"""Extract statically known variable names without evaluating Tcl substitutions."""

from tclint.syntax_tree import BareWord, CompoundBareWord, Node, QuotedWord, VarSub


def variable_name(node: Node) -> str | None:
    contents = node.contents
    if isinstance(contents, str):
        return contents
    if isinstance(node, (CompoundBareWord, QuotedWord)) and node.children:
        first = node.children[0]
        last = node.children[-1]
        if (
            isinstance(first, BareWord)
            and isinstance(last, BareWord)
            and "(" in first.value
            and last.value.endswith(")")
        ):
            # Substitutions in an array index do not change the array's name.
            return first.value.split("(", 1)[0] or None
    return None


def array_key_parts(node: Node, *, preserve_variables: bool = False) -> tuple[str | None, ...]:
    """Keep comma-separated literal index components; substitutions are unknown."""
    contents = node.contents
    if not isinstance(contents, str):
        if not isinstance(node, (CompoundBareWord, QuotedWord)) or not variable_name(node):
            return ()
        chunks = []
        for child in node.children:
            if isinstance(child, BareWord):
                chunks.append(child.value)
            elif preserve_variables and isinstance(child, VarSub) and not child.children:
                chunks.append("${" + child.value + "}" if child.braced else "$" + child.value)
            else:
                chunks.append("\0")
        contents = "".join(chunks)
    if "(" not in contents or not contents.endswith(")"):
        return ()
    return tuple(
        part if part and not any(char in part for char in ("\0[]\\" if preserve_variables else "\0$[]\\")) else None
        for part in contents.split("(", 1)[1][:-1].split(",")
    )