VISIBILITY_RANKING = 3

def start_end_date_for_period(period, default_start_date=False, default_end_date=False):
    """Return the start and end date for a goal period based on today

    :param str default_start_date: string date in DEFAULT_SERVER_DATE_FORMAT format
    :param str default_end_date: string date in DEFAULT_SERVER_DATE_FORMAT format

    :return: (start_date, end_date), dates in string format, False if the period is
    not defined or unknown"""
    today = date.today()
    if period == 'daily':
        start_date = today
        end_date = start_date
    elif period == 'weekly':
        start_date = today + relativedelta(weekday=MO(-1))
        end_date = start_date + timedelta(days=7)
    elif period == 'monthly':
        start_date = today.replace(day=1)
        end_date = today + relativedelta(months=1, day=1, days=-1)
    elif period == 'yearly':
        start_date = today.replace(month=1, day=1)
        end_date = today.replace(month=12, day=31)
    else:  # period == 'once':
        start_date = default_start_date  # for manual goal, start each time
        end_date = default_end_date

        return (start_date, end_date)

    return fields.Datetime.to_string(start_date), fields.Datetime.to_string(end_date)

class Challenge(models.Model):
    """Gamification challenge

    Set of predifined objectives assigned to people with rules for recurrence and
    rewards

    If 'user_ids' is defined and 'period' is different than 'one', the set will
    be assigned to the users for each period (eg: every 1st of each month if
    'monthly' is selected)
    """

    _name = 'gamification.challenge'
    _description = 'Gamification Challenge'
    _inherit = 'mail.thread'
    _order = 'end_date, start_date, name, id'

    @api.model
    def default_get(self, fields_list):
        res = super().default_get(fields_list)
        if 'user_domain' in fields_list and 'user_domain' not in res:
            user_group_id = self.env.ref('base.group_user')
            res['user_domain'] = f'["&", ("groups_id", "=", "{user_group_id.name}"), ("active", "=", True)]'
        return res

    # description
    name = fields.Char("Challenge Name", required=True, translate=True)
    description = fields.Text("Description", translate=True)
    state = fields.Selection([
            ('draft', "Draft"),
            ('inprogress', "In Progress"),
            ('done', "Done"),
        ], default='draft', copy=False,
        string="State", required=True, tracking=True)
    manager_id = fields.Many2one(
        'res.users', default=lambda self: self.env.uid,
        string="Responsible")
    # members
    user_ids = fields.Many2many('res.users', 'gamification_challenge_users_rel', string="Participants")
    user_domain = fields.Char("User domain")        # Alternative to a list of users
    user_count = fields.Integer('# Users', compute='_compute_user_count')
    # periodicity
    period = fields.Selection([
            ('once', "Non recurring"),
            ('daily', "Daily"),
            ('weekly', "Weekly"),
            ('monthly', "Monthly"),
            ('yearly', "Yearly")
        ], default='once',
        string="Periodicity",
        help="Period of automatic goal assignment. If none is selected, should be launched manually.",
        required=True)
    start_date = fields.Date("Start Date", help="The day a new challenge will be automatically started. If no periodicity is set, will use this date as the goal start date.")
    end_date = fields.Date("End Date", help="The day a new challenge will be automatically closed. If no periodicity is set, will use this date as the goal end date.")

    invited_user_ids = fields.Many2many('res.users', 'gamification_invited_user_ids_rel', string="Suggest to users")

    line_ids = fields.One2many('gamification.challenge.line', 'challenge_id',
                                  string="Lines",
                                  help="List of goals that will be set",
                                  required=True, copy=True)

    reward_id = fields.Many2one('gamification.badge', string="For Every Succeeding User")
    reward_first_id = fields.Many2one('gamification.badge', string="For 1st user")
    reward_second_id = fields.Many2one('gamification.badge', string="For 2nd user")
    reward_third_id = fields.Many2one('gamification.badge', string="For 3rd user")
    reward_failure = fields.Boolean("Reward Bests if not Succeeded?")
    reward_realtime = fields.Boolean("Reward as soon as every goal is reached", default=True, help="With this option enabled, a user can receive a badge only once. The top 3 badges are still rewarded only at the end of the challenge.")

