# frozen_string_literal: true

class Reviewable < ActiveRecord::Base
  class UpdateConflict < StandardError; end

  class InvalidAction < StandardError
    def initialize(action_id, klass)
      @action_id, @klass = action_id, klass
      super("Can't perform `#{action_id}` on #{klass.name}")
    end
  end

  before_save :apply_review_group
  attr_accessor :created_new
  validates_presence_of :type, :status, :created_by_id
  belongs_to :target, polymorphic: true
  belongs_to :created_by, class_name: 'User'
  belongs_to :target_created_by, class_name: 'User'
  belongs_to :reviewable_by_group, class_name: 'Group'

  # Optional, for filtering
  belongs_to :topic
  belongs_to :category

  has_many :reviewable_histories
  has_many :reviewable_scores, -> { order(created_at: :desc) }

  after_create do
    log_history(:created, created_by)
  end

  after_commit(on: :create) do
    DiscourseEvent.trigger(:reviewable_created, self)
  end

  after_commit(on: [:create, :update]) do
    Jobs.enqueue(:notify_reviewable, reviewable_id: self.id) if pending?
  end

  # Can be used if several actions are equivalent
  def self.action_aliases
    {}
  end

  # The gaps are in case we want more precision in the future
  def self.priorities
    @priorities ||= Enum.new(
      low: 0,
      medium: 5,
      high: 10
    )
  end

  # The gaps are in case we want more precision in the future
  def self.sensitivity
    @sensitivity ||= Enum.new(
      disabled: 0,
      low: 9,
      medium: 6,
      high: 3
    )
  end

  def self.statuses
    @statuses ||= Enum.new(
      pending: 0,
      approved: 1,
      rejected: 2,
      ignored: 3,
      deleted: 4
    )
  end

  # This number comes from looking at forums in the wild and what numbers work.
  # As the site accumulates real data it'll be based on the site activity instead.
  def self.typical_sensitivity
    12.5
  end

  # Generate `pending?`, `rejected?`, etc helper methods
  statuses.each do |name, id|
    define_method("#{name}?") { status == id }
    self.class.define_method(name) { where(status: id) }
  end

  def self.default_visible
    where("score >= ?", min_score_for_priority)
  end

  def self.valid_type?(type)
    return false unless type =~ /^Reviewable[A-Za-z]+$/
    type.constantize <= Reviewable
  rescue NameError
    false
  end

  def self.types
    %w[ReviewableFlaggedPost ReviewableQueuedPost ReviewableUser ReviewablePost]
  end

  def self.custom_filters
    @reviewable_filters ||= []
  end

  def self.add_custom_filter(new_filter)
    custom_filters << new_filter
  end

  def self.clear_custom_filters!
    @reviewable_filters = []
  end

  def created_new!
    self.created_new = true
    self.topic = target.topic if topic.blank? && target.is_a?(Post)
    self.target_created_by_id = target.is_a?(Post) ? target.user_id : nil
    self.category_id = topic.category_id if category_id.blank? && topic.present?
  end

  # Create a new reviewable, or if the target has already been reviewed return it to the
  # pending state and re-use it.
  #
  # You probably want to call this to create your reviewable rather than `.create`.
  def self.needs_review!(
    target: nil,
    topic: nil,
    created_by:,
    payload: nil,
    reviewable_by_moderator: false,
    potential_spam: true
  )
    reviewable = new(
      target: target,
      topic: topic,
      created_by: created_by,
      reviewable_by_moderator: reviewable_by_moderator,
      payload: payload,
      potential_spam: potential_spam
    )
    reviewable.created_new!

    if target.blank?
      # If there is no target there's no chance of a conflict
      reviewable.save!
    else
      # In this case, a reviewable might already exist for this (type, target_id) index.
      # ActiveRecord can only validate indexes using a SELECT before the INSERT which
      # is not safe under concurrency. Instead, we perform an UPDATE on the status, and return
      # the previous value. We then know:
      #
      #   a) if a previous row existed
      #   b) if it was changed
      #
      # And that allows us to complete our logic.

