# frozen_string_literal: true

module NotesActions
  include RendersNotes
  include Gitlab::Utils::StrongMemoize
  extend ActiveSupport::Concern

  # last_fetched_at is an integer number of microseconds, which is the same
  # precision as PostgreSQL "timestamp" fields. It's important for them to have
  # identical precision for accurate pagination
  MICROSECOND = 1_000_000

  included do
    before_action :set_polling_interval_header, only: [:index]
    before_action :require_noteable!, only: [:index, :create]
    before_action :authorize_admin_note!, only: [:update, :destroy]
    before_action :note_project, only: [:create]
  end

  def index
    notes, meta = gather_notes
    notes = prepare_notes_for_rendering(notes)
    notes = notes.select { |n| n.readable_by?(current_user) }
    notes =
      if use_note_serializer?
        note_serializer.represent(notes)
      else
        notes.map { |note| note_json(note) }
      end

    # We know there's more data, so tell the frontend to poll again after 1ms
    set_polling_interval_header(interval: 1) if meta[:more]

    # Only present an ETag for the empty response to ensure pagination works
    # as expected
    ::Gitlab::EtagCaching::Middleware.skip!(response) if notes.present?

    render json: meta.merge(notes: notes)
  end

  # rubocop:disable Gitlab/ModuleWithInstanceVariables
  def create
    @note = Notes::CreateService.new(note_project, current_user, create_note_params).execute

    respond_to do |format|
      format.json do
        json = {
          commands_changes: @note.commands_changes&.slice(:emoji_award, :time_estimate, :spend_time)
        }

        if @note.persisted? && return_discussion?
          json[:valid] = true

          discussion = @note.discussion
          prepare_notes_for_rendering(discussion.notes)
          json[:discussion] = discussion_serializer.represent(discussion, context: self)
        else
          prepare_notes_for_rendering([@note])

          json.merge!(note_json(@note))
        end

        if @note.errors.present? && @note.errors.keys != [:commands_only]
          render json: json, status: :unprocessable_entity
        else
          render json: json
        end
      end
      format.html { redirect_back_or_default }
    end
  end
  # rubocop:enable Gitlab/ModuleWithInstanceVariables

  # rubocop:disable Gitlab/ModuleWithInstanceVariables
  def update
    @note = Notes::UpdateService.new(project, current_user, update_note_params).execute(note)
    unless @note
      head :gone
      return
    end

    prepare_notes_for_rendering([@note])

    respond_to do |format|
      format.json { render json: note_json(@note) }
      format.html { redirect_back_or_default }
    end
  end
  # rubocop:enable Gitlab/ModuleWithInstanceVariables

  def destroy
    if note.editable?
      Notes::DestroyService.new(project, current_user).execute(note)
    end

    respond_to do |format|
      format.js { head :ok }
    end
  end

  private

  # Lower bound (last_fetched_at as specified in the request) is already set in
  # the finder. Here, we select between returning all notes since then, or a
  # page's worth of notes.
  def gather_notes
    if Feature.enabled?(:paginated_notes, noteable.try(:resource_parent))
      gather_some_notes
    else
      gather_all_notes
    end
  end

  def gather_all_notes
    now = Time.current
    notes = merge_resource_events(notes_finder.execute.inc_relations_for_view)

    [notes, { last_fetched_at: (now.to_i * MICROSECOND) + now.usec }]
  end

  def gather_some_notes
    paginator = ::Gitlab::UpdatedNotesPaginator.new(
      notes_finder.execute.inc_relations_for_view,
      last_fetched_at: last_fetched_at
    )

    notes = paginator.notes

    # Fetch all the synthetic notes in the same time range as the real notes.
    # Although we don't limit the number, their text is under our control so
    # should be fairly cheap to process.
    notes = merge_resource_events(notes, fetch_until: paginator.next_fetched_at)

    [notes, paginator.metadata]
  end

  def merge_resource_events(notes, fetch_until: nil)
    return notes if notes_filter == UserPreference::NOTES_FILTERS[:only_comments]

