lcs-diff/patch.py
2025-09-20 19:26:03 -07:00

66 lines
1.9 KiB
Python

import argparse
parser = argparse.ArgumentParser(description="Prints to stdout the patched document")
parser.add_argument('original', help='original document')
parser.add_argument('patch', help='patch file')
args = parser.parse_args()
fa = open(args.original,'r')
la = fa.read().split('\n')
# a workspace for us to edit, each element being a list that 1) originally contains a corresponding line
# in a, 2) may be emptied if that line is removed, 3) may be where we insert new content
ws = [[l] for l in la]
fp = open(args.patch,'r')
lp = fp.read().split('\n')
def str2intv(s):
if "," in s:
x, y = s.split(',')
else:
x, y = s, s
return int(x)-1, int(y)
def ws_rm(desc, lp, nb):
l,r = str2intv(desc)
for p in range(l,r):
nb += 1
assert lp[nb][:2] == "< "
assert ws[p][0] == lp[nb][2:],\
f"Patch file wants to delete '{lp[nb][2:]}', but originally line {p} is '{ws[p][0]}'"
ws[p] = list()
return nb + 1, l
def ws_insert(p, desc, lp, nb):
l,r = str2intv(desc)
for _ in range(l,r):
nb += 1
assert lp[nb][:2] == "> "
ws[p].append(lp[nb][2:])
return nb + 1
nb = 0
while nb < len(lp):
line = lp[nb]
if line:
assert line[0] != '<' and line[0] != '>', f"Expected description at line {nb}, but got {line}"
else:
nb += 1
continue
idx_d = line.find('d')
if idx_d != -1:
nb, _ = ws_rm(line[:idx_d], lp, nb)
continue
idx_a = line.find('a')
if idx_a != -1:
p = int(line[:idx_a]) - 1
nb = ws_insert(p, line[idx_a+1:], lp, nb)
continue
idx_c = line.find('c')
if idx_c != -1:
nb, p = ws_rm(line[:idx_c], lp, nb)
nb = ws_insert(p, line[idx_c+1:], lp, nb)
continue
assert False, f"Unreachable. Cannot parse line {nb}: {line}"
flatws = [line for _ in ws for line in _]
print('\n'.join(flatws), end="") # Don't want to print additional new line