feat(import): strip non-printables from CSV/ADIF uploads

Adds Microwaveprop.Radio.TextSanitizer to remove BOM, zero-width
spaces/joiners, C0 control bytes (except CR/LF/TAB), and DEL, and to
collapse NBSP and other unicode whitespace into a regular space.

CSV: applied to the whole upload at the top of preview/2.
ADIF: applied per-field-value after extraction so the byte-counted
length tags still slice the right substring.

lib/microwaveprop/radio/adif_import.ex

@@ -12,6 +12,7 @@ defmodule Microwaveprop.Radio.AdifImport do
   alias Microwaveprop.Radio.BandResolver
   alias Microwaveprop.Radio.Contact
   alias Microwaveprop.Radio.ImportMatcher
+  alias Microwaveprop.Radio.TextSanitizer
   alias Microwaveprop.Repo
 
   @dedup_window_seconds 3600
@@ -161,7 +162,7 @@ defmodule Microwaveprop.Radio.AdifImport do
 
       # Value starts right after the closing > of the tag.
       value_offset = tag_start + tag_len
-      value = :binary.part(record_string, value_offset, size)
+      value = record_string |> :binary.part(value_offset, size) |> TextSanitizer.sanitize()
 
       # Standard ADIF fields take precedence over app-defined ones
       if raw_name != name and Map.has_key?(acc, name) do

lib/microwaveprop/radio/csv_import.ex

@@ -27,6 +27,7 @@ defmodule Microwaveprop.Radio.CsvImport do
   alias Microwaveprop.Radio.Contact
   alias Microwaveprop.Radio.ImportMatcher
   alias Microwaveprop.Radio.ImportRun
+  alias Microwaveprop.Radio.TextSanitizer
   alias Microwaveprop.Repo
   alias Microwaveprop.Workers.ContactImportWorker
   alias Microwaveprop.Workers.ContactWeatherEnqueueWorker
@@ -125,7 +126,7 @@ defmodule Microwaveprop.Radio.CsvImport do
           | {:error, :no_data_rows}
           | {:error, {:missing_required_columns, [String.t()]}}
   def preview(csv_string, submitter_email) do
-    with {:ok, rows} <- parse_csv(csv_string, submitter_email) do
+    with {:ok, rows} <- parse_csv(TextSanitizer.sanitize(csv_string), submitter_email) do
       {valid, invalid} = split_parsed(rows)
       existing = load_existing_for_dedup(valid)
       {unique, duplicates, refinements} = dedupe(valid, existing)

lib/microwaveprop/radio/text_sanitizer.ex

@@ -0,0 +1,52 @@
+defmodule Microwaveprop.Radio.TextSanitizer do
+  @moduledoc """
+  Strip non-printable characters from user-uploaded log text. Removes BOM,
+  zero-width spaces/joiners, C0 control bytes (except CR/LF/TAB), and DEL;
+  collapses non-breaking and other unicode whitespace into a regular space.
+
+  Used by CSV and ADIF importers because field values frequently arrive
+  with stray NBSPs from website copy-paste, BOM markers from Windows
+  exports, etc.
+  """
+
+  @spec sanitize(nil) :: nil
+  @spec sanitize(String.t()) :: String.t()
+  def sanitize(nil), do: nil
+  def sanitize(""), do: ""
+
+  def sanitize(string) when is_binary(string) do
+    string
+    |> :unicode.characters_to_list()
+    |> Enum.reduce([], fn cp, acc ->
+      case sanitize_codepoint(cp) do
+        :strip -> acc
+        replacement -> [replacement | acc]
+      end
+    end)
+    |> Enum.reverse()
+    |> :unicode.characters_to_binary()
+  end
+
+  defp sanitize_codepoint(?\t), do: ?\t
+  defp sanitize_codepoint(?\n), do: ?\n
+  defp sanitize_codepoint(?\r), do: ?\r
+
+  # C0 control characters and DEL — strip.
+  defp sanitize_codepoint(cp) when cp < 0x20 or cp == 0x7F, do: :strip
+
+  # NBSP and other unicode whitespace → regular space.
+  defp sanitize_codepoint(0x00A0), do: ?\s
+  defp sanitize_codepoint(cp) when cp >= 0x2000 and cp <= 0x200A, do: ?\s
+  defp sanitize_codepoint(0x202F), do: ?\s
+  defp sanitize_codepoint(0x205F), do: ?\s
+  defp sanitize_codepoint(0x3000), do: ?\s
+
+  # Zero-width characters (ZWSP, ZWNJ, ZWJ, word-joiner, BOM) — strip.
+  defp sanitize_codepoint(0x200B), do: :strip
+  defp sanitize_codepoint(0x200C), do: :strip
+  defp sanitize_codepoint(0x200D), do: :strip
+  defp sanitize_codepoint(0x2060), do: :strip
+  defp sanitize_codepoint(0xFEFF), do: :strip
+
+  defp sanitize_codepoint(cp), do: cp
+end

test/microwaveprop/radio/adif_import_test.exs

@@ -66,6 +66,24 @@ defmodule Microwaveprop.Radio.AdifImportTest do
       assert row.attrs["user_declared_prop_mode"] == nil
     end
 
