r"""
Visitor for <maligngroup> (alignment group marker) MathML elements.

The <maligngroup/> element is an empty element used within table cells (<mtd>)
to mark alignment groups. It's used to control horizontal alignment across
table columns for complex multi-line expressions.

In LaTeX conversion, alignment groups are handled implicitly by the array/matrix
environment's column specifications (e.g., {lll} for left-aligned columns).
Therefore, maligngroup markers are treated as transparent (no output).
"""

from lxml import etree as ET
from ..core.interfaces import Visitor, Strategy
from ..utils import local_name as _local


class MaligngroupVisitor(Visitor):
    r"""
    Handles <maligngroup/> (alignment group marker) MathML elements.

    Treats maligngroup as an invisible marker since LaTeX handles alignment
    through column specifications in array/matrix environments. The element
    is completely ignored in conversion.

    Examples:
        Alignment group in cell:
            <mtd>
                <maligngroup/>
                <mi>x</mi>
            </mtd>
            → x (maligngroup ignored)

        Multiple alignment groups:
            <mtd>
                <maligngroup groupalign="left"/>
                <mi>a</mi>
                <maligngroup groupalign="right"/>
                <mi>b</mi>
            </mtd>
            → a b (both maligngroup markers ignored)

        Group with alignment attribute:
            <maligngroup groupalign="center"/>
            → (empty - no output)

    Note:
        LaTeX doesn't support MathML's alignment group concept. Alignment
        is controlled by column specifications in the array/matrix preamble
        (e.g., {ccc} for center-aligned, {lll} for left-aligned).
        Therefore, maligngroup elements produce no output.
    """

    def __init__(self, strategy: Strategy):
        """Initialize the Maligngroup visitor."""
        super().__init__(strategy)

    def visit(self, node: ET.Element) -> str:
        r"""
        Convert <maligngroup/> element (returns empty string).

        Args:
            node: The <maligngroup/> element to convert

        Returns:
            Empty string (maligngroup is invisible in LaTeX)

        Raises:
            ValueError: If node is not a <maligngroup/> element
        """
        if not self.can_handle(node):
            raise ValueError(f"MaligngroupVisitor cannot handle element '{node.tag}'")

        # Maligngroup is an invisible alignment marker - no output
        return ""

    def can_handle(self, node: ET.Element) -> bool:
        """Check if this visitor can handle the given node."""
        return _local(node.tag) == 'maligngroup'

    @property
    def element_name(self) -> str:
        """Get the element name this visitor handles."""
        return 'maligngroup'

    def __repr__(self) -> str:
        """String representation for debugging."""
        return f"MaligngroupVisitor(strategy={self.strategy.name})"