# app/api/endpoints/export.py — stitch committed spine and serve as download
from __future__ import annotations

import logging
from pathlib import Path

from fastapi import APIRouter, Depends, HTTPException
from fastapi.responses import FileResponse

from app.api.deps import get_conn, get_data_dir
from app.models.schemas.node import ExportRequest
from app.services import chain as chain_svc
from app.services.export import ExportFormat, make_export_path, stitch

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


@router.post("/{chain_id}/export")
async def export_chain(
    chain_id: str,
    body: ExportRequest,
    conn=Depends(get_conn),
    data_dir: str = Depends(get_data_dir),
) -> FileResponse:
    """
    Stitch node audio files into a single download.

    If body.node_ids is provided, those nodes are used in order.
    Otherwise the committed spine (root → leaf) is used.
    Raises 409 if any targeted node has no audio.
    """
    if body.node_ids is not None:
        nodes = [chain_svc.get_node(conn, nid) for nid in body.node_ids]
        if any(n is None for n in nodes):
            raise HTTPException(status_code=404, detail="One or more nodes not found.")
    else:
        nodes = chain_svc.get_committed_spine(conn, chain_id)
        if not nodes:
            raise HTTPException(
                status_code=404,
                detail="Chain not found or has no committed nodes.",
            )

    audio_paths = [n["audio_path"] for n in nodes if n]  # type: ignore[index]
    missing = [n["id"] for n in nodes if n and n["audio_path"] is None]  # type: ignore[index]
    if missing:
        raise HTTPException(
            status_code=409,
            detail=f"Nodes {missing} have no audio yet.",
        )

    fmt: ExportFormat = body.format  # type: ignore[assignment]
    output_path = make_export_path(data_dir, chain_id, fmt)

    try:
        await stitch(audio_paths, output_path, fmt)
    except Exception as exc:
        logger.exception("Export failed for chain %s: %s", chain_id, exc)
        raise HTTPException(status_code=500, detail=f"Export failed: {exc}") from exc

    media_type = "audio/wav" if fmt == "wav" else "audio/mpeg"
    filename = f"sparrow_export_{chain_id[:8]}.{fmt}"
    return FileResponse(output_path, media_type=media_type, filename=filename)