# /opt/docker/dev/service_finder/backend/app/api/v1/endpoints/expenses.py
import logging
from decimal import Decimal
from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func
from app.api.deps import get_db, get_current_user, RequireOrgCapability
from app.models import Asset, AssetCost, AssetEvent, OrganizationMember, SystemParameter, OrgRole
from app.schemas.asset_cost import AssetCostCreate
from datetime import datetime, timezone

logger = logging.getLogger(__name__)

# Cost category IDs that are service/maintenance/repair related
# These trigger automatic AssetEvent creation
SERVICE_RELATED_CATEGORY_IDS = {2, 16, 17, 18}  # MAINTENANCE, MAINT_SERVICE, MAINT_OIL, MAINT_BRAKES

# Fuel category IDs - auto-approved even for DRIVER role
FUEL_CATEGORY_IDS = {1}  # FUEL

router = APIRouter()


async def _resolve_user_role_in_org(
    db: AsyncSession,
    user_id: int,
    organization_id: int
) -> str:
    """
    Resolve the user's role within the given organization.
    
    Returns:
        str: The role string (OWNER, ADMIN, MEMBER, DRIVER, etc.)
        Returns 'MEMBER' as default if no membership found.
    """
    stmt = select(OrganizationMember.role).where(
        OrganizationMember.user_id == user_id,
        OrganizationMember.organization_id == organization_id,
        OrganizationMember.status == "active"
    ).limit(1)
    result = await db.execute(stmt)
    role = result.scalar_one_or_none()
    return role or "MEMBER"


async def _check_org_capability(
    db: AsyncSession,
    user_id: int,
    organization_id: int,
    capability_name: str
) -> bool:
    """
    RBAC Phase 2: JSONB-alapú képesség-ellenőrzés.
    
    Lekéri a user szervezeti szerepkörét, majd a fleet.org_roles tábla
    permissions JSONB oszlopából ellenőrzi a kért képességet.
    
    Returns:
        bool: True ha a user rendelkezik a képességgel.
    """
    # 1. Get user's org role
    member_stmt = select(OrganizationMember.role).where(
        OrganizationMember.user_id == user_id,
        OrganizationMember.organization_id == organization_id,
        OrganizationMember.status == "active"
    ).limit(1)
    member_result = await db.execute(member_stmt)
    org_role_name = member_result.scalar_one_or_none()
    
    if not org_role_name:
        return False
    
    # 2. Get permissions from fleet.org_roles table
    role_stmt = select(OrgRole.permissions).where(
        OrgRole.name_key == org_role_name,
        OrgRole.is_active == True
    ).limit(1)
    role_result = await db.execute(role_stmt)
    permissions = role_result.scalar_one_or_none()
    
    if not permissions:
        # Fallback to OrganizationMember.permissions
        member_perm_stmt = select(OrganizationMember.permissions).where(
            OrganizationMember.user_id == user_id,
            OrganizationMember.organization_id == organization_id,
            OrganizationMember.status == "active"
        ).limit(1)
        member_perm_result = await db.execute(member_perm_stmt)
        permissions = member_perm_result.scalar_one_or_none() or {}
    
    if not isinstance(permissions, dict):
        permissions = {}
    
    return permissions.get(capability_name, False)


def _calculate_net_from_gross(amount_gross: Decimal, vat_rate: Decimal) -> Decimal:
    """
    Calculate net amount from gross amount and VAT rate.
    
    GROSS-FIRST (Masterbook 2.0.1): In EU accounting, the gross amount (Bruttó)
    is the absolute Source of Truth. Net is calculated back from gross.
    
    Formula: net = gross / (1 + vat_rate / 100)
    
    If vat_rate is 0 or None, net = gross (0% VAT content).
    """
    if vat_rate is None or vat_rate == 0:
        return amount_gross
    return (amount_gross / (Decimal("1") + vat_rate / Decimal("100"))).quantize(Decimal("0.01"))


@router.post("/", status_code=201)
async def create_expense(
    expense: AssetCostCreate,
    db: AsyncSession = Depends(get_db),
    current_user = Depends(get_current_user)
):
    """
    Create a new expense (fuel, service, tax, insurance) for an asset.
    Uses AssetCostCreate schema which includes mileage_at_cost, cost_type, etc.

