#!/usr/bin/env python

import re, os, sys, fnmatch


# Regex pattern to extract the directory path in a #define FILE_DIR
filedir_pattern = re.compile(r'^#define\s*FILE_DIR\s*"(.*?)"')

# Regex pattern to extract any single quoted piece of text. This can also
# match single quoted strings inside of double quotes, which is part of a
# regular text string and should not be replaced. The replacement function
# however will any match that doesn't appear to be a filename so these
# extra matches should not be a problem.
rename_pattern = re.compile(r"'(.+?)'")

# Only filenames matching this pattern will have their resources renamed
source_pattern = re.compile(r"^.*?\.(dm|dmm)$")

# Open the .dme file and return a list of all FILE_DIR paths in it
def read_filedirs(filename):
	result = []
	with open(filename, "rt") as dme_file:
		# Read each line from the file and check for regex pattern match
		for row in dme_file:
			match = filedir_pattern.match(row)
			if match:
				result.append(match.group(1))
	return result

# Search through a list of directories, and build a dictionary which
# maps every file to its full pathname (relative to the .dme file)
# If the same filename appears in more than one directory, the earlier
# directory in the list takes preference.
def index_files(file_dirs):
	result = {}

	# Reverse the directory list so the earlier directories take precedence
	# by replacing the previously indexed file of the same name
	for directory in reversed(file_dirs):
		for name in os.listdir(directory):
			# Replace backslash path separators on Windows with forward slash
			# Force "name" to lowercase when used as a key since BYOND resource
			# names are case insensitive, even on Linux.
			if name.find(".") == -1:
				continue
			result[name.lower()] = directory.replace('\\', '/') + '/' + name

	return result

# Recursively search for every .dm/.dmm file in the .dme file directory. For
# each file, search it for any resource names in single quotes, and replace
# them with the full path previously found by index_files()
def rewrite_sources(resources):
	# Create a closure for the regex replacement function to capture the
	# resources dictionary which can't be passed directly to this function
	def replace_func(name):
		key = name.group(1).lower()
		if key in resources:
			replacement = resources[key]
		else:
			replacement = name.group(1)
		return "'" + replacement + "'"
	
	# Search recursively for all .dm and .dmm files
	for (dirpath, dirs, files) in os.walk("."):
		for name in files:
			if source_pattern.match(name):
				path = dirpath + '/' + name
				source_file = open(path, "rt")
				output_file = open(path + ".tmp", "wt")

				# Read file one line at a time and perform replacement of all
				# single quoted resource names with the fullpath to that resource
				# file. Write the updated text back out to a temporary file.
				for row in source_file:
					row = rename_pattern.sub(replace_func, row)
					output_file.write(row)

				output_file.close()
				source_file.close()

				# Delete original source file and replace with the temporary
				# output. On Windows, an atomic rename() operation is not
				# possible like it is under POSIX.
				os.remove(path)
				os.rename(path + ".tmp", path)

dirs = read_filedirs("vgstation13.dme");
resources = index_files(dirs)
rewrite_sources(resources)