# 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: 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: key do
          File.open(path_for(key), "rb") do |file|
            while data = file.read(5.megabytes)
              yield data
            end
          end
        end
      else
        instrument :download, key: key do
          File.binread path_for(key)
        end
      end
    end

    def download_chunk(key, range)
      instrument :download_chunk, key: key, range: range do
        File.open(path_for(key), "rb") do |file|
          file.seek range.begin
          file.read range.size
        end
      end
    end

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

    def delete_prefixed(prefix)
      instrument :delete_prefixed, prefix: prefix do
        Dir.glob(path_for("#{prefix}*")).each do |path|
          FileUtils.rm_rf(path)
        end
      end
    end

    def exist?(key)
      instrument :exist, key: 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: key do |payload|
        content_disposition = content_disposition_with(type: disposition, filename: filename)
        verified_key_with_expiration = ActiveStorage.verifier.generate(
          {
            key: key,
            disposition: content_disposition,
            content_type: content_type
          },
          { expires_in: expires_in,
          purpose: :blob_key }
        )

        generated_url = url_helpers.rails_disk_service_url(verified_key_with_expiration,
          host: current_host,
          disposition: content_disposition,
          content_type: content_type,
          filename: filename
        )
        payload[:url] = generated_url

        generated_url
      end
    end

    def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:)
      instrument :url, key: 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 = url_helpers.update_rails_disk_service_url(verified_token_with_expiration, host: current_host)

        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

      def url_helpers
        @url_helpers ||= Rails.application.routes.url_helpers
      end

      def current_host
        ActiveStorage::Current.host
      end
  end
end