import json
from fastapi import APIRouter, HTTPException
from app.config import BACKGROUND_SNAPSHOT_PATH, BACKGROUND_PATH, energy_axis, NUM_CHANNELS, ENERGY_OFFSET, ENERGY_SLOPE
from app.theoretical_bg import generate_continuum_only
from app.noise import extract_continuum
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("/continuum")
async def get_continuum(cps: float = 6.0, live_time_s: float = 3600.0):
    """CsI(Tl) detector response continuum only (no photopeaks, no noise)."""
    return generate_continuum_only(cps=cps, live_time_s=live_time_s)


@router.get("/fit")
async def fit_background():
    """Fit the parametric CsI(Tl) detector response model to measured background data.

    Returns the fitted curve, parameters, and quality metrics.
    """
    from app.bg_calibration import calibrate_background, build_calibrated_continuum

    # Load measured data
    measured_counts = None
    live_time = 0

    if BACKGROUND_PATH.exists():
        try:
            bg_data = np.load(str(BACKGROUND_PATH), allow_pickle=True).item()
            measured_counts = bg_data["counts"].astype(np.float64)[:NUM_CHANNELS]
            live_time = float(bg_data["duration"])
        except Exception:
            pass

    if measured_counts is None and BACKGROUND_SNAPSHOT_PATH.exists():
        try:
            with open(BACKGROUND_SNAPSHOT_PATH) as f:
                snapshot = json.load(f)
            measured_counts = np.array(snapshot.get("spectrum", [])[:NUM_CHANNELS], dtype=np.float64)
            live_time = float(snapshot.get("live_time_s", 0))
        except Exception:
            pass

    if measured_counts is None or live_time < 600:
        raise HTTPException(status_code=404, detail="No measured background available for fitting")

    channels = np.arange(NUM_CHANNELS, dtype=np.float64)
    e_axis = ENERGY_OFFSET + ENERGY_SLOPE * channels

    # Run calibration
    measured_cps = measured_counts / live_time
    result = calibrate_background(measured_cps, e_axis)

    if "error" in result:
        raise HTTPException(status_code=500, detail=f"Fitting failed: {result['error']}")

    # Build fitted curve at same scale as measured
    fitted_counts = build_calibrated_continuum(e_axis, measured_counts.sum(), result)

    return {
        "energy_kev": [round(float(E), 2) for E in e_axis],
        "measured_counts": [round(float(c), 1) for c in measured_counts],
        "fitted_counts": [round(float(c), 1) for c in fitted_counts],
        "method": result.get("method", "spline"),
        "r_squared": result["r_squared"],
        "residuals_rms": result["residuals_rms"],
        "live_time_s": round(live_time, 1),
    }


@router.get("/noise")
async def get_background_noise():
    """Detector's intrinsic continuum curve (isotope peaks subtracted).

    Returns the smooth detector response shape without any isotope
    photopeak signatures. Works with any detector type.
    """
    counts = None

    if BACKGROUND_PATH.exists():
        try:
            bg_data = np.load(str(BACKGROUND_PATH), allow_pickle=True).item()
            counts = bg_data["counts"].astype(np.float64)[:NUM_CHANNELS]
        except Exception:
            pass

    if counts is None and BACKGROUND_SNAPSHOT_PATH.exists():
        try:
            with open(BACKGROUND_SNAPSHOT_PATH) as f:
                snapshot = json.load(f)
            counts = np.array(snapshot.get("spectrum", [])[:NUM_CHANNELS], dtype=np.float64)
        except Exception:
            pass

    if counts is None:
        raise HTTPException(status_code=404, detail="No background data available")

    channels = np.arange(NUM_CHANNELS, dtype=np.float64)
    e_axis = ENERGY_OFFSET + ENERGY_SLOPE * channels
    continuum = extract_continuum(counts, energy_axis=e_axis)

    return {
        "energy_kev": [round(float(E), 2) for E in e_axis],
        "counts": [round(float(c), 1) for c in continuum],
    }