require 'cgi'

module Parse

  class Query
    attr_accessor :where
    attr_accessor :class_name
    attr_accessor :order_by
    attr_accessor :order
    attr_accessor :limit
    attr_accessor :skip
    attr_accessor :count

    def initialize(cls_name)
      @class_name = cls_name
      @where = {}
      @order = :ascending
      @ors = []
    end

    def add_constraint(field, constraint)
      raise ArgumentError, "cannot add constraint to an $or query" if @ors.size > 0
      current = where[field]
      if current && current.is_a?(Hash) && constraint.is_a?(Hash)
        current.merge! constraint
      else
        where[field] = constraint
      end
    end
    #private :add_constraint

    def or(query)
      raise ArgumentError, "you must pass an entire #{self.class} to \#or" unless query.is_a?(self.class)
      @ors << query
      self
    end

    def eq(field, value)
      add_constraint field, value
      self
    end
    
    def not_eq(field, value)
      add_constraint field, { "$ne" => value }
      self
    end

    def regex(field, expression)
      add_constraint field, { "$regex" => expression }
      self
    end

    def less_than(field, value)
      add_constraint field, { "$lt" => value }
      self
    end

    def less_eq(field, value)
      add_constraint field, { "$lte" => value }
      self
    end

    def greater_than(field, value)
      add_constraint field, { "$gt" => value }
      self
    end

    def greater_eq(field, value)
      add_constraint field, { "$gte" => value }
      self
    end

    def value_in(field, values)
      add_constraint field, { "$in" => values }
      self
    end

    def exists(field, value = true)
      add_constraint field, { "$exists" => value }
      self
    end

    def in_query(field, query)
      query_hash = {Parse::Protocol::KEY_CLASS_NAME => query.class_name, "where" => query.where}
      add_constraint(field, "$inQuery" => query_hash)
      self
    end
    
    def limit(num)
      @limit = num
      self
    end
    
    def order(field, order = :ascending)
      @order_by = field
      @order = order
      self
    end

    def count
      @count = true
      self
    end

    def where_as_json
      if @ors.size > 0
        {"$or" => [self.where] + @ors.map{|query| query.where_as_json}}
      else
        @where
      end
    end

    def get
      uri   = Protocol.class_uri @class_name
      if @class_name == Parse::Protocol::CLASS_USER
        uri = Protocol.user_uri
      end


      query = { "where" => CGI.escape(where_as_json.to_json) }
      set_order(query)
      [:count, :limit, :skip].each {|a| merge_attribute(a, query)}

      response = Parse.client.request uri, :get, nil, query
      Parse.parse_json class_name, response
    end

    private

    def set_order(query)
      return unless @order_by
      order_string = @order_by
      order_string = "-#{order_string}" if @order == :descending
      query.merge!(:order => order_string)
    end

    def merge_attribute(attribute, query)
      value = self.instance_variable_get("@#{attribute.to_s}")
      return if value.nil?
      query.merge!(attribute => value)
    end
  end

end