    visibility_mode = fields.Selection([
            ('personal', "Individual Goals"),
            ('ranking', "Leader Board (Group Ranking)"),
        ], default='personal',
        string="Display Mode", required=True)

    report_message_frequency = fields.Selection([
            ('never', "Never"),
            ('onchange', "On change"),
            ('daily', "Daily"),
            ('weekly', "Weekly"),
            ('monthly', "Monthly"),
            ('yearly', "Yearly")
        ], default='never',
        string="Report Frequency", required=True)
    report_message_group_id = fields.Many2one('discuss.channel', string="Send a copy to", help="Group that will receive a copy of the report in addition to the user")
    report_template_id = fields.Many2one('mail.template', default=lambda self: self._get_report_template(), string="Report Template", required=True)
    remind_update_delay = fields.Integer("Non-updated manual goals will be reminded after", help="Never reminded if no value or zero is specified.")
    last_report_date = fields.Date("Last Report Date", default=fields.Date.today)
    next_report_date = fields.Date("Next Report Date", compute='_get_next_report_date', store=True)

    challenge_category = fields.Selection([
        ('hr', 'Human Resources / Engagement'),
        ('other', 'Settings / Gamification Tools'),
    ], string="Appears in", required=True, default='hr',
       help="Define the visibility of the challenge through menus")

    @api.depends('user_ids')
    def _compute_user_count(self):
        mapped_data = {}
        if self.ids:
            query = """
                SELECT gamification_challenge_id, count(res_users_id)
                  FROM gamification_challenge_users_rel rel
             LEFT JOIN res_users users
                    ON users.id=rel.res_users_id AND users.active = TRUE
                 WHERE gamification_challenge_id IN %s
              GROUP BY gamification_challenge_id
            """
            self.env.cr.execute(query, [tuple(self.ids)])
            mapped_data = dict(
                (challenge_id, user_count)
                for challenge_id, user_count in self.env.cr.fetchall()
            )
        for challenge in self:
            challenge.user_count = mapped_data.get(challenge.id, 0)

    REPORT_OFFSETS = {
        'daily': timedelta(days=1),
        'weekly': timedelta(days=7),
        'monthly': relativedelta(months=1),
        'yearly': relativedelta(years=1),
    }
    @api.depends('last_report_date', 'report_message_frequency')
    def _get_next_report_date(self):
        """ Return the next report date based on the last report date and
        report period.
        """
        for challenge in self:
            last = challenge.last_report_date
            offset = self.REPORT_OFFSETS.get(challenge.report_message_frequency)

            if offset:
                challenge.next_report_date = last + offset
            else:
                challenge.next_report_date = False

    def _get_report_template(self):
        template = self.env.ref('gamification.simple_report_template', raise_if_not_found=False)

        return template.id if template else False

    @api.model_create_multi
    def create(self, vals_list):
        """Overwrite the create method to add the user of groups"""
        for vals in vals_list:
            if vals.get('user_domain'):
                users = self._get_challenger_users(ustr(vals.get('user_domain')))

                if not vals.get('user_ids'):
                    vals['user_ids'] = []
                vals['user_ids'].extend((4, user.id) for user in users)

        return super().create(vals_list)

    def write(self, vals):
        if vals.get('user_domain'):
            users = self._get_challenger_users(ustr(vals.get('user_domain')))

            if not vals.get('user_ids'):
                vals['user_ids'] = []
            vals['user_ids'].extend((4, user.id) for user in users)

        write_res = super(Challenge, self).write(vals)

        if vals.get('report_message_frequency', 'never') != 'never':
            # _recompute_challenge_users do not set users for challenges with no reports, subscribing them now
            for challenge in self:
                challenge.message_subscribe([user.partner_id.id for user in challenge.user_ids])

        if vals.get('state') == 'inprogress':
            self._recompute_challenge_users()
            self._generate_goals_from_challenge()

        elif vals.get('state') == 'done':
            self._check_challenge_reward(force=True)

        elif vals.get('state') == 'draft':
            # resetting progress
            if self.env['gamification.goal'].search([('challenge_id', 'in', self.ids), ('state', '=', 'inprogress')], limit=1):
                raise exceptions.UserError(_("You can not reset a challenge with unfinished goals."))

        return write_res


    ##### Update #####

    @api.model # FIXME: check how cron functions are called to see if decorator necessary
    def _cron_update(self, ids=False, commit=True):
        """Daily cron check.

