fix(narr): handle cdo 2.5.1 mixed name/code output

parse_cdo_row/1 assumed cdo -outputtab,code,lev,value would always emit
numeric codes in the first column, but Debian's cdo 2.5.1 (the version
in the prod container) emits mixed output:

- 'codeNN' with a literal 'code' prefix for most GRIB1 parameters
- Short GRIB1 names for a few: 2tag2 (PRES sfc), saip (DPT 2m),
  tpag10 (HGT)

Result: every row fell through to :error, yielding a 'no parseable
values' error and 986 discarded NarrFetchWorker jobs.

Fix: normalize the code token by stripping 'code' prefix when present
and mapping known 2.5.1 short names. UGRD/VGRD intentionally omitted
(no discard evidence yet) — comment documents the add-when-they-surface
plan.

Also exposed parse_cdo_outputtab/1 as @doc false for testability.

lib/microwaveprop/weather/narr_client.ex

@@ -55,6 +55,19 @@ defmodule Microwaveprop.Weather.NarrClient do
     221 => "HPBL"
   }
 
+  # cdo 2.5.1 on Debian ignores `-outputtab,code` for records whose GRIB1
+  # parameter table entry has a shortname, emitting the shortname string
+  # instead of the numeric code. Mapping verified against prod discard
+  # output: 2tag2=PRES (985 mb surface pressure), saip=DPT (292 K 2-m
+  # dewpoint), tpag10=HGT (983 m at 900 hPa geopotential height). UGRD
+  # and VGRD aren't yet observed in that output — add them when they
+  # surface in a real discard.
+  @cdo_shortname_to_code %{
+    "2tag2" => 1,
+    "saip" => 17,
+    "tpag10" => 7
+  }
+
   @doc """
   Builds the NCEI HTTPS URL for the NARR analysis GRIB1 file at `valid_time`.
 
@@ -305,7 +318,8 @@ defmodule Microwaveprop.Weather.NarrClient do
     end
   end
 
-  defp parse_cdo_outputtab(stdout) do
+  @doc false
+  def parse_cdo_outputtab(stdout) do
     raw =
       stdout
       |> String.split("\n", trim: true)
@@ -329,12 +343,17 @@ defmodule Microwaveprop.Weather.NarrClient do
     end
   end
 
-  # Rows are three whitespace-separated numeric columns: <code> <lev> <value>.
-  # Header, cdi warnings, and cdo progress lines lack the three-number shape
+  # Rows are three whitespace-separated columns: <code> <lev> <value>. The
+  # <code> token is one of:
+  #   * a bare integer (cdo 2.6 on Mac / dev)
+  #   * `codeNN` with "code" prefix (cdo 2.5.1 on Debian / prod)
+  #   * a GRIB1 shortname like `2tag2` / `saip` / `tpag10` (cdo 2.5.1 again,
+  #     for params whose GRIB1 parameter-table entry has a shortname)
+  # Header, cdi warnings, and cdo progress lines lack the three-column shape
   # and fall through to :error.
   defp parse_cdo_row(line) do
     with [code_str, lev_str, value_str] <- String.split(line, ~r/\s+/, trim: true),
-         {code_int, ""} <- Integer.parse(code_str),
+         {:ok, code_int} <- normalize_cdo_code_token(code_str),
          {:ok, name} <- Map.fetch(@cdo_code_to_name, code_int),
          {lev_int, ""} <- Integer.parse(lev_str),
          {value_float, ""} <- Float.parse(value_str) do
@@ -344,6 +363,29 @@ defmodule Microwaveprop.Weather.NarrClient do
     end
   end
 
+  # Resolves the first column of a cdo `-outputtab,code,...` row to its
+  # numeric GRIB1 parameter code. Handles all three cdo output dialects
+  # we've seen in the wild (see `parse_cdo_row/1` for context).
+  defp normalize_cdo_code_token("code" <> rest) do
+    case Integer.parse(rest) do
+      {code_int, ""} -> {:ok, code_int}
+      _ -> :error
+    end
+  end
+
+  defp normalize_cdo_code_token(token) do
+    case Integer.parse(token) do
+      {code_int, ""} ->
+        {:ok, code_int}
+
+      _ ->
+        case Map.fetch(@cdo_shortname_to_code, token) do
+          {:ok, code_int} -> {:ok, code_int}
+          :error -> :error
+        end
+    end
+  end
+
   defp build_profile_attrs(raw) do
     profile = build_pressure_profile(raw)
 

test/microwaveprop/weather/narr_client_test.exs

@@ -248,6 +248,53 @@ defmodule Microwaveprop.Weather.NarrClientTest do
     end
   end
 
+  describe "parse_cdo_outputtab/1" do
+    # cdo 2.5.1 on Debian (prod) emits mixed output despite `-outputtab,code`:
+    # rows whose first token is either `codeNN` (numeric code with "code" prefix)
+    # or a GRIB1 shortname like `2tag2` / `saip` / `tpag10`. cdo 2.6 on Mac
+    # (dev) emits bare integers. The parser must handle both.
+    test "parses a cdo 2.5.1 output fixture with codeNN + shortname tokens" do
+      # Trimmed multi-line fixture modeled on real prod discard output.
+      # Codes: 221=HPBL, 1=PRES (2tag2), 11=TMP, 17=DPT (saip), 54=PWAT,
+      # 7=HGT (tpag10), 51=SPFH.
+      stdout = """
+      #    name    lev    value
+       cdo(1) remapnn: some warning line
+        code221      0 1387.958
+          2tag2      0 98509.35
+         code11      2 299.4731
+           saip      2 292.6315
+         code54      0 37.28385
+         tpag10  90000 983.7363
+         code11  10000 209.1171
+         tpag10  85000 1547.8
+         code11  85000 291.52
+         code51  85000 0.0104
+      """
+
+      assert {:ok, attrs} = NarrClient.parse_cdo_outputtab(stdout)
+
+      # HPBL at sfc (code 221) = 1387.958 m
+      assert_in_delta attrs.hpbl_m, 1387.958, 0.01
+      # PRES at sfc (2tag2 → code 1) = 98509.35 Pa → 985.09 mb
+      assert_in_delta attrs.surface_pressure_mb, 985.09, 0.1
+      # TMP at 2m (code 11, lev 2) = 299.47 K → 26.32 C
+      assert_in_delta attrs.surface_temp_c, 26.32, 0.1
+      # DPT at 2m (saip → code 17, lev 2) = 292.63 K → 19.48 C
+      assert_in_delta attrs.surface_dewpoint_c, 19.48, 0.1
+      # PWAT (code 54) = 37.28 mm
+      assert_in_delta attrs.pwat_mm, 37.28, 0.01
+
+      # Profile — 900 hPa has HGT+TMP+SPFH? No, only TMP is there at 900. Only
+      # 850 hPa has all three (TMP, HGT, SPFH) → one profile entry.
+      assert length(attrs.profile) == 1
+      [level_850] = attrs.profile
+      assert_in_delta level_850["pres"], 850.0, 0.01
+      assert_in_delta level_850["tmpc"], 18.37, 0.5
+      assert_in_delta level_850["hght"], 1547.8, 0.5
+    end
+  end
+
   describe "fetch_profile_at/2" do
     @inv_fixture "test/fixtures/narr/narr-a_221_20100615_1200_000.inv"
     @grb_fixture "test/fixtures/narr/narr_dfw_2010-06-15_12z.grb"