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require "cabin/namespace"
# Logging context exists to make it easy to add and later undo any changes made
# to the context data associated with a given Logging::Channel
#
# Usage:
#
# context = channel.context
# context["foo"] = "Hello world!"
# channel.info("Sample log") # output includes { "foo" => "Hello world!" }
# context.clear
# channel.info("Sample log 2") # context cleared, key "foo" removed.
#
# Essentially, a Cabin::Context acts as a transactional proxy on top of a
# Cabin::Channel. Any changes you make in a context are passed through to
# the channel while keeping an ordered record of the changes made so
# you can unroll those changes when the context is no longer needed..
#
class Cabin::Context
def initialize(channel)
@changes = []
@channel = channel
end # def initialize
def on_clear(&block)
@clear_callback = block
end # def on_clear
def []=(key, value)
# Maintain a record of what was changed so clear() can undo this context.
# This record is in reverse order so it can be undone in reverse later.
@changes.unshift([key, value, @channel[key]])
@channel[key] = value
end # def []=
def [](key)
@channel[key]
end # def []
# Undo any changes made to the channel by this context.
def clear
@changes.each do |key, value, original|
if original.nil?
@channel.remove(key)
else
@channel[key] = original
end
end
end # def clear
end # class Cabin::Context
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