class ElasticAPM::TraceContext

def self.parse(header)
  raise InvalidTraceparentHeader unless header.length == 55
  raise InvalidTraceparentHeader unless header[0..1] == VERSION
  new.tap do |t|
    t.version, t.trace_id, t.parent_id, t.flags =
      header.split('-').tap do |values|
        values[-1] = Util.hex_to_bits(values[-1])
      end
    raise InvalidTraceparentHeader if HEX_REGEX =~ t.trace_id
    raise InvalidTraceparentHeader if HEX_REGEX =~ t.parent_id
  end
end

def child
  dup.tap do |tc|
    tc.parent_id = tc.id
    tc.id = hex(ID_LENGTH)
  end
end

def ensure_parent_id
  @parent_id ||= hex(ID_LENGTH)
end

def flags
  format('0000000%d', recorded? ? 1 : 0)
end

def flags=(flags)
  @flags = flags
  self.recorded = flags[7] == '1'
end

def hex(len)
  SecureRandom.hex(len)
end

def hex_flags
  format('%02x', flags.to_i(2))
end

def initialize(
  version: VERSION,
  trace_id: nil,
  span_id: nil,
  id: nil,
  recorded: true
)
  @version = version
  @trace_id = trace_id || hex(TRACE_ID_LENGTH)
  # TODO: rename to parent_id with next major version bump
  @parent_id = span_id
  @id = id || hex(ID_LENGTH)
  @recorded = recorded
end

def span_id
  @parent_id
end

def span_id=(span_id)
  @parent_id = span_id
end

def to_header
  format('%s-%s-%s-%s', version, trace_id, id, hex_flags)
end