svg-backend/backend/app/services/svg_display_processor.py

from __future__ import annotations

import logging
import re
from typing import Any

from lxml import etree

from app.core.config import settings


logger = logging.getLogger(__name__)

ALLOWED_MODES = {"passthrough", "optimized"}


def _parse_length(value: str | None) -> float | None:
    if not value:
        return None
    cleaned = value.strip().replace("px", "")
    try:
        return float(cleaned)
    except ValueError:
        return None


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


def _is_hidden(node: etree._Element) -> bool:
    display = (node.attrib.get("display") or "").strip().lower()
    visibility = (node.attrib.get("visibility") or "").strip().lower()
    style = (node.attrib.get("style") or "").replace(" ", "").lower()
    return (
        display == "none"
        or visibility == "hidden"
        or "display:none" in style
        or "visibility:hidden" in style
    )


def _is_seat_related(node: etree._Element) -> bool:
    probe = " ".join(
        [
            node.attrib.get("id", ""),
            node.attrib.get("class", ""),
            node.attrib.get("data-seat-id", ""),
            node.attrib.get("data-sector-id", ""),
            node.attrib.get("data-group-id", ""),
        ]
    ).lower()
    return any(token in probe for token in ["seat", "sector", "group", "place"])


def _font_size(node: etree._Element) -> float | None:
    direct = _parse_length(node.attrib.get("font-size"))
    if direct is not None:
        return direct

    style = node.attrib.get("style") or ""
    match = re.search(r"font-size\s*:\s*([0-9.]+)", style, flags=re.IGNORECASE)
    if match:
        return _parse_length(match.group(1))
    return None


def _is_technical_text(node: etree._Element) -> bool:
    patterns = [
        item.strip().lower()
        for item in settings.svg_display_technical_text_patterns.split(",")
        if item.strip()
    ]
    haystack = " ".join(
        [
            node.attrib.get("id", ""),
            node.attrib.get("class", ""),
            "".join(node.itertext()),
        ]
    ).lower()
    return any(pattern in haystack for pattern in patterns)


def _force_viewbox(root: etree._Element) -> None:
    if not settings.svg_display_force_viewbox:
        return
    if root.attrib.get("viewBox"):
        return

    width = _parse_length(root.attrib.get("width"))
    height = _parse_length(root.attrib.get("height"))
    if width and height:
        w = int(width) if width.is_integer() else width
        h = int(height) if height.is_integer() else height
        root.attrib["viewBox"] = f"0 0 {w} {h}"


def _extract_meta(root: etree._Element) -> dict[str, Any]:
    return {
        "view_box": root.attrib.get("viewBox"),
        "width": root.attrib.get("width"),
        "height": root.attrib.get("height"),
    }


def generate_display_svg(content: bytes, mode: str) -> tuple[bytes, dict[str, Any]]:
    if mode not in ALLOWED_MODES:
        raise ValueError(f"Unsupported display mode: {mode}")

    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)

    defs_count = len(root.xpath("//*[local-name()='defs']"))
    use_count = len(root.xpath("//*[local-name()='use']"))
    style_count = len(root.xpath("//*[local-name()='style']"))
    clip_count = len(root.xpath("//*[local-name()='clipPath']"))

    logger.info(
        "display_svg.generate mode=%s size_bytes=%s has_style=%s defs=%s use=%s clipPath=%s",
        mode,
        len(content),
        bool(style_count),
        defs_count,
        use_count,
        clip_count,
    )

    removed_hidden_count = 0
    removed_small_text_count = 0
    removed_technical_text_count = 0

    if mode == "optimized":
        for node in list(root.iter()):
            tag_name = _local_name(node.tag)

            if settings.svg_display_remove_hidden_elements and not _is_seat_related(node) and _is_hidden(node):
                parent = node.getparent()
                if parent is not None:
                    parent.remove(node)
                    removed_hidden_count += 1
                continue

            if tag_name in {"text", "tspan"}:
                if settings.svg_display_hide_small_text and not _is_seat_related(node):
                    size = _font_size(node)
                    if size is not None and size < settings.svg_display_min_text_font_size:
                        parent = node.getparent()
                        if parent is not None:
                            parent.remove(node)
                            removed_small_text_count += 1
                        continue

                if settings.svg_display_hide_technical_text and not _is_seat_related(node) and _is_technical_text(node):
                    parent = node.getparent()
                    if parent is not None:
                        parent.remove(node)
                        removed_technical_text_count += 1
                    continue

    _force_viewbox(root)

    output = etree.tostring(
        root,
        encoding="utf-8",
        xml_declaration=True,
        pretty_print=False,
    )

    meta = _extract_meta(root)
    meta.update(
        {
            "mode": mode,
            "removed_hidden_count": removed_hidden_count,
            "removed_small_text_count": removed_small_text_count,
            "removed_technical_text_count": removed_technical_text_count,
        }
    )
    return output, meta