# app/models/comment.rb
class Comment < ApplicationRecord
  belongs_to :post
  belongs_to :user

  # 自关联：支持无限嵌套
  belongs_to :parent, class_name: "Comment", optional: true
  has_many :replies, class_name: "Comment", foreign_key: :parent_id, dependent: :destroy

  # 排序：顶级评论时间倒序，子评论时间正序
  scope :top_level, -> { where(parent_id: nil) }
  scope :ordered, -> { order(created_at: :asc) }

  # 构建嵌套树（视图用）
  def self.build_tree(comments)
    comments = comments.includes(:user).to_a
    tree = []
    map = {}

    comments.each do |comment|
      map[comment.id] = comment
      comment.replies = []
    end

    comments.each do |comment|
      if comment.parent_id
        map[comment.parent_id]&.replies << comment
      else
        tree << comment
      end
    end

    tree
  end
end