from __future__ import annotations

from decimal import Decimal, ROUND_HALF_UP
from pathlib import Path
from typing import Any

from .load import _read_json, default_data_dir

TWOPLACES = Decimal("0.01")


def _money(value: Decimal) -> Decimal:
    return value.quantize(TWOPLACES, rounding=ROUND_HALF_UP)


def load_credit_wallets(data_dir=None) -> dict[str, Any]:
    root = data_dir or default_data_dir()
    path = Path(root) / "credit_wallets.json"
    if not path.exists():
        return {"version": 1, "currency": "EUR", "wallets": []}
    return _read_json(path)


def build_credit_summary(raw: dict, usage_by_member: dict[str, Decimal], period: str) -> dict:
    wallets = []
    for item in raw.get("wallets", []):
        member_id = item["member_id"]
        allowance = Decimal(str(item.get("monthly_allowance_eur", "0")))
        used = usage_by_member.get(member_id, Decimal(str(item.get("used_eur", "0"))))
        remaining = max(Decimal("0"), allowance - used)
        wallets.append(
            {
                "member_id": member_id,
                "period": period,
                "monthly_allowance_eur": _money(allowance),
                "used_eur": _money(used),
                "remaining_eur": _money(remaining),
                "overage_eur": _money(max(Decimal("0"), used - allowance)),
            }
        )

    return {
        "period": period,
        "currency": raw.get("currency", "EUR"),
        "wallet_count": len(wallets),
        "wallets": wallets,
        "notes": "Observatory-only credit accounting; no customer billing in MVP.",
    }