import uuid
from datetime import datetime, timezone

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

from api.database import get_session
from api.models.agent_message import AgentMessage
from api.models.capability_catalog import CapabilityCatalog
from api.models.capability_request import CapabilityRequest
from api.models.domain import Domain
from api.models.task import Task
from api.schemas.capability_request import (
    CatalogCreate,
    CatalogRead,
    CapabilityRequestAccept,
    CapabilityRequestCreate,
    CapabilityRequestRead,
    CapabilityRequestStatusPatch,
)

router = APIRouter(tags=["capability-requests"])

# ---------------------------------------------------------------------------
# Lifecycle guard
# ---------------------------------------------------------------------------

_VALID_TRANSITIONS: dict[str, set[str]] = {
    "requested":        {"accepted", "rejected", "withdrawn"},
    "accepted":         {"in_progress", "rejected", "withdrawn"},
    "in_progress":      {"ready_for_review", "rejected", "withdrawn"},
    "ready_for_review": {"completed", "in_progress", "withdrawn"},
    "completed":        set(),
    "rejected":         set(),
    "withdrawn":        set(),
}


# ---------------------------------------------------------------------------
# Capability Catalog endpoints
# ---------------------------------------------------------------------------

@router.post("/capability-catalog/", response_model=CatalogRead, status_code=status.HTTP_201_CREATED)
async def create_catalog_entry(
    body: CatalogCreate,
    session: AsyncSession = Depends(get_session),
) -> CapabilityCatalog:
    domain = await _resolve_domain(body.domain, session)
    entry = CapabilityCatalog(
        domain_id=domain.id,
        capability_type=body.capability_type,
        title=body.title,
        description=body.description,
        keywords=body.keywords,
    )
    session.add(entry)
    try:
        await session.commit()
    except Exception:
        await session.rollback()
        raise HTTPException(
            status_code=409,
            detail=f"Catalog entry '{body.title}' for type '{body.capability_type}' already exists in domain '{body.domain}'",
        )
    await session.refresh(entry)
    return entry


@router.get("/capability-catalog/", response_model=list[CatalogRead])
async def list_catalog(
    domain: str | None = Query(None),
    capability_type: str | None = Query(None),
    status_filter: str | None = Query(None, alias="status"),
    session: AsyncSession = Depends(get_session),
) -> list[CapabilityCatalog]:
    q = select(CapabilityCatalog).order_by(CapabilityCatalog.created_at.desc())
    if domain:
        d = await _resolve_domain(domain, session)
        q = q.where(CapabilityCatalog.domain_id == d.id)
    if capability_type:
        q = q.where(CapabilityCatalog.capability_type == capability_type)
    if status_filter and status_filter != "all":
        q = q.where(CapabilityCatalog.status == status_filter)
    elif not status_filter:
        q = q.where(CapabilityCatalog.status == "active")
    result = await session.execute(q)
    return list(result.scalars().all())


# ---------------------------------------------------------------------------
# Capability Request endpoints
# ---------------------------------------------------------------------------

@router.post("/capability-requests/", response_model=CapabilityRequestRead, status_code=status.HTTP_201_CREATED)
async def create_request(
    body: CapabilityRequestCreate,
    session: AsyncSession = Depends(get_session),
) -> CapabilityRequest:
    req_domain = await _resolve_domain(body.requesting_domain, session)

    # Route to provider
    fulfilling_domain_id, catalog_entry_id = await _route_capability(
        session, body.capability_type, body.description or ""
    )

    req = CapabilityRequest(
        title=body.title,
        description=body.description,
        capability_type=body.capability_type,
        priority=body.priority,
        requesting_domain_id=req_domain.id,
        requesting_agent=body.requesting_agent,
        requesting_workstream_id=body.requesting_workstream_id,
        blocking_task_id=body.blocking_task_id,
        fulfilling_domain_id=fulfilling_domain_id,
        catalog_entry_id=catalog_entry_id,
    )
    session.add(req)
    await session.flush()  # get req.id before creating notification

    # Auto-notify
    if fulfilling_domain_id:
        ful_domain = await session.get(Domain, fulfilling_domain_id)
        to_agent = ful_domain.slug if ful_domain else "broadcast"
    else:
        to_agent = "broadcast"

    _add_notification(
        session,
        from_agent="system",
        to_agent=to_agent,
        subject=f"[capability-request] {body.title}",
        body=(
            f"New capability request from **{body.requesting_agent}** "
            f"({body.requesting_domain}):\n\n"
            f"**Type:** {body.capability_type}\n"
            f"**Priority:** {body.priority}\n\n"
            f"{body.description or '(no description)'}"
        ),
    )

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


@router.get("/capability-requests/", response_model=list[CapabilityRequestRead])
async def list_requests(
    domain: str | None = Query(None, description="Filter by requesting OR fulfilling domain slug"),
    status_filter: str | None = Query(None, alias="status"),
    capability_type: str | None = Query(None),
    session: AsyncSession = Depends(get_session),
) -> list[CapabilityRequest]:
    q = select(CapabilityRequest).order_by(CapabilityRequest.created_at.desc())
    if domain:
        d = await _resolve_domain(domain, session)
        q = q.where(
            (CapabilityRequest.requesting_domain_id == d.id)
            | (CapabilityRequest.fulfilling_domain_id == d.id)
        )
    if status_filter:
        q = q.where(CapabilityRequest.status == status_filter)
    if capability_type:
        q = q.where(CapabilityRequest.capability_type == capability_type)
    result = await session.execute(q)
    return list(result.scalars().all())


