# read-only tree implementation

@cython.internal
cdef class _ReadOnlyProxy:
    u"A read-only proxy class suitable for PIs/Comments (for internal use only!)."
    cdef bint _free_after_use
    cdef xmlNode* _c_node
    cdef _ReadOnlyProxy _source_proxy
    cdef list _dependent_proxies
    def __cinit__(self):
        self._c_node = NULL
        self._free_after_use = 0

    cdef int _assertNode(self) except -1:
        u"""This is our way of saying: this proxy is invalid!
        """
        if not self._c_node:
            raise ReferenceError("Proxy invalidated!")
        return 0

    cdef int _raise_unsupported_type(self) except -1:
        raise TypeError(f"Unsupported node type: {self._c_node.type}")

    cdef void free_after_use(self):
        u"""Should the xmlNode* be freed when releasing the proxy?
        """
        self._free_after_use = 1

    property tag:
        u"""Element tag
        """
        def __get__(self):
            self._assertNode()
            if self._c_node.type == tree.XML_ELEMENT_NODE:
                return _namespacedName(self._c_node)
            elif self._c_node.type == tree.XML_PI_NODE:
                return ProcessingInstruction
            elif self._c_node.type == tree.XML_COMMENT_NODE:
                return Comment
            elif self._c_node.type == tree.XML_ENTITY_REF_NODE:
                return Entity
            else:
                self._raise_unsupported_type()

    property text:
        u"""Text before the first subelement. This is either a string or 
        the value None, if there was no text.
        """
        def __get__(self):
            self._assertNode()
            if self._c_node.type == tree.XML_ELEMENT_NODE:
                return _collectText(self._c_node.children)
            elif self._c_node.type in (tree.XML_PI_NODE,
                                       tree.XML_COMMENT_NODE):
                if self._c_node.content is NULL:
                    return ''
                else:
                    return funicode(self._c_node.content)
            elif self._c_node.type == tree.XML_ENTITY_REF_NODE:
                return f'&{funicode(self._c_node.name)};'
            else:
                self._raise_unsupported_type()
        
    property tail:
        u"""Text after this element's end tag, but before the next sibling
        element's start tag. This is either a string or the value None, if
        there was no text.
        """
        def __get__(self):
            self._assertNode()
            return _collectText(self._c_node.next)

    property sourceline:
        u"""Original line number as found by the parser or None if unknown.
        """
        def __get__(self):
            cdef long line
            self._assertNode()
            line = tree.xmlGetLineNo(self._c_node)
            if line > 0:
                return line
            else:
                return None

    def __repr__(self):
        self._assertNode()
        if self._c_node.type == tree.XML_ELEMENT_NODE:
            return "<Element %s at 0x%x>" % (strrepr(self.tag), id(self))
        elif self._c_node.type == tree.XML_COMMENT_NODE:
            return "<!--%s-->" % strrepr(self.text)
        elif self._c_node.type == tree.XML_ENTITY_NODE:
            return "&%s;" % strrepr(funicode(self._c_node.name))
        elif self._c_node.type == tree.XML_PI_NODE:
            text = self.text
            if text:
                return "<?%s %s?>" % (strrepr(self.target), text)
            else:
                return "<?%s?>" % strrepr(self.target)
        else:
            self._raise_unsupported_type()

    def __getitem__(self, x):
        u"""Returns the subelement at the given position or the requested
        slice.
        """
        cdef xmlNode* c_node = NULL
        cdef Py_ssize_t step = 0, slicelength = 0
        cdef Py_ssize_t c, i
        cdef _node_to_node_function next_element
        cdef list result
        self._assertNode()
        if isinstance(x, slice):
            # slicing
            if _isFullSlice(<slice>x):
                return _collectChildren(self)
            _findChildSlice(<slice>x, self._c_node, &c_node, &step, &slicelength)
            if c_node is NULL:
                return []
            if step > 0:
                next_element = _nextElement
            else:
                step = -step
                next_element = _previousElement
            result = []
            c = 0
            while c_node is not NULL and c < slicelength:
                result.append(_newReadOnlyProxy(self._source_proxy, c_node))
                result.append(_elementFactory(self._doc, c_node))
                c = c + 1
                for i from 0 <= i < step:
                    c_node = next_element(c_node)
            return result
        else:
            # indexing
            c_node = _findChild(self._c_node, x)
            if c_node is NULL:
                raise IndexError, u"list index out of range"
            return _newReadOnlyProxy(self._source_proxy, c_node)

