btrc-hub/backend/app/controllers/posts_controller.rb

class PostsController < ApplicationController
  # GET /posts
  def index
    limit = params[:limit].presence&.to_i
    cursor = params[:cursor].presence

    created_at = ('COALESCE(posts.original_created_before - INTERVAL 1 SECOND,' +
                  'posts.original_created_from,' +
                  'posts.created_at)')
    q = filtered_posts.order(Arel.sql("#{ created_at } DESC"))
    q = q.where("#{ created_at } < ?", Time.iso8601(cursor)) if cursor

    posts = limit ? q.limit(limit + 1) : q

    next_cursor = nil
    if limit && posts.size > limit
      next_cursor = posts.last.created_at.iso8601(6)
      posts = posts.first(limit)
    end

    render json: { posts: posts.map { |post|
      post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }).tap do |json|
        json['thumbnail'] =
            if post.thumbnail.attached?
              rails_storage_proxy_url(post.thumbnail, only_path: false)
            else
              nil
            end
      end
    }, next_cursor: }
  end

  def random
    post = filtered_posts.order('RAND()').first
    return head :not_found unless post

    viewed = current_user&.viewed?(post) || false

    render json: (post
                  .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
                  .merge(viewed:))
  end

  # GET /posts/1
  def show
    post = Post.includes(:tags).find(params[:id])
    return head :not_found unless post

    viewed = current_user&.viewed?(post) || false

    render json: (post
                  .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
                  .merge(related: post.related(limit: 20), viewed:))
  end

  # POST /posts
  def create
    return head :unauthorized unless current_user
    return head :forbidden unless current_user.member?

    # TODO: URL が正規のものがチェック，不正ならエラー
    # TODO: URL は必須にする（タイトルは省略可）．
    # TODO: サイトに応じて thumbnail_base 設定
    title = params[:title]
    url = params[:url]
    thumbnail = params[:thumbnail]
    tag_names = params[:tags].to_s.split(' ')
    original_created_from = params[:original_created_from]
    original_created_before = params[:original_created_before]

    post = Post.new(title:, url:, thumbnail_base: '', uploaded_user: current_user,
                    original_created_from:, original_created_before:)
    post.thumbnail.attach(thumbnail)
    if post.save
      post.resized_thumbnail!
      sync_post_tags!(post, Tag.normalise_tags(tag_names))
      render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
             status: :created
    else
      render json: { errors: post.errors.full_messages }, status: :unprocessable_entity
    end
  end

  def viewed
    return head :unauthorized unless current_user

    current_user.viewed_posts << Post.find(params[:id])
    head :no_content
  end

  def unviewed
    return head :unauthorized unless current_user

    current_user.viewed_posts.delete(Post.find(params[:id]))
    head :no_content
  end

  # PATCH/PUT /posts/1
  def update
    return head :unauthorized unless current_user
    return head :forbidden unless current_user.member?

    title = params[:title]
    tag_names = params[:tags].to_s.split(' ')
    original_created_from = params[:original_created_from]
    original_created_before = params[:original_created_before]

    post = Post.find(params[:id].to_i)
    if post.update(title:, original_created_from:, original_created_before:)
      sync_post_tags!(post,
                      (post.tags.where(category: 'nico').to_a +
                       Tag.normalise_tags(tag_names)))
      render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
             status: :ok
    else
      render json: post.errors, status: :unprocessable_entity
    end
  end

  # DELETE /posts/1
  def destroy
  end

  private

  def filtered_posts
    tag_names = params[:tags]&.split(' ')
    match_type = params[:match]
    if tag_names.present?
      filter_posts_by_tags(tag_names, match_type)
    else
      Post.all
    end
  end

  def filter_posts_by_tags tag_names, match_type
    posts = Post.joins(:tags)
    if match_type == 'any'
      posts = posts.where(tags: { name: tag_names }).distinct
    else
      tag_names.each do |tag|
        posts = posts.where(id: Post.joins(:tags).where(tags: { name: tag }))
      end
    end
    posts.distinct
  end

  def sync_post_tags! post, desired_tags
    desired_tags.each do |t|
      t.save! if t.new_record?
    end

    desired_ids = desired_tags.map(&:id).to_set
    current_ids = post.tags.pluck(:id).to_set

    to_add = desired_ids - current_ids
    to_remove = current_ids - desired_ids

    Tag.where(id: to_add).find_each do |tag|
      begin
        PostTag.create!(post:, tag:, created_user: current_user)
      rescue ActiveRecord::RecordNotUnique
        ;
      end
    end

    PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
      pt.discard_by!(current_user)
    end
  end
end