# frozen_string_literal: true

class TopicUser < ActiveRecord::Base
  self.ignored_columns = [
    :highest_seen_post_number, # Remove after 01 Jan 2022
  ]

  belongs_to :user
  belongs_to :topic

  # used for serialization
  attr_accessor :post_action_data

  scope :level,
        lambda { |topic_id, level|
          where(topic_id: topic_id).where(
            "COALESCE(topic_users.notification_level, :regular) >= :level",
            regular: TopicUser.notification_levels[:regular],
            level: TopicUser.notification_levels[level],
          )
        }

  scope :tracking, lambda { |topic_id| level(topic_id, :tracking) }

  scope :watching, lambda { |topic_id| level(topic_id, :watching) }

  def topic_bookmarks
    Bookmark.where(topic: topic, user: user)
  end

  # Class methods
  class << self
    # Enums
    def notification_levels
      NotificationLevels.topic_levels
    end

    def notification_reasons
      @notification_reasons ||=
        Enum.new(
          created_topic: 1,
          user_changed: 2,
          user_interacted: 3,
          created_post: 4,
          auto_watch: 5,
          auto_watch_category: 6,
          auto_mute_category: 7,
          auto_track_category: 8,
          plugin_changed: 9,
          auto_watch_tag: 10,
          auto_mute_tag: 11,
          auto_track_tag: 12,
        )
    end

    def auto_notification(user_id, topic_id, reason, notification_level)
      should_change =
        TopicUser
          .where(user_id: user_id, topic_id: topic_id)
          .where(
            "notifications_reason_id IS NULL OR (notification_level < :max AND notification_level > :min)",
            max: notification_level,
            min: notification_levels[:regular],
          )
          .exists?

      if should_change
        change(
          user_id,
          topic_id,
          notification_level: notification_level,
          notifications_reason_id: reason,
        )
      end
    end

    def auto_notification_for_staging(
      user_id,
      topic_id,
      reason,
      notification_level = notification_levels[:watching]
    )
      change(
        user_id,
        topic_id,
        notification_level: notification_level,
        notifications_reason_id: reason,
      )
    end

    def unwatch_categories!(user, category_ids)
      track_threshold = user.user_option.auto_track_topics_after_msecs

      sql = <<~SQL
        UPDATE topic_users tu
        SET notification_level = CASE
          WHEN t.user_id = :user_id THEN :watching
          WHEN total_msecs_viewed > :track_threshold AND :track_threshold >= 0 THEN :tracking
          ELSE :regular
        end
        FROM topics t
        WHERE t.id = tu.topic_id AND tu.notification_level <> :muted AND category_id IN (:category_ids) AND tu.user_id = :user_id
      SQL

      DB.exec(
        sql,
        watching: notification_levels[:watching],
        tracking: notification_levels[:tracking],
        regular: notification_levels[:regular],
        muted: notification_levels[:muted],
        category_ids: category_ids,
        user_id: user.id,
        track_threshold: track_threshold,
      )
    end

    # Find the information specific to a user in a forum topic
    def lookup_for(user, topics)
      # If the user isn't logged in, there's no last read posts
      return {} if user.blank? || topics.blank?

      topic_ids = topics.map(&:id)
      create_lookup(TopicUser.where(topic_id: topic_ids, user_id: user.id))
    end

    def create_lookup(topic_users)
      topic_users = topic_users.to_a
      result = {}
      return result if topic_users.blank?
      topic_users.each { |ftu| result[ftu.topic_id] = ftu }
      result
    end

    def get(topic, user)
      topic = topic.id if topic.is_a?(Topic)
      user = user.id if user.is_a?(User)
      TopicUser.find_by(topic_id: topic, user_id: user)
    end

    # Change attributes for a user (creates a record when none is present). First it tries an update
    # since there's more likely to be an existing record than not. If the update returns 0 rows affected
    # it then creates the row instead.
    def change(user_id, topic_id, attrs)
      # For plugin compatibility, remove after 01 Jan 2022
      attrs.delete(:highest_seen_post_number) if attrs[:highest_seen_post_number]

