from __future__ import annotations

from lxml import etree

from app.core.config import settings


DANGEROUS_TAGS = {"script"}
SVG_NS = "http://www.w3.org/2000/svg"
XLINK_NS = "http://www.w3.org/1999/xlink"
XLINK_HREF = f"{{{XLINK_NS}}}href"


def _local_name(tag: str) -> str:
    if "}" in tag:
        return tag.split("}", 1)[1]
    return tag


def _is_external_ref(value: str) -> bool:
    low = value.strip().lower()
    return (
        low.startswith("http://")
        or low.startswith("https://")
        or low.startswith("file:")
        or low.startswith("javascript:")
        or low.startswith("data:")
        or low.startswith("//")
    )


def sanitize_svg_bytes(content: bytes) -> tuple[bytes, int, int]:
    parser = etree.XMLParser(
        resolve_entities=False,
        remove_blank_text=False,
        remove_comments=False,
        no_network=True,
        recover=False,
        huge_tree=True,
    )
    root = etree.fromstring(content, parser=parser)

    removed_elements_count = 0
    removed_attributes_count = 0

    for node in list(root.iter()):
        tag_name = _local_name(node.tag)

        if tag_name in DANGEROUS_TAGS:
            parent = node.getparent()
            if parent is not None:
                parent.remove(node)
                removed_elements_count += 1
            continue

        if settings.svg_forbid_foreign_object_v1 and tag_name == "foreignObject":
            parent = node.getparent()
            if parent is not None:
                parent.remove(node)
                removed_elements_count += 1
            continue

        if settings.svg_forbid_image_v1 and tag_name == "image":
            href = node.attrib.get("href") or node.attrib.get(XLINK_HREF)
            if href and _is_external_ref(href):
                parent = node.getparent()
                if parent is not None:
                    parent.remove(node)
                    removed_elements_count += 1
                continue

        for attr_name in list(node.attrib.keys()):
            local_attr = _local_name(attr_name).lower()
            value = node.attrib.get(attr_name) or ""

            if local_attr.startswith("on"):
                del node.attrib[attr_name]
                removed_attributes_count += 1
                continue

            if local_attr in {"href"}:
                if value and not value.startswith("#") and _is_external_ref(value):
                    del node.attrib[attr_name]
                    removed_attributes_count += 1
                    continue

            if attr_name == XLINK_HREF:
                if value and not value.startswith("#") and _is_external_ref(value):
                    del node.attrib[attr_name]
                    removed_attributes_count += 1
                    continue

    sanitized = etree.tostring(
        root,
        encoding="utf-8",
        xml_declaration=True,
        pretty_print=False,
    )
    return sanitized, removed_elements_count, removed_attributes_count