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

router = APIRouter()


def _load_snapshot():
    """Load the live snapshot file, or raise 404."""
    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:
            return json.load(f)
    except (json.JSONDecodeError, OSError):
        raise HTTPException(status_code=500, detail="Background snapshot file corrupt")


def _load_reference():
    """Load the 24h reference background, or return None."""
    if not BACKGROUND_PATH.exists():
        return None
    try:
        bg_data = np.load(str(BACKGROUND_PATH), allow_pickle=True).item()
        return {
            "counts": [round(float(c), 1) for c in bg_data["counts"][:NUM_CHANNELS]],
            "live_time_s": round(float(bg_data["duration"]), 1),
        }
    except Exception:
        return None


@router.get("")
async def get_background_info():
    """Background metadata: elapsed time, CPS, top peaks."""
    snapshot = _load_snapshot()
    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():
    """Live background spectrum (from snapshot) with energy axis."""
    snapshot = _load_snapshot()
    live_time = snapshot.get("live_time_s", 0)

    return {
        "channels": list(range(NUM_CHANNELS)),
        "energy_kev": energy_axis(),
        "counts": snapshot.get("spectrum", [0] * 1024)[:NUM_CHANNELS],
        "live_time_s": live_time,
        "cps": snapshot.get("cps", 0),
        "top_peaks": snapshot.get("top_peaks", []),
        "reference_available": BACKGROUND_PATH.exists(),
    }


@router.get("/reference")
async def get_background_reference():
    """24h reference background spectrum for overlay comparison."""
    ref = _load_reference()
    if ref is None:
        raise HTTPException(status_code=404, detail="No 24h reference background available")

    return {
        "channels": list(range(NUM_CHANNELS)),
        "energy_kev": energy_axis(),
        "counts": ref["counts"],
        "live_time_s": ref["live_time_s"],
    }


@router.get("/theoretical")
async def get_theoretical_bg(cps: float = 6.0, live_time_s: float = 3600.0):
    """Theoretical natural background spectrum (K-40, U-238 chain, Th-232 chain)."""
    return generate_theoretical_bg(cps=cps, live_time_s=live_time_s)


@router.get("/continuum")
async def get_continuum(cps: float = 6.0, live_time_s: float = 3600.0):
    """CsI(Tl) continuum shape only (hump + Compton tail, no photopeaks, no noise).

    Matches the model used in training (generate_realistic_continuum).
    """
    return generate_continuum_only(cps=cps, live_time_s=live_time_s)