@router.get("/capability-requests/{request_id}", response_model=CapabilityRequestRead)
async def get_request(
    request_id: uuid.UUID,
    session: AsyncSession = Depends(get_session),
) -> CapabilityRequest:
    return await _get_request_or_404(request_id, session)


@router.post("/capability-requests/{request_id}/accept", response_model=CapabilityRequestRead)
async def accept_request(
    request_id: uuid.UUID,
    body: CapabilityRequestAccept,
    session: AsyncSession = Depends(get_session),
) -> CapabilityRequest:
    req = await _get_request_or_404(request_id, session)
    _check_transition(req.status, "accepted")

    now = datetime.now(tz=timezone.utc)
    req.status = "accepted"
    req.fulfilling_agent = body.fulfilling_agent
    req.fulfilling_workstream_id = body.fulfilling_workstream_id
    req.accepted_at = now

    # If no fulfilling domain was set by routing, infer from the accepting agent's context
    # (The agent can also PATCH it later if needed)

    _add_notification(
        session,
        from_agent=body.fulfilling_agent,
        to_agent=req.requesting_agent,
        subject=f"[capability-accepted] {req.title}",
        body=f"Your capability request **{req.title}** has been accepted by **{body.fulfilling_agent}**.",
    )

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


@router.patch("/capability-requests/{request_id}/status", response_model=CapabilityRequestRead)
async def patch_request_status(
    request_id: uuid.UUID,
    body: CapabilityRequestStatusPatch,
    session: AsyncSession = Depends(get_session),
) -> CapabilityRequest:
    req = await _get_request_or_404(request_id, session)
    _check_transition(req.status, body.status)

    req.status = body.status
    if body.note:
        req.resolution_note = body.note

    now = datetime.now(tz=timezone.utc)

    # Status-specific side effects
    if body.status == "completed":
        req.completed_at = now
        # Auto-unblock the blocking task
        if req.blocking_task_id:
            task = await session.get(Task, req.blocking_task_id)
            if task and task.status == "blocked":
                task.status = "todo"
                task.blocking_reason = None

        _add_notification(
            session,
            from_agent="system",
            to_agent=req.requesting_agent,
            subject=f"[capability-completed] {req.title}",
            body=(
                f"Capability request **{req.title}** has been completed.\n\n"
                f"{body.note or ''}"
            ),
        )
    elif body.status == "ready_for_review":
        _add_notification(
            session,
            from_agent=req.fulfilling_agent or "system",
            to_agent=req.requesting_agent,
            subject=f"[capability-ready] {req.title} -- please review",
            body=(
                f"Capability **{req.title}** is ready for your review and optimization.\n\n"
                f"{body.note or ''}"
            ),
        )
    elif body.status == "rejected":
        _add_notification(
            session,
            from_agent=req.fulfilling_agent or "system",
            to_agent=req.requesting_agent,
            subject=f"[capability-rejected] {req.title}",
            body=(
                f"Capability request **{req.title}** has been rejected.\n\n"
                f"**Reason:** {body.note or '(no reason given)'}"
            ),
        )
    elif body.status == "in_progress":
        _add_notification(
            session,
            from_agent=req.fulfilling_agent or "system",
            to_agent=req.requesting_agent,
            subject=f"[capability-in-progress] {req.title}",
            body=f"Work on capability **{req.title}** is now in progress.",
        )

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


# ---------------------------------------------------------------------------
# Routing algorithm
# ---------------------------------------------------------------------------

async def _route_capability(
    session: AsyncSession, capability_type: str, description: str
) -> tuple[uuid.UUID | None, uuid.UUID | None]:
    """Find the best-matching domain for a capability request.

    Returns (domain_id, catalog_entry_id) or (None, None) for broadcast.
    """
    q = select(CapabilityCatalog).where(
        CapabilityCatalog.capability_type == capability_type,
        CapabilityCatalog.status == "active",
    )
    entries = list((await session.execute(q)).scalars().all())

    if len(entries) == 1:
        return entries[0].domain_id, entries[0].id

    if len(entries) > 1 and description:
        desc_lower = description.lower()
        scored: list[tuple[int, CapabilityCatalog]] = []
        for entry in entries:
            score = sum(1 for kw in (entry.keywords or []) if kw.lower() in desc_lower)
            scored.append((score, entry))
        scored.sort(key=lambda x: -x[0])
        if scored[0][0] > 0 and (len(scored) < 2 or scored[0][0] > scored[1][0]):
            return scored[0][1].domain_id, scored[0][1].id

    return None, None


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------

def _add_notification(
    session: AsyncSession,
    from_agent: str,
    to_agent: str,
    subject: str,
    body: str,
) -> None:
    """Create an AgentMessage notification in the current session (no commit)."""
    msg = AgentMessage(
        from_agent=from_agent,
        to_agent=to_agent,
        subject=subject,
        body=body,
    )
    session.add(msg)


async def _resolve_domain(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


async def _get_request_or_404(request_id: uuid.UUID, session: AsyncSession) -> CapabilityRequest:
    req = await session.get(CapabilityRequest, request_id)
    if req is None:
        raise HTTPException(status_code=404, detail=f"Capability request '{request_id}' not found")
    return req


def _check_transition(current: str, target: str) -> None:
    allowed = _VALID_TRANSITIONS.get(current, set())
    if target not in allowed:
        raise HTTPException(
            status_code=422,
            detail=(
                f"Cannot transition from '{current}' to '{target}'. "
                f"Allowed: {sorted(allowed) or 'none (terminal state)'}"
            ),
        )