        - Start planned challenges (in draft and with start_date = today)
        - Create the missing goals (eg: modified the challenge to add lines)
        - Update every running challenge
        """
        # in cron mode, will do intermediate commits
        # cannot be replaced by a parameter because it is intended to impact side-effects of
        # write operations
        self = self.with_context(commit_gamification=commit)
        # start scheduled challenges
        planned_challenges = self.search([
            ('state', '=', 'draft'),
            ('start_date', '<=', fields.Date.today())
        ])
        if planned_challenges:
            planned_challenges.write({'state': 'inprogress'})

        # close scheduled challenges
        scheduled_challenges = self.search([
            ('state', '=', 'inprogress'),
            ('end_date', '<', fields.Date.today())
        ])
        if scheduled_challenges:
            scheduled_challenges.write({'state': 'done'})

        records = self.browse(ids) if ids else self.search([('state', '=', 'inprogress')])

        return records._update_all()

    def _update_all(self):
        """Update the challenges and related goals."""
        if not self:
            return True

        Goals = self.env['gamification.goal']

        # include yesterday goals to update the goals that just ended
        # exclude goals for users that have not interacted with the
        # webclient since the last update or whose session is no longer
        # valid.
        yesterday = fields.Date.to_string(date.today() - timedelta(days=1))
        self.env.cr.execute("""SELECT gg.id
                        FROM gamification_goal as gg
                        JOIN bus_presence as bp ON bp.user_id = gg.user_id
                       WHERE gg.write_date <= bp.last_presence
                         AND bp.last_presence >= now() AT TIME ZONE 'UTC' - interval '%(session_lifetime)s seconds'
                         AND gg.closed IS NOT TRUE
                         AND gg.challenge_id IN %(challenge_ids)s
                         AND (gg.state = 'inprogress'
                              OR (gg.state = 'reached' AND gg.end_date >= %(yesterday)s))
                      GROUP BY gg.id
        """, {
            'session_lifetime': SESSION_LIFETIME,
            'challenge_ids': tuple(self.ids),
            'yesterday': yesterday
        })

        Goals.browse(goal_id for [goal_id] in self.env.cr.fetchall()).update_goal()

        self._recompute_challenge_users()
        self._generate_goals_from_challenge()

        for challenge in self:
            if challenge.last_report_date != fields.Date.today():
                if challenge.next_report_date and fields.Date.today() >= challenge.next_report_date:
                    challenge.report_progress()
                else:
                    # goals closed but still opened at the last report date
                    closed_goals_to_report = Goals.search([
                        ('challenge_id', '=', challenge.id),
                        ('start_date', '>=', challenge.last_report_date),
                        ('end_date', '<=', challenge.last_report_date)
                    ])
                    if closed_goals_to_report:
                        # some goals need a final report
                        challenge.report_progress(subset_goals=closed_goals_to_report)

        self._check_challenge_reward()
        return True

    def _get_challenger_users(self, domain):
        user_domain = ast.literal_eval(domain)
        return self.env['res.users'].search(user_domain)

    def _recompute_challenge_users(self):
        """Recompute the domain to add new users and remove the one no longer matching the domain"""
        for challenge in self.filtered(lambda c: c.user_domain):
            current_users = challenge.user_ids
            new_users = self._get_challenger_users(challenge.user_domain)

            if current_users != new_users:
                challenge.user_ids = new_users

        return True

    def action_start(self):
        """Start a challenge"""
        return self.write({'state': 'inprogress'})

    def action_check(self):
        """Check a challenge

        Create goals that haven't been created yet (eg: if added users)
        Recompute the current value for each goal related"""
        self.env['gamification.goal'].search([
            ('challenge_id', 'in', self.ids),
            ('state', '=', 'inprogress')
        ]).unlink()

        return self._update_all()

    def action_report_progress(self):
        """Manual report of a goal, does not influence automatic report frequency"""
        for challenge in self:
            challenge.report_progress()
        return True

    def action_view_users(self):
        """ Redirect to the participants (users) list. """
        action = self.env["ir.actions.actions"]._for_xml_id("base.action_res_users")
        action['domain'] = [('id', 'in', self.user_ids.ids)]
        return action