    def __len__(self):
        u"""Returns the number of subelements.
        """
        cdef Py_ssize_t c
        cdef xmlNode* c_node
        self._assertNode()
        c = 0
        c_node = self._c_node.children
        while c_node is not NULL:
            if tree._isElement(c_node):
                c = c + 1
            c_node = c_node.next
        return c

    def __nonzero__(self):
        cdef xmlNode* c_node
        self._assertNode()
        c_node = _findChildBackwards(self._c_node, 0)
        return c_node != NULL

    def __deepcopy__(self, memo):
        u"__deepcopy__(self, memo)"
        return self.__copy__()
        
    cpdef __copy__(self):
        u"__copy__(self)"
        cdef xmlDoc* c_doc
        cdef xmlNode* c_node
        cdef _Document new_doc
        if self._c_node is NULL:
            return self
        c_doc = _copyDocRoot(self._c_node.doc, self._c_node) # recursive
        new_doc = _documentFactory(c_doc, None)
        root = new_doc.getroot()
        if root is not None:
            return root
        # Comment/PI
        c_node = c_doc.children
        while c_node is not NULL and c_node.type != self._c_node.type:
            c_node = c_node.next
        if c_node is NULL:
            return None
        return _elementFactory(new_doc, c_node)

    def __iter__(self):
        return iter(self.getchildren())

    def iterchildren(self, tag=None, *, reversed=False):
        u"""iterchildren(self, tag=None, reversed=False)

        Iterate over the children of this element.
        """
        children = self.getchildren()
        if tag is not None and tag != '*':
            children = [ el for el in children if el.tag == tag ]
        if reversed:
            children = children[::-1]
        return iter(children)

    cpdef getchildren(self):
        u"""Returns all subelements. The elements are returned in document
        order.
        """
        cdef xmlNode* c_node
        cdef list result
        self._assertNode()
        result = []
        c_node = self._c_node.children
        while c_node is not NULL:
            if tree._isElement(c_node):
                result.append(_newReadOnlyProxy(self._source_proxy, c_node))
            c_node = c_node.next
        return result

    def getparent(self):
        u"""Returns the parent of this element or None for the root element.
        """
        cdef xmlNode* c_parent
        self._assertNode()
        c_parent = self._c_node.parent
        if c_parent is NULL or not tree._isElement(c_parent):
            return None
        else:
            return _newReadOnlyProxy(self._source_proxy, c_parent)

    def getnext(self):
        u"""Returns the following sibling of this element or None.
        """
        cdef xmlNode* c_node
        self._assertNode()
        c_node = _nextElement(self._c_node)
        if c_node is not NULL:
            return _newReadOnlyProxy(self._source_proxy, c_node)
        return None

    def getprevious(self):
        u"""Returns the preceding sibling of this element or None.
        """
        cdef xmlNode* c_node
        self._assertNode()
        c_node = _previousElement(self._c_node)
        if c_node is not NULL:
            return _newReadOnlyProxy(self._source_proxy, c_node)
        return None


@cython.final
@cython.internal
cdef class _ReadOnlyPIProxy(_ReadOnlyProxy):
    u"A read-only proxy for processing instructions (for internal use only!)"
    property target:
        def __get__(self):
            self._assertNode()
            return funicode(self._c_node.name)

@cython.final
@cython.internal
cdef class _ReadOnlyEntityProxy(_ReadOnlyProxy):
    u"A read-only proxy for entity references (for internal use only!)"
    property name:
        def __get__(self):
            return funicode(self._c_node.name)

        def __set__(self, value):
            value_utf = _utf8(value)
            if u'&' in value or u';' in value:
                raise ValueError(f"Invalid entity name '{value}'")
            tree.xmlNodeSetName(self._c_node, _xcstr(value_utf))

    property text:
        def __get__(self):
            return f'&{funicode(self._c_node.name)};'


@cython.internal
cdef class _ReadOnlyElementProxy(_ReadOnlyProxy):
    u"The main read-only Element proxy class (for internal use only!)."

    property attrib:
        def __get__(self):
            self._assertNode()
            return dict(_collectAttributes(self._c_node, 3))

    property prefix:
        u"""Namespace prefix or None.
        """
        def __get__(self):
            self._assertNode()
            if self._c_node.ns is not NULL:
                if self._c_node.ns.prefix is not NULL:
                    return funicode(self._c_node.ns.prefix)
            return None

    def get(self, key, default=None):
        u"""Gets an element attribute.
        """
        self._assertNode()
        return _getNodeAttributeValue(self._c_node, key, default)

    def keys(self):
        u"""Gets a list of attribute names. The names are returned in an
        arbitrary order (just like for an ordinary Python dictionary).
        """
        self._assertNode()
        return _collectAttributes(self._c_node, 1)

