# models/track_mailer.rb:
# Emails which go to users who are tracking things.
#
# Copyright (c) 2008 UK Citizens Online Democracy. All rights reserved.
# Email: hello@mysociety.org; WWW: http://www.mysociety.org/

class TrackMailer < ApplicationMailer
    def event_digest(user, email_about_things)
        @user, @email_about_things = user, email_about_things

        post_redirect = PostRedirect.new(
            :uri => user_url(user) + "#email_subscriptions",
            :user_id => user.id)
        post_redirect.save!
        @unsubscribe_url = confirm_url(:email_token => post_redirect.email_token)

        headers('Auto-Submitted' => 'auto-generated', # http://tools.ietf.org/html/rfc3834
                'Precedence' => 'bulk')# http://www.vbulletin.com/forum/project.php?issueid=27687 (Exchange hack)
        # 'Return-Path' => blackhole_email, 'Reply-To' => @from # we don't care about bounces for tracks
        # (We let it return bounces for now, so we can manually kill the tracks that bounce so Yahoo
        # etc. don't decide we are spammers.)

        mail(:from => contact_from_name_and_email,
             :to => user.name_and_email,
             :subject => _("Your {{site_name}} email alert", :site_name => site_name))
    end

    def contact_from_name_and_email
        "#{AlaveteliConfiguration::track_sender_name} <#{AlaveteliConfiguration::track_sender_email}>"
    end

    # Send email alerts for tracked things.  Never more than one email
    # a day, nor about events which are more than a week old, nor
    # events about which emails have been sent within the last two
    # weeks.

    # Useful query to run by hand to see how many alerts are due:
    #   User.find(:all, :conditions => [ "last_daily_track_email < ?", Time.now - 1.day ]).size
    def self.alert_tracks
        done_something = false
        now = Time.now()
        one_week_ago = now - 7.days
        User.find_each(:conditions => [ "last_daily_track_email < ?",
                                         now - 1.day ]) do |user|
            next if !user.should_be_emailed? || !user.receive_email_alerts

            email_about_things = []
            track_things = TrackThing.find(:all, :conditions => [ "tracking_user_id = ? and track_medium = ?", user.id, 'email_daily' ])
            for track_thing in track_things
                # What have we alerted on already?
                #
                # We only use track_things_sent_emails records which are less than 14 days old.
                # In the search query loop below, we also only use items described in last 7 days.
                # An item described that recently definitely can't appear in track_things_sent_emails
                # earlier, so this is safe (with a week long margin of error). If the alerts break
                # for a whole week, then they will miss some items. Tough.
                done_info_request_events = {}
                tt_sent = track_thing.track_things_sent_emails.find(:all, :conditions => ['created_at > ?', now - 14.days])
                for t in tt_sent
                    if not t.info_request_event_id.nil?
                        done_info_request_events[t.info_request_event_id] = 1
                    end
                end

                # Query for things in this track. We use described_at for the
                # ordering, so we catch anything new (before described), or
                # anything whose new status has been described.
                xapian_object = ActsAsXapian::Search.new([InfoRequestEvent], track_thing.track_query,
                    :sort_by_prefix => 'described_at',
                    :sort_by_ascending => true,
                    :collapse_by_prefix => nil,
                    :limit => 100)
                # Go through looking for unalerted things
                alert_results = []
                for result in xapian_object.results
                    if result[:model].class.to_s != "InfoRequestEvent"
                        raise "need to add other types to TrackMailer.alert_tracks (unalerted)"
                    end

                    next if track_thing.created_at >= result[:model].described_at # made before the track was created
                    next if result[:model].described_at < one_week_ago # older than 1 week (see 14 days / 7 days in comment above)
                    next if done_info_request_events.include?(result[:model].id) # definitely already done

                    # OK alert this one
                    alert_results.push(result)
                end
                # If there were more alerts for this track, then store them
                if alert_results.size > 0
                    email_about_things.push([track_thing, alert_results, xapian_object])
                end
            end

            # If we have anything to send, then send everything for the user in one mail
            if email_about_things.size > 0
                # Send the email

                I18n.with_locale(user.get_locale) do
                    TrackMailer.event_digest(user, email_about_things).deliver
                end
            end

            # Record that we've now sent those alerts to that user
            for track_thing, alert_results in email_about_things
                for result in alert_results
                    track_things_sent_email = TrackThingsSentEmail.new
                    track_things_sent_email.track_thing_id = track_thing.id
                    if result[:model].class.to_s == "InfoRequestEvent"
                        track_things_sent_email.info_request_event_id = result[:model].id
                    else
                        raise "need to add other types to TrackMailer.alert_tracks (mark alerted)"
                    end
                    track_things_sent_email.save!
                end
            end
            user.last_daily_track_email = now
            user.no_xapian_reindex = true
            user.save!
            done_something = true
        end
        return done_something
    end

    def self.alert_tracks_loop
        # Run alert_tracks in an endless loop, sleeping when there is nothing to do
        while true
            sleep_seconds = 1
            while !alert_tracks
                sleep sleep_seconds
                sleep_seconds *= 2
                sleep_seconds = 300 if sleep_seconds > 300
            end
        end
    end

end