class Event < ActiveRecord::Base
  include Sortable
  include IgnorableColumn
  default_scope { reorder(nil).where.not(author_id: nil) }

  CREATED   = 1
  UPDATED   = 2
  CLOSED    = 3
  REOPENED  = 4
  PUSHED    = 5
  COMMENTED = 6
  MERGED    = 7
  JOINED    = 8 # User joined project
  LEFT      = 9 # User left project
  DESTROYED = 10
  EXPIRED   = 11 # User left project due to expiry

  ACTIONS = HashWithIndifferentAccess.new(
    created:    CREATED,
    updated:    UPDATED,
    closed:     CLOSED,
    reopened:   REOPENED,
    pushed:     PUSHED,
    commented:  COMMENTED,
    merged:     MERGED,
    joined:     JOINED,
    left:       LEFT,
    destroyed:  DESTROYED,
    expired:    EXPIRED
  ).freeze

  TARGET_TYPES = HashWithIndifferentAccess.new(
    issue:          Issue,
    milestone:      Milestone,
    merge_request:  MergeRequest,
    note:           Note,
    project:        Project,
    snippet:        Snippet,
    user:           User
  ).freeze

  RESET_PROJECT_ACTIVITY_INTERVAL = 1.hour

  delegate :name, :email, :public_email, :username, to: :author, prefix: true, allow_nil: true
  delegate :title, to: :issue, prefix: true, allow_nil: true
  delegate :title, to: :merge_request, prefix: true, allow_nil: true
  delegate :title, to: :note, prefix: true, allow_nil: true

  belongs_to :author, class_name: "User"
  belongs_to :project
  belongs_to :target, polymorphic: true # rubocop:disable Cop/PolymorphicAssociations
  has_one :push_event_payload

  # Callbacks
  after_create :reset_project_activity
  after_create :set_last_repository_updated_at, if: :push?

  # Scopes
  scope :recent, -> { reorder(id: :desc) }
  scope :code_push, -> { where(action: PUSHED) }

  scope :in_projects, -> (projects) do
    sub_query = projects
      .except(:order)
      .select(1)
      .where('projects.id = events.project_id')

    where('EXISTS (?)', sub_query).recent
  end

  scope :with_associations, -> do
    # We're using preload for "push_event_payload" as otherwise the association
    # is not always available (depending on the query being built).
    includes(:author, :project, project: :namespace)
      .preload(:target, :push_event_payload)
  end

  scope :for_milestone_id, ->(milestone_id) { where(target_type: "Milestone", target_id: milestone_id) }

  self.inheritance_column = 'action'

  # "data" will be removed in 10.0 but it may be possible that JOINs happen that
  # include this column, hence we're ignoring it as well.
  ignore_column :data

  class << self
    def model_name
      ActiveModel::Name.new(self, nil, 'event')
    end

    def find_sti_class(action)
      if action.to_i == PUSHED
        PushEvent
      else
        Event
      end
    end

    def subclass_from_attributes(attrs)
      # Without this Rails will keep calling this method on the returned class,
      # resulting in an infinite loop.
      return unless self == Event

      action = attrs.with_indifferent_access[inheritance_column].to_i

      PushEvent if action == PUSHED
    end

    # Update Gitlab::ContributionsCalendar#activity_dates if this changes
    def contributions
      where("action = ? OR (target_type IN (?) AND action IN (?)) OR (target_type = ? AND action = ?)",
            Event::PUSHED,
            %w(MergeRequest Issue), [Event::CREATED, Event::CLOSED, Event::MERGED],
            "Note", Event::COMMENTED)
    end

    def limit_recent(limit = 20, offset = nil)
      recent.limit(limit).offset(offset)
    end

