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module MetadataSupport
extend ActiveSupport::Concern
included do
class << self
def has_metadata?
!!@has_metadata
end
def has_metadata opts={}
@has_metadata = true
define_method :metadata do
attr_name = opts[:attr_name] || :metadata
@wrapped_metadata ||= begin
wrapped = MetadataSupport::MetadataWrapper.new self.read_attribute(attr_name)
wrapped.attribute_name = attr_name
wrapped.owner = self
wrapped
end
end
define_method :metadata= do |val|
@wrapped_metadata = nil
super val
end
define_method :set_metadata! do |name, value|
self.metadata.send "#{name}=", value
self.save!
end
end
end
end
def has_metadata?
self.class.has_metadata?
end
def merge_metadata_from source
return unless source.has_metadata?
source_metadata = source.metadata
res = {}
self.metadata.each do |k, v|
unless self.metadata.is_timestamp_attr?(k)
ts = self.metadata.timestamp_attr(k)
if source_metadata[ts] && source_metadata[ts] > self.metadata[ts]
res[k] = source_metadata[k]
else
res[k] = v
end
end
end
self.metadata = res
self
end
class MetadataWrapper < OpenStruct
attr_accessor :attribute_name, :owner
def is_timestamp_attr? name
name =~ /_updated_at$/
end
def timestamp_attr name
"#{name}_updated_at".to_sym
end
def as_json *args
@table.as_json *args
end
def method_missing(mid, *args)
out = super(mid, *args)
owner.send :write_attribute, attribute_name, @table
out = out&.to_time if args.length == 0 && is_timestamp_attr?(mid)
out
end
def each
@table.each do |k,v|
yield k, v
end
end
def new_ostruct_member name
unless is_timestamp_attr?(name)
timestamp_attr_name = timestamp_attr(name)
end
name = name.to_sym
unless respond_to?(name)
if timestamp_attr_name
define_singleton_method(timestamp_attr_name) { @table[timestamp_attr_name]&.to_time }
define_singleton_method(name) { @table[name] }
else
# we are defining an accessor for a timestamp
define_singleton_method(name) { @table[name]&.to_time }
end
define_singleton_method("#{name}=") do |x|
modifiable[timestamp_attr_name] = Time.now if timestamp_attr_name
modifiable[name] = x
owner.send :write_attribute, attribute_name, @table
end
modifiable[timestamp_attr_name] = Time.now if timestamp_attr_name
end
name
end
end
end
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