from typing import Any

CELL_GAP = " | "
_TEXT_KEYS = ("summary", "text", "expression", "credit")
_INLINE_KEYS = ("text", "alternative_text", "expression")


def _button(button: dict[str, Any]) -> str:
    label = _inline(button.get("text"))
    url = button.get("url")
    return f"{label} ({url})" if isinstance(url, str) else label


def _inline(value: object) -> str:
    if isinstance(value, str):
        return value
    if isinstance(value, list):
        return "".join(_inline(item) for item in value)
    if not isinstance(value, dict):
        return ""
    button = value.get("button")
    if isinstance(button, dict):
        return _button(button)
    return next((_inline(value[key]) for key in _INLINE_KEYS if key in value), "")


def _children(block: dict[str, Any], key: str) -> list[Any]:
    value = block.get(key)
    return value if isinstance(value, list) else []


def _row(row: object) -> str:
    cells = row if isinstance(row, list) else []
    return CELL_GAP.join(
        _inline(cell.get("text")) for cell in cells if isinstance(cell, dict)
    )


def _block(block: object) -> list[str]:
    if not isinstance(block, dict):
        return []
    lines = [_inline(block[key]) for key in _TEXT_KEYS if key in block]
    lines += [_row(row) for row in _children(block, "cells")]
    lines += [
        _button(button)
        for button in _children(block, "buttons")
        if isinstance(button, dict)
    ]
    for key in ("items", "blocks"):
        for child in _children(block, key):
            lines += _block(child)
    lines += _block(block.get("caption"))
    lines = [line for line in lines if line]
    label = block.get("label")
    if isinstance(label, str) and lines:
        lines[0] = f"{label} {lines[0]}"
    return lines


def rich_text(rich: object) -> str | None:
    return "\n".join(_block(rich)) or None