327 lines
9.5 KiB
Elixir
327 lines
9.5 KiB
Elixir
defmodule Aprsme.EncodingUtils do
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@moduledoc """
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Utilities for handling encoding issues in APRS packet data.
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APRS packets can contain arbitrary bytes that may not be valid UTF-8,
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which causes issues when trying to JSON encode the data for transmission
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to web clients.
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"""
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alias Aprs.Types.MicE
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@doc """
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Sanitizes a binary to ensure it can be safely JSON encoded.
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If the binary is valid UTF-8, returns it as-is.
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If it contains invalid UTF-8 sequences, replaces them with the Unicode
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replacement character (<28>) or removes them entirely.
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## Examples
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iex> Aprsme.EncodingUtils.sanitize_string("Hello World")
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"Hello World"
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iex> Aprsme.EncodingUtils.sanitize_string(<<72, 101, 108, 108, 111, 211, 87, 111, 114, 108, 100>>)
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"HelloÓWorld"
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"""
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@spec sanitize_string(binary() | nil | any()) :: binary() | nil | any()
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def sanitize_string(binary) when is_binary(binary) do
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cleaned =
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if String.valid?(binary) do
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binary
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else
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:unicode.characters_to_binary(binary, :latin1, :utf8)
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end
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cleaned
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|> String.replace(<<0>>, "")
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|> String.replace(~r/[\x01-\x08\x0B\x0C\x0E-\x1F\x7F]/, "")
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|> String.graphemes()
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|> Enum.filter(&String.valid?/1)
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|> Enum.join()
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|> String.trim()
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end
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def sanitize_string(nil), do: nil
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def sanitize_string(other), do: other
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@doc """
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Converts various types to float for consistent display.
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## Examples
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iex> Aprsme.EncodingUtils.to_float(1)
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1.0
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iex> Aprsme.EncodingUtils.to_float(1.5)
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1.5
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iex> Aprsme.EncodingUtils.to_float("2.3")
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2.3
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iex> Aprsme.EncodingUtils.to_float("bad")
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nil
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iex> Aprsme.EncodingUtils.to_float(nil)
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nil
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"""
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@spec to_float(any()) :: float() | nil
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def to_float(value) when is_float(value), do: value
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def to_float(value) when is_integer(value), do: value * 1.0
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def to_float(%Decimal{} = value), do: Decimal.to_float(value)
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def to_float(value) when is_binary(value) do
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case Float.parse(value) do
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{float, _} -> float
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:error -> nil
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end
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end
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def to_float(_), do: nil
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@doc """
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Converts various types to Decimal for database storage.
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## Examples
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iex> is_struct(Aprsme.EncodingUtils.to_decimal(1), Decimal)
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true
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iex> is_struct(Aprsme.EncodingUtils.to_decimal(1.5), Decimal)
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true
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iex> is_struct(Aprsme.EncodingUtils.to_decimal("2.3"), Decimal)
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true
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iex> Aprsme.EncodingUtils.to_decimal("bad")
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nil
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iex> Aprsme.EncodingUtils.to_decimal(nil)
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nil
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"""
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@spec to_decimal(any()) :: Decimal.t() | nil
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def to_decimal(%Decimal{} = d), do: d
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def to_decimal(f) when is_float(f), do: Decimal.from_float(f)
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def to_decimal(i) when is_integer(i), do: Decimal.new(i)
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def to_decimal(s) when is_binary(s) do
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case Decimal.parse(s) do
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{d, _} ->
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d
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:error ->
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case Float.parse(s) do
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{f, _} -> Decimal.from_float(f)
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:error -> nil
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end
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end
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end
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def to_decimal(_), do: nil
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@doc """
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Sanitizes all string fields in packet data before database storage.
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## Examples
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iex> Aprsme.EncodingUtils.sanitize_packet_strings(["abc", <<255>>])
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["abc", "ÿ"]
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iex> Aprsme.EncodingUtils.sanitize_packet_strings(%{"foo" => <<0, 65, 66, 67>>})
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%{"foo" => "\0ABC"}
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iex> Aprsme.EncodingUtils.sanitize_packet_strings(nil)
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nil
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"""
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@spec sanitize_packet_strings(any()) :: any()
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def sanitize_packet_strings(%DateTime{} = dt), do: dt
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def sanitize_packet_strings(%NaiveDateTime{} = ndt), do: ndt
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def sanitize_packet_strings(%_struct{} = struct), do: struct |> Map.from_struct() |> sanitize_packet_strings()
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def sanitize_packet_strings(list) when is_list(list), do: Enum.map(list, &sanitize_packet_strings/1)
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def sanitize_packet_strings(binary) when is_binary(binary) do
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s = sanitize_string(binary)
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if is_binary(s), do: s, else: ""
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end
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def sanitize_packet_strings(other), do: other
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@doc """
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Normalizes data_type field to ensure it's always a string.
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## Examples
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iex> Aprsme.EncodingUtils.normalize_data_type(%{data_type: :weather})
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%{data_type: "weather"}
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iex> Aprsme.EncodingUtils.normalize_data_type(%{"data_type" => :foo})
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%{"data_type" => "foo"}
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iex> Aprsme.EncodingUtils.normalize_data_type(%{data_type: "bar"})
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%{data_type: "bar"}
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iex> Aprsme.EncodingUtils.normalize_data_type(%{"data_type" => "baz"})
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%{"data_type" => "baz"}
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iex> Aprsme.EncodingUtils.normalize_data_type(%{foo: 1})
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%{foo: 1}
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"""
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@spec normalize_data_type(map()) :: map()
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def normalize_data_type(%{data_type: data_type} = attrs) when is_atom(data_type) do
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%{attrs | data_type: to_string(data_type)}
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end
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def normalize_data_type(%{"data_type" => data_type} = attrs) when is_atom(data_type) do
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%{attrs | "data_type" => to_string(data_type)}
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end
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def normalize_data_type(attrs) when is_map(attrs) do
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case {Map.has_key?(attrs, :data_type), Map.get(attrs, :data_type)} do
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{true, data_type} when is_atom(data_type) ->
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%{attrs | data_type: to_string(data_type)}
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_ ->
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attrs
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end
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end
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def normalize_data_type(attrs), do: attrs
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@doc """
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List of weather-related fields used for packet classification.
