import io
import struct
import os

class MOTFile:
    """MOT File TODO"""

    def __init__(self, data):
        self.data = data

    @property
    def is_valid(self):
        """Returns true iff the data size is equal to the size of all
        contained files"""
        try:
            return len(self.data) == self.offset(self.num_files - 1) + self.size(self.num_files-1)
        except:
            return False

    @property
    def num_files(self):
        return struct.unpack("I", self.data[:4])[0]

    @property
    def header_size(self):
        size = 4 + self.num_files * 4
        # Round to a multiple of 16
        return ((size + 15) // 16) * 16

    def offset(self, i):
        if i == 0:
            return self.header_size
        else:
            return self.size(i-1) + self.offset(i-1)

        return struct.unpack("I", self.data[4+(i*8):8+(i*8)])[0]

    def size(self, i):
        start = 4 + i*4
        return struct.unpack("I", self.data[start:start+4])[0]

    def file(self, i):
        offset = self.offset(i)
        size = self.size(i)
        return self.data[offset:offset+size]

    def describe(self):
        res = io.StringIO()
        res.write(f"Total Size: {len(self.data)}\n")
        res.write(f"Valid: {self.is_valid}\n")
        for n in range(self.num_files):
            offset = self.offset(n)
            size = self.size(n)
            res.write(f"{n:01d}: offset {offset}, size {size}\n")
        return res.getvalue()

    def unpack_to(self, path):
        os.makedirs(path, exist_ok=True)
        for i in range(self.num_files):
            fbytes = self.file(i)
            if MOTFile(fbytes).is_valid:
                MOTFile(fbytes).unpack_to(os.path.join(path, f"{i:03d}"))
            else:
                with open(os.path.join(path, f"{i:03d}"), "wb") as f:
                    f.write(fbytes)