import io
from .matcher import SignatureMatcher, Match

class SquashFS(SignatureMatcher):
    """
    Finding a Squash file system
    https://dr-emann.github.io/squashfs/

    superblock
    -> compression options
    -> data blocks & fragments
    -> inode table
    -> directory table
    -> fragment table
    -> export table
    -> uid/gid lookup table
    -> xattr table
    """
    def __init__(self, file):
        self.name = "SquashFS"
        self.signature = b'hsqs'
        super().__init__(file)

    def is_valid(self):
        for match in self.search():
            start = match
            header = io.BytesIO(self.file[start:start+ 4*5 + 2*6 + 8*8])
            magic = header.read(4)
            inode = header.read(4)
            modification_time = header.read(4)
            block_size = header.read(4)
            fragment_entry_count = header.read(4)
            compression_id = header.read(2)
            block_log = header.read(2)
            flags = header.read(2)
            id_count = header.read(2)
            version_major = header.read(2)
            version_minor = header.read(2)
            root_inode_ref = header.read(8)
            bytes_used = header.read(8)
            id_table_start = header.read(8)
            xattr_id_table_start = header.read(8)
            inode_table_start = header.read(8)
            directory_table_start = header.read(8)
            fragment_table_start = header.read(8)
            export_table_start = header.read(8)

            # size how to get?
            self.matches += [Match(start, 0)]
        return len(self.matches) != 0