r"""
Visitor for <mphantom> (phantom/invisible content) MathML elements.

The <mphantom> element renders its content invisibly but reserves the space
it would normally occupy. This is useful for alignment and spacing purposes.

In LaTeX, this is converted using the \phantom{} command.
"""

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


class MphantomVisitor(Visitor):
    r"""
    Handles <mphantom> (phantom/invisible content) MathML elements.

    Converts phantom content to LaTeX \phantom{} command, which creates
    an invisible placeholder that reserves space.

    Examples:
        Simple phantom:
            <mphantom><mi>x</mi></mphantom>
            → \phantom{x}

        Phantom expression:
            <mphantom><mrow><mi>a</mi><mo>+</mo><mi>b</mi></mrow></mphantom>
            → \phantom{a+b}

        Phantom for alignment:
            <mrow>
                <mi>x</mi>
                <mphantom><mo>+</mo></mphantom>
                <mi>y</mi>
            </mrow>
            → x\phantom{+}y

        Phantom fraction:
            <mphantom><mfrac><mi>a</mi><mi>b</mi></mfrac></mphantom>
            → \phantom{\frac{a}{b}}

    Note:
        The phantom command is useful for:
        - Vertical alignment across equations
        - Horizontal spacing that matches specific content
        - Creating symmetric layouts
    """

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

    def visit(self, node: ET.Element) -> str:
        r"""
        Convert <mphantom> element to LaTeX \phantom{} command.

        Args:
            node: The <mphantom> element to convert

        Returns:
            LaTeX string with \phantom{content}

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

        # Convert children to get the content
        content = self._convert_children(node)

        # If empty, return empty phantom
        if not content or not content.strip():
            return "\\phantom{}"

        # Wrap content in \phantom{}
        return f"\\phantom{{{content}}}"

    def _convert_children(self, node: ET.Element) -> str:
        """
        Convert all child elements to LaTeX.

        Args:
            node: The <mphantom> element

        Returns:
            LaTeX string with all children converted
        """
        parts = []
        for child in node:
            parts.append(self._convert_child(child))
        return ''.join(parts)

    def _convert_child(self, child: ET.Element) -> str:
        """Convert a child element to LaTeX."""
        tag = _local(child.tag)

        # Import visitors as needed to avoid circular imports
        if tag == 'mi':
            from .mi_visitor import MiVisitor
            return MiVisitor(self.strategy).visit(child)
        elif tag == 'mo':
            from .mo_visitor import MoVisitor
            return MoVisitor(self.strategy).visit(child)
        elif tag == 'mn':
            from .mn_visitor import MnVisitor
            return MnVisitor(self.strategy).visit(child)
        elif tag == 'mfrac':
            from .mfrac_visitor import MfracVisitor
            return MfracVisitor(self.strategy).visit(child)
        elif tag == 'msup':
            from .msup_visitor import MsupVisitor
            return MsupVisitor(self.strategy).visit(child)
        elif tag == 'msub':
            from .msub_visitor import MsubVisitor
            return MsubVisitor(self.strategy).visit(child)
        elif tag == 'mrow':
            from .mrow_visitor import MrowVisitor
            return MrowVisitor(self.strategy).visit(child)
        elif tag == 'msqrt':
            from .msqrt_visitor import MsqrtVisitor
            return MsqrtVisitor(self.strategy).visit(child)
        elif tag == 'mroot':
            from .mroot_visitor import MrootVisitor
            return MrootVisitor(self.strategy).visit(child)
        elif tag == 'msubsup':
            from .msubsup_visitor import MsubsupVisitor
            return MsubsupVisitor(self.strategy).visit(child)
        elif tag == 'munder':
            from .munder_visitor import MunderVisitor
            return MunderVisitor(self.strategy).visit(child)
        elif tag == 'mover':
            from .mover_visitor import MoverVisitor
            return MoverVisitor(self.strategy).visit(child)
        elif tag == 'munderover':
            from .munderover_visitor import MunderoverVisitor
            return MunderoverVisitor(self.strategy).visit(child)
        elif tag == 'mfenced':
            from .mfenced_visitor import MfencedVisitor
            return MfencedVisitor(self.strategy).visit(child)
        elif tag == 'mtable':
            from .mtable_visitor import MtableVisitor
            return MtableVisitor(self.strategy).visit(child)
        elif tag == 'mtext':
            from .mtext_visitor import MtextVisitor
            return MtextVisitor(self.strategy).visit(child)
        elif tag == 'mstyle':
            from .mstyle_visitor import MstyleVisitor
            return MstyleVisitor(self.strategy).visit(child)
        elif tag == 'mspace':
            from .mspace_visitor import MspaceVisitor
            return MspaceVisitor(self.strategy).visit(child)
        elif tag == 'menclose':
            from .menclose_visitor import MencloseVisitor
            return MencloseVisitor(self.strategy).visit(child)
        elif tag == 'mmultiscripts':
            from .mmultiscripts_visitor import MmultiscriptsVisitor
            return MmultiscriptsVisitor(self.strategy).visit(child)
        elif tag == 'maction':
            from .maction_visitor import MactionVisitor
            return MactionVisitor(self.strategy).visit(child)
        elif tag == 'merror':
            from .merror_visitor import MerrorVisitor
            return MerrorVisitor(self.strategy).visit(child)
        elif tag == 'mpadded':
            from .mpadded_visitor import MpaddedVisitor
            return MpaddedVisitor(self.strategy).visit(child)
        elif tag == 'mphantom':
            from .mphantom_visitor import MphantomVisitor
            return MphantomVisitor(self.strategy).visit(child)
        elif tag == 'ms':
            from .ms_visitor import MsVisitor
            return MsVisitor(self.strategy).visit(child)
        elif tag == 'mglyph':
            from .mglyph_visitor import MglyphVisitor
            return MglyphVisitor(self.strategy).visit(child)
        elif tag == 'maligngroup':
            from .maligngroup_visitor import MaligngroupVisitor
            return MaligngroupVisitor(self.strategy).visit(child)
        elif tag == 'malignmark':
            from .malignmark_visitor import MalignmarkVisitor
            return MalignmarkVisitor(self.strategy).visit(child)
        elif tag == 'mlabeledtr':
            from .mlabeledtr_visitor import MlabeledtrVisitor
            return MlabeledtrVisitor(self.strategy).visit(child)
        else:
            # Fallback: return text content for unknown elements
            import sys
            print(f"[WARNING] Unknown element <{tag}> in mphantom, using text fallback", file=sys.stderr)
            return _text_content(child)

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

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

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