    def values(self):
        u"""Gets element attributes, as a sequence. The attributes are returned
        in an arbitrary order.
        """
        self._assertNode()
        return _collectAttributes(self._c_node, 2)

    def items(self):
        u"""Gets element attributes, as a sequence. The attributes are returned
        in an arbitrary order.
        """
        self._assertNode()
        return _collectAttributes(self._c_node, 3)

cdef _ReadOnlyProxy _newReadOnlyProxy(
    _ReadOnlyProxy source_proxy, xmlNode* c_node):
    cdef _ReadOnlyProxy el
    if c_node.type == tree.XML_ELEMENT_NODE:
        el = _ReadOnlyElementProxy.__new__(_ReadOnlyElementProxy)
    elif c_node.type == tree.XML_PI_NODE:
        el = _ReadOnlyPIProxy.__new__(_ReadOnlyPIProxy)
    elif c_node.type in (tree.XML_COMMENT_NODE,
                         tree.XML_ENTITY_REF_NODE):
        el = _ReadOnlyProxy.__new__(_ReadOnlyProxy)
    else:
        raise TypeError(f"Unsupported element type: {c_node.type}")
    el._c_node = c_node
    _initReadOnlyProxy(el, source_proxy)
    return el

cdef inline _initReadOnlyProxy(_ReadOnlyProxy el,
                               _ReadOnlyProxy source_proxy):
    if source_proxy is None:
        el._source_proxy = el
        el._dependent_proxies = [el]
    else:
        el._source_proxy = source_proxy
        source_proxy._dependent_proxies.append(el)

cdef _freeReadOnlyProxies(_ReadOnlyProxy sourceProxy):
    cdef xmlNode* c_node
    cdef _ReadOnlyProxy el
    if sourceProxy is None:
        return
    if sourceProxy._dependent_proxies is None:
        return
    for el in sourceProxy._dependent_proxies:
        c_node = el._c_node
        el._c_node = NULL
        if el._free_after_use:
            tree.xmlFreeNode(c_node)
    del sourceProxy._dependent_proxies[:]

# opaque wrapper around non-element nodes, e.g. the document node
#
# This class does not imply any restrictions on modifiability or
# read-only status of the node, so use with caution.

@cython.internal
cdef class _OpaqueNodeWrapper:
    cdef tree.xmlNode* _c_node
    def __init__(self):
        raise TypeError, u"This type cannot be instantiated from Python"

@cython.final
@cython.internal
cdef class _OpaqueDocumentWrapper(_OpaqueNodeWrapper):
    cdef int _assertNode(self) except -1:
        u"""This is our way of saying: this proxy is invalid!
        """
        assert self._c_node is not NULL, u"Proxy invalidated!"
        return 0

    cpdef append(self, other_element):
        u"""Append a copy of an Element to the list of children.
        """
        cdef xmlNode* c_next
        cdef xmlNode* c_node
        self._assertNode()
        c_node = _roNodeOf(other_element)
        if c_node.type == tree.XML_ELEMENT_NODE:
            if tree.xmlDocGetRootElement(<tree.xmlDoc*>self._c_node) is not NULL:
                raise ValueError, u"cannot append, document already has a root element"
        elif c_node.type not in (tree.XML_PI_NODE, tree.XML_COMMENT_NODE):
            raise TypeError, f"unsupported element type for top-level node: {c_node.type}"
        c_node = _copyNodeToDoc(c_node, <tree.xmlDoc*>self._c_node)
        c_next = c_node.next
        tree.xmlAddChild(self._c_node, c_node)
        _moveTail(c_next, c_node)

    def extend(self, elements):
        u"""Append a copy of all Elements from a sequence to the list of
        children.
        """
        self._assertNode()
        for element in elements:
            self.append(element)

cdef _OpaqueNodeWrapper _newOpaqueAppendOnlyNodeWrapper(xmlNode* c_node):
    cdef _OpaqueNodeWrapper node
    if c_node.type in (tree.XML_DOCUMENT_NODE, tree.XML_HTML_DOCUMENT_NODE):
        node = _OpaqueDocumentWrapper.__new__(_OpaqueDocumentWrapper)
    else:
        node = _OpaqueNodeWrapper.__new__(_OpaqueNodeWrapper)
    node._c_node = c_node
    return node

