#!/usr/bin/env python3
"""v6 T17 — F2 (24 V vehicle input fuse) gets a real, orderable part.

F2 carried the placeholder "TBD-2A-1812" (value "2A/63V-slow-1812"). The JLC catalogue has
no 1812 fuse that is both 2 A time-lag and rated >= 63 V (1812 PPTCs top out at 33–36 V,
below what the SMBJ33A on /24V_IN lets through during a load dump).
Chosen: Littelfuse 0454002.MR — NANO2 Slo-Blo, 2 A, 125 V, 50 A breaking, 2410 body.
LCSC C179005 (Extended, 1136 in stock on 25-Sep).

Schematic: Value, Footprint (Fuse:Fuse_Littelfuse-NANO2-451_453 — same NANO2 land as the
454 series; verify against the 0454 datasheet) and LCSC.
Board: LCSC value + Value only. The footprint swap (1812 -> NANO2, 6.1 x 2.7 mm) is a layout
step: in the PCB editor, right-click F2 -> Change Footprint -> Fuse:Fuse_Littelfuse-NANO2-451_453.

    python3 T17.py hbox-watchdog-v6.kicad_sch hbox-watchdog-v6.kicad_pcb [--apply]
"""
import re, sys, shutil

REF = 'F2'
NEW = {'Value': '2A/125V-SloBlo-NANO2', 'LCSC': 'C179005',
       'Footprint': 'Fuse:Fuse_Littelfuse-NANO2-451_453'}
OLD_LCSC = 'TBD-2A-1812'

def span(s, i):
    d = 0; instr = False; j = i
    while True:
        c = s[j]
        if c == '"' and s[j-1] != '\\': instr = not instr
        elif not instr:
            if c == '(': d += 1
            elif c == ')':
                d -= 1
                if d == 0: return j + 1
        j += 1

def edit(s, head, props, ch, tag):
    m = re.search(r'\n\t\t\(property "Reference" "%s"\n' % REF, s)
    a = s.rfind('\n\t(' + head, 0, m.start()) + 1; e = span(s, a); b = s[a:e]
    for k, v in props.items():
        pm = re.search(r'\n\t\t\(property "%s" "([^"]*)"' % k, b)
        if not pm: raise SystemExit(f'{tag}: {REF} has no {k} property')
        if pm.group(1) == v: continue
        if k == 'LCSC' and pm.group(1) not in (OLD_LCSC, ''): raise SystemExit(f'{tag}: unexpected LCSC {pm.group(1)}')
        b = b[:pm.start()] + f'\n\t\t(property "{k}" "{v}"' + b[pm.end():]
        ch.append(f'{tag} {REF}: {k} "{pm.group(1)}" -> "{v}"')
    return s[:a] + b + s[e:]

def main():
    sch, pcb = sys.argv[1], sys.argv[2]; apply = '--apply' in sys.argv
    S0 = open(sch).read(); P0 = open(pcb).read(); ch = []
    S = edit(S0, 'symbol', NEW, ch, 'sch')
    P = edit(P0, 'footprint', {'Value': NEW['Value'], 'LCSC': NEW['LCSC']}, ch, 'pcb')
    for t in (S, P):
        u = re.sub(r'"(?:[^"\\]|\\.)*"', '', t); assert u.count('(') == u.count(')')
    print('\n'.join(ch) or 'nothing to do (already applied)')
    if ch and apply:
        for f, t in ((sch, S), (pcb, P)):
            shutil.copy2(f, f + '.T17bak'); open(f, 'w').write(t)
        print('APPLIED (backups .T17bak)')
    elif ch:
        print('DRY RUN — re-run with --apply')

if __name__ == '__main__':
    main()