# /opt/docker/dev/service_finder/backend/app/schemas/asset_cost.py
from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
from typing import Optional, Dict, Any
from datetime import datetime, date
from decimal import Decimal
from uuid import UUID

class AssetCostBase(BaseModel):
    """Base schema — matches the AssetCost SQLAlchemy model fields.
    
    GROSS-FIRST (Masterbook 2.0.1): amount_gross is the primary/required field.
    In EU accounting, the gross amount (Bruttó) is the absolute Source of Truth.
    amount_net is optional — if only gross is provided, net = gross (0% VAT).
    If vat_rate is also provided, net is calculated back from gross.
    """
    amount_gross: Optional[Decimal] = Field(None, description="Bruttó összeg (ÁFA-val) — ELSŐDLEGES forrás, de lehet NULL legacy rekordoknál")
    amount_net: Optional[Decimal] = Field(None, description="Nettó összeg (ÁFA nélkül) — OPCIONÁLIS, ha nincs megadva, bruttóból számolva")

    @model_validator(mode='before')
    @classmethod
    def safety_net_gross_from_net(cls, data: Any) -> Any:
        """SAFETY NET (Graceful Degradation): If the incoming payload contains
        amount_net but amount_gross is missing/None, automatically copy amount_net
        to amount_gross. This protects against legacy/cached browsers that still
        send amount_net in their payloads.

        GROSS-FIRST (Masterbook 2.0.1): The backend is strictly Gross-first.
        """
        if isinstance(data, dict):
            has_net = data.get('amount_net') is not None
            has_gross = data.get('amount_gross') is not None
            if has_net and not has_gross:
                data['amount_gross'] = data['amount_net']
        return data
    vat_rate: Optional[Decimal] = Field(None, description="ÁFA kulcs (pl. 27.00)")
    currency: str = "HUF"
    cost_date: datetime = Field(default_factory=lambda: datetime.now(), validation_alias="date", description="Költség rögzítésének dátuma/időpontja")
    invoice_number: Optional[str] = None
    data: Dict[str, Any] = Field(default_factory=dict)  # nyugta adatai, GPS koordináták
    category_id: int  # FK a CostCategory táblához
    mileage_at_cost: Optional[int] = None  # Stored inside data JSONB
    description: Optional[str] = None      # Stored inside data JSONB

    # === BESZÁLLÍTÓI ADATOK (B2B expansion) ===
    vendor_organization_id: Optional[int] = Field(None, description="Beszállító szervezet ID (FK fleet.organizations)")
    external_vendor_name: Optional[str] = Field(None, max_length=200, description="Szabadon gépelhető beszállító név (ha nincs a rendszerben)")

    # === KÖNYVELÉSI DÁTUMOK ===
    invoice_date: Optional[date] = Field(None, description="Számla kiállításának dátuma")
    fulfillment_date: Optional[date] = Field(None, description="Teljesítés dátuma")

    @model_validator(mode='after')
    def validate_gross_first(self):
        """Gross-First validation: ensure amount_gross is the primary source.
        
        If amount_net is not provided but vat_rate is, calculate net from gross.
        If neither amount_net nor vat_rate is provided, net = gross (0% VAT).
        If amount_gross is None (legacy data), default to 0 to prevent 500 errors.
        """
        gross = self.amount_gross
        net = self.amount_net
        vat = self.vat_rate
        
        # Fault tolerance: if gross is None (legacy NULL), default to 0
        if gross is None:
            self.amount_gross = Decimal("0")
            gross = self.amount_gross
        
        if net is None and vat is not None and vat > 0:
            # Net will be calculated in the service layer from gross & vat
            pass
        elif net is None:
            # No net and no vat → net = gross (0% VAT content)
            self.amount_net = gross
            self.vat_rate = Decimal("0")
        return self

class AssetCostCreate(AssetCostBase):
    asset_id: UUID
    organization_id: Optional[int] = None  # Auto-resolved from asset if not provided
    status: Optional[str] = Field(None, description="Költség státusz (DRAFT, PENDING_APPROVAL, APPROVED) - auto-set by backend")
    linked_asset_event_id: Optional[UUID] = Field(None, description="Kapcsolódó AssetEvent ID (kétirányú hivatkozáshoz)")


class AssetCostUpdate(BaseModel):
    """Schema for updating an existing expense via PUT /expenses/{expense_id}.
    
    All fields are optional — only provided fields will be updated.
    The expense_id is passed via path parameter, asset_id and organization_id
    are immutable after creation.
    """
    category_id: Optional[int] = None
    amount_gross: Optional[Decimal] = None
    amount_net: Optional[Decimal] = None
    vat_rate: Optional[Decimal] = None
    currency: Optional[str] = None
    date: Optional[datetime] = None
    mileage_at_cost: Optional[int] = None
    description: Optional[str] = None
    invoice_number: Optional[str] = None
    vendor_organization_id: Optional[int] = None
    external_vendor_name: Optional[str] = None
    invoice_date: Optional[date] = None
    fulfillment_date: Optional[date] = None
    data: Optional[Dict[str, Any]] = None


class AssetCostResponse(AssetCostBase):
    """Response schema — matches DB columns from vehicle.asset_costs."""
    id: UUID
    asset_id: UUID
    organization_id: int
    status: str = "DRAFT"
    linked_asset_event_id: Optional[UUID] = None
    
    # Derived / enriched fields (not in DB model directly)
    category_name: Optional[str] = None  # Resolved from CostCategory relationship
    category_code: Optional[str] = None  # Resolved from CostCategory relationship
    description: Optional[str] = None    # Extracted from data['description']
    mileage_at_cost: Optional[int] = None  # Extracted from data['mileage_at_cost']

    # Enriched vendor name (resolved from vendor_organization_id relationship)
    vendor_name: Optional[str] = None  # Resolved from Organization.name via vendor_organization_id
    
    model_config = ConfigDict(from_attributes=True)