import io

from .matcher import SignatureMatcher, Match

class Ambarella(SignatureMatcher):
    def __init__(self, file):
        self.name = "Ambarella Firmware Section"
        self.signature = b'\x90\xeb\x24\xa3'
        super().__init__(file)

    def is_valid(self):
        for match in self.search():
            # walk back for the firmware section header
            start = match - 4*5
            header = io.BytesIO(self.file[start:start+228+4*6])
            crc = header.read(4)
            version_major = header.read(2)
            version_minor = header.read(2)
            filesize = header.read(4)
            memory = header.read(4)
            flag = header.read(4)
            magic = header.read(4)
            zeros = header.read()

            # for ambarella firmware, the magic is placed at offset 20
            # and after the magic, 228 bytes of \x00 must be placed
            # then crc value must match the CRC(<filesize> bytes after header)


            is_matched = magic == self.signature
            is_matched &= zeros == bytes(228)
            # is_matched &= crc == self.crc(self.file[start + 228+4*6:start + filesize + 228+4*6])
            if is_matched:
                # add the header offset to list of matches
                filesize = int.from_bytes(filesize, 'little')
                self.matches += [Match(start, 228 + 4*6 + filesize)]

        return len(self.matches) != 0