xml

@dataclass
class XmlSerializer(AbstractSerializer):
    """Xml serializer for data classes.

    Args:
        config: The serializer config instance
        context: The models context instance
        writer: The xml writer class
    """

    config: SerializerConfig = field(default_factory=SerializerConfig)
    context: XmlContext = field(default_factory=XmlContext)
    writer: Type[XmlWriter] = field(default=default_writer())

    def render(self, obj: Any, ns_map: Optional[Dict] = None) -> str:
        """Serialize the input model instance to xml string.

        Args:
            obj: The input model instance to serialize
            ns_map: A user defined namespace prefix-URI map

        Returns:
            The serialized xml string output.
        """
        output = StringIO()
        self.write(output, obj, ns_map)
        return output.getvalue()

    def write(self, out: TextIO, obj: Any, ns_map: Optional[Dict] = None):
        """Serialize the given object to the output text stream.

        Args:
            out: The output text stream
            obj: The input model instance to serialize
            ns_map: A user defined namespace prefix-URI map
        """
        events = self.write_object(obj)
        handler = self.writer(
            config=self.config,
            output=out,
            ns_map=namespaces.clean_prefixes(ns_map) if ns_map else {},
        )
        handler.write(events)

    def write_object(self, obj: Any) -> EventIterator:
        """Convert a user model, or derived element instance to sax events.

        Args:
            obj: A user model, or derived element instance

        Yields:
            An iterator of sax events.
        """
        qname = xsi_type = None
        if isinstance(obj, self.context.class_type.derived_element):
            meta = self.context.build(
                obj.value.__class__, globalns=self.config.globalns
            )
            qname = obj.qname
            obj = obj.value
            xsi_type = self.real_xsi_type(qname, meta.target_qname)

        yield from self.write_dataclass(obj, qname=qname, xsi_type=xsi_type)

    def write_dataclass(
        self,
        obj: Any,
        namespace: Optional[str] = None,
        qname: Optional[str] = None,
        nillable: bool = False,
        xsi_type: Optional[str] = None,
    ) -> EventIterator:
        """Convert a model instance to sax events.

        Optionally override the qualified name and the
        xsi attributes type and nil.

        Args:
            obj: A model instance
            namespace: The field namespace URI
            qname: Override the field qualified name
            nillable: Specifies whether the field is nillable
            xsi_type: Override the field xsi type

        Yields:
            An iterator of sax events.
        """
        meta = self.context.build(
            obj.__class__,
            namespace,
            globalns=self.config.globalns,
        )
        qname = qname or meta.qname
        nillable = nillable or meta.nillable
        namespace, tag = namespaces.split_qname(qname)

        yield XmlWriterEvent.START, qname

        for key, value in self.next_attribute(
            obj, meta, nillable, xsi_type, self.config.ignore_default_attributes
        ):
            yield XmlWriterEvent.ATTR, key, value

        for var, value in self.next_value(obj, meta):
            yield from self.write_value(value, var, namespace)

        yield XmlWriterEvent.END, qname

    def write_xsi_type(
        self,
        value: Any,
        var: XmlVar,
        namespace: Optional[str],
    ) -> EventIterator:
        """Convert a xsi:type value to sax events.

        The value can be assigned to wildcard, element or compound fields

        Args:
            value: A model instance
            var: The field metadata instance
            namespace: The field namespace URI

        Yields:
            An iterator of sax events.
        """
        if var.is_wildcard:
            choice = var.find_value_choice(value, True)
            if choice:
                yield from self.write_value(value, choice, namespace)
            else:
                yield from self.write_dataclass(value, namespace)
        elif var.is_element:
            xsi_type = self.xsi_type(var, value, namespace)
            yield from self.write_dataclass(
                value,
                namespace,
                var.qname,
                var.nillable,
                xsi_type,
            )
        else:
            # var elements/compound
            meta = self.context.fetch(value.__class__, namespace)
            yield from self.write_dataclass(value, qname=meta.target_qname)

    def write_value(
        self, value: Any, var: XmlVar, namespace: Optional[str]
    ) -> EventIterator:
        """Convert any value to sax events according to the var instance.

        The order of the checks is important as more than one condition
        can be true.

        Args:
            value: The input value
            var: The field metadata instance
            namespace: The class namespace URI

        Yields:
            An iterator of sax events.
        """
        if var.mixed:
            yield from self.write_mixed_content(value, var, namespace)
        elif var.is_text:
            yield from self.write_data(value, var)
        elif var.tokens:
            yield from self.write_tokens(value, var, namespace)
        elif var.is_elements:
            yield from self.write_elements(value, var, namespace)
        elif var.list_element and collections.is_array(value):
            yield from self.write_list(value, var, namespace)
        else:
            yield from self.write_any_type(value, var, namespace)

    def write_list(
        self,
        values: Iterable,
        var: XmlVar,
        namespace: Optional[str],
    ) -> EventIterator:
        """Convert an array of values to sax events.

