prop/test/microwaveprop/weather/ncei_metar_client_test.exs

defmodule Microwaveprop.Weather.NceiMetarClientTest do
  use ExUnit.Case, async: true

  alias Microwaveprop.Weather.NceiMetarClient

  @sample_line "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17012KT 10SM CLR 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094"

  describe "parse/1" do
    test "parses a single KDFW observation" do
      [obs] = NceiMetarClient.parse(@sample_line)

      assert obs.icao == "KDFW"
      assert obs.observed_at == ~U[2026-03-01 00:00:00Z]
      # T02110094 → 21.1°C = 70.0°F, 9.4°C = 48.9°F
      assert_in_delta obs.temp_f, 70.0, 0.2
      assert_in_delta obs.dewpoint_f, 48.9, 0.2
      assert obs.wind_speed_kts == 12.0
      assert obs.wind_direction_deg == 170
      assert_in_delta obs.altimeter_setting, 29.97, 0.01
      assert obs.sky_condition == "CLR"
    end

    test "parses multiple lines" do
      text = """
      03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17012KT 10SM CLR 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094
      03927KDFW DFW20260301000510303/01/26 00:05:31  5-MIN KDFW 010605Z 17012KT 10SM CLR 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094
      """

      obs = NceiMetarClient.parse(text)
      assert length(obs) == 2
      assert Enum.at(obs, 0).observed_at == ~U[2026-03-01 00:00:00Z]
      assert Enum.at(obs, 1).observed_at == ~U[2026-03-01 00:05:00Z]
    end

    test "skips blank or too-short lines" do
      assert NceiMetarClient.parse("") == []
      assert NceiMetarClient.parse("short\n\n") == []
    end

    test "handles negative temperatures via M prefix" do
      line =
        "03927KDFW DFW20260115120010103/15/26 12:00:31  5-MIN KDFW 151200Z 36005KT 10SM CLR M02/M08 A3032 560 47 1400 360/05 RMK AO2"

      [obs] = NceiMetarClient.parse(line)

      # M02 = -2°C = 28.4°F, M08 = -8°C = 17.6°F
      assert_in_delta obs.temp_f, 28.4, 0.2
      assert_in_delta obs.dewpoint_f, 17.6, 0.2
    end

    test "extracts wind speed/direction from the VVVKKT group" do
      # 17015KT = 170° at 15 kt.
      line =
        "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17015KT 10SM CLR 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094"

      [obs] = NceiMetarClient.parse(line)
      assert obs.wind_direction_deg == 170
      assert obs.wind_speed_kts == 15.0
    end

    test "returns nil wind values when the wind group is missing" do
      # Valid METAR without a wind group (CALM-ish). extract_wind_* should
      # fall through to nil rather than crashing.
      line =
        "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 10SM CLR 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094"

      [obs] = NceiMetarClient.parse(line)
      assert obs.wind_speed_kts == nil
      assert obs.wind_direction_deg == nil
    end

    test "concatenates multiple sky tokens" do
      # Layered ceiling: SCT030 + BKN080.
      line =
        "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17012KT 10SM SCT030 BKN080 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094"

      [obs] = NceiMetarClient.parse(line)
      assert obs.sky_condition =~ "SCT030"
      assert obs.sky_condition =~ "BKN080"
    end

    test "sky_condition is nil when no cloud-layer token is present" do
      # No CLR/FEW/SCT/BKN/OVC/VV token at all.
      line =
        "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17012KT 10SM 21/09 A2997 560 47 1400 160/12 RMK AO2 T02110094"

      [obs] = NceiMetarClient.parse(line)
      assert obs.sky_condition == nil
    end

    test "altimeter_setting is nil when the A-group is absent" do
      line =
        "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17012KT 10SM CLR 21/09 560 47 1400 160/12 RMK AO2 T02110094"

      [obs] = NceiMetarClient.parse(line)
      assert obs.altimeter_setting == nil
    end

    test "skips a long line whose date/time header is garbage" do
      # ≥60 bytes so parse_line/1 doesn't short-circuit on the length guard,
      # but the date/time fields are non-numeric — parse_datetime/2 returns
      # :error and the line is dropped.
      line = String.duplicate("X", 80)
      assert NceiMetarClient.parse(line) == []
    end

    test "parse/1 returns [] for a single trailing newline" do
      assert NceiMetarClient.parse("\n") == []
    end

    test "parse/1 drops a line that is exactly 60 bytes of padding with an invalid date" do
      # 5 WBAN + 4 ICAO + 4 FAA + 8 date + 4 hhmm = 25 bytes of header,
      # 60 bytes total to satisfy the length guard.
      line = String.duplicate("A", 60)
      assert NceiMetarClient.parse(line) == []
    end

    test "falls back to the coarse temp/dew pair when no T-group is in the remark" do
      # No T-group → extract_temp_f falls through to the "21/09" field,
      # which gives integer °C temperatures.
      line =
        "03927KDFW DFW20260301000010303/01/26 00:00:31  5-MIN KDFW 010600Z 17012KT 10SM CLR 21/09 A2997 560 47 1400 160/12 RMK AO2"

      [obs] = NceiMetarClient.parse(line)
      # 21°C = 69.8°F, 9°C = 48.2°F — coarser than the T-group but
      # within ±0.3°F.
      assert_in_delta obs.temp_f, 69.8, 0.3
      assert_in_delta obs.dewpoint_f, 48.2, 0.3
    end
  end
end