"""⑤ bgm — Suno V5 인스트루멘털 BGM.

보컬이 있으면 나레이션과 주파수·의미가 겹쳐 둘 다 안 들리므로 반드시 instrumental로 뽑고,
목표 길이는 나레이션 실측 길이에서 역산한다.
"""
import asyncio

import httpx

from answers.narration_answer import BgmStyle
from models.bgm import BgmAudio
from settings import settings

SUNO_API = "https://api.sunoapi.org/api/v1"
SUNO_MODEL = "V5_5"          # duration 파라미터가 V5_5 + customMode에서만 먹는다

POLL_INTERVAL = 15
POLL_ATTEMPTS = 20
MIN_SECONDS, MAX_SECONDS = 10, 30     # duration 허용 범위 하한이 10초다
SECONDS_MARGIN = 2


def target_seconds(narration_total: float) -> int:
    return int(min(MAX_SECONDS, max(MIN_SECONDS, round(narration_total) + SECONDS_MARGIN)))


async def request_generation(client: httpx.AsyncClient, style: BgmStyle, seconds: int,
                             title: str) -> str:
    response = await client.post(
        f"{SUNO_API}/generate",
        json={
            "model": SUNO_MODEL,
            "customMode": True,
            "instrumental": True,
            "duration": seconds,
            "prompt": style.prompt,
            "style": style.style,
            "title": title,
            "callBackUrl": settings.suno_callback_url,
        })
    response.raise_for_status()
    task_id = (response.json().get("data") or {}).get("taskId", "")
    if not task_id:
        raise RuntimeError(f"Suno가 taskId를 안 줬다: {response.text[:300]}")
    return task_id


async def wait_for_tracks(client: httpx.AsyncClient, task_id: str) -> list[dict]:
    for _ in range(POLL_ATTEMPTS):
        await asyncio.sleep(POLL_INTERVAL)
        response = await client.get(f"{SUNO_API}/generate/record-info", params={"taskId": task_id})
        response.raise_for_status()
        data = response.json().get("data") or {}
        status = data.get("status", "")
        if status == "SUCCESS":
            tracks = (data.get("response") or {}).get("sunoData", [])
            if not tracks:
                raise RuntimeError(f"트랙 없음 (taskId={task_id})")
            return tracks
        if "FAIL" in status or "ERROR" in status:
            raise RuntimeError(f"Suno 생성 실패: {status} (taskId={task_id})")
    raise RuntimeError(f"Suno 타임아웃 {POLL_INTERVAL * POLL_ATTEMPTS}초 (taskId={task_id})")


async def generate_bgm(style: BgmStyle, narration_total: float,
                       title: str = "festival bgm") -> BgmAudio:
    if not settings.suno_api_key:
        raise RuntimeError("SUNO_API_KEY 없음")
    seconds = target_seconds(narration_total)

    async with httpx.AsyncClient(
            timeout=180, headers={"Authorization": f"Bearer {settings.suno_api_key}"}) as client:
        task_id = await request_generation(client, style, seconds, title)
        tracks = await wait_for_tracks(client, task_id)
        # 목표 길이에 가장 가까운 트랙 — 가장 긴 것이 아니다
        track = min(tracks, key=lambda t: abs((t.get("duration") or 0) - seconds))
        download = await client.get(track["audioUrl"], follow_redirects=True)
        download.raise_for_status()

    return BgmAudio(mp3=download.content, seconds=seconds,
                    duration=float(track.get("duration") or 0), task_id=task_id)