    ResourceEvents::MergeIntoNotesService
      .new(noteable, current_user, last_fetched_at: last_fetched_at, fetch_until: fetch_until)
      .execute(notes)
  end

  def note_html(note)
    render_to_string(
      "shared/notes/_note",
      layout: false,
      formats: [:html],
      locals: { note: note }
    )
  end

  def note_json(note)
    attrs = {}

    if note.persisted?
      attrs[:valid] = true

      if return_discussion?
        discussion = note.discussion
        prepare_notes_for_rendering(discussion.notes)

        attrs[:discussion] = discussion_serializer.represent(discussion, context: self)
      elsif use_note_serializer?
        attrs.merge!(note_serializer.represent(note))
      else
        attrs.merge!(
          id: note.id,
          discussion_id: note.discussion_id(noteable),
          html: note_html(note),
          note: note.note,
          on_image: note.try(:on_image?)
        )

        discussion = note.to_discussion(noteable)
        unless discussion.individual_note?
          attrs.merge!(
            discussion_resolvable: discussion.resolvable?,

            diff_discussion_html: diff_discussion_html(discussion),
            discussion_html: discussion_html(discussion)
          )

          attrs[:discussion_line_code] = discussion.line_code if discussion.diff_discussion?
        end
      end
    else
      attrs.merge!(
        valid: false,
        errors: note.errors
      )
    end

    attrs
  end

  def diff_discussion_html(discussion)
    return unless discussion.diff_discussion?

    on_image = discussion.on_image?

    if params[:view] == 'parallel' && !on_image
      template = "discussions/_parallel_diff_discussion"
      locals =
        if params[:line_type] == 'old'
          { discussions_left: [discussion], discussions_right: nil }
        else
          { discussions_left: nil, discussions_right: [discussion] }
        end
    else
      template = "discussions/_diff_discussion"
      @fresh_discussion = true # rubocop:disable Gitlab/ModuleWithInstanceVariables

      locals = { discussions: [discussion], on_image: on_image }
    end

    render_to_string(
      template,
      layout: false,
      formats: [:html],
      locals: locals
    )
  end

  def discussion_html(discussion)
    return if discussion.individual_note?

    render_to_string(
      "discussions/_discussion",
      layout: false,
      formats: [:html],
      locals: { discussion: discussion }
    )
  end

  def authorize_admin_note!
    return access_denied! unless can?(current_user, :admin_note, note)
  end

  def create_note_params
    params.require(:note).permit(
      :type,
      :note,
      :line_code, # LegacyDiffNote
      :position # DiffNote
    ).tap do |create_params|
      create_params.merge!(
        params.permit(:merge_request_diff_head_sha, :in_reply_to_discussion_id)
      )

      # These params are also sent by the client but we need to set these based on
      # target_type and target_id because we're checking permissions based on that
      create_params[:noteable_type] = noteable.class.name

      case noteable
      when Commit
        create_params[:commit_id] = noteable.id
      when MergeRequest
        create_params[:noteable_id] = noteable.id
        # Notes on MergeRequest can have an extra `commit_id` context
        create_params[:commit_id] = params.dig(:note, :commit_id)
      else
        create_params[:noteable_id] = noteable.id
      end
    end
  end

  def update_note_params
    params.require(:note).permit(:note, :position)
  end

  def set_polling_interval_header(interval: 6000)
    Gitlab::PollingInterval.set_header(response, interval: interval)
  end

  def noteable
    @noteable ||= notes_finder.target || @note&.noteable # rubocop:disable Gitlab/ModuleWithInstanceVariables
  end

  def require_noteable!
    render_404 unless noteable
  end

  def last_fetched_at
    strong_memoize(:last_fetched_at) do
      microseconds = request.headers['X-Last-Fetched-At'].to_i

      seconds = microseconds / MICROSECOND
      frac = microseconds % MICROSECOND

      Time.zone.at(seconds, frac)
    end
  end

  def notes_filter
    current_user&.notes_filter_for(params[:target_type])
  end

  def notes_finder
    @notes_finder ||= NotesFinder.new(current_user, finder_params)
  end

  def note_serializer
    ProjectNoteSerializer.new(project: project, noteable: noteable, current_user: current_user)
  end

  def discussion_serializer
    DiscussionSerializer.new(project: project, noteable: noteable, current_user: current_user, note_entity: ProjectNoteEntity)
  end

  def note_project
    strong_memoize(:note_project) do
      next nil unless project

      note_project_id = params[:note_project_id]

      the_project =
        if note_project_id.present?
          Project.find(note_project_id)
        else
          project
        end

      next access_denied! unless can?(current_user, :create_note, the_project)

      the_project
    end
  end

  def return_discussion?
    Gitlab::Utils.to_boolean(params[:return_discussion])
  end

  def use_note_serializer?
    return false if params['html']

    noteable.discussions_rendered_on_frontend?
  end
end