152 lines
4.8 KiB
Ruby
152 lines
4.8 KiB
Ruby
# This module takes care of updating cache columns for Markdown-containing
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# fields. Use like this in the body of your class:
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#
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# include CacheMarkdownField
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# cache_markdown_field :foo
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# cache_markdown_field :bar
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# cache_markdown_field :baz, pipeline: :single_line
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#
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# Corresponding foo_html, bar_html and baz_html fields should exist.
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module CacheMarkdownField
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extend ActiveSupport::Concern
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# Increment this number every time the renderer changes its output
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CACHE_VERSION = 2
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# changes to these attributes cause the cache to be invalidates
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INVALIDATED_BY = %w[author project].freeze
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# Knows about the relationship between markdown and html field names, and
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# stores the rendering contexts for the latter
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class FieldData
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def initialize
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@data = {}
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end
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delegate :[], :[]=, to: :@data
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def markdown_fields
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@data.keys
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end
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def html_field(markdown_field)
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"#{markdown_field}_html"
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end
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def html_fields
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markdown_fields.map {|field| html_field(field) }
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end
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end
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def skip_project_check?
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false
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end
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# Returns the default Banzai render context for the cached markdown field.
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def banzai_render_context(field)
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raise ArgumentError.new("Unknown field: #{field.inspect}") unless
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cached_markdown_fields.markdown_fields.include?(field)
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# Always include a project key, or Banzai complains
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project = self.project if self.respond_to?(:project)
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context = cached_markdown_fields[field].merge(project: project)
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# Banzai is less strict about authors, so don't always have an author key
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context[:author] = self.author if self.respond_to?(:author)
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context
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end
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# Update every column in a row if any one is invalidated, as we only store
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# one version per row
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def refresh_markdown_cache!(do_update: false)
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options = { skip_project_check: skip_project_check? }
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updates = cached_markdown_fields.markdown_fields.map do |markdown_field|
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[
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cached_markdown_fields.html_field(markdown_field),
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Banzai::Renderer.cacheless_render_field(self, markdown_field, options)
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]
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end.to_h
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updates['cached_markdown_version'] = CacheMarkdownField::CACHE_VERSION
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updates.each {|html_field, data| write_attribute(html_field, data) }
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update_columns(updates) if persisted? && do_update
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end
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def cached_html_up_to_date?(markdown_field)
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html_field = cached_markdown_fields.html_field(markdown_field)
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cached = cached_html_for(markdown_field).present? && __send__(markdown_field).present?
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return false unless cached
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markdown_changed = attribute_changed?(markdown_field) || false
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html_changed = attribute_changed?(html_field) || false
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CacheMarkdownField::CACHE_VERSION == cached_markdown_version &&
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(html_changed || markdown_changed == html_changed)
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end
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def invalidated_markdown_cache?
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cached_markdown_fields.html_fields.any? {|html_field| attribute_invalidated?(html_field) }
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end
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def attribute_invalidated?(attr)
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__send__("#{attr}_invalidated?")
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end
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def cached_html_for(markdown_field)
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raise ArgumentError.new("Unknown field: #{field}") unless
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cached_markdown_fields.markdown_fields.include?(markdown_field)
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__send__(cached_markdown_fields.html_field(markdown_field))
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end
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included do
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cattr_reader :cached_markdown_fields do
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FieldData.new
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end
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# Always exclude _html fields from attributes (including serialization).
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# They contain unredacted HTML, which would be a security issue
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alias_method :attributes_before_markdown_cache, :attributes
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def attributes
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attrs = attributes_before_markdown_cache
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attrs.delete('cached_markdown_version')
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cached_markdown_fields.html_fields.each do |field|
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attrs.delete(field)
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end
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attrs
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end
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# Using before_update here conflicts with elasticsearch-model somehow
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before_create :refresh_markdown_cache!, if: :invalidated_markdown_cache?
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before_update :refresh_markdown_cache!, if: :invalidated_markdown_cache?
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end
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class_methods do
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private
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# Specify that a field is markdown. Its rendered output will be cached in
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# a corresponding _html field. Any custom rendering options may be provided
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# as a context.
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def cache_markdown_field(markdown_field, context = {})
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cached_markdown_fields[markdown_field] = context
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html_field = cached_markdown_fields.html_field(markdown_field)
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invalidation_method = "#{html_field}_invalidated?".to_sym
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# The HTML becomes invalid if any dependent fields change. For now, assume
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# author and project invalidate the cache in all circumstances.
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define_method(invalidation_method) do
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changed_fields = changed_attributes.keys
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invalidations = changed_fields & [markdown_field.to_s, *INVALIDATED_BY]
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!invalidations.empty? || !cached_html_up_to_date?(markdown_field)
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end
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end
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end
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end
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