"""Adds xref targets to the top of files."""

import sys

import os

testing = False

DONT_TOUCH = (

        './index.txt',

        )

def target_name(fn):

    if fn.endswith('.txt'):

        fn = fn[:-4]

    return '_' + fn.lstrip('./').replace('/', '-')

def process_file(fn, lines):

    lines.insert(0, '\n')

    lines.insert(0, '.. %s:\n' % target_name(fn))

    try:

        f = open(fn, 'w')

    except IOError:

        print("Can't open %s for writing. Not touching it." % fn)

        return

    try:

        f.writelines(lines)

    except IOError:

        print("Can't write to %s. Not touching it." % fn)

    finally:

        f.close()

def has_target(fn):

    try:

        f = open(fn, 'r')

    except IOError:

        print("Can't open %s. Not touching it." % fn)

        return (True, None)

    readok = True

    try:

        lines = f.readlines()

    except IOError:

        print("Can't read %s. Not touching it." % fn)

        readok = False

    finally:

        f.close()

        if not readok:

            return (True, None)

    #print fn, len(lines)

    if len(lines) < 1:

        print("Not touching empty file %s." % fn)

        return (True, None)

    if lines[0].startswith('.. _'):

        return (True, None)

    return (False, lines)

def main(argv=None):

    if argv is None:

        argv = sys.argv

    if len(argv) == 1:

        argv.extend('.')

    files = []

    for root in argv[1:]:

        for (dirpath, dirnames, filenames) in os.walk(root):

            files.extend([(dirpath, f) for f in filenames])

    files.sort()

    files = [os.path.join(p, fn) for p, fn in files if fn.endswith('.txt')]

    #print files

    for fn in files:

        if fn in DONT_TOUCH:

            print("Skipping blacklisted file %s." % fn)

            continue

        target_found, lines = has_target(fn)

        if not target_found:

            if testing:

                print '%s: %s' % (fn, lines[0]),

            else:

                print "Adding xref to %s" % fn

                process_file(fn, lines)

        else:

            print "Skipping %s: already has a xref" % fn

if __name__ == '__main__':

    sys.exit(main())