      # Sometimes people pass objs instead of the ids. We can handle that.
      topic_id = topic_id.id if topic_id.is_a?(::Topic)
      user_id = user_id.id if user_id.is_a?(::User)

      topic_id = topic_id.to_i
      user_id = user_id.to_i

      TopicUser.transaction do
        attrs = attrs.dup
        if attrs[:notification_level]
          attrs[:notifications_changed_at] ||= DateTime.now
          attrs[:notifications_reason_id] ||= TopicUser.notification_reasons[:user_changed]
        end
        attrs_array = attrs.to_a

        attrs_sql = attrs_array.map { |t| "#{t[0]} = ?" }.join(", ")
        vals = attrs_array.map { |t| t[1] }

        rows = TopicUser.where(topic_id: topic_id, user_id: user_id).update_all([attrs_sql, *vals])

        create_missing_record(user_id, topic_id, attrs) if rows == 0
      end

      if attrs[:notification_level]
        notification_level_change(
          user_id,
          topic_id,
          attrs[:notification_level],
          attrs[:notifications_reason_id],
        )
      end
    rescue ActiveRecord::RecordNotUnique
      # In case of a race condition to insert, do nothing
    end

    def notification_level_change(user_id, topic_id, notification_level, reason_id)
      message = { notification_level_change: notification_level }
      message[:notifications_reason_id] = reason_id if reason_id
      MessageBus.publish("/topic/#{topic_id}", message, user_ids: [user_id])

      DiscourseEvent.trigger(
        :topic_notification_level_changed,
        notification_level,
        user_id,
        topic_id,
      )
    end

    def create_missing_record(user_id, topic_id, attrs)
      now = DateTime.now

      unless attrs[:notification_level]
        category_notification_level =
          CategoryUser
            .where(user_id: user_id)
            .where("category_id IN (SELECT category_id FROM topics WHERE id = :id)", id: topic_id)
            .where(
              "notification_level IN (:levels)",
              levels: [
                CategoryUser.notification_levels[:watching],
                CategoryUser.notification_levels[:tracking],
              ],
            )
            .order("notification_level DESC")
            .limit(1)
            .pluck(:notification_level)
            .first

        tag_notification_level =
          TagUser
            .where(user_id: user_id)
            .where("tag_id IN (SELECT tag_id FROM topic_tags WHERE topic_id = :id)", id: topic_id)
            .where(
              "notification_level IN (:levels)",
              levels: [
                CategoryUser.notification_levels[:watching],
                CategoryUser.notification_levels[:tracking],
              ],
            )
            .order("notification_level DESC")
            .limit(1)
            .pluck(:notification_level)
            .first

        if category_notification_level &&
             !(tag_notification_level && (tag_notification_level > category_notification_level))
          attrs[:notification_level] = category_notification_level
          attrs[:notifications_changed_at] = DateTime.now
          attrs[:notifications_reason_id] = (
            if category_notification_level == CategoryUser.notification_levels[:watching]
              TopicUser.notification_reasons[:auto_watch_category]
            else
              TopicUser.notification_reasons[:auto_track_category]
            end
          )
        elsif tag_notification_level
          attrs[:notification_level] = tag_notification_level
          attrs[:notifications_changed_at] = DateTime.now
          attrs[:notifications_reason_id] = (
            if tag_notification_level == TagUser.notification_levels[:watching]
              TopicUser.notification_reasons[:auto_watch_tag]
            else
              TopicUser.notification_reasons[:auto_track_tag]
            end
          )
        end
      end

      unless attrs[:notification_level]
        if Topic.private_messages.where(id: topic_id).exists? &&
             Notification.where(
               user_id: user_id,
               topic_id: topic_id,
               notification_type: Notification.types[:invited_to_private_message],
             ).exists?
          group_notification_level =
            Group
              .joins(
                "LEFT OUTER JOIN group_users gu ON gu.group_id = groups.id AND gu.user_id = #{user_id}",
              )
              .joins("LEFT OUTER JOIN topic_allowed_groups tag ON tag.topic_id = #{topic_id}")
              .where("gu.id IS NOT NULL AND tag.id IS NOT NULL")
              .pluck(:default_notification_level)
              .first

          if group_notification_level.present?
            attrs[:notification_level] = group_notification_level
          else
            attrs[:notification_level] = notification_levels[:watching]
          end
        else
          auto_track_after = UserOption.where(user_id: user_id).pick(:auto_track_topics_after_msecs)
          auto_track_after ||= SiteSetting.default_other_auto_track_topics_after_msecs

          if auto_track_after >= 0 && auto_track_after <= (attrs[:total_msecs_viewed].to_i || 0)
            attrs[:notification_level] ||= notification_levels[:tracking]
          end
        end
      end

      TopicUser.create!(
        attrs.merge!(
          user_id: user_id,
          topic_id: topic_id,
          first_visited_at: now,
          last_visited_at: now,
        ),
      )

      DiscourseEvent.trigger(:topic_first_visited_by_user, topic_id, user_id)
    end

    def track_visit!(topic_id, user_id)
      now = DateTime.now
      rows = TopicUser.where(topic_id: topic_id, user_id: user_id).update_all(last_visited_at: now)

      change(user_id, topic_id, last_visited_at: now, first_visited_at: now) if rows == 0
    end

