class Scope
  def initialize(parent = {})
    @parent = parent
    @symbols = {}
  end

  def [](name)
    @symbols[name] || @parent[name]
  end

  def []=(name, value)
    @symbols[name] = value
  end

  def merge(scope)
    @symbols.merge!(scope)
  end

  def override_scope(scope)
    scope.merge!(@symbols)
    @symbols = scope
  end

  def retrieve_scope
    @symbols
  end

  def define(name, &block)
    self[name] =  Function.new(&block)
  end

  def syntax(name, &block)
    self[name] =  Syntax.new(&block)
  end
end

class TopLevel < Scope
  def initialize
    super

    syntax('set') do |scope, cells|
      scope[cells.first.text_value] = cells[1].eval(scope)
    end

    syntax('post') do |scope, cells|
      uri = cells.shift.text_value.gsub('"', '')
      payload = {}
      cells.each do |key|
        payload[key.text_value] = scope[key.text_value]
      end
      begin
        response = RestClient.post uri, payload
        scope = scope.merge(response) if response.is_a?(Hash)
      rescue RestClient::Exception => e
        scope['_errors'] = e.message
      end
      scope
    end

    define('+') {|a,b| a.to_f + b.to_f }
    define('-') {|a,b| a.to_f - b.to_f }
    define('*') {|a,b| a.to_f * b.to_f }
    define('/') {|a,b| a.to_f / b.to_f }
    define('=') {|a,b| a == b }
    define('>') {|a,b| a.to_f > b.to_f }
    define('<') {|a,b| a.to_f < b.to_f }
    define('>=') {|a,b| a.to_f >= b.to_f }
    define('<=') {|a,b| a.to_f <= b.to_f }
    define('and') {|a,b| !!a && !!b }
    define('or') {|a,b| !!a || !!b }
    define('sum') { |*args| args.flatten.map(&:to_f).reduce(:+) }
    define('if') { |*args| args.compact!; args[0] ? args[1] : args[2] }
  end
end