"""RPC handlers + event payload builders for messaging transport (REQ-021/022).

Handlers are transport-agnostic: they accept a parsed `RpcRequest` payload
and return an `RpcResponse`. Wiring them onto `MessagingTransport.consume_*`
happens in the runtime layer.
"""
from __future__ import annotations

import logging
from datetime import date as date_cls
from datetime import datetime, timezone
from typing import Optional
from uuid import UUID

from trex_core.application.intents import BuyIntent, IntentService, SellIntent
from trex_core.application.messaging import RpcRequest, RpcResponse
from trex_core.application.portfolio import (
    PauseStore,
    SnapshotStore,
    View,
    build_snapshot_envelope,
)
from trex_core.application.watchdog import WatchdogStore
from trex_core.domain.slot import (
    SlotNotFoundError,
    SlotRepository,
    SlotService,
    SlotState,
)

_log = logging.getLogger(__name__)


# ---- intent RPC handler -----------------------------------------------------

def make_intent_rpc_handler(
    intent_service: IntentService,
    *,
    slot_service: Optional[SlotService] = None,
    watchdog_store: Optional[WatchdogStore] = None,
):
    """Build the RPC handler for `trex.intent.req`.

    Payload shape:
        {
          "intent_type": "buy" | "sell",
          "intent_id":   "<idempotency key, = correlation_id>",
          ... fields per BuyIntent / SellIntent ...
        }
      or (REQ-040):
        {"action": "update_thresholds", "slot_id": ...,
         "stop_loss_price"?, "take_profit_price"?, "forced_close_at"?}

    Response shape:
        {"intent_id": str, "status": "admitted"|"rejected", "slot_id": str|None, "reason": str|None}
      or for update_thresholds:
        {"status": "updated"|"ignored"|"error", "slot_id": str, "reason"?: str}

    Dedup uses `intent_log.try_insert(intent_id, ...)` (REQ-007 gate). The
    request's `correlation_id` is reused as `intent_id` so the messaging
    layer and the application share a single idempotency source of truth
    (REQ-023 AC-1).
    """

    def handler(req: RpcRequest) -> RpcResponse:
        body = req.payload or {}
        # REQ-040: update_thresholds action (separate from buy/sell intents).
        if str(body.get("action") or "").lower() == "update_thresholds":
            return _handle_update_thresholds(body, slot_service, watchdog_store)
        intent_id = str(body.get("intent_id") or req.correlation_id)
        intent_type = str(body.get("intent_type") or "").lower()
        try:
            if intent_type == "buy":
                buy = BuyIntent(
                    intent_id=intent_id,
                    trading_date=_parse_date(body.get("trading_date")),
                    symbol=str(body.get("symbol") or ""),
                    qty=_opt_float(body.get("qty")),
                    allocated_capital=_opt_float(body.get("allocated_capital")),
                    entry_price=_opt_float(body.get("entry_price")),
                    strategy_id=_opt_str(body.get("strategy_id")),
                    sell_strategy_id=_opt_str(body.get("sell_strategy_id")),
                    portfolio_id=_opt_str(body.get("portfolio_id")),
                    forced_close_at=_opt_dt(body.get("forced_close_at")),
                    stop_loss_price=_opt_decimal(body.get("stop_loss_price")),
                    take_profit_price=_opt_decimal(body.get("take_profit_price")),
                )
                d = intent_service.submit_buy(buy)
            elif intent_type == "sell":
                sell = SellIntent(
                    intent_id=intent_id,
                    slot_id=UUID(str(body["slot_id"])),
                    reason=str(body.get("reason") or "discretionary_sell"),
                    sell_strategy_id=_opt_str(body.get("sell_strategy_id")),
                )
                d = intent_service.submit_sell(sell)
            else:
                return RpcResponse(payload={
                    "intent_id": intent_id, "status": "rejected",
                    "slot_id": None, "reason": f"unknown_intent_type:{intent_type}",
                })
        except (KeyError, ValueError) as exc:
            return RpcResponse(payload={
                "intent_id": intent_id, "status": "rejected",
                "slot_id": None, "reason": f"bad_request:{exc}",
            })
        return RpcResponse(payload={
            "intent_id": d.intent_id,
            "status": d.status,
            "slot_id": (str(d.slot_id) if d.slot_id else None),
            "reason": d.reason,
        })

    return handler


def _handle_update_thresholds(
    body: dict,
    slot_service: Optional[SlotService],
    watchdog_store: Optional[WatchdogStore],
) -> RpcResponse:
    """REQ-040: update stop_loss/take_profit/forced_close_at on a holding slot.

