from __future__ import annotations

import re
from pathlib import Path

_FILE_PLACEHOLDER_RE = re.compile(r"\{\{file:([^}]+)\}\}")



def expand_file_placeholders(
    text: str,
    *,
    workspace_root: Path,
    seen: set[Path] | None = None,
) -> str:
    workspace_root = workspace_root.resolve()
    active = set() if seen is None else set(seen)

    def replace(match: re.Match[str]) -> str:
        raw_ref = match.group(1).strip()
        include_path = Path(raw_ref)
        if not include_path.is_absolute():
            include_path = workspace_root / include_path
        include_path = include_path.resolve()
        if include_path in active:
            raise ValueError(f"cyclic {{file:...}} include detected at {include_path}")
        included = include_path.read_text(encoding="utf-8")
        return expand_file_placeholders(
            included,
            workspace_root=workspace_root,
            seen={*active, include_path},
        )

    return _FILE_PLACEHOLDER_RE.sub(replace, text)



def materialize_expanded_card(
    card_path: Path,
    *,
    workspace_root: Path,
    out_dir: Path,
) -> Path:
    card_path = card_path.resolve()
    expanded = expand_file_placeholders(
        card_path.read_text(encoding="utf-8"),
        workspace_root=workspace_root,
        seen={card_path},
    )
    out_dir.mkdir(parents=True, exist_ok=True)
    output_path = out_dir / f".{card_path.stem}.expanded{card_path.suffix}"
    output_path.write_text(expanded, encoding="utf-8")
    return output_path