        Args:
            values: A list, set, tuple instance
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        if var.wrapper is not None:
            yield XmlWriterEvent.START, var.wrapper
            for value in values:
                yield from self.write_value(value, var, namespace)
            yield XmlWriterEvent.END, var.wrapper
        else:
            for value in values:
                yield from self.write_value(value, var, namespace)

    def write_tokens(
        self, value: Any, var: XmlVar, namespace: Optional[str]
    ) -> EventIterator:
        """Convert an array of token values to sax events.

        Args:
            value: A list, set, tuple instance
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        if value or var.nillable or var.required:
            if value and collections.is_array(value[0]):
                for val in value:
                    yield from self.write_element(val, var, namespace)
            else:
                yield from self.write_element(value, var, namespace)

    def write_mixed_content(
        self,
        values: List,
        var: XmlVar,
        namespace: Optional[str],
    ) -> EventIterator:
        """Convert mixed content values to sax events.

        Args:
            values: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        for value in values:
            yield from self.write_any_type(value, var, namespace)

    def write_any_type(
        self, value: Any, var: XmlVar, namespace: Optional[str]
    ) -> EventIterator:
        """Convert a value assigned to a xs:anyType field to sax events.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        if isinstance(value, self.context.class_type.any_element):
            yield from self.write_any_element(value, var, namespace)
        elif isinstance(value, self.context.class_type.derived_element):
            yield from self.write_derived_element(value, namespace)
        elif self.context.class_type.is_model(value):
            yield from self.write_xsi_type(value, var, namespace)
        elif var.is_element:
            yield from self.write_element(value, var, namespace)
        else:
            yield from self.write_data(value, var)

    def write_derived_element(
        self, value: Any, namespace: Optional[str]
    ) -> EventIterator:
        """Convert a derived element instance to sax events.

        Args:
            value: A list instance of mixed type values
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        if self.context.class_type.is_model(value.value):
            meta = self.context.fetch(value.value.__class__)
            qname = value.qname
            xsi_type = self.real_xsi_type(qname, meta.target_qname)

            yield from self.write_dataclass(
                value.value, namespace, qname=qname, xsi_type=xsi_type
            )
        else:
            datatype = DataType.from_value(value.value)

            yield XmlWriterEvent.START, value.qname
            yield XmlWriterEvent.ATTR, QNames.XSI_TYPE, QName(str(datatype))
            yield XmlWriterEvent.DATA, value.value
            yield XmlWriterEvent.END, value.qname

    def write_any_element(
        self, value: Any, var: XmlVar, namespace: Optional[str]
    ) -> EventIterator:
        """Convert a generic any element instance to sax events.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        if value.qname:
            namespace, tag = namespaces.split_qname(value.qname)
            yield XmlWriterEvent.START, value.qname

        for key, val in value.attributes.items():
            yield XmlWriterEvent.ATTR, key, val

        yield XmlWriterEvent.DATA, value.text

        for child in value.children:
            yield from self.write_any_type(child, var, namespace)

        if value.qname:
            yield XmlWriterEvent.END, value.qname

        if value.tail:
            yield XmlWriterEvent.DATA, value.tail

    def xsi_type(
        self, var: XmlVar, value: Any, namespace: Optional[str]
    ) -> Optional[str]:
        """Return the xsi:type for the given value and field metadata instance.

        If the value type is either a child or parent for one of the var types,
        we need to declare it as n xsi:type.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace

        Raises:
            SerializerError: If the value type is completely unrelated to
                the field types.
        """
        if not value or value.__class__ in var.types:
            return None

        clazz = var.clazz
        if clazz is None or self.context.is_derived(value, clazz):
            meta = self.context.fetch(value.__class__, namespace)
            return self.real_xsi_type(var.qname, meta.target_qname)

        raise SerializerError(
            f"{value.__class__.__name__} is not derived from {clazz.__name__}"
        )

    def write_elements(
        self, value: Any, var: XmlVar, namespace: Optional[str]
    ) -> EventIterator:
        """Convert the value assigned to a compound field to sax events.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.
        """
        if collections.is_array(value):
            for val in value:
                yield from self.write_choice(val, var, namespace)
        else:
            yield from self.write_choice(value, var, namespace)

    def write_choice(
        self, value: Any, var: XmlVar, namespace: Optional[str]
    ) -> EventIterator:
        """Convert a single value assigned to a compound field to sax events.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace

        Yields:
            An iterator of sax events.

