#!/usr/bin/env python3
"""Find the count=0 sentinel in the BCM4500 firmware data at 0x4000+."""
import sys
sys.path.insert(0, 'tools')
from skywalker_lib import SkyWalker1

CMD_EEPROM_READ = 0xC0
sw = SkyWalker1()
sw.open()


def ee(addr, length):
    return sw._vendor_in(CMD_EEPROM_READ, value=addr, index=length, length=length)


print('=== Scanning for count=0 sentinel from 0x4000 ===')
print()

blocks = 0
total_bytes = 0
addr = 0x4000

while addr < 0x8000:
    data = ee(addr, 20)
    count = data[0]

    if count == 0:
        print(f'  SENTINEL FOUND at 0x{addr:04X} after {blocks} blocks ({total_bytes} payload bytes)')
        break

    if count > 16:
        print(f'  INVALID count=0x{count:02X} at 0x{addr:04X} after {blocks} blocks')
        # Show context
        for ctx_addr in range(max(0x4000, addr - 60), addr + 60, 20):
            d = ee(ctx_addr, 20)
            marker = ' ← INVALID' if ctx_addr == addr else ''
            print(f'    0x{ctx_addr:04X}: count={d[0]:3d} A9=0x{d[1]:02X} AA=0x{d[2]:02X}{marker}')
        break

    # Valid block
    a9 = data[1]
    aa = data[2]
    ab_bytes = count
    total_bytes += ab_bytes

    if blocks < 5 or blocks % 100 == 0:
        ab = data[4:4 + min(count, 8)]
        print(f'  Block {blocks:4d} @ 0x{addr:04X}: count={count:2d} A9=0x{a9:02X} AA=0x{aa:02X} '
              f'AB=[{ab.hex(" ")}{"..." if count > 8 else ""}]')

    blocks += 1
    addr += 20

else:
    print(f'  NO SENTINEL found before 0x8000 ({blocks} blocks scanned)')

print()
print(f'Summary: {blocks} blocks, {total_bytes} payload bytes')
print(f'Address range: 0x4000 - 0x{addr:04X}')

# Show the sentinel and what follows
if addr < 0x8000:
    print()
    print(f'--- Data around sentinel at 0x{addr:04X} ---')
    for a in range(max(0x4000, addr - 40), addr + 60, 20):
        d = ee(a, 20)
        cnt = d[0]
        if cnt == 0:
            print(f'  0x{a:04X}: [SENTINEL count=0] rest: {d[1:].hex(" ")}')
        elif 1 <= cnt <= 16:
            print(f'  0x{a:04X}: count={cnt} A9=0x{d[1]:02X} AA=0x{d[2]:02X}')
        else:
            print(f'  0x{a:04X}: [non-PLL: 0x{cnt:02X}] {d[:16].hex(" ")}')

sw.close()
print()
print('=== Done ===')