    **Role-Based Auto-Approval:**
    - OWNER/ADMIN → status = APPROVED
    - DRIVER → status = PENDING_APPROVAL (except fuel, which is auto-approved)
    
    **Smart Linking (Double-Entry Avoidance):**
    - If the cost category is service-related (MAINTENANCE, MAINT_SERVICE, MAINT_OIL, MAINT_BRAKES),
      an AssetEvent is automatically created with MISSING_TECH_DATA status
      and linked via linked_asset_event_id / linked_expense_id.
    """
    # Validate asset exists
    stmt = select(Asset).where(Asset.id == expense.asset_id)
    result = await db.execute(stmt)
    asset = result.scalar_one_or_none()
    if not asset:
        raise HTTPException(status_code=404, detail="Asset not found.")
    
    # Dynamic Gatekeeper: Check draft expense limit
    if asset.status == "draft":
        # 1. Get VEHICLE_DRAFT_MAX_EXPENSES parameter
        param_stmt = select(SystemParameter).where(
            SystemParameter.key == "VEHICLE_DRAFT_MAX_EXPENSES",
            SystemParameter.scope_level == "global"
        )
        param_result = await db.execute(param_stmt)
        param = param_result.scalar_one_or_none()
        
        if param:
            limit = param.value.get("limit", 10)  # Default to 10 if not found
        else:
            limit = 10  # Default fallback
        
        # 2. Count existing expenses for this asset
        count_stmt = select(func.count(AssetCost.id)).where(AssetCost.asset_id == asset.id)
        count_result = await db.execute(count_stmt)
        expense_count = count_result.scalar()
        
        # 3. Check if limit reached
        if expense_count >= limit:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=f"DRAFT_LIMIT_REACHED: Draft vehicles are limited to {limit} expenses. This asset already has {expense_count} expenses."
            )
    
    # Determine organization_id: prefer explicit from payload, fallback to asset fields
    organization_id = expense.organization_id or asset.current_organization_id or asset.owner_org_id
    if not organization_id:
        # B2C fallback: if the asset is owned by a person (not an org),
        # try to find the current user's default organization
        org_stmt = select(OrganizationMember).where(
            OrganizationMember.user_id == current_user.id,
            OrganizationMember.is_verified == True
        ).limit(1)
        org_result = await db.execute(org_stmt)
        org_member = org_result.scalar_one_or_none()
        if org_member:
            organization_id = org_member.organization_id
        else:
            # Last resort: any membership (even unverified)
            org_stmt = select(OrganizationMember).where(
                OrganizationMember.user_id == current_user.id
            ).limit(1)
            org_result = await db.execute(org_stmt)
            org_member = org_result.scalar_one_or_none()
            if org_member:
                organization_id = org_member.organization_id
            else:
                raise HTTPException(status_code=400, detail="Asset has no associated organization.")
    
    # ── RBAC PHASE 2: CAPABILITY-BASED AUTO-APPROVAL ──
    # JSONB-alapú képesség-ellenőrzés a fleet.org_roles tábla permissions oszlopából
    user_role = await _resolve_user_role_in_org(db, current_user.id, organization_id)
    
    # Check if user has can_approve_expense capability → auto-approved
    can_approve = await _check_org_capability(db, current_user.id, organization_id, "can_approve_expense")
    
    # Determine expense status based on capabilities
    if can_approve:
        # User has can_approve_expense → auto-approved
        expense_status = "APPROVED"
    elif expense.category_id in FUEL_CATEGORY_IDS:
        # Fuel costs are auto-approved even without can_approve_expense
        expense_status = "APPROVED"
    else:
        # User lacks can_approve_expense → pending approval
        expense_status = "PENDING_APPROVAL"
    
    logger.info(
        f"Capability-based approval for user {current_user.id} (role={user_role}) "
        f"in org {organization_id}: can_approve_expense={can_approve}, status={expense_status}"
    )
    
    # ── GROSS-FIRST VAT HANDLING (Masterbook 2.0.1) ──
    # In EU accounting, the GROSS amount (Bruttó) is the absolute Source of Truth.
    amount_gross = expense.amount_gross
    vat_rate = expense.vat_rate
    amount_net = expense.amount_net
    