        Raises:
            SerializerError: If the value doesn't match any choice field.
        """
        if isinstance(value, self.context.class_type.derived_element):
            choice = var.find_choice(value.qname)
            value = value.value

            if self.context.class_type.is_model(value):
                func = self.write_xsi_type
            else:
                func = self.write_element

        elif isinstance(value, self.context.class_type.any_element) and value.qname:
            choice = var.find_choice(value.qname)
            func = self.write_any_type
        else:
            check_subclass = self.context.class_type.is_model(value)
            choice = var.find_value_choice(value, check_subclass)
            func = self.write_value

            if not choice and check_subclass:
                func = self.write_xsi_type
                choice = var

        if not choice:
            raise SerializerError(
                f"XmlElements undefined choice: `{var.name}` for `{type(value)}`"
            )

        yield from func(value, choice, namespace)

    def write_element(
        self,
        value: Any,
        var: XmlVar,
        namespace: Optional[str],
    ) -> EventIterator:
        """Convert a value assigned to an element field to sax events.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance
            namespace: The class namespace (unused)

        Yields:
            An iterator of sax events.
        """
        yield XmlWriterEvent.START, var.qname

        if var.nillable:
            yield XmlWriterEvent.ATTR, QNames.XSI_NIL, "true"

        if value is not None and value != "" and var.any_type:
            datatype = DataType.from_value(value)
            if datatype != DataType.STRING:
                yield XmlWriterEvent.ATTR, QNames.XSI_TYPE, QName(str(datatype))

        yield XmlWriterEvent.DATA, self.encode(value, var)
        yield XmlWriterEvent.END, var.qname

    @classmethod
    def write_data(cls, value: Any, var: XmlVar) -> EventIterator:
        """Convert a value assigned to a text field to sax events.

        Args:
            value: A list instance of mixed type values
            var: The field metadata instance

        Yields:
            An iterator of sax events.
        """
        yield XmlWriterEvent.DATA, cls.encode(value, var)

    @classmethod
    def next_value(cls, obj: Any, meta: XmlMeta) -> Iterator[Tuple[XmlVar, Any]]:
        """Produce the next non attribute value of a model instance to convert.

        The generator will produce the values in the order the fields
        are defined in the model or by their sequence number.

        Sequential fields need to be rendered together in parallel order
        eg: <a1/><a2/><a1/><a/2></a1>

        Args:
            obj: The input model instance
            meta: The model metadata instance

        Yields:
            An iterator of field metadata instance and value tuples.
        """
        index = 0
        attrs = meta.get_element_vars()
        stop = len(attrs)
        while index < stop:
            var = attrs[index]

            if var.sequence is None:
                value = getattr(obj, var.name)
                if value is not None or var.nillable:
                    yield var, value
                index += 1
                continue

            indices = range(index, stop)
            end = next(
                i for i in indices[::-1] if attrs[i].sequence == var.sequence
            )  # pragma: no cover
            sequence = attrs[index : end + 1]
            index = end + 1
            j = 0

            rolling = True
            while rolling:
                rolling = False
                for var in sequence:
                    values = getattr(obj, var.name)
                    if collections.is_array(values):
                        if j < len(values):
                            rolling = True
                            value = values[j]
                            if value is not None or var.nillable:
                                yield var, value
                    elif j == 0:
                        rolling = True
                        if values is not None or var.nillable:
                            yield var, values

                j += 1

    @classmethod
    def next_attribute(
        cls,
        obj: Any,
        meta: XmlMeta,
        nillable: bool,
        xsi_type: Optional[str],
        ignore_optionals: bool,
    ) -> Iterator[Tuple[str, Any]]:
        """Produce the next attribute value to convert.

        Args:
            obj: The input model instance
            meta: The model metadata instance
            nillable: Specifies if the current element supports nillable content
            xsi_type: The real xsi:type of the object
            ignore_optionals: Specifies if optional attributes with default
                values should be ignored.

        Yields:
            An iterator of attribute name-value pairs.
        """
        for var in meta.get_attribute_vars():
            if var.is_attribute:
                value = getattr(obj, var.name)
                if (
                    value is None
                    or (collections.is_array(value) and not value)
                    or (ignore_optionals and var.is_optional(value))
                ):
                    continue

                yield var.qname, cls.encode(value, var)
            else:
                yield from getattr(obj, var.name, EMPTY_MAP).items()

        if xsi_type:
            yield QNames.XSI_TYPE, QName(xsi_type)

        if nillable:
            yield QNames.XSI_NIL, "true"

    @classmethod
    def encode(cls, value: Any, var: XmlVar) -> Any:
        """Encode a value for xml serialization.

        Converts values to strings. QName instances is an exception,
        those values need to wait until the XmlWriter assigns prefixes
        to namespaces per element node. Enums and Tokens may contain
        QName(s) so they also get a special treatment.

        We can't do all the conversions in the writer because we would
        need to carry the xml vars inside the writer. Instead of that we
        do the easy encoding here and leave the qualified names for
        later.

        Args:
            value: The simple type vale to encode
            var: The field metadata instance

        Returns:
            The encoded value.
        """
        if isinstance(value, (str, QName)) or var is None:
            return value

        if collections.is_array(value):
            return [cls.encode(v, var) for v in value]

        if isinstance(value, Enum):
            return cls.encode(value.value, var)

        return converter.serialize(value, format=var.format)

    @classmethod
    def real_xsi_type(cls, qname: str, target_qname: Optional[str]) -> Optional[str]:
        """Compare the qname with the target qname and return the real xsi:type.

        Args:
            qname: The field type qualified name
            target_qname: The value type qualified name

        Returns:
            None if the qname and target qname match, otherwise
            return the target qname.
        """
        return target_qname if target_qname != qname else None