drrb/puppet-library

# -*- encoding: utf-8 -*-
# Puppet Library
# Copyright (C) 2014 drrb
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

module PuppetLibrary::Http
    module Cache
        class InMemory
            ARBITRARY_CACHE_TTL_SECONDS = 10
            def initialize(seconds_to_live = ARBITRARY_CACHE_TTL_SECONDS)
                @reaper = Reaper.new(seconds_to_live)
            end

            def get(key = "entry")
                entry = retrieve(key)
                if entry
                    return entry.value unless @reaper.wants_to_kill? entry
                end

                value = yield
                save(key, Entry.new(value))
                return value
            end

            def retrieve(key)
                cache[key]
            end

            def save(key, entry)
                cache[key] = entry
            end

            def clear
                @cache.clear
            end

            private
            def cache
                @cache ||= {}
            end

            class Entry
                attr_accessor :value

                def initialize(value)
                    @birth = Time.now
                    @value = value
                end

                def age
                    Time.now - @birth
                end
            end

            class Reaper
                def initialize(time_to_let_live)
                    @time_to_let_live = time_to_let_live
                end

                def wants_to_kill?(entry)
                    entry.age > @time_to_let_live
                end
            end
        end
    end
end