# Helpful utility methods for building queries to a Solr server
# This includes helpers that the Direct connection can use --  not specific to http, for example
module RSolr::Connection::Utils
  
  # Performs URI escaping so that you can construct proper
  # query strings faster.  Use this rather than the cgi.rb
  # version since it's faster.  (Stolen from Rack).
  def escape(s)
    s.to_s.gsub(/([^ a-zA-Z0-9_.-]+)/n) {
      #'%'+$1.unpack('H2'*$1.size).join('%').upcase
      '%'+$1.unpack('H2'*bytesize($1)).join('%').upcase
    }.tr(' ', '+')
  end
  
  # encodes the string as utf-8 in Ruby 1.9
  # returns the unaltered string in Ruby 1.8
  def encode_utf8 string
    (string.respond_to?(:force_encoding) and string.respond_to?(:encoding)) ?
      string.force_encoding(Encoding::UTF_8) : string
  end
  
  # Return the bytesize of String; uses String#size under Ruby 1.8 and
  # String#bytesize under 1.9.
  if ''.respond_to?(:bytesize)
    def bytesize(string)
      string.bytesize
    end
  else
    def bytesize(string)
      string.size
    end
  end
  
  # creates and returns a url as a string
  # "url" is the base url
  # "params" is an optional hash of GET style query params
  # "string_query" is an extra query string that will be appended to the 
  # result of "url" and "params".
  def build_url url='', params={}, string_query=''
    queries = [string_query, hash_to_query(params)]
    queries.delete_if{|i| i.to_s.empty?}
    url += "?#{queries.join('&')}" unless queries.empty?
    url
  end

  # converts a key value pair to an escaped string:
  # Example:
  # build_param(:id, 1) == "id=1"
  def build_param(k,v)
    "#{escape(k)}=#{escape(v)}"
  end

  #
  # converts hash into URL query string, keys get an alpha sort
  # if a value is an array, the array values get mapped to the same key:
  #   hash_to_query(:q=>'blah-query', :fq=>['f1', 'f1'], :facet=>true, 'facet.field'=>['location_facet', 'format_facet'])
  # returns:
  #   ?q=blah-query&fq=f1&fq=f2&facet=true&facet.field=location_facet&facet.field=format.facet
  #
  # if a value is empty/nil etc., it is tossed out
  #
  def hash_to_query(params)
    mapped = params.map do |k, v|
      next if v.to_s.empty?
      if v.class == Array
        hash_to_query(v.map { |x| [k, x] })
      else
        build_param k, v
      end
    end
    mapped.compact.join("&")
  end
  
end