"""Enumerate vnpy_ctastrategy CTA strategies + their parameters.

Used by the backtest UI dropdown and dynamic parameter form. Falls back to a
static name list when vnpy_ctastrategy is not importable (e.g. local dev).
Task S1.3.
"""
from __future__ import annotations

import importlib
import pkgutil

# Fallback strategy names (when vnpy_ctastrategy import fails).
STRATEGY_NAMES: list[str] = ["DoubleMaStrategy", "BollChannelStrategy", "AtrRsiStrategy"]


def _load_strategy_classes() -> dict[str, type]:
    """Import all Strategy classes from vnpy_ctastrategy.strategies."""
    classes: dict[str, type] = {}
    try:
        mod = importlib.import_module("vnpy_ctastrategy.strategies")
        for _, name, _ in pkgutil.iter_modules(mod.__path__):
            try:
                m = importlib.import_module(f"vnpy_ctastrategy.strategies.{name}")
                for attr in dir(m):
                    obj = getattr(m, attr)
                    if isinstance(obj, type) and attr.endswith("Strategy") and hasattr(obj, "parameters"):
                        classes[attr] = obj
            except Exception:
                continue
    except Exception:
        pass
    return classes


def list_strategies() -> list[dict]:
    """Return [{name, class_name}, ...] for the UI dropdown."""
    classes = _load_strategy_classes()
    if classes:
        return [{"name": n, "class_name": n} for n in sorted(classes)]
    return [{"name": n, "class_name": n} for n in STRATEGY_NAMES]


def strategy_params(name: str) -> dict:
    """Return {parameters: [...], defaults: {...}} for a strategy's dynamic form."""
    classes = _load_strategy_classes()
    cls = classes.get(name)
    if cls is None:
        return {"parameters": [], "defaults": {}}
    params = list(getattr(cls, "parameters", []))
    defaults = {p: getattr(cls, p, None) for p in params}
    return {"parameters": params, "defaults": defaults}


def get_strategy_class(name: str) -> type | None:
    """Return the strategy class by name (None if unavailable)."""
    return _load_strategy_classes().get(name)