module Backend
  # ActiveModel for representing the backend files (special ones and source files too)
  class File
    include ActiveModel::Model

    BUFFER_SIZE = 40_960

    attr_accessor :name
    attr_reader :response

    validates :name, presence: true
    validate :backend_file_errors

    def initialize(attributes = {})
      super
      @file ||= nil
      @response = {}
      @last_read_query = {}
    end

    # Sets the content File object for that model instance, calculates the right response data
    def file=(input_stream)
      Tempfile.open('backend_file', "#{Rails.root}/tmp", encoding: 'ascii-8bit') do |tempfile|
        buffer = ''
        tempfile.write(buffer) while input_stream.read(BUFFER_SIZE, buffer)
        @file = tempfile
      end
    end

    # Sets the content File object from a path
    def file_from_path(path)
      @file = ::File.open(path)
      @response = { type: MiniMime.lookup_by_filename(@file.path).try(:content_type), status: 200, size: @file.size }
      @file.close
    end

    # Returns a File object (closed) that have the content of the Backend file
    def file(query = {})
      if @file.nil? && valid? # Read it from Backend
        Connection.get(full_path(query)) do |backend_response|
          Tempfile.open('backend_file', Dir.tmpdir, encoding: 'ascii-8bit') do |tempfile|
            backend_response.read_body do |buffer|
              tempfile.write(buffer)
            end
            @file = tempfile
            @response = { type: backend_response['Content-Type'], status: backend_response.code, size: @file.size }
          end
        end
        @last_read_query = query
      end
      @file
    rescue => e
      @backend_file_errors = e.message
      valid?
      nil
    end

    # Converts file into a String if it's valid
    def to_s(query = {})
      file(query)
      !@file.nil? && valid? ? ::File.open(@file.path).read : nil
    end

    # Reloads from Backend the file content
    def reload
      @file = nil
      @response = {}
      file(@last_read_query)
    end

    # Tries to save the file to the backend and return the response, otherwise will raise an StandardError
    # If "content" parameter is provided then is passed directly to the backend, otherwise it creates
    # a temp file and then send it to the backend
    def save!(query = {}, content = nil)
      backend_response = nil
      if content
        backend_response = Connection.put(full_path(query), content)
        reload
      else
        @file.open
        backend_response = Connection.put(full_path(query), @file)
        @response = { type: backend_response['Content-Type'], status: backend_response.code, size: backend_response.content_length }
        @file.close
      end
      backend_response
    end

    # Tries to save the file to the backend. Returns nil if some StandardError is raised
    def save(query = {}, content = nil)
      save!(query, content)
    rescue => e
      @backend_file_errors = e.message
      valid?
      nil
    end

    # Tries to destroy the file from the backend, freeze the object and return the response, otherwise will raise an StandardError
    def destroy!(query = {})
      backend_response = Connection.delete(full_path(query))
      @response = { type: backend_response['Content-Type'], status: backend_response.code, size: backend_response.content_length }
      freeze
      @response
    end

    # Tries to destroy the file from the backend. Returns nil if some StandardError is raised
    def destroy(query = {})
      destroy!(query)
    rescue => e
      @backend_file_errors = e.message
      valid?
      nil
    end

    # TODO: Replace SuseBackend.build_query_from_hash with this function asap
    def self.query_from_list(params, key_list = nil)
      key_list ||= params.keys
      query = params.slice(*key_list).to_query
      query.present? ? "?#{query}" : query
    end

    private

    # Validation of errors perfoming commands on the backend
    def backend_file_errors
      return if @backend_file_errors.blank?
      errors.add(:content, @backend_file_errors)
    end
  end
end
