# Before
Event.where("start_at <= ? AND (end_at IS NULL OR end_at > ?)", Time.current, Time.current)

# After
class Event < ActiveRecord::Base
  in_time_scope
end

Event.in_time

class Event < ActiveRecord::Base
  in_time_scope
end

# Class scope
Event.in_time                          # Records active now
Event.in_time(Time.parse("2024-06-01")) # Records active at specific time

# Instance method
event.in_time?                          # Is this record active now?
event.in_time?(some_time)               # Was it active at that time?

# NULL-allowed columns → NULL-aware query
WHERE (start_at IS NULL OR start_at <= ?) AND (end_at IS NULL OR end_at > ?)

# NOT NULL columns → simple query
WHERE start_at <= ? AND end_at > ?

class Article < ActiveRecord::Base
  in_time_scope :published   # → Article.in_time_published
  in_time_scope :featured    # → Article.in_time_featured
end

class Campaign < ActiveRecord::Base
  in_time_scope start_at: { column: :available_at },
                end_at: { column: :expired_at }
end

# Time.current = 2024-10-20 → row id=3 (latest) is selected
Price.in_time

# 2024-10-12 → row id=2 (latest before 10/12) is selected
Price.in_time(Time.parse("2024-10-12"))

class Price < ActiveRecord::Base
  in_time_scope start_at: { null: false }, end_at: { column: nil }
end

# Bonus: efficient has_one with NOT EXISTS
class User < ActiveRecord::Base
  has_one :current_price, -> { latest_in_time(:user_id) }, class_name: "Price"
end

User.includes(:current_price)  # No N+1, fetches only latest per user

# Time.current = 2024-10-20 → id=1 (ABC) and id=3 (DEF) selected (not yet expired)
Coupon.in_time

# 2024-10-06 → id=1 (ABC) and id=3 (DEF) selected (XYZ expired on 10/05)
Coupon.in_time(Time.parse("2024-10-06"))

class Coupon < ActiveRecord::Base
  in_time_scope start_at: { column: nil }, end_at: { null: false }
end

# Records not yet started (start_at > time)
Event.before_in_time
event.before_in_time?

# Records already ended (end_at <= time)
Event.after_in_time
event.after_in_time?

# Records outside time window (before OR after)
Event.out_of_time
event.out_of_time?  # Logical inverse of in_time?

Article.before_in_time_published  # Not yet published
Article.after_in_time_published   # Publication ended
Article.out_of_time_published     # Not currently published