    Only the keys actually present in the payload are forwarded, so an absent
    field keeps its value while an explicit ``null`` clears it (AC-4 vs AC-5).
    On success the slot's watchdog last_seen_at is reset (AC-3) — receiving an
    update_thresholds is itself a strategy-module liveness signal.
    """
    if slot_service is None:
        return RpcResponse(payload={"status": "error", "reason": "update_thresholds_unsupported"})
    try:
        slot_id = UUID(str(body["slot_id"]))
    except (KeyError, ValueError) as exc:
        return RpcResponse(payload={"status": "error", "reason": f"bad_request:{exc}"})
    kwargs: dict = {}
    if "stop_loss_price" in body:
        kwargs["stop_loss_price"] = _opt_decimal(body["stop_loss_price"])
    if "take_profit_price" in body:
        kwargs["take_profit_price"] = _opt_decimal(body["take_profit_price"])
    if "forced_close_at" in body:
        kwargs["forced_close_at"] = _opt_dt(body["forced_close_at"])
    actor = str(body.get("actor") or "strategy")
    try:
        status = slot_service.update_thresholds(slot_id, actor=actor, **kwargs)
    except SlotNotFoundError:
        return RpcResponse(payload={
            "status": "ignored", "slot_id": str(slot_id), "reason": "slot_not_found",
        })
    if status == "updated" and watchdog_store is not None:
        watchdog_store.update(str(slot_id))  # AC-3: liveness signal
    payload = {"status": status, "slot_id": str(slot_id)}
    if status == "ignored":
        payload["reason"] = "not_holding"  # AC-6
    return RpcResponse(payload=payload)


# ---- snapshot RPC handler ---------------------------------------------------

def make_snapshot_rpc_handler(
    slot_repo: SlotRepository,
    slot_service: SlotService,
    *,
    snapshot_store: Optional[SnapshotStore] = None,
    pause_store: Optional[PauseStore] = None,
    default_total_slots: int = 10,
    watchdog_store: Optional[WatchdogStore] = None,
):
    """Build the RPC handler for `trex.snapshot.req` (REQ-028).

    When `snapshot_store` + `pause_store` are provided (production wiring),
    returns the BAT-008 envelope:
        {
          "assets":          list of {symbol, asset_id, cash_balance,
                                       asset_quantity, active_strategy_id,
                                       strategy_params},
          "view":            "all" | "buyable" | "held",
          "available_slots": int,
          "degraded":        bool,
          "reason":          DegradedReason value or null,
          "message":         sanitized text or null
        }

    Without those, falls back to the BAT-007 slot+capacity stub shape so
    older callers and existing tests don't break.
    """

    def handler(req: RpcRequest) -> RpcResponse:
        body = req.payload or {}
        day = _parse_date(body.get("trading_date")) if body.get("trading_date") else _today()

        # REQ-034: update watchdog for all holding slots visible in this RPC.
        if watchdog_store is not None:
            for s in slot_repo.list_slots(day):
                if s.status is SlotState.HOLDING:
                    watchdog_store.update(str(s.slot_id))

        # --- BAT-008 envelope path (snapshot store wired) ---
        if snapshot_store is not None and pause_store is not None:
            requested_view = str(body.get("view") or "all").lower()
            try:
                view = View(requested_view)
            except ValueError:
                view = View.ALL
            strategy_key = _opt_str(body.get("strategy_key"))
            cap = slot_service.compute_slot_capacity(day, default_total_slots)
            envelope = build_snapshot_envelope(
                store=snapshot_store,
                pause_store=pause_store,
                slot_repo=slot_repo,
                available_slots=cap.idle_count,
                view=view,
                strategy_key=strategy_key,
                trading_date=day,
            )
            return RpcResponse(payload=envelope.to_dict())

