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class ActiveRecord::Base
  def merge_conditions(base_conditions, new_conditions, boolean_operator="AND")
    "(#{sanitize_sql(base_conditions)}) #{boolean_operator} (#{sanitize_sql(new_conditions)})"
  end
end

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# used for building a conditions string for an ActiveRecord find
# 
# usage:
#   
#   conditions = Conditioner.new
#   conditions << ['open = ? AND user_id = ?', 1, @user.id]
#   conditions << ['search_term LIKE ? ', "%#{params[:search_term]}"]
#   
#   Opportunity.find(:all, :conditions => conditions.to_conditions)
#   # select * from opportunity WHERE open = 1 AND user_id = 1 AND search_term LIKE '%hello%'
class Conditioner
  
  attr_reader :conditions 

  def initialize
    @conditions = []
  end
  
  # adds an array to the conditioner
  #
  # usage:
  #
  #   conditions = Conditioner.new
  #   conditions << ['open = ? AND user_id = ?', 1, @user.id]
  #
  def <<(con)
    @conditions << ActiveRecord::Base.send(:sanitize_sql_array, con)
  end
  
  alias_method :add, :<<
  
  
  # outputs the conditions in a string
  #
  # params:
  #
  #  * seperator (choose either AND or OR, defaults to AND)
  def to_conditions(seperator="AND")
    @conditions.join(" #{seperator} ")
  end
  
  
end

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# Merges two sets of condition options for ActiveRecord::Base find calls
def merge_conditions(base_conditions, new_conditions, boolean_operator="AND")
  return base_conditions if new_conditions.blank?
  return new_conditions  if base_conditions.blank?

  "(#{sanitize_sql(base_conditions)}) #{boolean_operator} (#{sanitize_sql(new_conditions)})"
end

# Permanently pulls any conditions found in options and merges them with the base set of conditions
def pull_conditions_and_merge!(base_conditions, options, boolean_operator="AND")
  option_conditions = options.delete(:conditions)
  merge_conditions(base_conditions, option_conditions, boolean_operator)
end

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DB[:users].filter(:country => "US").or("confirmed = ?", 1).filter("ids NOT IN (?)", [1, 10, 100])
#=> SELECT * FROM users WHERE country = 'US' OR confirmed = 1 AND ids NOT IN (1,10,100)