      update_args = {
        status: statuses[:pending],
        id: target.id,
        type: target.class.name,
        potential_spam: potential_spam == true ? true : nil
      }

      row = DB.query_single(<<~SQL, update_args)
        UPDATE reviewables
        SET status = :status,
          potential_spam = COALESCE(:potential_spam, reviewables.potential_spam)
        FROM reviewables AS old_reviewables
        WHERE reviewables.target_id = :id
          AND reviewables.target_type = :type
        RETURNING old_reviewables.status
      SQL
      old_status = row[0]

      if old_status.blank?
        reviewable.save!
      else
        reviewable = find_by(target: target)
        reviewable.log_history(:transitioned, created_by) if old_status != statuses[:pending]
      end
    end

    reviewable
  end

  def add_score(
    user,
    reviewable_score_type,
    reason: nil,
    created_at: nil,
    take_action: false,
    meta_topic_id: nil,
    force_review: false
  )

    type_bonus = PostActionType.where(id: reviewable_score_type).pluck(:score_bonus)[0] || 0
    take_action_bonus = take_action ? 5.0 : 0.0
    user_accuracy_bonus = ReviewableScore.user_accuracy_bonus(user)
    sub_total = ReviewableScore.calculate_score(user, type_bonus, take_action_bonus)

    rs = reviewable_scores.new(
      user: user,
      status: ReviewableScore.statuses[:pending],
      reviewable_score_type: reviewable_score_type,
      score: sub_total,
      user_accuracy_bonus: user_accuracy_bonus,
      meta_topic_id: meta_topic_id,
      take_action_bonus: take_action_bonus,
      created_at: created_at || Time.zone.now
    )
    rs.reason = reason.to_s if reason
    rs.save!

    update(score: self.score + rs.score, latest_score: rs.created_at, force_review: force_review)
    topic.update(reviewable_score: topic.reviewable_score + rs.score) if topic

    DiscourseEvent.trigger(:reviewable_score_updated, self)

    rs
  end

  def self.set_priorities(values)
    values.each do |k, v|
      id = Reviewable.priorities[k]
      PluginStore.set('reviewables', "priority_#{id}", v) unless id.nil?
    end
  end

  def self.sensitivity_score_value(sensitivity, scale)
    return Float::MAX if sensitivity == 0

    ratio = sensitivity / Reviewable.sensitivity[:low].to_f
    high = (
      PluginStore.get('reviewables', "priority_#{Reviewable.priorities[:high]}") ||
      typical_sensitivity
    ).to_f

    # We want this to be hard to reach
    ((high.to_f * ratio) * scale).truncate(2)
  end

  def self.sensitivity_score(sensitivity, scale: 1.0)
    # If the score is less than the default visibility, bring it up to that level.
    # Otherwise we have the confusing situation where a post might be hidden and
    # moderators would never see it!
    [sensitivity_score_value(sensitivity, scale), min_score_for_priority].max
  end

  def self.score_to_auto_close_topic
    sensitivity_score(SiteSetting.auto_close_topic_sensitivity, scale: 2.5)
  end

  def self.spam_score_to_silence_new_user
    sensitivity_score(SiteSetting.silence_new_user_sensitivity, scale: 0.6)
  end

  def self.score_required_to_hide_post
    sensitivity_score(SiteSetting.hide_post_sensitivity)
  end

  def self.min_score_for_priority(priority = nil)
    priority ||= SiteSetting.reviewable_default_visibility
    id = Reviewable.priorities[priority.to_sym]
    return 0.0 if id.nil?
    PluginStore.get('reviewables', "priority_#{id}").to_f
  end

  def history
    reviewable_histories.order(:created_at)
  end

  def log_history(reviewable_history_type, performed_by, edited: nil)
    reviewable_histories.create!(
      reviewable_history_type: ReviewableHistory.types[reviewable_history_type],
      status: status,
      created_by: performed_by,
      edited: edited
    )
  end

  def apply_review_group
    return unless SiteSetting.enable_category_group_moderation? &&
      category.present? &&
      category.reviewable_by_group_id

    self.reviewable_by_group_id = category.reviewable_by_group_id
  end

  def actions_for(guardian, args = nil)
    args ||= {}

    Actions.new(self, guardian).tap do |actions|
      build_actions(actions, guardian, args)
    end
  end

  def editable_for(guardian, args = nil)
    args ||= {}
    EditableFields.new(self, guardian, args).tap do |fields|
      build_editable_fields(fields, guardian, args)
    end
  end

  # subclasses must implement "build_actions" to list the actions they're capable of
  def build_actions(actions, guardian, args)
    raise NotImplementedError
  end

  # subclasses can implement "build_editable_fields" to list stuff that can be edited
  def build_editable_fields(actions, guardian, args)
  end

  def update_fields(params, performed_by, version: nil)
    return true if params.blank?

