from __future__ import annotations
from typing import List, Optional
from datetime import datetime
from pydantic import BaseModel, Field


class LocalProblem(BaseModel):
    id: str = Field(..., description="Unique problem identifier")
    asset: str
    venue: str
    objective: str = Field("min_spread", description="High-level objective tag")
    parameters: Optional[dict] = Field(default_factory=dict)
    price_target: Optional[float] = None
    tolerance: Optional[float] = None
    constraints: Optional[dict] = None
    created_at: datetime = Field(default_factory=datetime.utcnow)


class SharedVariables(BaseModel):
    contract_id: str
    version: int
    signals: dict | None = None
    variables: dict | None = None
    privacy_budget: Optional[float] = 0.0


class DualVariables(BaseModel):
    contract_id: str = ""
    version: int
    shadow_prices: dict


class PlanDelta(BaseModel):
    contract_id: Optional[str] = None
    delta: dict
    timestamp: datetime = Field(default_factory=datetime.utcnow)
    author_signature: Optional[str] = None
    author: Optional[str] = None

    def to_json(self) -> str:
        import json
        return json.dumps(self.dict(), default=str)


class AuditLog(BaseModel):
    contract_id: Optional[str] = None
    entry: dict
    timestamp: datetime = Field(default_factory=datetime.utcnow)
    signature: Optional[str] = None