# app/api/endpoints/stems.py — 4-stem separation (Paid tier)
from __future__ import annotations

import logging
from pathlib import Path

from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException

from app.api.deps import get_conn, get_data_dir
from app.models.schemas.node import StemResult
from app.services import chain as chain_svc
from app.services import stems as stems_svc
from app.tiers import require_tier

logger = logging.getLogger(__name__)
router = APIRouter(prefix="/api/stems", tags=["stems"])


@router.post("/{node_id}", response_model=StemResult, status_code=202)
async def separate_stems(
    node_id: str,
    background_tasks: BackgroundTasks,
    tier: str | None = None,
    conn=Depends(get_conn),
    data_dir: str = Depends(get_data_dir),
) -> dict:
    """
    Run 4-stem separation (Demucs htdemucs) on a ready node.

    Requires Paid tier. Returns stem file paths immediately — paths will
    be valid once the background task completes. Poll GET /api/nodes/{node_id}
    or listen on the chain SSE stream for completion signals.

    tier: passed as query param, e.g. ?tier=paid
    """
    require_tier("stems", tier)

    node = chain_svc.get_node(conn, node_id)
    if node is None:
        raise HTTPException(status_code=404, detail="Node not found.")
    if node["audio_path"] is None:
        raise HTTPException(status_code=409, detail="Node has no audio.")

    stems_dir = stems_svc.make_stems_dir(data_dir, node["chain_id"], node_id)
    stem_paths = stems_svc._stem_paths(stems_dir, Path(node["audio_path"]).stem)

    background_tasks.add_task(
        _run_separation,
        source_audio_path=node["audio_path"],
        stems_dir=stems_dir,
    )

    return StemResult(
        node_id=node_id,
        vocals=stem_paths["vocals"],
        drums=stem_paths["drums"],
        bass=stem_paths["bass"],
        other=stem_paths["other"],
    )


async def _run_separation(source_audio_path: str, stems_dir: str) -> None:
    try:
        await stems_svc.separate(source_audio_path, stems_dir)
        logger.info("Stems complete: %s", stems_dir)
    except Exception as exc:
        logger.exception("Stem separation failed: %s", exc)