#302

backend/app/controllers/theatre_programmes_controller.rb

@@ -12,6 +12,8 @@ class TheatreProgrammesController < ApplicationController
                  .order(position: :desc).limit(100)
                  .limit(limit)
 
-    render json: programmes.as_json(include: { post: PostRepr::BASE })
+    render json: programmes.map { |programme|
+      programme.as_json.merge(post: PostRepr.base(programme.post))
+    }
   end
 end

backend/app/controllers/theatre_skip_events_controller.rb

@@ -0,0 +1,24 @@
+class TheatreSkipEventsController < ApplicationController
+  def index
+    limit = params[:limit].to_i
+    limit = 50 if limit <= 0
+
+    events =
+        TheatreSkipEvent
+        .where(theatre_id: params[:theatre_id])
+        .includes(:skipped_by_user, :users, :tags, post: { tags: :tag_name })
+        .order(created_at: :desc)
+        .limit(limit)
+
+    render json: events.map { |event|
+      { id: event.id,
+        theatre_id: event.theatre_id,
+        post: PostRepr.base(event.post),
+        skipped_by_user: UserRepr.base(event.skipped_by_user),
+        voters: event.users.map { |user| UserRepr.base(user) },
+        tags: event.tags.map { |tag| TagRepr.inline(tag) },
+        programme_position: event.programme_position,
+        created_at: event.created_at }
+    }
+  end
+end

backend/app/controllers/theatres_controller.rb

@@ -31,9 +31,7 @@ class TheatresController < ApplicationController
       post_started_at = theatre.current_post_started_at
     end
 
-    render json: {
-        host_flg:, post_id:, post_started_at:,
-        watching_users: theatre.watching_users.as_json(only: [:id, :name]) }
+    render json: theatre_info_json(theatre, host_flg:, post_id:, post_started_at:)
   end
 
   def next_post
@@ -44,14 +42,95 @@ class TheatresController < ApplicationController
     return head :forbidden if theatre.host_user != current_user
 
     ApplicationRecord.transaction do
-      post = Post.where("url LIKE '%nicovideo.jp%'")
-             .order('RAND()')
-             .first
-      theatre.update!(current_post: post, current_post_started_at: Time.current)
-      position = (theatre.programmes.maximum(:position) || 0) + 1
-      theatre.programmes.create!(position:, post:)
+      theatre.lock!
+      TheatrePostAdvancer.call(theatre:)
     end
 
     head :no_content
   end
+
+  def skip_vote
+    return head :unauthorized unless current_user
+
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    skipped = false
+
+    ApplicationRecord.transaction do
+      theatre.lock!
+      if theatre.current_post
+        TheatreWatchingUser.find_or_initialize_by(theatre:, user: current_user).tap {
+          _1.expires_at = 30.seconds.from_now
+        }.save!
+
+        TheatreSkipVote.find_or_create_by!(theatre:, post: theatre.current_post, user: current_user)
+
+        vote_status = skip_vote_status(theatre)
+        if vote_status[:votes_count] >= vote_status[:required_count]
+          TheatreSkipFinalizer.call(theatre:, user: current_user)
+          TheatrePostAdvancer.call(theatre:)
+          skipped = true
+        end
+      end
+    end
+
+    theatre.reload
+    render json: theatre_info_json(theatre, skipped:)
+  end
+
+  def unskip_vote
+    return head :unauthorized unless current_user
+
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    if theatre.current_post
+      TheatreSkipVote.where(theatre:, post: theatre.current_post, user: current_user).delete_all
+    end
+
+    render json: theatre_info_json(theatre, skipped: false)
+  end
+
+  def post_selection_weights
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    render json: TheatrePostSelector.new(theatre:).weight_json
+  end
+
+  private
+
+  def theatre_info_json(theatre, host_flg: nil, post_id: nil, post_started_at: nil, skipped: nil)
+    host_flg = theatre.host_user_id == current_user&.id if host_flg.nil?
+    post_id = theatre.current_post_id if post_id.nil?
+    post_started_at = theatre.current_post_started_at if post_started_at.nil?
+
+    json = { host_flg:,
+             post_id:,
+             post_started_at:,
+             post_elapsed_ms: post_started_at ? ((Time.current - post_started_at) * 1000).floor : nil,
+             watching_users: theatre.watching_users.as_json(only: [:id, :name]),
+             skip_vote: skip_vote_status(theatre) }
+    json[:skipped] = skipped unless skipped.nil?
+    json
+  end
+
+  def skip_vote_status(theatre)
+    watching_user_ids = theatre.watching_users.ids
+    watching_users_count = watching_user_ids.size
+    required_count = (watching_users_count / 2) + 1
+    post = theatre.current_post
+    votes =
+        if post
+          TheatreSkipVote.where(theatre:, post:, user_id: watching_user_ids)
+        else
+          TheatreSkipVote.none
+        end
+
+    { votes_count: post ? votes.count : 0,
+      required_count:,
+      watching_users_count:,
+      voted: post && current_user ? votes.exists?(user_id: current_user.id) : false }
+  end
 end

