import json

import numpy as np

from zarr.errors import MetadataError


def decode_metadata(b):
    s = str(b, "ascii")
    meta = json.loads(s)
    zarr_format = meta.get("zarr_format", None)
    if zarr_format != 1:
        raise MetadataError(f"unsupported zarr format: {zarr_format}")
    try:
        meta = dict(
            zarr_format=meta["zarr_format"],
            shape=tuple(meta["shape"]),
            chunks=tuple(meta["chunks"]),
            dtype=decode_dtype(meta["dtype"]),
            compression=meta["compression"],
            compression_opts=meta["compression_opts"],
            fill_value=meta["fill_value"],
            order=meta["order"],
        )
    except Exception as e:
        raise MetadataError(f"error decoding metadata: {e}")
    else:
        return meta


def encode_metadata(meta):
    meta = dict(
        zarr_format=1,
        shape=meta["shape"],
        chunks=meta["chunks"],
        dtype=encode_dtype(meta["dtype"]),
        compression=meta["compression"],
        compression_opts=meta["compression_opts"],
        fill_value=meta["fill_value"],
        order=meta["order"],
    )
    s = json.dumps(meta, indent=4, sort_keys=True, ensure_ascii=True)
    b = s.encode("ascii")
    return b


def encode_dtype(d):
    if d.fields is None:
        return d.str
    else:
        return d.descr


def _decode_dtype_descr(d):
    # need to convert list of lists to list of tuples
    if isinstance(d, list):
        # recurse to handle nested structures
        d = [(f, _decode_dtype_descr(v)) for f, v in d]
    return d


def decode_dtype(d):
    d = _decode_dtype_descr(d)
    return np.dtype(d)
