import argparse, os, struct, csv, sys


def align16(x):
    return (x + 15) & ~15


def collect(args):
    items = []
    if args.csv and os.path.exists(args.csv):
        with open(args.csv, newline="", encoding="utf-8") as f:
            for row in csv.DictReader(f):
                items.append((row["name"], row["file"]))
    else:
        for root, dirs, files in os.walk(args.dir):
            for fn in files:
                full = os.path.join(root, fn)
                rel = os.path.relpath(full, args.dir)
                name = rel.replace("/", "\\")
                items.append((name, rel))
    return items


def main():
    ap = argparse.ArgumentParser(description="Rebuild a Dragon .res archive from a directory (16-byte aligned blobs).")
    ap.add_argument("dir")
    ap.add_argument("out")
    ap.add_argument("--csv", default=None)
    args = ap.parse_args()

    items = collect(args)
    blobs = []
    for name, rel in items:
        full = os.path.join(args.dir, rel)
        if not os.path.isfile(full):
            print("missing: %s" % full, file=sys.stderr)
            sys.exit(2)
        blobs.append((name, open(full, "rb").read()))

    hdr = 4
    for name, _ in blobs:
        hdr += 4 + len(name) + 8
    data_start = align16(hdr)

    out = bytearray()
    out += struct.pack("<I", len(blobs))
    index = bytearray()
    offset = data_start
    payload = bytearray()
    for i, (name, blob) in enumerate(blobs):
        nb = name.encode("latin1")
        index += struct.pack("<I", len(nb)) + nb + struct.pack("<II", offset, len(blob))
        payload += blob
        if i != len(blobs) - 1:
            pad = align16(len(blob)) - len(blob)
            payload += b"\x00" * pad
            offset += len(blob) + pad
        else:
            offset += len(blob)
    assert len(index) + 4 == hdr, (len(index) + 4, hdr)
    out += index
    out += b"\x00" * (data_start - len(out))
    out += payload

    with open(args.out, "wb") as f:
        f.write(out)
    print("repacked %d files -> %s (%d bytes)" % (len(blobs), args.out, len(out)))


if __name__ == "__main__":
    main()