"""bce.py RAWFILE: report erases/scrolls done while a background colour is set (what a
back-colour-erase terminal would paint).  Tracks cursor row/col roughly.
Claude Opus 5.5, 2026-10-19; written for 2089, https://github.com/nfinit/2089."""
import re, sys
data = open(sys.argv[1], 'rb').read().decode('latin-1')
row = col = 0; bg = None; out = []
i = 0
seq = re.compile(r'\x1b\[([0-9;?]*)([@-~])|\x1b([()][0-9A-Za-z])|\x1b([0-9A-Za-z=>])')
while i < len(data):
    m = seq.match(data, i)
    if m:
        p, f = m.group(1), m.group(2)
        if f:
            args = [int(x) if x.isdigit() else 0 for x in (p or '').replace('?', '').split(';')] if p else []
            if f == 'm':
                for a in (args or [0]):
                    if a == 0 or a == 49: bg = None
                    elif 40 <= a <= 47 or 100 <= a <= 107: bg = a
            elif f == 'H' or f == 'f':
                row = (args[0] if args and args[0] else 1) - 1
                col = (args[1] if len(args) > 1 and args[1] else 1) - 1
            elif f == 'A': row -= args[0] if args and args[0] else 1
            elif f == 'B': row += args[0] if args and args[0] else 1
            elif f == 'C': col += args[0] if args and args[0] else 1
            elif f == 'D': col -= args[0] if args and args[0] else 1
            elif f in 'KJLMPX@' and bg is not None:
                out.append('ESC[%s%s at row %d col %d with background %d' % (p, f, row + 1, col + 1, bg))
            elif f == 'r':
                pass
        elif m.group(4) == 'M':
            row -= 1
        i = m.end(); continue
    c = data[i]
    if c == '\n':
        if row == 23 and bg is not None: out.append('LF scroll at bottom with background %d' % bg)
        row = min(row + 1, 23)
    elif c == '\r': col = 0
    elif c == '\b': col -= 1
    elif c == '\t': col = (col // 8 + 1) * 8
    elif c >= ' ': col += 1
    i += 1
print('\n'.join(out) if out else 'no erase or scroll while a background colour is set')