from os import listdir
import struct
import io

from .buffer import Buffer
from .i18n import splitFileName, getScore, locale

class ResourceError(Exception):
    def __init__(self, code=None):
        self.code = code

class ResourceFile(object):
    def __init__(self, fileName, buf=None):
        self.__name = fileName

        if buf is not None:
            buffer = buf
            ownBuffer = False
        else:
            buffer = Buffer()
            ownBuffer = True

        try:
            self.__stream = open(self.__name, 'rb')
            sign = self.__stream.read(4)
            if sign != b'CRF\x00':
                raise ResourceError(code='invalid')

            major = self.readInt()
            minor = self.readInt()
            priority = self.readInt()

            if major != 2 or minor < 0:
                raise ResourceError(code='incompatible')
        except ResourceError as e:
            raise Exception("Invalid resource file: {}".format(e.code))
        except IOError as e:
            raise Exception("Error loading resource file '{}': {}".format(self.__name, e.message))

    def readInt(self):
        return struct.unpack('i', self.__stream.read(4))[0]

    def readString(self):
        string = b''

        while True:
            b = self.__stream.read(1)

            if b == b'\x00' or b == b'':
                break

            string += b

        return string.decode('ascii')

    def getDirectory(self):
        try:
            self.__stream.seek(-8, io.SEEK_END);
        except IOError:
            raise Exception("Error reading {} directory".format(self.__name))

        start = self.readInt()
        count = self.readInt()

        try:
            self.__stream.seek(start, io.SEEK_SET);
        except IOError:
            raise Exception("Error reading {} directory".format(self.__name))

        directory = []

        try:
            for i in range(0, count):
                directory.append({
                    "name": self.readString(),
                    "unpackedSize": self.readInt(),
                    "offset": self.readInt(),
                    "packedSize": self.readInt(),
                    "level": self.readInt(),
                    "group": self.readString(),
                })
        except IOError:
            raise Exception("Error reading {} directory".format(self.__name))

        return directory

class ResourcesCollection:
    def __init__(self, directories):
        self.__files = []
        self.__buffer = None
        self.__resources = {}
        self.loadResourceFiles(directories)
        self.processFiles()

    def loadResourceFiles(self, directories):
        for directory in directories:
            try:
                for name in listdir(directory):
                    if not name.startswith('.') and name.endswith('.res'):
                        self.__files.append(
                            ResourceFile(directory + '/' + name,
                                         buf=self.__buffer))
            except OSError:
                pass

    def processFiles(self):
        for res_file in self.__files:
            directory = res_file.getDirectory()

            for de in directory:
                name, ext, language, country = splitFileName(de['name'])
                score = getScore(language, country, locale)

                if score > 0:
                    resName = name + '.' + ext
                    res = self.__resources.get(resName, None)

                    if not res:
                        res = Resource(res_file, score, de, resName)
                        self.__resources[resName] = res

                        if len(de.group) > 0:
                            groups[de.group].append(res)
                    else:
                        res.addVariant(file, score, de)

            directory.clear()