import argparse
import json
import os


def main(args):
    db_path = os.path.join(args.output_db_path, f"{args.output_db_name}.db")
    index_path = os.path.join(
        args.output_db_path, f"{args.output_db_name}.index"
    )
    db_fp = open(db_path, "wb")
    index = {}
    db_offset = 0
    for chain_alignment_dir in os.listdir(args.alignment_dir):
        cad_path = os.path.join(args.alignment_dir, chain_alignment_dir)
        for f in os.listdir(cad_path):
            f_path = os.path.join(cad_path, f)
            with open(f_path, "rb") as fp:
                file_bytes = fp.read()

            l = len(file_bytes)
            file_list = index.setdefault(chain_alignment_dir, [])
            file_list.append((f, db_offset, l))
            
            db_fp.write(file_bytes)
            db_offset += l

    db_fp.close()

    with open(index_path, "w") as fp:
        json.dump(index, fp)
            


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "alignment_dir", type=str, 
        help="""Path to precomputed alignment directory, with one subdirectory 
                per chain."""
    )
    parser.add_argument("output_db_path", type=str)
    parser.add_argument("output_db_name", type=str)

    args = parser.parse_args()

    main(args)