# frozen_string_literal: true

require "fileutils"
require "pathname"
require "digest/md5"
require "active_support/core_ext/numeric/bytes"

module ActiveStorage
  # Wraps a local disk path as an Active Storage service. See ActiveStorage::Service for the generic API
  # documentation that applies to all services.
  class Service::DiskService < Service
    attr_reader :root

    def initialize(root:)
      @root = root
    end

    def upload(key, io, checksum: nil)
      instrument :upload, key, checksum: checksum do
        IO.copy_stream(io, make_path_for(key))
        ensure_integrity_of(key, checksum) if checksum
      end
    end

    def download(key)
      if block_given?
        instrument :streaming_download, key do
          File.open(path_for(key), "rb") do |file|
            while data = file.read(64.kilobytes)
              yield data
            end
          end
        end
      else
        instrument :download, key do
          File.binread path_for(key)
        end
      end
    end

    def delete(key)
      instrument :delete, key do
        begin
          File.delete path_for(key)
        rescue Errno::ENOENT
          # Ignore files already deleted
        end
      end
    end

    def exist?(key)
      instrument :exist, key do |payload|
        answer = File.exist? path_for(key)
        payload[:exist] = answer
        answer
      end
    end

    def url(key, expires_in:, filename:, disposition:, content_type:)
      instrument :url, key do |payload|
        verified_key_with_expiration = ActiveStorage.verifier.generate(key, expires_in: expires_in, purpose: :blob_key)

        generated_url =
          if defined?(Rails.application)
            Rails.application.routes.url_helpers.rails_disk_service_path \
              verified_key_with_expiration,
              filename: filename, disposition: content_disposition_with(type: disposition, filename: filename), content_type: content_type
          else
            "/rails/active_storage/disk/#{verified_key_with_expiration}/#{filename}?content_type=#{content_type}" \
              "&disposition=#{content_disposition_with(type: disposition, filename: filename)}"
          end

        payload[:url] = generated_url

        generated_url
      end
    end

    def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
      instrument :url, key do |payload|
        verified_token_with_expiration = ActiveStorage.verifier.generate(
          {
            key: key,
            content_type: content_type,
            content_length: content_length,
            checksum: checksum
          },
          { expires_in: expires_in,
          purpose: :blob_token }
        )

        generated_url =
          if defined?(Rails.application)
            Rails.application.routes.url_helpers.update_rails_disk_service_path verified_token_with_expiration
          else
            "/rails/active_storage/disk/#{verified_token_with_expiration}"
          end

        payload[:url] = generated_url

        generated_url
      end
    end

    def headers_for_direct_upload(key, content_type:, **)
      { "Content-Type" => content_type }
    end

    private
      def path_for(key)
        File.join root, folder_for(key), key
      end

      def folder_for(key)
        [ key[0..1], key[2..3] ].join("/")
      end

      def make_path_for(key)
        path_for(key).tap { |path| FileUtils.mkdir_p File.dirname(path) }
      end

      def ensure_integrity_of(key, checksum)
        unless Digest::MD5.file(path_for(key)).base64digest == checksum
          delete key
          raise ActiveStorage::IntegrityError
        end
      end
  end
end
