import uuid

from fastapi import APIRouter, Depends, HTTPException, Query, status
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from api.database import get_session
from api.models.domain import Domain
from api.models.extension_point import ExtensionPoint
from api.models.managed_repo import ManagedRepo
from api.models.technical_debt import TechnicalDebt
from api.models.topic import Topic
from api.models.workstream import Workstream, WorkstreamStatus
from api.schemas.domain import DomainCreate, DomainDetail, DomainRead, DomainRename, DomainUpdate, RepoStub

router = APIRouter(prefix="/domains", tags=["domains"])


@router.get("/", response_model=list[DomainRead])
async def list_domains(
    status: str | None = Query(None, description="active | archived | all"),
    session: AsyncSession = Depends(get_session),
) -> list[Domain]:
    q = select(Domain).order_by(Domain.name)
    if status and status != "all":
        q = q.where(Domain.status == status)
    elif status is None:
        q = q.where(Domain.status == "active")
    result = await session.execute(q)
    return list(result.scalars().all())


@router.post("/", response_model=DomainRead, status_code=status.HTTP_201_CREATED)
async def create_domain(
    body: DomainCreate,
    session: AsyncSession = Depends(get_session),
) -> Domain:
    existing = await session.execute(select(Domain).where(Domain.slug == body.slug))
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=409, detail=f"Domain slug '{body.slug}' already exists")
    domain = Domain(slug=body.slug, name=body.name, description=body.description)
    session.add(domain)
    await session.commit()
    await session.refresh(domain)
    return domain


@router.get("/{slug}/", response_model=DomainDetail)
async def get_domain(
    slug: str,
    session: AsyncSession = Depends(get_session),
) -> DomainDetail:
    domain = await _get_domain_by_slug(slug, session)

    # Count topics
    topic_count_row = await session.execute(
        select(func.count()).select_from(Topic).where(Topic.domain_id == domain.id)
    )
    topic_count = topic_count_row.scalar_one()

    # Count active workstreams (via topics)
    topic_ids_row = await session.execute(
        select(Topic.id).where(Topic.domain_id == domain.id)
    )
    topic_ids = [r[0] for r in topic_ids_row.all()]

    ws_count = 0
    if topic_ids:
        ws_count_row = await session.execute(
            select(func.count()).select_from(Workstream)
            .where(Workstream.topic_id.in_(topic_ids))
            .where(Workstream.status == WorkstreamStatus.active)
        )
        ws_count = ws_count_row.scalar_one()

    # Count EPs and TDs
    ep_count_row = await session.execute(
        select(func.count()).select_from(ExtensionPoint)
        .where(ExtensionPoint.domain_id == domain.id)
    )
    ep_count = ep_count_row.scalar_one()

    td_count_row = await session.execute(
        select(func.count()).select_from(TechnicalDebt)
        .where(TechnicalDebt.domain_id == domain.id)
    )
    td_count = td_count_row.scalar_one()

    # Repos
    repos_row = await session.execute(
        select(ManagedRepo).where(ManagedRepo.domain_id == domain.id)
        .where(ManagedRepo.status == "active")
        .order_by(ManagedRepo.name)
    )
    repos = list(repos_row.scalars().all())

    return DomainDetail(
        id=domain.id,
        slug=domain.slug,
        name=domain.name,
        description=domain.description,
        status=domain.status,
        created_at=domain.created_at,
        updated_at=domain.updated_at,
        topic_count=topic_count,
        workstream_count=ws_count,
        ep_count=ep_count,
        td_count=td_count,
        repos=[RepoStub.model_validate(r) for r in repos],
    )


@router.patch("/{slug}/rename", response_model=DomainRead)
async def rename_domain(
    slug: str,
    body: DomainRename,
    session: AsyncSession = Depends(get_session),
) -> Domain:
    domain = await _get_domain_by_slug(slug, session)

    if body.new_slug != slug:
        conflict = await session.execute(select(Domain).where(Domain.slug == body.new_slug))
        if conflict.scalar_one_or_none():
            raise HTTPException(status_code=409, detail=f"Slug '{body.new_slug}' already taken")

    old_slug = domain.slug
    domain.slug = body.new_slug
    domain.name = body.new_name

    await session.commit()
    await session.refresh(domain)
    return domain


@router.patch("/{slug}/archive", response_model=DomainRead)
async def archive_domain(
    slug: str,
    session: AsyncSession = Depends(get_session),
) -> Domain:
    domain = await _get_domain_by_slug(slug, session)

    # Reject if any active topics exist for this domain
    active_topics = await session.execute(
        select(func.count()).select_from(Topic)
        .where(Topic.domain_id == domain.id)
        .where(Topic.status == "active")
    )
    if active_topics.scalar_one() > 0:
        raise HTTPException(
            status_code=409,
            detail="Cannot archive domain with active topics. Archive or reassign topics first.",
        )

    domain.status = "archived"
    await session.commit()
    await session.refresh(domain)
    return domain


async def _get_domain_by_slug(slug: str, session: AsyncSession) -> Domain:
    result = await session.execute(select(Domain).where(Domain.slug == slug))
    domain = result.scalar_one_or_none()
    if domain is None:
        raise HTTPException(status_code=404, detail=f"Domain '{slug}' not found")
    return domain