    # Update the last read and the last seen post count, but only if it doesn't exist.
    # This would be a lot easier if psql supported some kind of upsert
    UPDATE_TOPIC_USER_SQL = <<~SQL
      UPDATE topic_users
      SET
        last_read_post_number = GREATEST(:post_number, tu.last_read_post_number),
        total_msecs_viewed = LEAST(tu.total_msecs_viewed + :msecs,86400000),
        notification_level =
           case when tu.notifications_reason_id is null and (tu.total_msecs_viewed + :msecs) >
              coalesce(uo.auto_track_topics_after_msecs,:threshold) and
              coalesce(uo.auto_track_topics_after_msecs, :threshold) >= 0
              and t.archetype = 'regular' then
                :tracking
           else
              tu.notification_level
           end
    FROM topic_users tu
    join topics t on t.id = tu.topic_id
    join users u on u.id = :user_id
    join user_options uo on uo.user_id = :user_id
    WHERE
         tu.topic_id = topic_users.topic_id AND
         tu.user_id = topic_users.user_id AND
         tu.topic_id = :topic_id AND
         tu.user_id = :user_id
    RETURNING
      topic_users.notification_level,
      tu.notification_level old_level,
      tu.last_read_post_number,
      t.archetype
    SQL

    INSERT_TOPIC_USER_SQL =
      "INSERT INTO topic_users (user_id, topic_id, last_read_post_number, last_visited_at, first_visited_at, notification_level)
                  SELECT :user_id, :topic_id, :post_number, :now, :now, :new_status
                  FROM topics AS ft
                  JOIN users u on u.id = :user_id
                  WHERE ft.id = :topic_id
                    AND NOT EXISTS(SELECT 1
                                   FROM topic_users AS ftu
                                   WHERE ftu.user_id = :user_id and ftu.topic_id = :topic_id)"

    def update_last_read(user, topic_id, post_number, new_posts_read, msecs, opts = {})
      return if post_number.blank?
      msecs = 0 if msecs.to_i < 0

      args = {
        user_id: user.id,
        topic_id: topic_id,
        post_number: post_number,
        now: DateTime.now,
        msecs: msecs,
        tracking: notification_levels[:tracking],
        threshold: SiteSetting.default_other_auto_track_topics_after_msecs,
      }

      rows = DB.query(UPDATE_TOPIC_USER_SQL, args)

      if rows.length == 1
        before = rows[0].old_level.to_i
        after = rows[0].notification_level.to_i
        before_last_read = rows[0].last_read_post_number.to_i
        archetype = rows[0].archetype

        if before_last_read < post_number
          # The user read at least one new post
          publish_read(
            topic_id: topic_id,
            post_number: post_number,
            user: user,
            notification_level: after,
            private_message: archetype == Archetype.private_message,
          )
        end

        user.update_posts_read!(new_posts_read, mobile: opts[:mobile]) if new_posts_read > 0

        notification_level_change(user.id, topic_id, after, nil) if before != after
      end

      if rows.length == 0
        # The user read at least one post in a topic that they haven't viewed before.
        args[:new_status] = notification_levels[:regular]
        if (
             user.user_option.auto_track_topics_after_msecs ||
               SiteSetting.default_other_auto_track_topics_after_msecs
           ) == 0
          args[:new_status] = notification_levels[:tracking]
        end

        publish_read(
          topic_id: topic_id,
          post_number: post_number,
          user: user,
          notification_level: args[:new_status],
          private_message: Topic.exists?(archetype: Archetype.private_message, id: topic_id),
        )

        user.update_posts_read!(new_posts_read, mobile: opts[:mobile])

        begin
          DB.exec(INSERT_TOPIC_USER_SQL, args)
        rescue PG::UniqueViolation
          # if record is inserted between two statements this can happen
          # we retry once to avoid failing the req
          if opts[:retry]
            raise
          else
            opts[:retry] = true
            update_last_read(user, topic_id, post_number, new_posts_read, msecs, opts)
          end
        end

        notification_level_change(user.id, topic_id, args[:new_status], nil)
      end
    end

    private

    def publish_read(topic_id:, post_number:, user:, notification_level: nil, private_message:)
      klass =
        if private_message
          PrivateMessageTopicTrackingState
        else
          TopicTrackingState
        end

      klass.publish_read(topic_id, post_number, user, notification_level)
    end
  end

