#!/usr/bin/env python3
"""Desktop pixel-diff for the header lang-toggle move (spec acceptance 7).

Compares two screenshot dirs (intro/results, EN+FR) and proves the ONLY change is
inside the header strip: the diff bbox must sit entirely above `hdr_bottom` (masked),
and everything below the header must be bit-identical. Prints a self-jitter baseline
DIR_A vs DIR_A2 (same version captured twice) for the jitter-controlled comparison.

Usage: python3 audit/lang_right_pixdiff.py BEFORE AFTER HDR_BOTTOM
       python3 audit/lang_right_pixdiff.py SELFJITTER DIR DIR2 HDR_BOTTOM
"""
import os, sys
from PIL import Image, ImageChops

# Usage: pixdiff.py BEFORE AFTER HDR_BOTTOM [PREFIX]
#        pixdiff.py SELFJITTER DIR DIR2 HDR_BOTTOM [PREFIX]
if sys.argv[1] == 'SELFJITTER':
    cross = False
    A, B, HB = sys.argv[2], sys.argv[3], int(sys.argv[4])
    PREFIX = sys.argv[5] if len(sys.argv) > 5 else None
else:
    cross = True
    A, B, HB = sys.argv[1], sys.argv[2], int(sys.argv[3])
    PREFIX = sys.argv[4] if len(sys.argv) > 4 else None

fa = sorted(f for f in os.listdir(A) if f.endswith('.png') and (PREFIX is None or f.startswith(PREFIX)))
zero, all_in_hdr = True, True
for f in fa:
    p = os.path.join(A, f)
    q = os.path.join(B, f)
    if not os.path.exists(q):
        if cross:
            print(f'{f}: MISSING in {B}'); zero = False; all_in_hdr = False
        else:
            print(f'{f}: (no self-jitter pair, skipping)')
        continue
    ia, ib = Image.open(p).convert('RGB'), Image.open(q).convert('RGB')
    if ia.size != ib.size:
        print(f'{f}: SIZE DIFF {ia.size} vs {ib.size}'); zero = False; all_in_hdr = False; continue
    W, H = ia.size
    d = ImageChops.difference(ia, ib)
    bbox = d.getbbox()
    if bbox is None:
        print(f'{f}: 0 px (identical)'); continue
    x0, y0, x1, y1 = bbox
    # mask the header strip: crop everything below HB and diff that
    below = ImageChops.difference(ia.crop((0, HB, W, H)), ib.crop((0, HB, W, H)))
    below_bbox = below.getbbox()
    hist = d.convert('L').histogram()
    ndiff = sum(hist[1:])
    below_hist = below.convert('L').histogram()
    ndiff_below = sum(below_hist[1:])
    if ndiff_below > 0:
        print(f'{f}: {ndiff} px total, {ndiff_below} px BELOW header (bbox {bbox})  <-- LEAK')
        zero = False; all_in_hdr = False
    else:
        tag = 'header-only' if cross else 'identical'
        print(f'{f}: {ndiff} px total, 0 px below y={HB}, bbox_top={y0} bbox_bot={y1}  [{tag}]')
        if not cross:
            zero = zero and (ndiff == 0)
print('---')
if cross:
    print('PIXDIFF-HEADER-ONLY' if all_in_hdr else 'PIXDIFF-LEAK-BELOW-HEADER')
    sys.exit(0 if all_in_hdr else 1)
else:
    print('SELFJITTER-ZERO' if zero else 'SELFJITTER-NONZERO')
    sys.exit(0 if zero else 1)