    def actions
      ACTIONS.keys
    end

    def target_types
      TARGET_TYPES.keys
    end
  end

  def visible_to_user?(user = nil)
    if push? || commit_note?
      Ability.allowed?(user, :download_code, project)
    elsif membership_changed?
      true
    elsif created_project?
      true
    elsif issue? || issue_note?
      Ability.allowed?(user, :read_issue, note? ? note_target : target)
    elsif merge_request? || merge_request_note?
      Ability.allowed?(user, :read_merge_request, note? ? note_target : target)
    else
      milestone?
    end
  end

  def project_name
    if project
      project.name_with_namespace
    else
      "(deleted project)"
    end
  end

  def target_title
    target.try(:title)
  end

  def created?
    action == CREATED
  end

  def push?
    false
  end

  def merged?
    action == MERGED
  end

  def closed?
    action == CLOSED
  end

  def reopened?
    action == REOPENED
  end

  def joined?
    action == JOINED
  end

  def left?
    action == LEFT
  end

  def expired?
    action == EXPIRED
  end

  def destroyed?
    action == DESTROYED
  end

  def commented?
    action == COMMENTED
  end

  def membership_changed?
    joined? || left? || expired?
  end

  def created_project?
    created? && !target && target_type.nil?
  end

  def created_target?
    created? && target
  end

  def milestone?
    target_type == "Milestone"
  end

  def note?
    target.is_a?(Note)
  end

  def issue?
    target_type == "Issue"
  end

  def merge_request?
    target_type == "MergeRequest"
  end

  def milestone
    target if milestone?
  end

  def issue
    target if issue?
  end

  def merge_request
    target if merge_request?
  end

  def note
    target if note?
  end

  def action_name
    if push?
      if new_ref?
        "pushed new"
      elsif rm_ref?
        "deleted"
      else
        "pushed to"
      end
    elsif closed?
      "closed"
    elsif merged?
      "accepted"
    elsif joined?
      'joined'
    elsif left?
      'left'
    elsif expired?
      'removed due to membership expiration from'
    elsif destroyed?
      'destroyed'
    elsif commented?
      "commented on"
    elsif created_project?
      if project.external_import?
        "imported"
      else
        "created"
      end
    else
      "opened"
    end
  end

  def target_iid
    target.respond_to?(:iid) ? target.iid : target_id
  end

  def commit_note?
    note? && target && target.for_commit?
  end

  def issue_note?
    note? && target && target.for_issue?
  end

  def merge_request_note?
    note? && target && target.for_merge_request?
  end

  def project_snippet_note?
    note? && target && target.for_snippet?
  end

  def note_target
    target.noteable
  end

  def note_target_id
    if commit_note?
      target.commit_id
    else
      target.noteable_id.to_s
    end
  end

  def note_target_reference
    return unless note_target

    # Commit#to_reference returns the full SHA, but we want the short one here
    if commit_note?
      note_target.short_id
    else
      note_target.to_reference
    end
  end

  def note_target_type
    if target.noteable_type.present?
      target.noteable_type.titleize
    else
      "Wall"
    end.downcase
  end

  def body?
    if push?
      push_with_commits?
    elsif note?
      true
    else
      target.respond_to? :title
    end
  end

  def reset_project_activity
    return unless project

    # Don't bother updating if we know the project was updated recently.
    return if recent_update?

    # At this point it's possible for multiple threads/processes to try to
    # update the project. Only one query should actually perform the update,
    # hence we add the extra WHERE clause for last_activity_at.
    Project.unscoped.where(id: project_id)
      .where('last_activity_at <= ?', RESET_PROJECT_ACTIVITY_INTERVAL.ago)
      .update_all(last_activity_at: created_at)
  end

  def authored_by?(user)
    user ? author_id == user.id : false
  end

  def to_partial_path
    # We are intentionally using `Event` rather than `self.class` so that
    # subclasses also use the `Event` implementation.
    Event._to_partial_path
  end

  private

  def recent_update?
    project.last_activity_at > RESET_PROJECT_ACTIVITY_INTERVAL.ago
  end

  def set_last_repository_updated_at
    Project.unscoped.where(id: project_id)
      .update_all(last_repository_updated_at: created_at)
  end
end