trex-core/trex_core/application/intents.py

"""Intent application service (REQ-007).

Turns a buy/sell intent submitted over HTTP into a single-writer slot
transition, with intent_id idempotency backed by a durable intent_log.

Idempotency model (dcy-002 OQ-1): `intent_store.try_insert` is the dedup
gate. On a duplicate intent_id it returns the prior decision without
re-driving any transition (NFR-3). Slot transitions go exclusively through
SlotService (advisory-lock serialized) so the single-writer invariant
holds (NFR-2). Concurrency on the last idle slot is resolved by retrying
on SlotStateMismatchError.
"""
from __future__ import annotations

from dataclasses import dataclass, field
from datetime import date, datetime
from typing import Any, Optional
from uuid import UUID

from trex_core.application.ports import IntentStore
from trex_core.domain.slot import (
    SlotRepository,
    SlotService,
    SlotState,
    SlotStateMismatchError,
)

_MAX_IDLE_RETRY = 8


@dataclass(frozen=True)
class IntentDecision:
    """Result of submitting an intent."""

    intent_id: str
    status: str  # 'admitted' | 'rejected'
    slot_id: Optional[UUID] = None
    reason: Optional[str] = None

    @property
    def admitted(self) -> bool:
        return self.status == "admitted"


@dataclass(frozen=True)
class BuyIntent:
    intent_id: str
    trading_date: date
    symbol: str
    qty: Optional[float] = None
    allocated_capital: Optional[float] = None
    entry_price: Optional[float] = None
    strategy_id: Optional[str] = None
    sell_strategy_id: Optional[str] = None
    portfolio_id: Optional[str] = None
    forced_close_at: Optional[datetime] = None
    extra: dict[str, Any] = field(default_factory=dict)


@dataclass(frozen=True)
class SellIntent:
    intent_id: str
    slot_id: UUID
    reason: str = "discretionary_sell"
    sell_strategy_id: Optional[str] = None
    extra: dict[str, Any] = field(default_factory=dict)


class IntentService:
    """Admission + slot transition for buy/sell intents (single writer)."""

    def __init__(
        self,
        slot_service: SlotService,
        slot_repo: SlotRepository,
        intent_store: IntentStore,
    ) -> None:
        self._svc = slot_service
        self._repo = slot_repo
        self._intents = intent_store

    # ------------------------------------------------------------
    def lookup(self, intent_id: str) -> Optional[IntentDecision]:
        """Return the recorded decision for an intent_id, or None (re-query)."""
        rec = self._intents.get(intent_id)
        if rec is None:
            return None
        return IntentDecision(rec.intent_id, rec.status, rec.slot_id, rec.reason)

    def submit_buy(self, intent: BuyIntent) -> IntentDecision:
        payload = {
            "trading_date": intent.trading_date.isoformat(),
            "symbol": intent.symbol,
            "qty": intent.qty,
            "allocated_capital": intent.allocated_capital,
            "entry_price": intent.entry_price,
            "strategy_id": intent.strategy_id,
            "sell_strategy_id": intent.sell_strategy_id,
            "portfolio_id": intent.portfolio_id,
        }
        prior = self._dedup(intent.intent_id, "buy", payload)
        if prior is not None:
            return prior

        decision = self._admit_buy(intent)
        self._intents.finalize(
            intent.intent_id, decision.status, decision.slot_id, decision.reason
        )
        return decision

    def submit_sell(self, intent: SellIntent) -> IntentDecision:
        payload = {
            "slot_id": str(intent.slot_id),
            "reason": intent.reason,
            "sell_strategy_id": intent.sell_strategy_id,
        }
        prior = self._dedup(intent.intent_id, "sell", payload)
        if prior is not None:
            return prior

        decision = self._admit_sell(intent)
        self._intents.finalize(
            intent.intent_id, decision.status, decision.slot_id, decision.reason
        )
        return decision

    # ------------------------------------------------------------
    def _dedup(self, intent_id: str, intent_type: str, payload: dict) -> Optional[IntentDecision]:
        """Return prior decision if intent_id already seen; else None (and reserve it)."""
        inserted = self._intents.try_insert(intent_id, intent_type, payload)
        if inserted:
            return None
        rec = self._intents.get(intent_id)
        if rec is None:  # extremely unlikely race; treat as not-yet-decided
            return IntentDecision(intent_id, "rejected", None, "duplicate_in_flight")
        return IntentDecision(intent_id, rec.status, rec.slot_id, rec.reason)

    def _admit_buy(self, intent: BuyIntent) -> IntentDecision:
        # Retry on the last-idle-slot race: another intent may claim the slot
        # between our find and transit (SlotStateMismatchError).
        for _ in range(_MAX_IDLE_RETRY):
            slot = self._repo.find_idle_slot(intent.trading_date)
            if slot is None:
                return IntentDecision(intent.intent_id, "rejected", None, "no_idle_slot")
            try:
                updated = self._svc.transit_slot(
                    slot.slot_id,
                    SlotState.IDLE,
                    SlotState.PENDING_BUY,
                    reason="buy_intent",
                    actor="intent_api",
                    symbol=intent.symbol,
                    qty=intent.qty,
                    allocated_capital=intent.allocated_capital,
                    entry_price=intent.entry_price,
                    strategy_id=intent.strategy_id,
                    sell_strategy_id=intent.sell_strategy_id,
                    portfolio_id=intent.portfolio_id,
                    forced_close_at=intent.forced_close_at,
                    extra={"intent_id": intent.intent_id, "symbol": intent.symbol},
                )
            except SlotStateMismatchError:
                continue  # slot was claimed concurrently; try another idle slot
            return IntentDecision(intent.intent_id, "admitted", updated.slot_id, None)
        return IntentDecision(intent.intent_id, "rejected", None, "idle_slot_contended")

    def _admit_sell(self, intent: SellIntent) -> IntentDecision:
        slot = self._repo.fetch_slot(intent.slot_id)
        if slot is None:
            return IntentDecision(intent.intent_id, "rejected", None, "slot_not_found")
        if slot.status is not SlotState.HOLDING:
            return IntentDecision(
                intent.intent_id, "rejected", None, f"slot_not_holding:{slot.status.value}"
            )
        try:
            updated = self._svc.transit_slot(
                slot.slot_id,
                SlotState.HOLDING,
                SlotState.PENDING_SELL,
                reason=intent.reason,
                actor="intent_api",
                sell_strategy_id=intent.sell_strategy_id,
                extra={"intent_id": intent.intent_id},
            )
        except SlotStateMismatchError:
            return IntentDecision(intent.intent_id, "rejected", None, "slot_state_changed")
        return IntentDecision(intent.intent_id, "admitted", updated.slot_id, None)