    ##### Automatic actions #####

    def _generate_goals_from_challenge(self):
        """Generate the goals for each line and user.

        If goals already exist for this line and user, the line is skipped. This
        can be called after each change in the list of users or lines.
        :param list(int) ids: the list of challenge concerned"""

        Goals = self.env['gamification.goal']
        for challenge in self:
            (start_date, end_date) = start_end_date_for_period(challenge.period, challenge.start_date, challenge.end_date)
            to_update = Goals.browse(())

            for line in challenge.line_ids:
                # there is potentially a lot of users
                # detect the ones with no goal linked to this line
                date_clause = ""
                query_params = [line.id]
                if start_date:
                    date_clause += " AND g.start_date = %s"
                    query_params.append(start_date)
                if end_date:
                    date_clause += " AND g.end_date = %s"
                    query_params.append(end_date)

                query = """SELECT u.id AS user_id
                             FROM res_users u
                        LEFT JOIN gamification_goal g
                               ON (u.id = g.user_id)
                            WHERE line_id = %s
                              {date_clause}
                        """.format(date_clause=date_clause)
                self.env.cr.execute(query, query_params)
                user_with_goal_ids = {it for [it] in self.env.cr._obj}

                participant_user_ids = set(challenge.user_ids.ids)
                user_squating_challenge_ids = user_with_goal_ids - participant_user_ids
                if user_squating_challenge_ids:
                    # users that used to match the challenge
                    Goals.search([
                        ('challenge_id', '=', challenge.id),
                        ('user_id', 'in', list(user_squating_challenge_ids))
                    ]).unlink()

                values = {
                    'definition_id': line.definition_id.id,
                    'line_id': line.id,
                    'target_goal': line.target_goal,
                    'state': 'inprogress',
                }

                if start_date:
                    values['start_date'] = start_date
                if end_date:
                    values['end_date'] = end_date

                # the goal is initialised over the limit to make sure we will compute it at least once
                if line.condition == 'higher':
                    values['current'] = min(line.target_goal - 1, 0)
                else:
                    values['current'] = max(line.target_goal + 1, 0)

                if challenge.remind_update_delay:
                    values['remind_update_delay'] = challenge.remind_update_delay

                for user_id in (participant_user_ids - user_with_goal_ids):
                    values['user_id'] = user_id
                    to_update |= Goals.create(values)

            to_update.update_goal()

            if self.env.context.get('commit_gamification'):
                self.env.cr.commit()

        return True

    ##### JS utilities #####

    def _get_serialized_challenge_lines(self, user=(), restrict_goals=(), restrict_top=0):
        """Return a serialised version of the goals information if the user has not completed every goal

        :param user: user retrieving progress (False if no distinction,
                     only for ranking challenges)
        :param restrict_goals: compute only the results for this subset of
                               gamification.goal ids, if False retrieve every
                               goal of current running challenge
        :param int restrict_top: for challenge lines where visibility_mode is
                                 ``ranking``, retrieve only the best
                                 ``restrict_top`` results and itself, if 0
                                 retrieve all restrict_goal_ids has priority
                                 over restrict_top

