from datetime import datetime
from typing import Optional

from pydantic import BaseModel, Field, validator

from app.models.transaction import TransactionType


class TransactionBase(BaseModel):
    """
    Base transaction schema with common attributes.
    """
    item_id: int = Field(..., description="ID of the item")
    quantity: int = Field(..., description="Transaction quantity", gt=0)
    transaction_type: TransactionType = Field(..., description="Type of transaction")
    unit_price: float = Field(..., description="Unit price", gt=0)
    reference: Optional[str] = Field(None, description="Reference number or order ID")
    notes: Optional[str] = Field(None, description="Additional notes")


class TransactionCreate(TransactionBase):
    """
    Schema for transaction creation.
    """
    
    @validator('transaction_type')
    def validate_transaction_type(cls, v):
        if v not in [TransactionType.STOCK_IN, TransactionType.STOCK_OUT]:
            raise ValueError('Transaction type must be either stock_in or stock_out')
        return v


class TransactionUpdate(BaseModel):
    """
    Schema for updating transaction information.
    """
    quantity: Optional[int] = Field(None, description="Transaction quantity", gt=0)
    unit_price: Optional[float] = Field(None, description="Unit price", gt=0)
    reference: Optional[str] = Field(None, description="Reference number or order ID")
    notes: Optional[str] = Field(None, description="Additional notes")


class TransactionInDBBase(TransactionBase):
    """
    Base schema for transactions from the database.
    """
    id: int = Field(..., description="Transaction ID")
    total_price: float = Field(..., description="Total transaction price")
    timestamp: datetime = Field(..., description="Transaction timestamp")
    user_id: int = Field(..., description="ID of the user who performed the transaction")

    class Config:
        from_attributes = True


class Transaction(TransactionInDBBase):
    """
    Schema for transaction information returned to clients.
    """
    pass


class TransactionWithDetails(TransactionInDBBase):
    """
    Schema for transaction with related entities.
    """
    from app.schemas.item import Item
    from app.schemas.user import User
    
    item: Item = Field(..., description="Transaction item")
    user: User = Field(..., description="User who performed the transaction")