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## Examples
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iex> Aprsme.EncodingUtils.weather_fields() |> Enum.member?(:temperature)
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true
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iex> :foo in Aprsme.EncodingUtils.weather_fields()
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false
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"""
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@spec weather_fields() :: [atom()]
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def weather_fields do
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[
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:temperature,
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:humidity,
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:wind_speed,
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:wind_direction,
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:wind_gust,
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:pressure,
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:rain_1h,
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:rain_24h,
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:rain_since_midnight,
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:snow,
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:luminosity
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]
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end
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@doc """
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Sanitizes all string fields in an APRS packet to ensure safe JSON encoding.
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## Examples
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iex> result = Aprsme.EncodingUtils.sanitize_packet(%{"information_field" => <<0, 65, 66, 67>>, "data_extended" => %{"comment" => <<0, 68, 69, 70>>}})
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iex> result["information_field"] == "\0ABC"
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true
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iex> result["data_extended"]["comment"] == "\0DEF"
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true
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"""
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@spec sanitize_packet(struct() | map()) :: struct() | map()
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def sanitize_packet(%Aprsme.Packet{} = packet) do
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%{
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packet
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| information_field: sanitize_string(packet.information_field),
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data_extended: sanitize_data_extended(packet.data_extended)
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}
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end
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def sanitize_packet(packet) when is_map(packet) do
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packet
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|> Map.update(:information_field, nil, &sanitize_string/1)
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|> Map.update(:data_extended, nil, &sanitize_data_extended/1)
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end
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@doc """
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Sanitizes string fields in the data_extended structure.
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## Examples
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iex> Aprsme.EncodingUtils.sanitize_data_extended(%{"comment" => <<0, 65, 66, 67>>})
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%{"comment" => "ABC"}
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iex> Aprsme.EncodingUtils.sanitize_data_extended(nil)
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nil
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"""
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@spec sanitize_data_extended(nil | map() | MicE.t() | any()) :: nil | map() | MicE.t() | any()
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def sanitize_data_extended(nil), do: nil
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def sanitize_data_extended(%{comment: comment} = data_extended) when is_map(data_extended) do
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%{data_extended | comment: sanitize_string(comment)}
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end
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def sanitize_data_extended(%MicE{message: message} = mic_e) do
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%{mic_e | message: sanitize_string(message)}
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end
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def sanitize_data_extended(data_extended) when is_map(data_extended) do
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# Handle generic maps by sanitizing all string values
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Enum.reduce(data_extended, %{}, fn {key, value}, acc ->
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sanitized_value = sanitize_map_value(value)
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Map.put(acc, key, sanitized_value)
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end)
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end
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def sanitize_data_extended(data_extended), do: data_extended
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defp sanitize_map_value(val) when is_binary(val), do: sanitize_string(val)
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defp sanitize_map_value(val), do: val
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# Private helper functions
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@doc """
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Converts a binary to a hex string representation for debugging.
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## Examples
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iex> Aprsme.EncodingUtils.to_hex(<<72, 101, 108, 108, 111>>)
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"48656C6C6F"
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"""
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@spec to_hex(binary()) :: String.t()
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def to_hex(binary) when is_binary(binary) do
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binary
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|> :binary.bin_to_list()
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|> Enum.map(&Integer.to_string(&1, 16))
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|> Enum.map_join("", &String.pad_leading(&1, 2, "0"))
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|> String.upcase()
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end
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@doc """
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Returns information about a binary's encoding validity.
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## Examples
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iex> Aprsme.EncodingUtils.encoding_info("Hello")
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%{valid_utf8: true, byte_count: 5, char_count: 5}
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iex> Aprsme.EncodingUtils.encoding_info(<<72, 101, 211, 108, 111>>)
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%{valid_utf8: false, byte_count: 5, invalid_at: 2}
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"""
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@spec encoding_info(binary()) :: map()
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def encoding_info(binary) when is_binary(binary) do
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valid = String.valid?(binary)
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byte_count = byte_size(binary)
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base_info = %{
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valid_utf8: valid,
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byte_count: byte_count
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}
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add_encoding_details(base_info, binary, valid)
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end
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defp add_encoding_details(base_info, binary, true) do
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Map.put(base_info, :char_count, String.length(binary))
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end
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defp add_encoding_details(base_info, binary, false) do
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# Try to find where the invalid sequence starts
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invalid_at = find_invalid_byte_position(binary, 0)
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Map.put(base_info, :invalid_at, invalid_at)
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end
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@spec find_invalid_byte_position(binary(), non_neg_integer()) :: non_neg_integer() | nil
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defp find_invalid_byte_position(<<>>, _pos), do: nil
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defp find_invalid_byte_position(<<head::binary-size(1), tail::binary>>, pos) do
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if String.valid?(head) do
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find_invalid_byte_position(tail, pos + 1)
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else
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pos
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end
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end
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defp find_invalid_byte_position(_, pos), do: pos
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end
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