backend/app/models/theatre.rb

@@ -8,6 +8,8 @@ class Theatre < ApplicationRecord
   has_many :watching_users, through: :active_theatre_watching_users, source: :user
 
   has_many :programmes, class_name: 'TheatreProgramme'
+  has_many :skip_votes, class_name: 'TheatreSkipVote', dependent: :delete_all
+  has_many :skip_events, class_name: 'TheatreSkipEvent', dependent: :delete_all
 
   belongs_to :host_user, class_name: 'User', optional: true
   belongs_to :current_post, class_name: 'Post', optional: true

backend/app/models/theatre_skip_event.rb

@@ -0,0 +1,10 @@
+class TheatreSkipEvent < ApplicationRecord
+  belongs_to :theatre
+  belongs_to :post
+  belongs_to :skipped_by_user, class_name: 'User'
+
+  has_many :voters, class_name: 'TheatreSkipEventVoter', dependent: :delete_all
+  has_many :event_tags, class_name: 'TheatreSkipEventTag', dependent: :delete_all
+  has_many :users, through: :voters
+  has_many :tags, through: :event_tags
+end

backend/app/models/theatre_skip_event_tag.rb

@@ -0,0 +1,6 @@
+class TheatreSkipEventTag < ApplicationRecord
+  self.primary_key = :theatre_skip_event_id, :tag_id
+
+  belongs_to :theatre_skip_event
+  belongs_to :tag
+end

backend/app/models/theatre_skip_event_voter.rb

@@ -0,0 +1,6 @@
+class TheatreSkipEventVoter < ApplicationRecord
+  self.primary_key = :theatre_skip_event_id, :user_id
+
+  belongs_to :theatre_skip_event
+  belongs_to :user
+end

backend/app/models/theatre_skip_vote.rb

@@ -0,0 +1,7 @@
+class TheatreSkipVote < ApplicationRecord
+  self.primary_key = :theatre_id, :post_id, :user_id
+
+  belongs_to :theatre
+  belongs_to :post
+  belongs_to :user
+end

backend/app/services/theatre_post_advancer.rb

@@ -0,0 +1,29 @@
+class TheatrePostAdvancer
+  def self.call(theatre:)
+    new(theatre:).call
+  end
+
+  def initialize(theatre:)
+    @theatre = theatre
+  end
+
+  def call
+    previous_post = theatre.current_post
+    post = TheatrePostSelector.new(theatre:).select
+
+    TheatreSkipVote.where(theatre:, post: previous_post).delete_all if previous_post
+
+    theatre.update!(current_post: post, current_post_started_at: post ? Time.current : nil)
+
+    if post
+      position = (theatre.programmes.maximum(:position) || 0) + 1
+      theatre.programmes.create!(position:, post:)
+    end
+
+    post
+  end
+
+  private
+
+  attr_reader :theatre
+end