    # Auto-calculate net from gross if vat_rate is provided but net is not
    if vat_rate is not None and amount_net is None:
        amount_net = _calculate_net_from_gross(amount_gross, vat_rate)
    # Auto-calculate vat_rate if net is provided but vat_rate is not
    elif amount_net is not None and vat_rate is None and amount_gross > 0:
        # vat_rate = ((gross / net) - 1) * 100
        vat_rate = ((amount_gross / amount_net) - Decimal("1")) * Decimal("100")
        vat_rate = vat_rate.quantize(Decimal("0.01"))
    # If only gross is provided (no net, no vat) → net = gross (0% VAT)
    elif amount_net is None and vat_rate is None:
        amount_net = amount_gross
        vat_rate = Decimal("0")
    
    # Prepare data JSON for extra fields (mileage_at_cost, description, etc.)
    data = expense.data.copy() if expense.data else {}
    if expense.mileage_at_cost is not None:
        data["mileage_at_cost"] = expense.mileage_at_cost
    if expense.description:
        data["description"] = expense.description
    
    try:
        # Create AssetCost instance with new fields
        new_cost = AssetCost(
            asset_id=expense.asset_id,
            organization_id=organization_id,
            category_id=expense.category_id,
            amount_net=amount_net,
            amount_gross=amount_gross,
            vat_rate=vat_rate,
            currency=expense.currency,
            date=expense.date,
            invoice_number=data.get("invoice_number"),
            status=expense_status,
            data=data
        )
        
        db.add(new_cost)
        await db.flush()  # Flush to get new_cost.id
        
        # ── PHASE 2: SMART LINKING - Auto-create AssetEvent for service-related costs ──
        event_id = None
        if expense.category_id in SERVICE_RELATED_CATEGORY_IDS:
            # Map cost category to event type
            event_type = _map_category_to_event_type(expense.category_id)
            
            description = expense.description or data.get("description", f"Service cost: {expense.category_id}")
            mileage = expense.mileage_at_cost
            
            # Determine event status based on capability
            # can_approve_expense → COMPLETED, otherwise → MISSING_TECH_DATA
            event_status = "COMPLETED" if can_approve else "MISSING_TECH_DATA"
            
            new_event = AssetEvent(
                asset_id=expense.asset_id,
                user_id=getattr(current_user, 'id', None),
                organization_id=organization_id,
                event_type=event_type,
                odometer_reading=mileage,
                description=description,
                cost_id=new_cost.id,
                linked_expense_id=new_cost.id,  # Bidirectional link
                status=event_status,
                event_date=expense.date or datetime.now(timezone.utc),
            )
            db.add(new_event)
            await db.flush()  # Flush to get new_event.id
            event_id = new_event.id
            
            # Update the cost record with the link back to the event
            new_cost.linked_asset_event_id = new_event.id
            
            logger.info(
                f"Smart Sync: Auto-created AssetEvent {event_id} (status={event_status}) "
                f"for AssetCost {new_cost.id} (category_id={expense.category_id}). "
                f"Bidirectional link established."
            )
        
        # Update Asset.current_mileage if mileage_at_cost is higher
        if expense.mileage_at_cost is not None and expense.mileage_at_cost > (asset.current_mileage or 0):
            asset.current_mileage = expense.mileage_at_cost
        
        await db.commit()
        await db.refresh(new_cost)
        
        return {
            "status": "success",
            "id": new_cost.id,
            "asset_id": new_cost.asset_id,
            "category_id": new_cost.category_id,
            "amount_gross": str(new_cost.amount_gross) if new_cost.amount_gross else None,
            "amount_net": str(new_cost.amount_net),
            "vat_rate": str(new_cost.vat_rate) if new_cost.vat_rate else None,
            "expense_status": new_cost.status,
            "date": new_cost.date.isoformat() if new_cost.date else None,
            "event_id": str(event_id) if event_id else None,
        }
    
    except Exception as e:
        await db.rollback()
        logger.error(f"Expense creation error for asset {expense.asset_id}: {e}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail="Hiba a költség rögzítésekor"
        )


def _map_category_to_event_type(category_id: int) -> str:
    """
    Map a cost category ID to the appropriate AssetEvent event_type.
    
    Returns:
        str: The event type string (SERVICE, REPAIR, etc.)
    """
    category_event_map = {
        2: "MAINTENANCE",    # MAINTENANCE
        16: "SERVICE",       # MAINT_SERVICE
        17: "SERVICE",       # MAINT_OIL
        18: "REPAIR",        # MAINT_BRAKES
    }
    return category_event_map.get(category_id, "MAINTENANCE")