class PostCreatePreflight
  class ValidationFailed < StandardError
    attr_reader :fields, :base_errors

    def initialize fields: { }, base_errors: []
      super('入力内容を確認してください．')
      @fields = fields
      @base_errors = base_errors
    end
  end

  def initialize attributes:, thumbnail: nil
    @attributes = attributes.symbolize_keys
    @thumbnail = thumbnail
  end

  def run
    preview = PostImportPreviewer.new.preview_rows(
        rows: [preview_row],
        fetch_metadata: false).first

    validate_thumbnail_upload!

    if preview[:validation_errors].present?
      raise ValidationFailed.new(fields: preview[:validation_errors])
    end

    {
        url: preview[:url],
        title: preview[:attributes]['title'],
        thumbnail_base: preview[:attributes]['thumbnail_base'],
        tags: preview[:attributes]['tags'],
        parent_post_ids: preview[:attributes]['parent_post_ids'],
        original_created_from: preview[:attributes]['original_created_from'],
        original_created_before: preview[:attributes]['original_created_before'],
        duration: preview[:attributes]['duration'],
        video_ms: preview[:attributes]['video_ms'],
        field_warnings: preview[:field_warnings],
        base_warnings: preview[:base_warnings],
        existing_post: existing_post_compact(preview[:existing_post_id]) }
  end

  private

  def preview_row
    {
        source_row: 1,
        url: @attributes[:url].to_s,
        attributes: {
            'title' => @attributes[:title].to_s,
            'thumbnail_base' => @attributes[:thumbnail_base].to_s,
            'original_created_from' => @attributes[:original_created_from].to_s,
            'original_created_before' => @attributes[:original_created_before].to_s,
            'duration' => @attributes[:duration].to_s,
            'video_ms' => @attributes[:video_ms],
            'tags' => @attributes[:tags].to_s,
            'parent_post_ids' => parent_post_ids_text },
        provenance: {
            'url' => 'manual',
            'title' => 'manual',
            'thumbnail_base' => 'manual',
            'original_created_from' => 'manual',
            'original_created_before' => 'manual',
            'duration' => 'manual',
            'video_ms' => 'manual',
            'tags' => 'manual',
            'parent_post_ids' => 'manual' },
        tag_sources: {
            'automatic' => '',
            'manual' => @attributes[:tags].to_s } }
  end

  def parent_post_ids_text
    Array(@attributes[:parent_post_ids]).flat_map { _1.to_s.split }.join(' ')
  end

  def validate_thumbnail_upload!
    return if @attributes[:thumbnail_base].present?
    return if @thumbnail.blank?

    attachment = Post.resized_thumbnail_attachment(@thumbnail)
    attachment[:io].close if attachment[:io].respond_to?(:close)
  rescue MiniMagick::Error
    raise ValidationFailed.new(fields: { thumbnail: ['サムネイル画像の変換に失敗しました．'] })
  end

  def existing_post_compact post_id
    return nil if post_id.blank?

    post = Post.with_attached_thumbnail.find_by(id: post_id)
    return nil if post.nil?

    {
        id: post.id,
        title: post.title,
        url: post.url,
        thumbnail_url:
            if post.thumbnail.attached?
              Rails.application.routes.url_helpers.rails_storage_proxy_url(
                  post.thumbnail,
                  only_path: false)
            end }
  end
end