# element proxies that allow restricted modification

@cython.internal
cdef class _ModifyContentOnlyProxy(_ReadOnlyProxy):
    u"""A read-only proxy that allows changing the text content.
    """
    property text:
        def __get__(self):
            self._assertNode()
            if self._c_node.content is NULL:
                return ''
            else:
                return funicode(self._c_node.content)

        def __set__(self, value):
            cdef tree.xmlDict* c_dict
            self._assertNode()
            if value is None:
                c_text = <const_xmlChar*>NULL
            else:
                value = _utf8(value)
                c_text = _xcstr(value)
            tree.xmlNodeSetContent(self._c_node, c_text)

@cython.final
@cython.internal
cdef class _ModifyContentOnlyPIProxy(_ModifyContentOnlyProxy):
    u"""A read-only proxy that allows changing the text/target content of a
    processing instruction.
    """
    property target:
        def __get__(self):
            self._assertNode()
            return funicode(self._c_node.name)

        def __set__(self, value):
            self._assertNode()
            value = _utf8(value)
            c_text = _xcstr(value)
            tree.xmlNodeSetName(self._c_node, c_text)

@cython.final
@cython.internal
cdef class _ModifyContentOnlyEntityProxy(_ModifyContentOnlyProxy):
    u"A read-only proxy for entity references (for internal use only!)"
    property name:
        def __get__(self):
            return funicode(self._c_node.name)

        def __set__(self, value):
            value = _utf8(value)
            assert u'&' not in value and u';' not in value, \
                f"Invalid entity name '{value}'"
            c_text = _xcstr(value)
            tree.xmlNodeSetName(self._c_node, c_text)


@cython.final
@cython.internal
cdef class _AppendOnlyElementProxy(_ReadOnlyElementProxy):
    u"""A read-only element that allows adding children and changing the
    text content (i.e. everything that adds to the subtree).
    """
    cpdef append(self, other_element):
        u"""Append a copy of an Element to the list of children.
        """
        cdef xmlNode* c_next
        cdef xmlNode* c_node
        self._assertNode()
        c_node = _roNodeOf(other_element)
        c_node = _copyNodeToDoc(c_node, self._c_node.doc)
        c_next = c_node.next
        tree.xmlAddChild(self._c_node, c_node)
        _moveTail(c_next, c_node)
            
    def extend(self, elements):
        u"""Append a copy of all Elements from a sequence to the list of
        children.
        """
        self._assertNode()
        for element in elements:
            self.append(element)

    property text:
        u"""Text before the first subelement. This is either a string or the
        value None, if there was no text.
        """
        def __get__(self):
            self._assertNode()
            return _collectText(self._c_node.children)

        def __set__(self, value):
            self._assertNode()
            if isinstance(value, QName):
                value = _resolveQNameText(self, value).decode('utf8')
            _setNodeText(self._c_node, value)


cdef _ReadOnlyProxy _newAppendOnlyProxy(
    _ReadOnlyProxy source_proxy, xmlNode* c_node):
    cdef _ReadOnlyProxy el
    if c_node.type == tree.XML_ELEMENT_NODE:
        el = _AppendOnlyElementProxy.__new__(_AppendOnlyElementProxy)
    elif c_node.type == tree.XML_PI_NODE:
        el = _ModifyContentOnlyPIProxy.__new__(_ModifyContentOnlyPIProxy)
    elif c_node.type == tree.XML_COMMENT_NODE:
        el = _ModifyContentOnlyProxy.__new__(_ModifyContentOnlyProxy)
    else:
        raise TypeError(f"Unsupported element type: {c_node.type}")
    el._c_node = c_node
    _initReadOnlyProxy(el, source_proxy)
    return el

cdef xmlNode* _roNodeOf(element) except NULL:
    cdef xmlNode* c_node
    if isinstance(element, _Element):
        c_node = (<_Element>element)._c_node
    elif isinstance(element, _ReadOnlyProxy):
        c_node = (<_ReadOnlyProxy>element)._c_node
    elif isinstance(element, _OpaqueNodeWrapper):
        c_node = (<_OpaqueNodeWrapper>element)._c_node
    else:
        raise TypeError, f"invalid argument type {type(element)}"

    if c_node is NULL:
        raise TypeError, u"invalid element"
    return c_node

cdef xmlNode* _nonRoNodeOf(element) except NULL:
    cdef xmlNode* c_node
    if isinstance(element, _Element):
        c_node = (<_Element>element)._c_node
    elif isinstance(element, _AppendOnlyElementProxy):
        c_node = (<_AppendOnlyElementProxy>element)._c_node
    elif isinstance(element, _OpaqueNodeWrapper):
        c_node = (<_OpaqueNodeWrapper>element)._c_node
    else:
        raise TypeError, f"invalid argument type {type(element)}"

    if c_node is NULL:
        raise TypeError, u"invalid element"
    return c_node
