"""Is the nucleus of NGC 5128 actually saturated, or was that a foreground star?

The earlier claim - that the core clips at 65313 ADU in a single 300 s sub -
came from taking the maximum inside a 300x300 px box centred on the frame. That
box is wide enough to contain a bright foreground star, so the measurement
proves only that SOMETHING in the middle of the frame is bright. This checks
where the bright pixels actually are, and what the galaxy itself peaks at once
stars are filtered out.
"""
import numpy as np
from astropy import units as u
from astropy.coordinates import SkyCoord
from astropy.io import fits
from astropy.wcs import WCS
from scipy.ndimage import median_filter

import layout

SUB = layout.path("calibrated-T32-qisback-NGC5128-20260721-190133"
                  "-Luminance-BIN2-W-300-002.fit")
MASTER = layout.path("master-Luminance.fit")

# NGC 5128's nucleus, from SIMBAD, not from "the middle of the frame".
NUCLEUS = SkyCoord("13h25m27.6s", "-43d01m08.8s")

with fits.open(MASTER) as hd:
    wcs = WCS(hd[0].header, naxis=2)
nx_c, ny_c = wcs.world_to_pixel(NUCLEUS)
print(f"nucleus lands at master pixel ({nx_c:.1f}, {ny_c:.1f})")

data = fits.getdata(SUB).astype(np.float32)
ny, nx = data.shape
print(f"single sub {nx} x {ny}, global max {data.max():.0f} ADU")

# Where are the saturated-ish pixels?
ys, xs = np.where(data > 60000)
print(f"{len(xs)} pixels above 60000 ADU")
if len(xs):
    # Cluster them crudely by proximity to see how many distinct objects.
    print(f"  x range {xs.min()}-{xs.max()}, y range {ys.min()}-{ys.max()}")
    cx, cy = nx / 2.0, ny / 2.0
    d = np.hypot(xs - cx, ys - cy)
    print(f"  distance from frame centre: min {d.min():.0f} px, "
          f"median {np.median(d):.0f} px, max {d.max():.0f} px")
    # The brightest pixel specifically
    iy, ix = np.unravel_index(np.argmax(data), data.shape)
    print(f"  brightest pixel at ({ix}, {iy}), "
          f"{np.hypot(ix - cx, iy - cy):.0f} px from frame centre")

# The galaxy's own peak: median filter removes stars, which are small, while
# leaving the smooth galaxy light essentially untouched.
h = 400
y0, y1 = int(ny / 2) - h, int(ny / 2) + h
x0, x1 = int(nx / 2) - h, int(nx / 2) + h
core = data[y0:y1, x0:x1]
smooth = median_filter(core, size=15)
print(f"\ninner {2*h}x{2*h} px box:")
print(f"  raw max            {core.max():9.1f} ADU")
print(f"  median-filtered max {smooth.max():9.1f} ADU   <- galaxy light")
iy, ix = np.unravel_index(np.argmax(smooth), smooth.shape)
print(f"  galaxy peak at frame pixel ({x0+ix}, {y0+iy})")

# How many pixels of the median-filtered (star-free) galaxy are near clipping?
for lvl in (30000, 50000, 60000):
    print(f"  star-free pixels above {lvl}: {(smooth > lvl).sum()}")

# And in the master stack.
mdata = fits.getdata(MASTER).astype(np.float32)
mcore = mdata[y0:y1, x0:x1]
msmooth = median_filter(mcore, size=15)
print(f"\nmaster stack inner box: raw max {mcore.max():.1f}, "
      f"star-free max {msmooth.max():.1f} ADU")
print(f"  master 99.995th percentile (the stretch white point) "
      f"{np.percentile(mdata, 99.995):.1f} ADU")