    (params[:payload] || {}).each { |k, v| self.payload[k] = v }
    self.category_id = params[:category_id] if params.has_key?(:category_id)

    result = false

    Reviewable.transaction do
      increment_version!(version)
      changes_json = changes.as_json
      changes_json.delete('version')

      result = save
      log_history(:edited, performed_by, edited: changes_json) if result
    end

    result
  end

  # Delegates to a `perform_#{action_id}` method, which returns a `PerformResult` with
  # the result of the operation and whether the status of the reviewable changed.
  def perform(performed_by, action_id, args = nil)
    args ||= {}

    # Support this action or any aliases
    aliases = self.class.action_aliases
    valid = [ action_id, aliases.to_a.select { |k, v| v == action_id }.map(&:first) ].flatten

    # Ensure the user has access to the action
    actions = actions_for(Guardian.new(performed_by), args)
    raise InvalidAction.new(action_id, self.class) unless valid.any? { |a| actions.has?(a) }

    perform_method = "perform_#{aliases[action_id] || action_id}".to_sym
    raise InvalidAction.new(action_id, self.class) unless respond_to?(perform_method)

    result = nil
    update_count = false
    Reviewable.transaction do
      increment_version!(args[:version])
      result = public_send(perform_method, performed_by, args)

      raise ActiveRecord::Rollback unless result.success?

      update_count = transition_to(result.transition_to, performed_by) if result.transition_to
      update_flag_stats(**result.update_flag_stats) if result.update_flag_stats

      recalculate_score if result.recalculate_score
    end
    if result && result.after_commit
      result.after_commit.call
    end
    Jobs.enqueue(:notify_reviewable, reviewable_id: self.id) if update_count

    result
  end

  def transition_to(status_symbol, performed_by)
    was_pending = pending?

    self.status = Reviewable.statuses[status_symbol]
    save!

    log_history(:transitioned, performed_by)
    DiscourseEvent.trigger(:reviewable_transitioned_to, status_symbol, self)

    if score_status = ReviewableScore.score_transitions[status_symbol]
      reviewable_scores.pending.update_all(
        status: score_status,
        reviewed_by_id: performed_by.id,
        reviewed_at: Time.zone.now
      )
    end

    was_pending
  end

  def post_options
    Discourse.deprecate(
      "Reviewable#post_options is deprecated. Please use #payload instead.",
      output_in_test: true
    )
  end

  def self.bulk_perform_targets(performed_by, action, type, target_ids, args = nil)
    args ||= {}
    viewable_by(performed_by).where(type: type, target_id: target_ids).each do |r|
      r.perform(performed_by, action, args)
    end
  end

  def self.viewable_by(user, order: nil, preload: true)
    return none unless user.present?

    result = self.order(order || 'reviewables.score desc, reviewables.created_at desc')

    if preload
      result = result.includes(
        { created_by: :user_stat },
        :topic,
        :target,
        :target_created_by,
        :reviewable_histories
      ).includes(reviewable_scores: { user: :user_stat, meta_topic: :posts })
    end
    return result if user.admin?

    group_ids = SiteSetting.enable_category_group_moderation? ? user.group_users.pluck(:group_id) : []

    result.where(
      '(reviewables.reviewable_by_moderator AND :staff) OR (reviewables.reviewable_by_group_id IN (:group_ids))',
      staff: user.staff?,
      group_ids: group_ids
    ).where("reviewables.category_id IS NULL OR reviewables.category_id IN (?)", Guardian.new(user).allowed_category_ids)
  end

  def self.pending_count(user)
    list_for(user).count
  end

  def self.list_for(
    user,
    ids: nil,
    status: :pending,
    category_id: nil,
    topic_id: nil,
    type: nil,
    limit: nil,
    offset: nil,
    priority: nil,
    username: nil,
    reviewed_by: nil,
    sort_order: nil,
    from_date: nil,
    to_date: nil,
    additional_filters: {}
  )
    order = case sort_order
            when 'score_asc'
              'reviewables.score ASC, reviewables.created_at DESC'
            when 'created_at'
              'reviewables.created_at DESC, reviewables.score DESC'
            when 'created_at_asc'
              'reviewables.created_at ASC, reviewables.score DESC'
            else
              'reviewables.score DESC, reviewables.created_at DESC'
    end

