class Sass::Script::Tree::StringInterpolation

def _perform(environment)
  res = ""
  before = @before.perform(environment)
  res << before.value
  mid = @mid.perform(environment)
  res << (mid.is_a?(Sass::Script::Value::String) ? mid.value : mid.to_s(:quote => :none))
  res << @after.perform(environment).value
  opts(Sass::Script::Value::String.new(res, before.type))
end

def _to_sass(string_or_interp, opts)
  result = string_or_interp.to_sass(opts)
  opts[:quote] == :none ? result : result.slice(1...-1)
end

def children
  [@before, @mid, @after].compact
end

def deep_copy
  node = dup
  node.instance_variable_set('@before', @before.deep_copy) if @before
  node.instance_variable_set('@mid', @mid.deep_copy)
  node.instance_variable_set('@after', @after.deep_copy) if @after
  node
end

def initialize(before, mid, after)
  @before = before
  @mid = mid
  @after = after
end

def inspect
  "(string_interpolation #{@before.inspect} #{@mid.inspect} #{@after.inspect})"
end

def quote
  quote_for(self) || '"'
end

def quote_for(string_or_interp)
  if string_or_interp.is_a?(Sass::Script::Tree::Literal)
    return nil if string_or_interp.value.value.empty?
    return '"' if string_or_interp.value.value.include?("'")
    return "'" if string_or_interp.value.value.include?('"')
    return nil
  end
  # Double-quotes take precedence over single quotes.
  before_quote = quote_for(string_or_interp.before)
  return '"' if before_quote == '"'
  after_quote = quote_for(string_or_interp.after)
  return '"' if after_quote == '"'
  # Returns "'" if either or both insist on single quotes, and nil
  # otherwise.
  before_quote || after_quote
end

def to_sass(opts = {})
  quote = type == :string ? opts[:quote] || quote_for(self) || '"' : :none
  opts = opts.merge(:quote => quote)
  res = ""
  res << quote if quote != :none
  res << _to_sass(before, opts)
  res << '#{' << @mid.to_sass(opts.merge(:quote => nil)) << '}'
  res << _to_sass(after, opts)
  res << quote if quote != :none
  res
end

def type
  @before.value.type
end