"""PaymentProvider interface and NoopPaymentProvider implementation.

docs/planning/economy.md US-2 (task 575fd14b5360).
"""

from __future__ import annotations

from dataclasses import dataclass, field
from datetime import datetime, timezone
from typing import Protocol
import uuid

ALLOWED_CREDIT_PACKS: set[int] = {100, 500, 1000, 5000}


@dataclass
class PurchaseSession:
    session_id: str
    user_id: int
    credits: int
    provider_ref: str
    status: str = "created"  # created, confirmed, failed
    created_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))


@dataclass
class Confirmation:
    confirmed: bool
    provider_ref: str
    credits: int
    user_id: int


class PaymentProvider(Protocol):
    """Pluggable payment provider protocol (e.g. Stripe, PayPal, Noop)."""

    async def create_purchase(
        self, user_id: int, credits: int, idempotency_key: str | None = None
    ) -> PurchaseSession:
        ...

    async def confirm(self, session_id: str) -> Confirmation:
        ...


class NoopPaymentProvider:
    """Deterministic, no-op payment provider for local development and testing.

    Returns confirmed=True with a simulated provider reference. Clearly non-production.
    """

    def __init__(self) -> None:
        self._sessions: dict[str, PurchaseSession] = {}

    async def create_purchase(
        self, user_id: int, credits: int, idempotency_key: str | None = None
    ) -> PurchaseSession:
        session_id = f"sess_{uuid.uuid4().hex[:16]}"
        provider_ref = f"noop_tx_{uuid.uuid4().hex[:12]}"
        sess = PurchaseSession(
            session_id=session_id,
            user_id=user_id,
            credits=credits,
            provider_ref=provider_ref,
            status="created",
        )
        self._sessions[session_id] = sess
        return sess

    async def confirm(self, session_id: str) -> Confirmation:
        sess = self._sessions.get(session_id)
        if sess is None:
            return Confirmation(
                confirmed=False,
                provider_ref="",
                credits=0,
                user_id=0,
            )

        sess.status = "confirmed"
        return Confirmation(
            confirmed=True,
            provider_ref=sess.provider_ref,
            credits=sess.credits,
            user_id=sess.user_id,
        )


payment_provider: PaymentProvider = NoopPaymentProvider()