        # --- BAT-007 legacy stub-shape path ---
        view_raw = str(body.get("view") or "all")
        strategy_filter = _opt_str(body.get("strategy_id"))
        slots = slot_repo.list_slots(day)
        if view_raw == "open":
            slots = [s for s in slots if s.status.value in ("pending_buy", "holding", "pending_sell")]
        if strategy_filter is not None:
            slots = [s for s in slots if s.strategy_id == strategy_filter]
        cap = slot_service.compute_slot_capacity(day, max(1, len(slot_repo.list_slots(day))))
        return RpcResponse(payload={
            "view": view_raw,
            "strategy_id": strategy_filter,
            "trading_date": day.isoformat(),
            "slots": [_slot_to_dict(s) for s in slots],
            "capacity": {
                "idle_count": cap.idle_count,
                "holding_count": cap.holding_count,
                "pending_count": cap.pending_count,
                "total_slots": cap.total_slots,
                "scarcity_ratio": cap.scarcity_ratio,
            },
        })

    return handler


# ---- pause/resume RPC handler (REQ-032 AC-4) --------------------------------

def make_pause_rpc_handler(pause_store: PauseStore):
    """RPC handler for the `trex.pause.req` control queue.

    Payload: {"action": "pause" | "resume" | "list", "portfolio_id": "..."}
    Response: {"status": "ok"|"error", "paused": [list-of-portfolio_id], "reason"?: str}
    """

    def handler(req: RpcRequest) -> RpcResponse:
        body = req.payload or {}
        action = str(body.get("action") or "").lower()
        pid = _opt_str(body.get("portfolio_id"))
        actor = str(body.get("actor") or "operator")
        try:
            if action == "pause":
                if not pid:
                    return _err("portfolio_id required")
                pause_store.pause(pid, actor=actor)
            elif action == "resume":
                if not pid:
                    return _err("portfolio_id required")
                pause_store.resume(pid)
            elif action == "list":
                pass
            else:
                return _err(f"unknown action: {action!r}")
        except Exception as exc:  # noqa: BLE001
            return _err(f"pause store error: {exc.__class__.__name__}")
        return RpcResponse(payload={
            "status": "ok",
            "paused": sorted(pause_store.list_paused()),
            "action": action,
        })

    return handler


def _err(reason: str) -> RpcResponse:
    return RpcResponse(payload={"status": "error", "reason": reason})


# ---- event payload builder --------------------------------------------------

def slot_transition_event_payload(slot, *, event_type: str) -> dict:
    """Build the event payload for a slot transition (REQ-023 AC-5).

    Carries the *current state* + a monotonic sequence (`updated_at` iso) so
    receivers can apply last-wins without ordering guarantees.
    """
    return {
        "event_type": event_type,
        "slot_id": str(slot.slot_id),
        "strategy_id": slot.strategy_id,
        "symbol": slot.symbol,
        "status": slot.status.value,
        "qty": float(slot.qty) if slot.qty is not None else None,
        "avg_price": float(slot.avg_price) if slot.avg_price is not None else None,
        "portfolio_id": slot.portfolio_id,
        "trading_date": slot.trading_date.isoformat(),
        "sequence_at": (slot.updated_at or datetime.now(tz=timezone.utc)).isoformat(),
    }


# ---- helpers ----------------------------------------------------------------

def _opt_str(v) -> Optional[str]:
    if v is None or v == "":
        return None
    return str(v)


def _opt_decimal(v):
    if v is None:
        return None
    from decimal import Decimal
    return Decimal(str(v))


def _opt_float(v) -> Optional[float]:
    if v is None:
        return None
    return float(v)


def _opt_dt(v) -> Optional[datetime]:
    if v is None:
        return None
    if isinstance(v, datetime):
        return v
    return datetime.fromisoformat(str(v))


def _parse_date(v) -> date_cls:
    if isinstance(v, date_cls):
        return v
    return date_cls.fromisoformat(str(v))


def _today() -> date_cls:
    return datetime.now(tz=timezone.utc).date()


def _slot_to_dict(s) -> dict:
    return {
        "slot_id": str(s.slot_id),
        "trading_date": s.trading_date.isoformat(),
        "status": s.status.value,
        "symbol": s.symbol,
        "qty": float(s.qty) if s.qty is not None else None,
        "avg_price": float(s.avg_price) if s.avg_price is not None else None,
        "entry_price": float(s.entry_price) if s.entry_price is not None else None,
        "allocated_capital": float(s.allocated_capital) if s.allocated_capital is not None else None,
        "strategy_id": s.strategy_id,
        "sell_strategy_id": s.sell_strategy_id,
        "portfolio_id": s.portfolio_id,
        "forced_close_at": s.forced_close_at.isoformat() if s.forced_close_at else None,
    }