        format list
        # if visibility_mode == 'ranking'
        {
            'name': <gamification.goal.description name>,
            'description': <gamification.goal.description description>,
            'condition': <reach condition {lower,higher}>,
            'computation_mode': <target computation {manually,count,sum,python}>,
            'monetary': <{True,False}>,
            'suffix': <value suffix>,
            'action': <{True,False}>,
            'display_mode': <{progress,boolean}>,
            'target': <challenge line target>,
            'own_goal_id': <gamification.goal id where user_id == uid>,
            'goals': [
                {
                    'id': <gamification.goal id>,
                    'rank': <user ranking>,
                    'user_id': <res.users id>,
                    'name': <res.users name>,
                    'state': <gamification.goal state {draft,inprogress,reached,failed,canceled}>,
                    'completeness': <percentage>,
                    'current': <current value>,
                }
            ]
        },
        # if visibility_mode == 'personal'
        {
            'id': <gamification.goal id>,
            'name': <gamification.goal.description name>,
            'description': <gamification.goal.description description>,
            'condition': <reach condition {lower,higher}>,
            'computation_mode': <target computation {manually,count,sum,python}>,
            'monetary': <{True,False}>,
            'suffix': <value suffix>,
            'action': <{True,False}>,
            'display_mode': <{progress,boolean}>,
            'target': <challenge line target>,
            'state': <gamification.goal state {draft,inprogress,reached,failed,canceled}>,
            'completeness': <percentage>,
            'current': <current value>,
        }
        """
        Goals = self.env['gamification.goal']
        (start_date, end_date) = start_end_date_for_period(self.period)

        res_lines = []
        for line in self.line_ids:
            line_data = {
                'name': line.definition_id.name,
                'description': line.definition_id.description,
                'condition': line.definition_id.condition,
                'computation_mode': line.definition_id.computation_mode,
                'monetary': line.definition_id.monetary,
                'suffix': line.definition_id.suffix,
                'action': True if line.definition_id.action_id else False,
                'display_mode': line.definition_id.display_mode,
                'target': line.target_goal,
            }
            domain = [
                ('line_id', '=', line.id),
                ('state', '!=', 'draft'),
            ]
            if restrict_goals:
                domain.append(('id', 'in', restrict_goals.ids))
            else:
                # if no subset goals, use the dates for restriction
                if start_date:
                    domain.append(('start_date', '=', start_date))
                if end_date:
                    domain.append(('end_date', '=', end_date))

            if self.visibility_mode == 'personal':
                if not user:
                    raise exceptions.UserError(_("Retrieving progress for personal challenge without user information"))

                domain.append(('user_id', '=', user.id))

                goal = Goals.search_fetch(domain, ['current', 'completeness', 'state'], limit=1)
                if not goal:
                    continue

                if goal.state != 'reached':
                    return []
                line_data.update({
                    fname: goal[fname]
                    for fname in ['id', 'current', 'completeness', 'state']
                })
                res_lines.append(line_data)
                continue

            line_data['own_goal_id'] = False,
            line_data['goals'] = []
            if line.condition=='higher':
                goals = Goals.search(domain, order="completeness desc, current desc")
            else:
                goals = Goals.search(domain, order="completeness desc, current asc")
            if not goals:
                continue

            for ranking, goal in enumerate(goals):
                if user and goal.user_id == user:
                    line_data['own_goal_id'] = goal.id
                elif restrict_top and ranking > restrict_top:
                    # not own goal and too low to be in top
                    continue

                line_data['goals'].append({
                    'id': goal.id,
                    'user_id': goal.user_id.id,
                    'name': goal.user_id.name,
                    'rank': ranking,
                    'current': goal.current,
                    'completeness': goal.completeness,
                    'state': goal.state,
                })
            if len(goals) < 3:
                # display at least the top 3 in the results
                missing = 3 - len(goals)
                for ranking, mock_goal in enumerate([{'id': False,
                                                      'user_id': False,
                                                      'name': '',
                                                      'current': 0,
                                                      'completeness': 0,
                                                      'state': False}] * missing,
                                                    start=len(goals)):
                    mock_goal['rank'] = ranking
                    line_data['goals'].append(mock_goal)

            res_lines.append(line_data)
        return res_lines

    ##### Reporting #####

    def report_progress(self, users=(), subset_goals=False):
        """Post report about the progress of the goals

