# frozen_string_literal: true

# Contains functionality shared between `DiffDiscussion` and `LegacyDiffDiscussion`.
module DiscussionOnDiff
  extend ActiveSupport::Concern

  NUMBER_OF_TRUNCATED_DIFF_LINES = 16

  TruncatedDiffLinesError = Class.new(StandardError)

  included do
    delegate :line_code,
      :original_line_code,
      :note_diff_file,
      :diff_line,
      :active?,
      :created_at_diff?,
      to: :first_note

    delegate :file_path,
      :blob,
      :highlighted_diff_lines,
      :diff_lines,
      to: :diff_file,
      allow_nil: true
  end

  def diff_discussion?
    true
  end

  def file_new_path
    first_note.position.new_path
  end

  def on_merge_request_commit?
    for_merge_request? && commit_id.present?
  end

  # Returns an array of at most 16 highlighted lines above a diff note
  def truncated_diff_lines(highlight: true, diff_limit: nil)
    return [] unless on_text?
    return [] if diff_line.nil?

    diff_limit = [diff_limit, NUMBER_OF_TRUNCATED_DIFF_LINES].compact.min
    lines = highlight ? highlighted_diff_lines : diff_lines

    initial_line_index = [diff_line.index - diff_limit + 1, 0].max

    prev_lines = []

    lines = lines[initial_line_index..diff_line.index]

    return [] if lines.nil?

    lines.each do |line|
      if line.meta?
        prev_lines.clear
      else
        prev_lines << line
      end
    end

    prev_lines
  end

  def diff_file
    strong_memoize(:diff_file) do
      # Falling back here is important as `note_diff_files` are created async.
      fetch_preloaded_diff_file || first_note.diff_file
    end
  end

  def line_code_in_diffs(diff_refs)
    if active?(diff_refs)
      line_code
    elsif diff_refs && created_at_diff?(diff_refs)
      original_line_code
    end
  end

  private

  def fetch_preloaded_diff_file
    fetch_preloaded_diff =
      context_noteable &&
      context_noteable.preloads_discussion_diff_highlighting? &&
      note_diff_file

    context_noteable.discussions_diffs.find_by_id(note_diff_file.id) if fetch_preloaded_diff
  end
end
