Kevin McConnell
66 lines
2.0 KiB
Ruby
66 lines
2.0 KiB
Ruby
module Bubble::Scorable
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extend ActiveSupport::Concern
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REFERENCE_DATE = Time.utc(2025, 1, 1)
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included do
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scope :ordered_by_activity, -> { order activity_score_order: :desc }
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# Staleness is measured by the amount of activity_score lost since it was last updated.
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# The factor 0.9 is chosen to make the decay curve closer to linear; an exponential
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# curve would make recent items appear stale very quickly, due to the sharp dropoff.
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scope :ordered_by_staleness, -> { order Arel.sql(
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"coalesce(activity_score * (1 - power(0.9, julianday('now') - julianday(activity_score_at))), 0) desc"
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) }
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end
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def rescore
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score = calculate_activity_score
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score_at = last_scorable_activity_at
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update! \
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activity_score: score,
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activity_score_at: score_at,
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activity_score_order: event_score_reference(score, score_at)
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end
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private
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def calculate_activity_score
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scorable_events.sum { |event| event_score(event) }
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end
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def event_score(event)
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days_ago = (last_scorable_activity_at - event.created_at) / 1.day
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event_weight(event) / (2**days_ago)
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end
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def event_weight(event)
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case
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when event.boosted? then 1
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when event.comment&.first_by_author_on_bubble? then 20
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when event.comment&.follows_comment_by_another_author? then 15
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when event.commented? then 10
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else 0
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end
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end
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def event_score_reference(score, activity_at)
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# The reference score is used to make the activity score comparable
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# across different bubbles, since it represents the bubble's activity
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# level at a consistent point in time.
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#
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# We store this as log2 to tame the huge/tiny numbers we'd otherwise get
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# when activity is far from the reference date.
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days_diff = (activity_at - REFERENCE_DATE) / 1.day
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Math.log2(1.0 + score) + days_diff
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end
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def last_scorable_activity_at
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scorable_events.maximum(:created_at) || created_at
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end
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def scorable_events
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events.where(action: [ :commented, :boosted ])
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end
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end
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