        :param users: users that are concerned by the report. If False, will
                      send the report to every user concerned (goal users and
                      group that receive a copy). Only used for challenge with
                      a visibility mode set to 'personal'.
        :param subset_goals: goals to restrict the report
        """

        challenge = self

        if challenge.visibility_mode == 'ranking':
            lines_boards = challenge._get_serialized_challenge_lines(restrict_goals=subset_goals)

            body_html = challenge.report_template_id.with_context(challenge_lines=lines_boards)._render_field('body_html', challenge.ids)[challenge.id]

            # send to every follower and participant of the challenge
            challenge.message_post(
                body=body_html,
                partner_ids=challenge.mapped('user_ids.partner_id.id'),
                subtype_xmlid='mail.mt_comment',
                email_layout_xmlid='mail.mail_notification_light',
                )
            if challenge.report_message_group_id:
                challenge.report_message_group_id.message_post(
                    body=body_html,
                    subtype_xmlid='mail.mt_comment')

        else:
            # generate individual reports
            for user in (users or challenge.user_ids):
                lines = challenge._get_serialized_challenge_lines(user, restrict_goals=subset_goals)
                if not lines:
                    continue

                body_html = challenge.report_template_id.with_user(user).with_context(challenge_lines=lines)._render_field('body_html', challenge.ids)[challenge.id]

                # notify message only to users, do not post on the challenge
                challenge.message_notify(
                    body=body_html,
                    partner_ids=[user.partner_id.id],
                    subtype_xmlid='mail.mt_comment',
                    email_layout_xmlid='mail.mail_notification_light',
                )
                if challenge.report_message_group_id:
                    challenge.report_message_group_id.message_post(
                        body=body_html,
                        subtype_xmlid='mail.mt_comment',
                        email_layout_xmlid='mail.mail_notification_light',
                    )
        return challenge.write({'last_report_date': fields.Date.today()})

    ##### Challenges #####
    def accept_challenge(self):
        user = self.env.user
        sudoed = self.sudo()
        sudoed.message_post(body=_("%s has joined the challenge", user.name))
        sudoed.write({'invited_user_ids': [(3, user.id)], 'user_ids': [(4, user.id)]})
        return sudoed._generate_goals_from_challenge()

    def discard_challenge(self):
        """The user discard the suggested challenge"""
        user = self.env.user
        sudoed = self.sudo()
        sudoed.message_post(body=_("%s has refused the challenge", user.name))
        return sudoed.write({'invited_user_ids': (3, user.id)})

    def _check_challenge_reward(self, force=False):
        """Actions for the end of a challenge

        If a reward was selected, grant it to the correct users.
        Rewards granted at:
            - the end date for a challenge with no periodicity
            - the end of a period for challenge with periodicity
            - when a challenge is manually closed
        (if no end date, a running challenge is never rewarded)
        """
        commit = self.env.context.get('commit_gamification') and self.env.cr.commit

        for challenge in self:
            (start_date, end_date) = start_end_date_for_period(challenge.period, challenge.start_date, challenge.end_date)
            yesterday = date.today() - timedelta(days=1)

            rewarded_users = self.env['res.users']
            challenge_ended = force or end_date == fields.Date.to_string(yesterday)
            if challenge.reward_id and (challenge_ended or challenge.reward_realtime):
                # not using start_date as intemportal goals have a start date but no end_date
                reached_goals = self.env['gamification.goal']._read_group([
                    ('challenge_id', '=', challenge.id),
                    ('end_date', '=', end_date),
                    ('state', '=', 'reached')
                ], groupby=['user_id'], aggregates=['__count'])
                for user, count in reached_goals:
                    if count == len(challenge.line_ids):
                        # the user has succeeded every assigned goal
                        if challenge.reward_realtime:
                            badges = self.env['gamification.badge.user'].search_count([
                                ('challenge_id', '=', challenge.id),
                                ('badge_id', '=', challenge.reward_id.id),
                                ('user_id', '=', user.id),
                            ])
                            if badges > 0:
                                # has already recieved the badge for this challenge
                                continue
                        challenge._reward_user(user, challenge.reward_id)
                        rewarded_users |= user
                        if commit:
                            commit()

            if challenge_ended:
                # open chatter message
                message_body = _("The challenge %s is finished.", challenge.name)

                if rewarded_users:
                    message_body += Markup("<br/>") + _(
                        "Reward (badge %(badge_name)s) for every succeeding user was sent to %(users)s.",
                        badge_name=challenge.reward_id.name,
                        users=", ".join(rewarded_users.mapped('display_name'))
                    )
                else:
                    message_body += Markup("<br/>") + _("Nobody has succeeded to reach every goal, no badge is rewarded for this challenge.")

