"""Cluster access authorization — platform admin only.

Lets the platform admin grant or revoke a cluster's accessibility to a
specific principal (USER / ORG / GROUP). The grant row stores a single
``principal_id`` FK; kind comes from the joined principals row at read
time.
"""

from datetime import datetime, timezone
from typing import List, Optional

from fastapi import APIRouter
from pydantic import BaseModel
from sqlmodel import select

from gpustack.api.exceptions import (
    AlreadyExistsException,
    InvalidException,
    NotFoundException,
)
from gpustack.schemas.cluster_access import ClusterAccess, ClusterAccessPublic
from gpustack.schemas.clusters import Cluster
from gpustack.schemas.principals import Principal, PrincipalType
from gpustack.schemas.users import User
from gpustack.server.deps import SessionDep, TenantContextDep

router = APIRouter()


class ClusterAccessGrant(BaseModel):
    # Discriminator kept on the input shape for client-side validation
    # — the server cross-checks against the joined ``principals`` row,
    # so a mismatched kind is rejected at the validator below.
    principal_type: PrincipalType
    principal_id: int


async def _load_cluster(session, cluster_id: int) -> Cluster:
    cluster = await Cluster.one_by_id(session, cluster_id)
    if not cluster or cluster.deleted_at is not None:
        raise NotFoundException(message="Cluster not found")
    return cluster


async def _validate_principal(
    session, principal_type: PrincipalType, principal_id: int
) -> Principal:
    """Ensure the principal exists, isn't soft-deleted, and matches
    the declared kind."""
    target = await Principal.one_by_id(session, principal_id)
    if not target or target.deleted_at is not None:
        raise InvalidException(message=f"Principal {principal_id} not found")
    if target.kind != principal_type:
        raise InvalidException(
            message=(
                f"Principal {principal_id} is a {target.kind.value}, "
                f"not a {principal_type.value}"
            )
        )
    if target.kind == PrincipalType.USER:
        # Disallow granting access to system users (workers etc.). They
        # already bypass cluster_access via ``is_system``.
        user = await User.one_by_field(session, "principal_id", principal_id)
        if user is None or user.is_system or user.deleted_at is not None:
            raise InvalidException(message=f"User principal {principal_id} not found")
    return target


async def _resolve_principal_views(
    session, rows: List[ClusterAccess]
) -> List[ClusterAccessPublic]:
    """Bulk-resolve display labels and kind for each row in a single
    principals lookup.
    """
    principal_ids = {r.principal_id for r in rows}
    principal_by_id: dict[int, Principal] = {}
    if principal_ids:
        result = await session.exec(
            select(Principal).where(Principal.id.in_(principal_ids))
        )
        principal_by_id = {p.id: p for p in result.all()}

    out: List[ClusterAccessPublic] = []
    for r in rows:
        p: Optional[Principal] = principal_by_id.get(r.principal_id)
        kind = p.kind if p else PrincipalType.USER
        # GROUP principals expose their owning ORG via parent_principal_id
        # so the UI can render quota slots; USER and ORG return None.
        parent = p.parent_principal_id if p and p.kind == PrincipalType.GROUP else None
        # ORG principals' "parent" for display purposes is themselves.
        if p and p.kind == PrincipalType.ORG:
            parent = p.id
        out.append(
            ClusterAccessPublic(
                cluster_id=r.cluster_id,
                principal_id=r.principal_id,
                principal_type=kind,
                principal_name=p.name if p else None,
                principal_parent_id=parent,
                granted_by=r.granted_by,
                created_at=r.created_at,
            )
        )
    return out


@router.get("/clusters/{cluster_id}/access", response_model=List[ClusterAccessPublic])
async def list_cluster_access(
    session: SessionDep, ctx: TenantContextDep, cluster_id: int
):
    await _load_cluster(session, cluster_id)
    stmt = select(ClusterAccess).where(ClusterAccess.cluster_id == cluster_id)
    rows = list((await session.exec(stmt)).all())
    return await _resolve_principal_views(session, rows)


@router.post("/clusters/{cluster_id}/access", response_model=ClusterAccessPublic)
async def grant_cluster_access(
    session: SessionDep,
    ctx: TenantContextDep,
    cluster_id: int,
    body: ClusterAccessGrant,
):
    await _load_cluster(session, cluster_id)
    await _validate_principal(session, body.principal_type, body.principal_id)

    existing_stmt = select(ClusterAccess).where(
        ClusterAccess.cluster_id == cluster_id,
        ClusterAccess.principal_id == body.principal_id,
    )
    if (await session.exec(existing_stmt)).first() is not None:
        raise AlreadyExistsException(message="Access already granted")

    try:
        access = ClusterAccess(
            cluster_id=cluster_id,
            principal_id=body.principal_id,
            granted_by=ctx.user.id,
            created_at=datetime.now(timezone.utc).replace(tzinfo=None),
        )
        session.add(access)
        await session.commit()
        await session.refresh(access)
    except Exception as e:
        await session.rollback()
        raise InvalidException(message=f"Failed to grant cluster access: {e}")

    enriched = await _resolve_principal_views(session, [access])
    return enriched[0]


@router.delete("/clusters/{cluster_id}/access/{principal_id}")
async def revoke_cluster_access(
    session: SessionDep,
    ctx: TenantContextDep,
    cluster_id: int,
    principal_id: int,
):
    await _load_cluster(session, cluster_id)
    stmt = select(ClusterAccess).where(
        ClusterAccess.cluster_id == cluster_id,
        ClusterAccess.principal_id == principal_id,
    )
    access = (await session.exec(stmt)).first()
    if not access:
        raise NotFoundException(message="Access grant not found")

    try:
        await session.delete(access)
        await session.commit()
    except Exception as e:
        await session.rollback()
        raise InvalidException(message=f"Failed to revoke cluster access: {e}")