"""Minimal reader of Enshrouded's KFC4 container: raw content blobs by their content key.

enshrouded.kfc header: 17 KFCLocation entries (u32 offset relative to the entry, u32 count) at 16 + i*8.
Location 1 = .dat containers, 7 = content keys (size, hash0, hash1, hash2), 8 = values
(offset u32, flags u16, container index u16, 8 bytes pad). Blobs live in enshrouded_NNN.dat.
"""
import pathlib
import struct


class KFC:
    def __init__(self, game):
        self.game = pathlib.Path(game)
        b = (self.game / "enshrouded.kfc").read_bytes()
        assert b[:4] == b"KFC4", "not a KFC4 file"
        locs = []
        for i in range(17):
            pos = 16 + i * 8
            off, cnt = struct.unpack_from("<II", b, pos)
            locs.append((pos + off if off else 0, cnt))
        ko, kc = locs[7]
        vo, vc = locs[8]
        assert kc == vc
        self.content = {}
        for i in range(kc):
            key = struct.unpack_from("<IIII", b, ko + i * 16)
            off, flags, ci = struct.unpack_from("<IHH", b, vo + i * 16)
            self.content[key] = (off, flags, ci)

    def read(self, size, hash0, hash1, hash2):
        e = self.content.get((size, hash0, hash1, hash2))
        if not e:
            return None
        off, _, ci = e
        with open(self.game / f"enshrouded_{ci:03d}.dat", "rb") as f:
            f.seek(off)
            return f.read(size)

    def read_hash(self, h: dict):
        """h: a descriptor's content hash {"size", "hash0", "hash1", "hash2"}."""
        return self.read(h["size"], h["hash0"], h["hash1"], h["hash2"])