# app/intent_schema.py
from __future__ import annotations
from typing import List, Optional, Literal, Union, Tuple
from pydantic import BaseModel, Field, ValidationError

# ---- Canonical intent names ----
IntentName = Literal[
    "reservation.create",
    "order.create",
    "hours.get",
    "menu.search",
    "smalltalk",
    "other",
]

# ---- Slot models ----
class ReservationSlots(BaseModel):
    name: Optional[str] = None
    party_size: Optional[int] = Field(default=None, ge=1, le=20)
    date: Optional[str] = None          # ISO preferred (YYYY-MM-DD) or “today”
    time: Optional[str] = None          # “19:00” or “7 pm”
    phone: Optional[str] = None

    model_config = {"extra": "ignore"}  # tolerate extra keys from LLM

class OrderItem(BaseModel):
    name: str
    qty: int = Field(default=1, ge=1)

    model_config = {"extra": "ignore"}

class OrderSlots(BaseModel):
    items: List[OrderItem] = Field(default_factory=list)
    notes: Optional[str] = None

    model_config = {"extra": "ignore"}

class MenuSlots(BaseModel):
    query: Optional[str] = None
    dietary: List[str] = Field(default_factory=list)  # e.g., ["vegan","gluten-free"]

    model_config = {"extra": "ignore"}

# ---- Envelope returned by the router/LLM ----
class IntentEnvelope(BaseModel):
    intent: IntentName
    need_more_info: bool = False
    ask_user: Optional[str] = None   # a single, polite follow-up question if info missing

    # Keep it loose at the API boundary; we’ll coerce it with helper below.
    slots: dict = Field(default_factory=dict)

    model_config = {"extra": "ignore"}

# ---- Helpers to validate slots into the right model ----
SlotsUnion = Union[ReservationSlots, OrderSlots, MenuSlots, dict]

def coerce_slots(intent: IntentName, slots: dict | None) -> Tuple[SlotsUnion, Optional[str]]:
    """
    Try to convert a loose slots dict into the correct typed model based on 'intent'.
    Returns (slots_obj, error_message). If cannot validate, returns (original_dict, message).
    This keeps the pipeline resilient while giving you typed access when possible.
    """
    raw = slots or {}
    try:
        if intent == "reservation.create":
            return ReservationSlots(**raw), None
        if intent == "order.create":
            return OrderSlots(**raw), None
        if intent == "menu.search":
            return MenuSlots(**raw), None
        # 'hours.get', 'smalltalk', 'other' often don’t need slots
        return raw, None
    except ValidationError as ve:
        return raw, f"slot_validation_failed: {ve.errors()}"