import panel as pn
pn.extension()

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
    levels=["Model", "Resolution", "Initialization"],
)
select

select.value

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
    levels=["Model", "Resolution", "Initialization"],
    layout=pn.Row
)
select

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
    levels=["Model", "Resolution", "Initialization"],
    layout={"type": pn.GridBox, "ncols": 2}
)
select

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
)
select.value

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
    value={"Model": "NAME", "Resolution": "12 km", "Initialization": "12Z"},
    levels=["Model", "Resolution", "Initialization"],
)
select

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
    value={"Initialization": "12Z", "Resolution": "0.5 deg"},
    levels=["Model", "Resolution", "Initialization"],
)
select

select = pn.widgets.NestedSelect(
    options={
        "NAME": {},
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
    },
    levels=["Model", "Resolution", "Initialization"],
)
select

select.value = {"Model": "NAME"}

def list_options(level, value):
    if level == "time_step":
        options = {"Daily": list_options, "Monthly": list_options}
    elif level == "level_type":
        options = {f"{value['time_step']}_upper": list_options, f"{value['time_step']}_lower": list_options}
    else:
        options = [f"{value['level_type']}.json", f"{value['level_type']}.csv"]

    return options

pn.widgets.NestedSelect(
    options=list_options,
    levels=["time_step", "level_type", "file_type"],
)

select = pn.widgets.NestedSelect(
    options={
        "GFS": {
            "0.25 deg": ["00Z", "06Z", "12Z", "18Z"],
            "0.5 deg": ["00Z", "12Z"],
            "1 deg": ["00Z", "12Z"],
        },
        "NAME": {
            "12 km": ["00Z", "12Z"],
            "3 km": ["00Z", "12Z"],
        },
    },
    value={"Model": "NAME", "Resolution": "12 km", "Initialization": "00Z"},
    levels=[
        {"name": "Model", "type": pn.widgets.RadioButtonGroup, "button_type": "primary"},
        {"name": "Resolution", "type": pn.widgets.Select, "width": 100},
        {"name": "Initialization", "type": pn.widgets.DiscreteSlider, "width": 100},
    ],
)
select