87 lines
2.8 KiB
Ruby
87 lines
2.8 KiB
Ruby
class EmailDigestArticleCollector
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def initialize(user)
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@user = user
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end
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def articles_to_send
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return [] unless should_receive_email?
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articles = if user_has_followings?
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experience_level_rating = (@user.experience_level || 5)
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experience_level_rating_min = experience_level_rating - 3.6
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experience_level_rating_max = experience_level_rating + 3.6
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@user.followed_articles
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.select(:title, :description, :path)
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.published
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.where("published_at > ?", cutoff_date)
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.where(email_digest_eligible: true)
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.where.not(user_id: @user.id)
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.where("score > ?", 12)
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.where("experience_level_rating > ? AND experience_level_rating < ?",
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experience_level_rating_min, experience_level_rating_max)
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.order(score: :desc)
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.limit(6)
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else
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Article.select(:title, :description, :path)
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.published
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.where("published_at > ?", cutoff_date)
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.where(featured: true, email_digest_eligible: true)
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.where.not(user_id: @user.id)
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.where("score > ?", 25)
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.order(score: :desc)
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.limit(6)
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end
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articles.length < 3 ? [] : articles
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end
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private
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def should_receive_email?
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return true unless last_email_sent_at
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# Has it been at least x days since @user received an email?
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Time.current - last_email_sent_at >= days_until_next_email
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end
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def days_until_next_email
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# Relies on hyperbolic tangent function to model the frequency of the digest email
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max_day = SiteConfig.periodic_email_digest_max
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min_day = SiteConfig.periodic_email_digest_min
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result = max_day * (1 - Math.tanh(2 * open_rate))
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result = result.round
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[result, min_day].max
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end
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def open_rate
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email_count = last_user_emails.count
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# Will stick with 50% open rate if @user has no/not-enough email digest history
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return 0.5 if email_count < 10
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past_opened_emails_count = last_user_emails.count { |msg| msg.opened_at.present? }
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past_opened_emails_count / email_count
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end
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def last_email_sent_at
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last_user_emails.last&.sent_at
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end
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def cutoff_date
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a_few_days_ago = 4.days.ago.utc
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return a_few_days_ago unless last_email_sent_at
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[a_few_days_ago, last_email_sent_at].max
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end
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def user_has_followings?
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@user.following_users_count.positive? || @user.cached_followed_tag_names.any?
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end
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def last_user_emails
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@last_user_emails ||= @user.email_messages.select(:sent_at,
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:opened_at).where(mailer: "DigestMailer#digest_email").limit(10)
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end
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end
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