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module Banzai
module Renderer
extend self
# Convert a Markdown String into an HTML-safe String of HTML
#
# Note that while the returned HTML will have been sanitized of dangerous
# HTML, it may post a risk of information leakage if it's not also passed
# through `post_process`.
#
# Also note that the returned String is always HTML, not XHTML. Views
# requiring XHTML, such as Atom feeds, need to call `post_process` on the
# result, providing the appropriate `pipeline` option.
#
# text - Markdown String
# context - Hash of context options passed to our HTML Pipeline
#
# Returns an HTML-safe String
def render(text, context = {})
cache_key = context.delete(:cache_key)
cache_key = full_cache_key(cache_key, context[:pipeline])
if cache_key
Gitlab::Metrics.measure(:banzai_cached_render) do
Rails.cache.fetch(cache_key) do
cacheless_render(text, context)
end
end
else
cacheless_render(text, context)
end
end
# Convert a Markdown-containing field on an object into an HTML-safe String
# of HTML. This method is analogous to calling render(object.field), but it
# can cache the rendered HTML in the object, rather than Redis.
#
# The context to use is learned from the passed-in object by calling
# #banzai_render_context(field), and cannot be changed. Use #render, passing
# it the field text, if a custom rendering is needed. The generated context
# is returned along with the HTML.
def render_field(object, field)
html_field = object.markdown_cache_field_for(field)
html = object.__send__(html_field)
return html if html.present?
html = cacheless_render_field(object, field)
object.update_column(html_field, html) unless object.new_record? || object.destroyed?
html
end
# Same as +render_field+, but without consulting or updating the cache field
def cacheless_render_field(object, field)
text = object.__send__(field)
context = object.banzai_render_context(field)
cacheless_render(text, context)
end
# Perform multiple render from an Array of Markdown String into an
# Array of HTML-safe String of HTML.
#
# As the rendered Markdown String can be already cached read all the data
# from the cache using Rails.cache.read_multi operation. If the Markdown String
# is not in the cache or it's not cacheable (no cache_key entry is provided in
# the context) the Markdown String is rendered and stored in the cache so the
# next render call gets the rendered HTML-safe String from the cache.
#
# For further explanation see #render method comments.
#
# texts_and_contexts - An Array of Hashes that contains the Markdown String (:text)
# an options passed to our HTML Pipeline (:context)
#
# If on the :context you specify a :cache_key entry will be used to retrieve it
# and cache the result of rendering the Markdown String.
#
# Returns an Array containing HTML-safe String instances.
#
# Example:
# texts_and_contexts
# => [{ text: '### Hello',
# context: { cache_key: [note, :note] } }]
def cache_collection_render(texts_and_contexts)
items_collection = texts_and_contexts.each_with_index do |item, index|
context = item[:context]
cache_key = full_cache_multi_key(context.delete(:cache_key), context[:pipeline])
item[:cache_key] = cache_key if cache_key
end
cacheable_items, non_cacheable_items = items_collection.partition { |item| item.key?(:cache_key) }
items_in_cache = []
items_not_in_cache = []
unless cacheable_items.empty?
items_in_cache = Rails.cache.read_multi(*cacheable_items.map { |item| item[:cache_key] })
items_not_in_cache = cacheable_items.reject do |item|
item[:rendered] = items_in_cache[item[:cache_key]]
items_in_cache.key?(item[:cache_key])
end
end
(items_not_in_cache + non_cacheable_items).each do |item|
item[:rendered] = render(item[:text], item[:context])
Rails.cache.write(item[:cache_key], item[:rendered]) if item[:cache_key]
end
items_collection.map { |item| item[:rendered] }
end
def render_result(text, context = {})
text = Pipeline[:pre_process].to_html(text, context) if text
Pipeline[context[:pipeline]].call(text, context)
end
# Perform post-processing on an HTML String
#
# This method is used to perform state-dependent changes to a String of
# HTML, such as removing references that the current user doesn't have
# permission to make (`RedactorFilter`).
#
# html - String to process
# context - Hash of options to customize output
# :pipeline - Symbol pipeline type
# :project - Project
# :user - User object
#
# Returns an HTML-safe String
def post_process(html, context)
context = Pipeline[context[:pipeline]].transform_context(context)
pipeline = Pipeline[:post_process]
if context[:xhtml]
pipeline.to_document(html, context).to_html(save_with: Nokogiri::XML::Node::SaveOptions::AS_XHTML)
else
pipeline.to_html(html, context)
end.html_safe
end
private
def cacheless_render(text, context = {})
Gitlab::Metrics.measure(:banzai_cacheless_render) do
result = render_result(text, context)
output = result[:output]
if output.respond_to?(:to_html)
output.to_html
else
output.to_s
end
end
end
def full_cache_key(cache_key, pipeline_name)
return unless cache_key
["banzai", *cache_key, pipeline_name || :full]
end
# To map Rails.cache.read_multi results we need to know the Rails.cache.expanded_key.
# Other option will be to generate stringified keys on our side and don't delegate to Rails.cache.expanded_key
# method.
def full_cache_multi_key(cache_key, pipeline_name)
return unless cache_key
Rails.cache.send(:expanded_key, full_cache_key(cache_key, pipeline_name))
end
end
end
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