                # reward bests
                reward_message = Markup("<br/> %(rank)d. %(user_name)s - %(reward_name)s")
                if challenge.reward_first_id:
                    (first_user, second_user, third_user) = challenge._get_topN_users(MAX_VISIBILITY_RANKING)
                    if first_user:
                        challenge._reward_user(first_user, challenge.reward_first_id)
                        message_body += Markup("<br/>") + _("Special rewards were sent to the top competing users. The ranking for this challenge is:")
                        message_body += reward_message % {
                            'rank': 1,
                            'user_name': first_user.name,
                            'reward_name': challenge.reward_first_id.name,
                        }
                    else:
                        message_body += _("Nobody reached the required conditions to receive special badges.")

                    if second_user and challenge.reward_second_id:
                        challenge._reward_user(second_user, challenge.reward_second_id)
                        message_body += reward_message % {
                            'rank': 2,
                            'user_name': second_user.name,
                            'reward_name': challenge.reward_second_id.name,
                        }
                    if third_user and challenge.reward_third_id:
                        challenge._reward_user(third_user, challenge.reward_third_id)
                        message_body += reward_message % {
                            'rank': 3,
                            'user_name': third_user.name,
                            'reward_name': challenge.reward_third_id.name,
                        }

                challenge.message_post(
                    partner_ids=[user.partner_id.id for user in challenge.user_ids],
                    body=message_body)
                if commit:
                    commit()

        return True

    def _get_topN_users(self, n):
        """Get the top N users for a defined challenge

        Ranking criterias:
            1. succeed every goal of the challenge
            2. total completeness of each goal (can be over 100)

        Only users having reached every goal of the challenge will be returned
        unless the challenge ``reward_failure`` is set, in which case any user
        may be considered.

        :returns: an iterable of exactly N records, either User objects or
                  False if there was no user for the rank. There can be no
                  False between two users (if users[k] = False then
                  users[k+1] = False
        """
        Goals = self.env['gamification.goal']
        (start_date, end_date) = start_end_date_for_period(self.period, self.start_date, self.end_date)
        challengers = []
        for user in self.user_ids:
            all_reached = True
            total_completeness = 0
            # every goal of the user for the running period
            goal_ids = Goals.search([
                ('challenge_id', '=', self.id),
                ('user_id', '=', user.id),
                ('start_date', '=', start_date),
                ('end_date', '=', end_date)
            ])
            for goal in goal_ids:
                if goal.state != 'reached':
                    all_reached = False
                if goal.definition_condition == 'higher':
                    # can be over 100
                    total_completeness += (100.0 * goal.current / goal.target_goal) if goal.target_goal else 0
                elif goal.state == 'reached':
                    # for lower goals, can not get percentage so 0 or 100
                    total_completeness += 100

            challengers.append({'user': user, 'all_reached': all_reached, 'total_completeness': total_completeness})

        challengers.sort(key=lambda k: (k['all_reached'], k['total_completeness']), reverse=True)
        if not self.reward_failure:
            # only keep the fully successful challengers at the front, could
            # probably use filter since the successful ones are at the front
            challengers = itertools.takewhile(lambda c: c['all_reached'], challengers)

        # append a tail of False, then keep the first N
        challengers = itertools.islice(
            itertools.chain(
                (c['user'] for c in challengers),
                itertools.repeat(False),
            ), 0, n
        )

        return tuple(challengers)

    def _reward_user(self, user, badge):
        """Create a badge user and send the badge to him

        :param user: the user to reward
        :param badge: the concerned badge
        """
        return self.env['gamification.badge.user'].create({
            'user_id': user.id,
            'badge_id': badge.id,
            'challenge_id': self.id
        })._send_badge()