+    test "strips non-printables (zero-width, BOM, control) from ADIF field values" do
+      # Zero-width space (U+200B = 0xE2 0x80 0x8B, 3 bytes) inside CALL and
+      # GRIDSQUARE. ADIF length tags count BYTES so the tag widths include
+      # the multi-byte payload — sanitization strips the zero-width chars
+      # and leaves the underlying ASCII intact.
+      adif =
+        "<STATION_CALLSIGN:4>W5XD" <>
+          "<CALL:7>K5\u200BTR" <>
+          "<GRIDSQUARE:7>EM\u200B00" <>
+          "<MY_GRIDSQUARE:4>EM12" <>
+          "<FREQ:9>10368.000<MODE:2>CW<QSO_DATE:8>20260328<TIME_ON:6>180000<EOR>\n"
+
+      assert {:ok, preview} = AdifImport.preview(adif, @submitter)
+      assert [row] = preview.valid
+      assert row.attrs["station2"] == "K5TR"
+      assert row.attrs["grid2"] == "EM00"
+    end
+
     test "captures ADIF NOTES into notes" do
       adif = """
       <STATION_CALLSIGN:4>W5XD<CALL:4>K5TR<GRIDSQUARE:4>EM00<MY_GRIDSQUARE:4>EM12<FREQ:9>10368.000<MODE:2>CW<QSO_DATE:8>20260328<TIME_ON:6>180000<NOTES:25>Rare Es along TX/OK front<EOR>

test/microwaveprop/radio/csv_import_test.exs

@@ -104,6 +104,18 @@ defmodule Microwaveprop.Radio.CsvImportTest do
       assert contact.station1 == "W5XD"
     end
 
+    test "strips non-printables (BOM, NBSP, zero-width) from uploaded CSV" do
+      # \uFEFF BOM at file start, NBSP between fields, zero-width space inside callsign.
+      csv =
+        "\uFEFF" <>
+          @valid_header <>
+          "\nW5XD,K5\u200BTR,EM12,EM00,10000,CW,2026-03-28T18:00:00Z\u00A0"
+
+      assert {:ok, %{imported: [contact], errors: []}} = CsvImport.import(csv, @submitter)
+      assert contact.station1 == "W5XD"
+      assert contact.station2 == "K5TR"
+    end
+
     test "skips blank lines between data rows" do
       csv =
         Enum.join(

test/microwaveprop/radio/text_sanitizer_test.exs

@@ -0,0 +1,56 @@
+defmodule Microwaveprop.Radio.TextSanitizerTest do
+  use ExUnit.Case, async: true
+
+  alias Microwaveprop.Radio.TextSanitizer
+
+  describe "sanitize/1" do
+    test "passes through plain ASCII unchanged" do
+      assert TextSanitizer.sanitize("K5ABC EM12 1296") == "K5ABC EM12 1296"
+    end
+
+    test "preserves CR, LF, and TAB" do
+      assert TextSanitizer.sanitize("a\nb\r\nc\td") == "a\nb\r\nc\td"
+    end
+
+    test "replaces NBSP (U+00A0) with regular space" do
+      assert TextSanitizer.sanitize("K5ABC\u00A0EM12") == "K5ABC EM12"
+    end
+
+    test "replaces narrow no-break space (U+202F) and figure space (U+2007) with space" do
+      assert TextSanitizer.sanitize("a\u202Fb\u2007c") == "a b c"
+    end
+
+    test "replaces all unicode general-punctuation spaces (U+2000–U+200A) with space" do
+      assert TextSanitizer.sanitize("a\u2000b\u2003c\u200Ad") == "a b c d"
+    end
+
+    test "strips BOM (U+FEFF) anywhere in the string" do
+      assert TextSanitizer.sanitize("\uFEFFK5ABC") == "K5ABC"
+      assert TextSanitizer.sanitize("K5\uFEFFABC") == "K5ABC"
+    end
+
+    test "strips zero-width joiners and non-joiners" do
+      assert TextSanitizer.sanitize("K5\u200BABC\u200C\u200D") == "K5ABC"
+    end
+
+    test "strips C0 control characters except TAB/CR/LF" do
+      assert TextSanitizer.sanitize("a\x00b\x07c\x1Bd") == "abcd"
+    end
+
+    test "strips DEL (U+007F)" do
+      assert TextSanitizer.sanitize("a\x7Fb") == "ab"
+    end
+
+    test "handles nil" do
+      assert TextSanitizer.sanitize(nil) == nil
+    end
+
+    test "handles empty string" do
+      assert TextSanitizer.sanitize("") == ""
+    end
+
+    test "preserves UTF-8 letters with diacritics" do
+      assert TextSanitizer.sanitize("café Müller") == "café Müller"
+    end
+  end
+end