from __future__ import annotations

from datetime import datetime, timezone
from uuid import uuid4

from sqlalchemy import JSON, DateTime, Float, Integer, String, Text
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column


def _utcnow() -> datetime:
    return datetime.now(timezone.utc)


class WWIBase(DeclarativeBase):
    pass


class WWIReorderRecommendation(WWIBase):
    """Persisted WWI stock reorder recommendation runs."""

    __tablename__ = "wwi_reorder_recommendations"

    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid4()))
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow, index=True)
    item_count: Mapped[int] = mapped_column(Integer)
    trigger_source: Mapped[str] = mapped_column(String(64), index=True)
    trace_id: Mapped[str | None] = mapped_column(String(32), nullable=True, index=True)
    span_id: Mapped[str | None] = mapped_column(String(16), nullable=True)
    payload: Mapped[list[dict]] = mapped_column(JSON, default=list)


class WWISupplierScore(WWIBase):
    """Persisted WWI supplier reliability scoring runs."""

    __tablename__ = "wwi_supplier_scores"

    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid4()))
    computed_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow, index=True)
    supplier_count: Mapped[int] = mapped_column(Integer)
    top_n: Mapped[int] = mapped_column(Integer)
    trigger_source: Mapped[str] = mapped_column(String(64), index=True)
    trace_id: Mapped[str | None] = mapped_column(String(32), nullable=True, index=True)
    span_id: Mapped[str | None] = mapped_column(String(16), nullable=True)
    payload: Mapped[list[dict]] = mapped_column(JSON, default=list)


class WWIWhatIfScenario(WWIBase):
    """User-submitted what-if simulation results."""

    __tablename__ = "wwi_whatif_scenarios"

    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid4()))
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow, index=True)
    stock_item_key: Mapped[int] = mapped_column(Integer, index=True)
    stock_item_name: Mapped[str] = mapped_column(String(200))
    demand_multiplier: Mapped[float] = mapped_column(Float)
    current_stock: Mapped[float] = mapped_column(Float)
    avg_daily_demand: Mapped[float] = mapped_column(Float)
    projected_days_until_stockout: Mapped[float | None] = mapped_column(Float, nullable=True)
    recommended_order_qty: Mapped[float] = mapped_column(Float)
    trace_id: Mapped[str | None] = mapped_column(String(32), nullable=True, index=True)
    span_id: Mapped[str | None] = mapped_column(String(16), nullable=True)
    result: Mapped[dict] = mapped_column(JSON, default=dict)


class WWIBusinessEvent(WWIBase):
    """Automatically generated business alert events."""

    __tablename__ = "wwi_business_events"

    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid4()))
    occurred_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_utcnow, index=True)
    event_type: Mapped[str] = mapped_column(String(50), index=True)   # LOW_STOCK, ORDER_DROP, SUPPLIER_RISK
    severity: Mapped[str] = mapped_column(String(20), index=True)     # HIGH, MEDIUM, LOW
    entity_key: Mapped[str] = mapped_column(String(100), index=True)
    entity_name: Mapped[str] = mapped_column(String(200))
    message: Mapped[str] = mapped_column(Text)
    trace_id: Mapped[str | None] = mapped_column(String(32), nullable=True, index=True)
    span_id: Mapped[str | None] = mapped_column(String(16), nullable=True)
    details: Mapped[dict] = mapped_column(JSON, default=dict)