    if username.present?
      user_id = User.find_by_username(username)&.id
      return [] if user_id.blank?
    end

    return [] if user.blank?
    result = viewable_by(user, order: order)

    result = by_status(result, status)
    result = result.where(id: ids) if ids
    result = result.where('reviewables.type = ?', type) if type
    result = result.where('reviewables.category_id = ?', category_id) if category_id
    result = result.where('reviewables.topic_id = ?', topic_id) if topic_id
    result = result.where("reviewables.created_at >= ?", from_date) if from_date
    result = result.where("reviewables.created_at <= ?", to_date) if to_date

    if reviewed_by
      reviewed_by_id = User.find_by_username(reviewed_by)&.id
      return [] if reviewed_by_id.nil?

      result = result.joins(<<~SQL
        INNER JOIN(
          SELECT reviewable_id
          FROM reviewable_histories
          WHERE reviewable_history_type = #{ReviewableHistory.types[:transitioned]} AND
          status <> #{Reviewable.statuses[:pending]} AND created_by_id = #{reviewed_by_id}
        ) AS rh ON rh.reviewable_id = reviewables.id
      SQL
      )
    end

    min_score = Reviewable.min_score_for_priority(priority)

    if min_score > 0 && status == :pending
      result = result.where("reviewables.score >= ? OR reviewables.force_review", min_score)
    elsif min_score > 0
      result = result.where("reviewables.score >= ?", min_score)
    end

    if !custom_filters.empty?
      result = custom_filters.reduce(result) do |memo, filter|
        key = filter.first
        filter_query = filter.last

        next(memo) unless additional_filters[key]
        filter_query.call(result, additional_filters[key])
      end
    end

    # If a reviewable doesn't have a target, allow us to filter on who created that reviewable.
    if user_id
      result = result.where(
        "(reviewables.target_created_by_id IS NULL AND reviewables.created_by_id = :user_id)
        OR (reviewables.target_created_by_id = :user_id)",
        user_id: user_id
      )
    end

    result = result.limit(limit) if limit
    result = result.offset(offset) if offset
    result
  end

  def serializer
    self.class.serializer_for(self)
  end

  def self.lookup_serializer_for(type)
    "#{type}Serializer".constantize
  rescue NameError
    ReviewableSerializer
  end

  def self.serializer_for(reviewable)
    type = reviewable.type
    @@serializers ||= {}
    @@serializers[type] ||= lookup_serializer_for(type)
  end

  def create_result(status, transition_to = nil)
    result = PerformResult.new(self, status)
    result.transition_to = transition_to
    yield result if block_given?
    result
  end

  def self.scores_with_topics
    ReviewableScore.joins(reviewable: :topic).where("reviewables.type = ?", name)
  end

  def self.count_by_date(start_date, end_date, category_id = nil, include_subcategories = false)
    query = scores_with_topics.where('reviewable_scores.created_at BETWEEN ? AND ?', start_date, end_date)

    if category_id
      if include_subcategories
        query = query.where("topics.category_id IN (?)", Category.subcategory_ids(category_id))
      else
        query = query.where("topics.category_id = ?", category_id)
      end
    end

    query
      .group("date(reviewable_scores.created_at)")
      .order('date(reviewable_scores.created_at)')
      .count
  end

  def explain_score
    DB.query(<<~SQL, reviewable_id: id)
      SELECT rs.reviewable_id,
        rs.user_id,
        CASE WHEN (u.admin OR u.moderator) THEN 5.0 ELSE u.trust_level END AS trust_level_bonus,
        us.flags_agreed,
        us.flags_disagreed,
        us.flags_ignored,
        rs.score,
        rs.user_accuracy_bonus,
        rs.take_action_bonus,
        COALESCE(pat.score_bonus, 0.0) AS type_bonus
      FROM reviewable_scores AS rs
      INNER JOIN users AS u ON u.id = rs.user_id
      LEFT OUTER JOIN user_stats AS us ON us.user_id = rs.user_id
      LEFT OUTER JOIN post_action_types AS pat ON pat.id = rs.reviewable_score_type
        WHERE rs.reviewable_id = :reviewable_id
    SQL
  end

