filter-errata

#!/usr/bin/python

import re
import sys

if len(sys.argv) != 2:
    print "Usage: myerrata versionmarker"
    exit(1)

# Version number we're being asked about
currentversion = sys.argv[1]
currentnumber = int(currentversion.split('-')[0])

print "Filtering errata for version marker " + currentversion + "..."

# Some regexps
commentre = re.compile('^\s*%')
versionre = re.compile('^\s*&\s*([0-9]+)-g[0-9a-f]{7}')

# Old and new errata files
errata = open("errata.tex",'r')
new = ""

# Move forward until the title
line = errata.readline()
while line != "%% VERSION MARKER\n":
    new += line
    line = errata.readline()

# Discard the comment
# Insert the version marker in the title
new += "\\\\since version " + currentversion + "\n"

# Move forward to the description
line = errata.readline()
while line != "%% BEGIN STARTPOINT\n":
    new += line
    line = errata.readline()

# Insert the version marker
new += "since version marker " + currentversion + "\n"

# Discard the "so far"
line = errata.readline()
while line != "%% END STARTPOINT\n":
    line = errata.readline()

# Now get up to the actual errata
line = errata.readline()
while line != "%% BEGIN ERRATA\n":
    new += line
    line = errata.readline()

# Parse each erratum and decide whether to include it
while line != "%% END ERRATA\n":
    # Skip comments
    while commentre.search(line):
        new += line
        line = errata.readline()
    # Now get the erratum, parsing the version number when we see it
    ver = float('inf')
    erratum = ''
    while not commentre.search(line):
        erratum += line
        vmatch = versionre.search(line)
        if vmatch:
            ver = int(vmatch.group(1))
        line = errata.readline()
    # If it applies to us, put it in
    if ver > currentnumber:
        new += erratum

# Finally, put the rest in.
while line:
    new += line
    line = errata.readline()

errata.close()

# New errata file
newfilename = "errata-since-" + currentversion + ".tex"

print "Writing filtered errata to " + newfilename + "."

newfile = open(newfilename,'w')
newfile.write(new)
newfile.close()