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lib/kino/utils.ex
defmodule Kino.Utils do
@moduledoc false
@doc """
Returns keyword list keys that hold a truthy value.
## Examples
iex> Kino.Utils.truthy_keys(cat: true, dog: false)
[:cat]
iex> Kino.Utils.truthy_keys(tea: :ok, coffee: nil)
[:tea]
"""
@spec truthy_keys(keyword()) :: list(atom())
def truthy_keys(keywords) when is_list(keywords) do
keywords
|> Enum.filter(&elem(&1, 1))
|> Keyword.keys()
end
@doc """
Checks if the given module exports the given function.
Loads the module if not loaded.
"""
@spec has_function?(module(), atom(), arity()) :: boolean()
def has_function?(module, function, arity) do
Code.ensure_loaded?(module) and function_exported?(module, function, arity)
end
@doc """
Checks if the given process is a supervisor.
"""
@spec supervisor?(atom() | pid()) :: boolean
def supervisor?(supervisor) do
with pid when is_pid(pid) <- GenServer.whereis(supervisor),
{:dictionary, dictionary} <- Process.info(pid, :dictionary),
{:supervisor, _, _} <- dictionary[:"$initial_call"],
do: true,
else: (_ -> false)
end
@doc """
Determines image type looking for the magic number in the binary.
"""
@spec get_image_type(binary()) :: Kino.Image.common_image_type() | nil
def get_image_type(<<0xFF, 0xD8, 0xFF, 0xE0, _rest::binary>>), do: :jpeg
def get_image_type(<<0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, _rest::binary>>), do: :png
def get_image_type(<<0x3C, 0x3F, 0x78, 0x6D, 0x6C, 0x20, _rest::binary>>), do: :svg
def get_image_type(<<0x47, 0x49, 0x46, 0x38, x::8, 0x61, _rest::binary>>)
when x in [0x37, 0x39],
do: :gif
def get_image_type(_image), do: nil
end