"""GraphRAG plugin routes — relationship CRUD and BFS graph traversal."""

from __future__ import annotations

import uuid

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

from app.core.db import get_db
from app.deps import get_current_user, require_permission
from app.plugins.builtins.graph_rag.models import EntityRelationship
from app.plugins.builtins.graph_rag.schemas import (
    RelationshipCreate,
    TraverseRequest,
)
from app.plugins.builtins.graph_rag.services import (
    create_relationship,
    delete_relationship,
    traverse_graph,
)

router = APIRouter(prefix="/api/v1/graph", tags=["graph-rag"])


@router.post("/relationships", status_code=status.HTTP_201_CREATED, dependencies=[Depends(require_permission("graph:write"))])
async def create_relationship_route(
    body: RelationshipCreate,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """Create a new relationship between two entities."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    user_id = uuid.UUID(current_user["user_id"])
    source_id = _parse_uuid(body.source_id, "source_id")
    target_id = _parse_uuid(body.target_id, "target_id")

    result = await create_relationship(
        db=db,
        tenant_id=tenant_id,
        source_type=body.source_type,
        source_id=source_id,
        target_type=body.target_type,
        target_id=target_id,
        relationship_type=body.relationship_type,
        metadata=body.metadata,
        owner_id=user_id,
    )

    if "error" in result:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail={"detail": result["error"], "code": result.get("code", "duplicate")},
        )

    return result


@router.get("/relationships", dependencies=[Depends(require_permission("graph:read"))])
async def list_relationships(
    source_type: str | None = Query(None, description="Filter by source entity type"),
    source_id: str | None = Query(None, description="Filter by source entity UUID"),
    target_type: str | None = Query(None, description="Filter by target entity type"),
    target_id: str | None = Query(None, description="Filter by target entity UUID"),
    relationship_type: str | None = Query(None, description="Filter by relationship type"),
    page: int = Query(1, ge=1),
    page_size: int = Query(50, ge=1, le=200),
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """List relationships with optional filters."""
    tenant_id = uuid.UUID(current_user["tenant_id"])

    base = select(EntityRelationship).where(
        EntityRelationship.tenant_id == tenant_id,
        EntityRelationship.deleted_at.is_(None),
    )

    if source_type:
        base = base.where(EntityRelationship.source_type == source_type)
    if source_id:
        base = base.where(EntityRelationship.source_id == _parse_uuid(source_id, "source_id"))
    if target_type:
        base = base.where(EntityRelationship.target_type == target_type)
    if target_id:
        base = base.where(EntityRelationship.target_id == _parse_uuid(target_id, "target_id"))
    if relationship_type:
        base = base.where(EntityRelationship.relationship_type == relationship_type)

    # Count total
    count_q = select(func.count()).select_from(base.subquery())
    total_result = await db.execute(count_q)
    total = total_result.scalar_one()

    # Paginated query
    offset = (page - 1) * page_size
    stmt = base.order_by(EntityRelationship.created_at.desc()).offset(offset).limit(page_size)
    result = await db.execute(stmt)
    relationships = result.scalars().all()

    return {
        "items": [
            {
                "id": str(r.id),
                "source_type": r.source_type,
                "source_id": str(r.source_id),
                "target_type": r.target_type,
                "target_id": str(r.target_id),
                "relationship_type": r.relationship_type,
                "metadata": r.meta,
                "owner_id": str(r.owner_id) if r.owner_id else None,
                "created_at": r.created_at.isoformat() if r.created_at else None,
            }
            for r in relationships
        ],
        "total": total,
    }


@router.post("/traverse", dependencies=[Depends(require_permission("graph:read"))])
async def traverse_graph_route(
    body: TraverseRequest,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """BFS traversal of the knowledge graph from a starting node."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    source_id = _parse_uuid(body.source_id, "source_id")

    result = await traverse_graph(
        db=db,
        tenant_id=tenant_id,
        source_type=body.source_type,
        source_id=source_id,
        max_hops=body.max_hops,
        relationship_types=body.relationship_types,
    )
    return result


@router.delete("/relationships/{relationship_id}", status_code=status.HTTP_204_NO_CONTENT, dependencies=[Depends(require_permission("graph:write"))])
async def delete_relationship_route(
    relationship_id: str,
    db: AsyncSession = Depends(get_db),
    current_user: dict = Depends(get_current_user),
):
    """Delete a relationship by ID."""
    tenant_id = uuid.UUID(current_user["tenant_id"])
    rid = _parse_uuid(relationship_id, "relationship_id")

    success = await delete_relationship(db, tenant_id, rid)
    if not success:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail={"detail": "Relationship not found", "code": "not_found"},
        )
    return Response(status_code=status.HTTP_204_NO_CONTENT)


def _parse_uuid(val: str, field: str) -> uuid.UUID:
    try:
        return uuid.UUID(val)
    except (ValueError, TypeError):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail={"detail": f"Invalid {field}", "code": "invalid_id"},
        ) from None