protected

  def recalculate_score
    # pending/agreed scores count
    sql = <<~SQL
      UPDATE reviewables
      SET score = COALESCE((
        SELECT sum(score)
        FROM reviewable_scores AS rs
        WHERE rs.reviewable_id = :id
          AND rs.status IN (:pending, :agreed)
      ), 0.0)
      WHERE id = :id
      RETURNING score
    SQL

    result = DB.query(
      sql,
      id: self.id,
      pending: ReviewableScore.statuses[:pending],
      agreed: ReviewableScore.statuses[:agreed]
    )

    # Update topic score
    sql = <<~SQL
      UPDATE topics
      SET reviewable_score = COALESCE((
        SELECT SUM(score)
        FROM reviewables AS r
        WHERE r.topic_id = :topic_id
          AND r.status IN (:pending, :approved)
      ), 0.0)
      WHERE id = :topic_id
    SQL

    DB.query(
      sql,
      topic_id: topic_id,
      pending: Reviewable.statuses[:pending],
      approved: Reviewable.statuses[:approved]
    )

    self.score = result[0].score

    DiscourseEvent.trigger(:reviewable_score_updated, self)

    self.score
  end

  def increment_version!(version = nil)
    version_result = nil

    if version
      version_result = DB.query_single(
        "UPDATE reviewables SET version = version + 1 WHERE id = :id AND version = :version RETURNING version",
        version: version,
        id: self.id
      )
    else
      # We didn't supply a version to update safely, so just increase it
      version_result = DB.query_single(
        "UPDATE reviewables SET version = version + 1 WHERE id = :id RETURNING version",
        id: self.id
      )
    end

    if version_result && version_result[0]
      self.version = version_result[0]
    else
      raise UpdateConflict.new
    end
  end

  def self.by_status(partial_result, status)
    return partial_result if status == :all

    if status == :reviewed
      partial_result.where(status: statuses.except(:pending).values)
    else
      partial_result.where(status: statuses[status])
    end
  end

private

  def update_flag_stats(status:, user_ids:)
    return unless [:agreed, :disagreed, :ignored].include?(status)

    # Don't count self-flags
    user_ids -= [post&.user_id]
    return if user_ids.blank?

    result = DB.query(<<~SQL, user_ids: user_ids)
      UPDATE user_stats
      SET flags_#{status} = flags_#{status} + 1
      WHERE user_id IN (:user_ids)
      RETURNING user_id, flags_agreed + flags_disagreed + flags_ignored AS total
    SQL

    user_ids = result.select { |r| r.total > Jobs::TruncateUserFlagStats.truncate_to }.map(&:user_id)
    return if user_ids.blank?

    Jobs.enqueue(:truncate_user_flag_stats, user_ids: user_ids)
  end
end

# == Schema Information
#
# Table name: reviewables
#
#  id                      :bigint           not null, primary key
#  type                    :string           not null
#  status                  :integer          default(0), not null
#  created_by_id           :integer          not null
#  reviewable_by_moderator :boolean          default(FALSE), not null
#  reviewable_by_group_id  :integer
#  category_id             :integer
#  topic_id                :integer
#  score                   :float            default(0.0), not null
#  potential_spam          :boolean          default(FALSE), not null
#  target_id               :integer
#  target_type             :string
#  target_created_by_id    :integer
#  payload                 :json
#  version                 :integer          default(0), not null
#  latest_score            :datetime
#  created_at              :datetime         not null
#  updated_at              :datetime         not null
#  force_review            :boolean          default(FALSE), not null
#  reject_reason           :text
#
# Indexes
#
#  index_reviewables_on_reviewable_by_group_id                 (reviewable_by_group_id)
#  index_reviewables_on_status_and_created_at                  (status,created_at)
#  index_reviewables_on_status_and_score                       (status,score)
#  index_reviewables_on_status_and_type                        (status,type)
#  index_reviewables_on_target_id_where_post_type_eq_post      (target_id) WHERE ((target_type)::text = 'Post'::text)
#  index_reviewables_on_topic_id_and_status_and_created_by_id  (topic_id,status,created_by_id)
#  index_reviewables_on_type_and_target_id                     (type,target_id) UNIQUE
#