import json
from fastapi import APIRouter, HTTPException
from app.config import BACKGROUND_SNAPSHOT_PATH, BACKGROUND_PATH, energy_axis, NUM_CHANNELS
import numpy as np

router = APIRouter()


@router.get("")
async def get_background_info():
    """Background metadata: elapsed time, CPS, top peaks."""
    if not BACKGROUND_SNAPSHOT_PATH.exists():
        raise HTTPException(status_code=404, detail="Background capture not available yet")

    try:
        with open(BACKGROUND_SNAPSHOT_PATH) as f:
            snapshot = json.load(f)
    except (json.JSONDecodeError, OSError):
        raise HTTPException(status_code=500, detail="Background snapshot file corrupt")

    # Check if full background is available
    full_available = BACKGROUND_PATH.exists()

    return {
        "elapsed_hours": snapshot.get("elapsed_hours", 0),
        "live_time_s": snapshot.get("live_time_s", 0),
        "total_counts": snapshot.get("total_counts", 0),
        "cps": snapshot.get("cps", 0),
        "top_peaks": snapshot.get("top_peaks", []),
        "full_background_available": full_available,
    }


@router.get("/spectrum")
async def get_background_spectrum():
    """Full background spectrum with energy axis."""
    if not BACKGROUND_SNAPSHOT_PATH.exists():
        raise HTTPException(status_code=404, detail="Background capture not available yet")

    try:
        with open(BACKGROUND_SNAPSHOT_PATH) as f:
            snapshot = json.load(f)
    except (json.JSONDecodeError, OSError):
        raise HTTPException(status_code=500, detail="Background snapshot file corrupt")

    counts = snapshot.get("spectrum", [0] * NUM_CHANNELS)

    # If full background file exists, use it for better data
    if BACKGROUND_PATH.exists():
        try:
            bg_data = np.load(str(BACKGROUND_PATH), allow_pickle=True).item()
            counts = [round(float(c), 1) for c in bg_data["counts"]]
            live_time = float(bg_data["duration"])
        except Exception:
            live_time = snapshot.get("live_time_s", 0)
    else:
        live_time = snapshot.get("live_time_s", 0)

    return {
        "channels": list(range(NUM_CHANNELS)),
        "energy_kev": energy_axis(),
        "counts": counts,
        "live_time_s": live_time,
        "cps": snapshot.get("cps", 0),
        "top_peaks": snapshot.get("top_peaks", []),
    }