module Gapic::Protobuf

def self.coerce hash, to:
  return hash if hash.is_a? to
  return nil if hash.nil?
  # Special case handling of certain types
  return time_to_timestamp hash if to == Google::Protobuf::Timestamp && hash.is_a?(Time)
  # Sanity check: input must be a Hash
  raise ArgumentError, "Value #{hash} must be a Hash or a #{to.name}" unless hash.is_a? Hash
  hash = coerce_submessages hash, to.descriptor
  to.new hash
end

def self.coerce_submessage val, field_descriptor
  if val.is_a? Array
    # Assume this is a repeated message field, iterate over it and coerce
    # each to the message class.
    # Protobuf will raise an error if this assumption is incorrect.
    val.map do |elem|
      coerce elem, to: field_descriptor.subtype.msgclass
    end
  elsif field_descriptor.label == :repeated
    # Non-array passed to a repeated field: assume this is a map, and that
    # a hash is being passed, and let protobuf handle the conversion.
    # Protobuf will raise an error if this assumption is incorrect.
    val
  else
    # Assume this is a normal single message, and coerce to the message
    # class.
    coerce val, to: field_descriptor.subtype.msgclass
  end
end

def self.coerce_submessages hash, message_descriptor
  return nil if hash.nil?
  coerced = {}
  hash.each do |key, val|
    field_descriptor = message_descriptor.lookup key.to_s
    coerced[key] =
      if field_descriptor&.type == :message
        coerce_submessage val, field_descriptor
      elsif field_descriptor&.type == :bytes && (val.is_a?(IO) || val.is_a?(StringIO))
        val.binmode.read
      else
        # For non-message fields, just pass the scalar value through.
        # Note: if field_descriptor is not found, we just pass the value
        # through and let protobuf raise an error.
        val
      end
  end
  coerced
end

def self.time_to_timestamp time
  Google::Protobuf::Timestamp.new seconds: time.to_i, nanos: time.nsec
end

def self.timestamp_to_time timestamp
  Time.at timestamp.seconds, timestamp.nanos, :nanosecond
end