  # Update the cached topic_user.liked column based on data
  # from the post_actions table. This is useful when posts
  # have moved around, or to ensure integrity of the data.
  #
  # By default this will update data for all topics and all users.
  # The parameters can be used to shrink the scope, and make it faster.
  # user_id, post_id and topic_id can optionally be arrays of ids.
  #
  # Providing post_id will automatically scope to the relevant user_id and topic_id.
  # A provided `topic_id` value will always take precedence, which is
  # useful when a post has been moved between topics.
  def self.update_post_action_cache(
    user_id: nil,
    post_id: nil,
    topic_id: nil,
    post_action_type: :like
  )
    raise ArgumentError, "post_action_type must equal :like" if post_action_type != :like
    raise ArgumentError, "post_id and user_id cannot be supplied together" if user_id && post_id
    action_type_name = "liked"

    builder = DB.build <<~SQL
      UPDATE topic_users tu
      SET #{action_type_name} = x.state
      FROM (
        SELECT CASE WHEN EXISTS (
          SELECT 1
          FROM post_actions pa
          JOIN posts p on p.id = pa.post_id
          JOIN topics t ON t.id = p.topic_id
          WHERE pa.deleted_at IS NULL AND
                p.deleted_at IS NULL AND
                t.deleted_at IS NULL AND
                pa.post_action_type_id = :action_type_id AND
                tu2.topic_id = t.id AND
                tu2.user_id = pa.user_id
          LIMIT 1
        ) THEN true ELSE false END state, tu2.topic_id, tu2.user_id
        FROM topic_users tu2
        /*where*/
      ) x
      WHERE x.topic_id = tu.topic_id AND x.user_id = tu.user_id AND x.state != tu.#{action_type_name}
    SQL

    builder.where("tu2.user_id IN (:user_id)", user_id: user_id) if user_id

    builder.where("tu2.topic_id IN (:topic_id)", topic_id: topic_id) if topic_id

    if post_id
      if !topic_id
        builder.where(
          "tu2.topic_id IN (SELECT topic_id FROM posts WHERE id IN (:post_id))",
          post_id: post_id,
        )
      end
      builder.where(<<~SQL, post_id: post_id)
        tu2.user_id IN (
          SELECT user_id FROM post_actions
          WHERE post_id IN (:post_id)
          AND post_action_type_id = :action_type_id
        )
      SQL
    end

    builder.exec(action_type_id: PostActionType.types[post_action_type])
  end

  # cap number of unread topics at count, bumping up last_read if needed
  def self.cap_unread!(user_id, count)
    sql = <<SQL
    UPDATE topic_users tu
    SET last_read_post_number = max_number
    FROM (
      SELECT MAX(post_number) max_number, p.topic_id FROM posts p
      WHERE deleted_at IS NULL
      GROUP BY p.topic_id
    ) m
    WHERE tu.user_id = :user_id AND
          m.topic_id = tu.topic_id AND
          tu.topic_id IN (
            #{TopicTrackingState.report_raw_sql(skip_new: true, select: "topics.id")}
            offset :count
          )
SQL

    DB.exec(sql, user_id: user_id, count: count)
  end

  def self.ensure_consistency!(topic_id = nil)
    update_post_action_cache(topic_id: topic_id)

    # TODO this needs some reworking, when we mark stuff skipped
    # we up these numbers so they are not in-sync
    # the simple fix is to add a column here, but table is already quite big
    # long term we want to split up topic_users and allow for this better
    builder = DB.build <<~SQL
      UPDATE topic_users t
        SET
          last_read_post_number = LEAST(GREATEST(last_read, last_read_post_number), max_post_number)
      FROM (
        SELECT topic_id, user_id, MAX(post_number) last_read
        FROM post_timings
        GROUP BY topic_id, user_id
      ) as X
      JOIN (
        SELECT p.topic_id, MAX(p.post_number) max_post_number from posts p
        GROUP BY p.topic_id
      ) as Y on Y.topic_id = X.topic_id
      /*where*/
    SQL

    builder.where <<~SQL
      X.topic_id = t.topic_id AND
      X.user_id = t.user_id AND
      (
        last_read_post_number <> LEAST(GREATEST(last_read, last_read_post_number), max_post_number)
      )
    SQL

    builder.where("t.topic_id = :topic_id", topic_id: topic_id) if topic_id

    builder.exec
  end
end

# == Schema Information
#
# Table name: topic_users
#
#  user_id                  :integer          not null
#  topic_id                 :integer          not null
#  posted                   :boolean          default(FALSE), not null
#  last_read_post_number    :integer
#  last_visited_at          :datetime
#  first_visited_at         :datetime
#  notification_level       :integer          default(1), not null
#  notifications_changed_at :datetime
#  notifications_reason_id  :integer
#  total_msecs_viewed       :integer          default(0), not null
#  cleared_pinned_at        :datetime
#  id                       :integer          not null, primary key
#  last_emailed_post_number :integer
#  liked                    :boolean          default(FALSE)
#  bookmarked               :boolean          default(FALSE)
#  last_posted_at           :datetime
#
# Indexes
#
#  index_topic_users_on_topic_id_and_notification_level  (topic_id,notification_level)
#  index_topic_users_on_topic_id_and_user_id             (topic_id,user_id) UNIQUE
#  index_topic_users_on_user_id_and_topic_id             (user_id,topic_id) UNIQUE
#