"""Best-effort OMML → readable LaTeX-like string for $$ / $ fences."""

from __future__ import annotations

_OMML_NS = "http://schemas.openxmlformats.org/officeDocument/2006/math"


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


def omml_to_latex(element) -> str:
    """Flatten OMML tree to a readable formula string (not perfect LaTeX)."""
    if element is None:
        return ""
    parts: list[str] = []
    _walk(element, parts)
    text = "".join(parts)
    text = " ".join(text.split())
    return text.strip()


def _walk(node, parts: list[str]) -> None:
    tag = _local(node.tag)

    if tag == "t":
        parts.append(node.text or "")
        return

    if tag == "f":  # fraction
        num = _child(node, "num")
        den = _child(node, "den")
        parts.append(r"\frac{")
        if num is not None:
            _walk(num, parts)
        parts.append("}{")
        if den is not None:
            _walk(den, parts)
        parts.append("}")
        return

    if tag == "sSup":
        base = _child(node, "e")
        sup = _child(node, "sup")
        if base is not None:
            _walk(base, parts)
        parts.append("^{")
        if sup is not None:
            _walk(sup, parts)
        parts.append("}")
        return

    if tag == "sSub":
        base = _child(node, "e")
        sub = _child(node, "sub")
        if base is not None:
            _walk(base, parts)
        parts.append("_{")
        if sub is not None:
            _walk(sub, parts)
        parts.append("}")
        return

    if tag == "sSubSup":
        base = _child(node, "e")
        sub = _child(node, "sub")
        sup = _child(node, "sup")
        if base is not None:
            _walk(base, parts)
        parts.append("_{")
        if sub is not None:
            _walk(sub, parts)
        parts.append("}^{")
        if sup is not None:
            _walk(sup, parts)
        parts.append("}")
        return

    if tag == "rad":
        deg = _child(node, "deg")
        e = _child(node, "e")
        if deg is not None and "".join(deg.itertext()).strip():
            parts.append(r"\sqrt[")
            _walk(deg, parts)
            parts.append("]{")
        else:
            parts.append(r"\sqrt{")
        if e is not None:
            _walk(e, parts)
        parts.append("}")
        return

    if tag == "nary":
        for child in node:
            _walk(child, parts)
        return

    if tag in ("oMath", "oMathPara", "e", "num", "den", "sup", "sub", "deg",
               "fPr", "ctrlPr", "rPr", "sSupPr", "sSubPr", "sSubSupPr", "radPr",
               "naryPr", "dPr", "boxPr", "argSz"):
        for child in node:
            _walk(child, parts)
        return

    if tag == "r":
        for child in node:
            _walk(child, parts)
        return

    if tag == "d":  # delimiter
        parts.append("(")
        for child in node:
            if _local(child.tag) != "dPr":
                _walk(child, parts)
        parts.append(")")
        return

    if tag in ("pPr", "rFonts", "sz", "szCs", "color", "jc"):
        return

    for child in node:
        _walk(child, parts)
    if node.tail:
        parts.append(node.tail)


def _child(node, local_name: str):
    for child in node:
        if _local(child.tag) == local_name:
            return child
    return None


def find_omml(paragraph_element) -> list:
    """Return all m:oMath / m:oMathPara elements under a paragraph."""
    if paragraph_element is None:
        return []
    found = []
    for el in paragraph_element.iter():
        tag = _local(el.tag)
        if tag in ("oMath", "oMathPara"):
            found.append(el)
    return found


def paragraph_has_omml(paragraph_element) -> bool:
    return bool(find_omml(paragraph_element))