import xml.etree.ElementTree as ET

SVG_NS = "http://www.w3.org/2000/svg"
XLINK_NS = "http://www.w3.org/1999/xlink"

ET.register_namespace("", SVG_NS)
ET.register_namespace("xlink", XLINK_NS)

_ANCHOR_TAGS = (f"{{{SVG_NS}}}a", "a")
_IMAGE_TAGS = (f"{{{SVG_NS}}}image", "image")
_HREF_ATTRS = ("href", f"{{{XLINK_NS}}}href")


def strip_svg_hyperlinks(svg_source, image_loader=None):
    """Return svg_source with every <a> wrapper unwrapped and dead links removed.

    NetBox wraps rack elevation devices in hyperlinks pointing at internal,
    relative object URLs. Those links are dead weight (and broken paths) once
    the SVG is saved and opened outside of a NetBox session, so this unwraps
    them while keeping their contents.

    <image> elements reference device photos by the same kind of internal,
    relative URL. Simply stripping their href would leave the device blank,
    so image_loader (href -> "data:...;base64,..." or None) is used to embed
    the image data directly instead. Without an image_loader, image hrefs are
    left untouched.
    """
    root = ET.fromstring(svg_source)
    _unwrap_anchors(root)
    _resolve_hrefs(root, image_loader)
    return ET.tostring(root, encoding="unicode")


def _unwrap_anchors(parent):
    replaced = False
    new_children = []
    for child in list(parent):
        _unwrap_anchors(child)
        if child.tag in _ANCHOR_TAGS:
            replaced = True
            new_children.extend(list(child))
        else:
            new_children.append(child)
    if replaced:
        for child in list(parent):
            parent.remove(child)
        for child in new_children:
            parent.append(child)


def _resolve_hrefs(element, image_loader):
    if element.tag in _IMAGE_TAGS:
        if image_loader is not None:
            for attr in _HREF_ATTRS:
                href = element.attrib.get(attr)
                if not href:
                    continue
                data_uri = image_loader(href)
                if data_uri:
                    element.attrib[attr] = data_uri
                else:
                    element.attrib.pop(attr, None)
    else:
        for attr in _HREF_ATTRS:
            element.attrib.pop(attr, None)
    for child in element:
        _resolve_hrefs(child, image_loader)