#
# Simple Ruby Cache
# Ken Wronkiewicz 
#
# Version 1.00 - Inital release - Ken Wronkiewicz
#
# Docs on https://www.wirewd.com/hacks/marginal/simplecache/
#
# Copyright (c) 2007 Ken Wronkiewicz
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or 
# sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following
# conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.

class Simplecache
  NOCACHE = :NOCACHE

  class Meta
    def initialize(data, forceexpire)
      @added = Time.new
      @used = Time.new
      @expires = Time.new + forceexpire
      @data = data
    end

    def do_access()
      @used = Time.new
      return @data;
    end

    attr_reader :added, :used, :data, :expires
  end

  class CacheControl
    def initialize(data, msg)
      @data = data;
      @msg = msg
    end
    
    attr_reader :data, :msg
  end
  
  def initialize(desiredcount, forceexpire)
    @desiredcount = desiredcount;
    @expire = forceexpire
    @data = Hash.new()
  end
  
  def has_key?(key)
    return @data.has_key?(key)
  end
  
  def clear
    @data.clear()
    @meta.clear()
  end
  
  def expire
    # first we want to expire any nodes.
    now = Time.new();
    @data.delete_if { |key,value|
      if value.expires() < now
	return true
      else
	return false
      end
    }
    # now, see if we still need to expire some
    numtodelete = 0;
    if(@desiredcount != nil)
      x = @data.size() - @desiredcount
      if x > 0 
	numtodelete = x;
      end
    end
    
    if numtodelete != 0
      sorted = @data.sort {
	|a,b| a[1].used <=> b[1].used
      }
      sorted[0,numtodelete].each { |x|
	@data.delete(x[0])
      }
    end
  end

  def work(key)
    if @data.has_key?(key)
      # expire *just* this node if it got too old and fall through.
      if @data[key].expires < Time.new()
	@data.delete(key)
      else
	return @data[key].do_access()
      end
    end
    data = yield
    if data.class != Simplecache::CacheControl
      @data[key] = Simplecache::Meta::new(data,@expire)
      return data
    else
      if data.msg == Simplecache::NOCACHE
	return data.data
      end
    end
  end
end