backend/app/services/theatre_post_selector.rb

@@ -0,0 +1,92 @@
+class TheatrePostSelector
+  Candidate = Struct.new(:post, :weight, :penalty, :tags, keyword_init: true)
+
+  def initialize(theatre:)
+    @theatre = theatre
+  end
+
+  def select
+    candidates = weighted_candidates
+    return nil if candidates.empty?
+
+    total = candidates.sum(&:weight)
+    target = rand * total
+
+    candidates.each do |candidate|
+      target -= candidate.weight
+      return candidate.post if target <= 0
+    end
+
+    candidates.last.post
+  end
+
+  def weight_json(limit: 20)
+    candidates = weighted_candidates
+    sorted = candidates.sort_by { |candidate| [candidate.weight, candidate.post.id] }
+
+    { tag_penalties: tag_penalty_json,
+      lightest_posts: post_weight_json(sorted.first(limit)),
+      heaviest_posts: post_weight_json(sorted.reverse.first(limit)) }
+  end
+
+  private
+
+  attr_reader :theatre
+
+  def weighted_candidates
+    @weighted_candidates ||= begin
+      penalties = tag_penalties
+      posts = eligible_posts.includes(tags: :tag_name).to_a
+
+      posts.map do |post|
+        post_tags = post.tags.to_a
+        penalty = post_tags.sum { |tag| penalties[tag.id].to_i }
+        Candidate.new(post:, penalty:, tags: post_tags, weight: 1.0 / (1.0 + penalty))
+      end
+    end
+  end
+
+  def eligible_posts
+    posts = Post.where("url LIKE '%nicovideo.jp%'")
+    posts = posts.where.not(id: theatre.current_post_id) if theatre.current_post_id
+    posts
+  end
+
+  def active_user_ids
+    @active_user_ids ||= theatre.watching_users.ids
+  end
+
+  def tag_penalties
+    @tag_penalties ||=
+        if active_user_ids.empty?
+          {}
+        else
+          TheatreSkipEventVoter
+          .joins(theatre_skip_event: :event_tags)
+          .where(user_id: active_user_ids)
+          .group('theatre_skip_event_tags.tag_id')
+          .count
+        end
+  end
+
+  def tag_penalty_json
+    return [] if tag_penalties.empty?
+
+    tags = Tag.where(id: tag_penalties.keys).includes(:tag_name).index_by(&:id)
+    tag_penalties.map { |tag_id, penalty|
+      tag = tags[tag_id]
+      next unless tag
+
+      { tag: TagRepr.inline(tag), penalty: }
+    }.compact.sort_by { |row| [-row[:penalty], row[:tag]['name'].to_s] }
+  end
+
+  def post_weight_json(candidates)
+    candidates.map { |candidate|
+      { post: PostRepr.base(candidate.post),
+        weight: candidate.weight,
+        penalty: candidate.penalty,
+        tags: candidate.tags.map { |tag| TagRepr.inline(tag) } }
+    }
+  end
+end

backend/app/services/theatre_skip_finalizer.rb

@@ -0,0 +1,40 @@
+class TheatreSkipFinalizer
+  def self.call(theatre:, user:)
+    new(theatre:, user:).call
+  end
+
+  def initialize(theatre:, user:)
+    @theatre = theatre
+    @user = user
+  end
+
+  def call
+    return unless theatre.current_post
+
+    post = theatre.current_post
+    voters = TheatreSkipVote.where(theatre:, post:).includes(:user).map(&:user)
+    return if voters.empty?
+
+    event = TheatreSkipEvent.create!(
+        theatre:,
+        post:,
+        skipped_by_user: user,
+        programme_position: theatre.programmes.maximum(:position))
+
+    voters.uniq(&:id).each do |voter|
+      TheatreSkipEventVoter.create!(theatre_skip_event: event, user: voter)
+    end
+
+    post.tags.find_each do |tag|
+      TheatreSkipEventTag.create!(theatre_skip_event: event, tag:)
+    end
+
+    TheatreSkipVote.where(theatre:, post:).delete_all
+
+    event
+  end
+
+  private
+
+  attr_reader :theatre, :user
+end