from fastapi import APIRouter, Depends, HTTPException, status, Query, Request
from sqlalchemy.orm import Session
from sqlalchemy import or_
from typing import List

from app.core.database import get_db
from app.core.redis import get_redis
from app.models.user import User
from app.models.role import Role
from app.models import AuditAction
from app.schemas.user import UserResponse, UserUpdate, CapacityUpdate
from app.middleware.auth import (
    get_current_user,
    require_permission,
    require_system_admin,
    check_department_access,
)
from app.middleware.audit import get_audit_metadata
from app.services.audit_service import AuditService

router = APIRouter()


@router.get("/search", response_model=List[UserResponse])
async def search_users(
    q: str = Query(..., min_length=1, max_length=100, description="Search query"),
    limit: int = Query(10, ge=1, le=50, description="Max results"),
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """
    Search users by name or email. Used for @mention autocomplete.
    Returns users matching the query, limited to same department unless system admin.
    """
    query = db.query(User).filter(
        User.is_active == True,
        or_(
            User.name.ilike(f"%{q}%"),
            User.email.ilike(f"%{q}%"),
        )
    )

    # Filter by department if not system admin
    if not current_user.is_system_admin and current_user.department_id:
        query = query.filter(User.department_id == current_user.department_id)

    users = query.limit(limit).all()
    return users


@router.get("", response_model=List[UserResponse])
async def list_users(
    skip: int = Query(0, ge=0, description="Number of users to skip"),
    limit: int = Query(100, ge=1, le=500, description="Max users to return"),
    db: Session = Depends(get_db),
    current_user: User = Depends(require_permission("users.read")),
):
    """
    List all users. Filtered by department if not system admin.
    """
    query = db.query(User)

    # Filter by department if not system admin
    if not current_user.is_system_admin and current_user.department_id:
        query = query.filter(User.department_id == current_user.department_id)

    users = query.offset(skip).limit(limit).all()
    return users


@router.get("/{user_id}", response_model=UserResponse)
async def get_user(
    user_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_permission("users.read")),
):
    """
    Get a specific user by ID.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Check department access
    if not check_department_access(current_user, user.department_id):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Access denied to this user",
        )

    return user


@router.patch("/{user_id}", response_model=UserResponse)
async def update_user(
    user_id: str,
    user_update: UserUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_permission("users.write")),
):
    """
    Update user information.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Check department access
    if not check_department_access(current_user, user.department_id):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Access denied to this user",
        )

    # Prevent modification of system admin properties by non-system-admins
    if user.is_system_admin and not current_user.is_system_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot modify system administrator",
        )

    # Update fields
    update_data = user_update.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        setattr(user, field, value)

    db.commit()
    db.refresh(user)
    return user


@router.patch("/{user_id}/role", response_model=UserResponse)
async def assign_role(
    user_id: str,
    role_id: str,
    request: Request,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_system_admin),
):
    """
    Assign a role to a user. Requires system admin.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Prevent modification of system admin
    if user.is_system_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot modify system administrator role",
        )

    # Verify role exists
    role = db.query(Role).filter(Role.id == role_id).first()
    if not role:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Role not found",
        )

    # Prevent assigning system role to non-system-admin
    if role.is_system_role:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot assign system role",
        )

    old_role_id = user.role_id
    user.role_id = role_id

    # Audit log for role change (high sensitivity)
    if old_role_id != role_id:
        AuditService.log_event(
            db=db,
            event_type="user.role_change",
            resource_type="user",
            action=AuditAction.UPDATE,
            user_id=current_user.id,
            resource_id=user.id,
            changes=[{"field": "role_id", "old_value": old_role_id, "new_value": role_id}],
            request_metadata=get_audit_metadata(request),
        )

    db.commit()
    db.refresh(user)
    return user


@router.patch("/{user_id}/admin", response_model=UserResponse)
async def set_admin_status(
    user_id: str,
    is_admin: bool,
    request: Request,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_system_admin),
):
    """
    Set or revoke system administrator status. Requires system admin.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Prevent self-modification
    if user.id == current_user.id:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot modify your own admin status",
        )

    old_admin_status = user.is_system_admin
    user.is_system_admin = is_admin

    # Audit log for admin change (critical sensitivity, triggers alert)
    if old_admin_status != is_admin:
        AuditService.log_event(
            db=db,
            event_type="user.admin_change",
            resource_type="user",
            action=AuditAction.UPDATE,
            user_id=current_user.id,
            resource_id=user.id,
            changes=[{"field": "is_system_admin", "old_value": old_admin_status, "new_value": is_admin}],
            request_metadata=get_audit_metadata(request),
        )

    db.commit()
    db.refresh(user)
    return user


@router.put("/{user_id}/capacity", response_model=UserResponse)
async def update_user_capacity(
    user_id: str,
    capacity: CapacityUpdate,
    request: Request,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
    redis_client=Depends(get_redis),
):
    """
    Update user's weekly capacity hours.

    Permission: admin, manager, or the user themselves can update capacity.
    - Admin/Manager can update any user's capacity
    - Regular users can only update their own capacity

    Capacity changes are recorded in the audit trail and workload cache is invalidated.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Permission check: admin, manager, or the user themselves can update capacity
    is_self = current_user.id == user_id
    is_admin = current_user.is_system_admin
    is_manager = False

    # Check if current user has manager role
    if current_user.role and current_user.role.name == "manager":
        is_manager = True

    if not is_self and not is_admin and not is_manager:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Only admin, manager, or the user themselves can update capacity",
        )

    # Store old capacity for audit log
    old_capacity = float(user.capacity) if user.capacity else None

    # Update capacity (validation is handled by Pydantic schema)
    user.capacity = capacity.capacity_hours
    new_capacity = float(capacity.capacity_hours)

    # Record capacity change in audit trail
    if old_capacity != new_capacity:
        AuditService.log_event(
            db=db,
            event_type="user.capacity_change",
            resource_type="user",
            action=AuditAction.UPDATE,
            user_id=current_user.id,
            resource_id=user.id,
            changes=[{
                "field": "capacity",
                "old_value": old_capacity,
                "new_value": new_capacity
            }],
            request_metadata=get_audit_metadata(request),
        )

    db.commit()
    db.refresh(user)

    # Invalidate workload cache for this user
    # Cache keys follow pattern: workload:{user_id}:* or workload:heatmap:*
    try:
        # Delete user-specific workload cache
        for key in redis_client.scan_iter(f"workload:{user_id}:*"):
            redis_client.delete(key)
        # Delete heatmap cache (contains all users' workload data)
        for key in redis_client.scan_iter("workload:heatmap:*"):
            redis_client.delete(key)
    except Exception:
        # Cache invalidation failure should not fail the request
        pass

    return user