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

  alias Microwaveprop.Weather.NarrClient

  describe "url_for/1" do
    test "builds the NCEI NARR HTTPS URL for a 3-hourly analysis time" do
      vt = ~U[2010-06-15 12:00:00Z]

      assert NarrClient.url_for(vt) ==
               "https://www.ncei.noaa.gov/data/north-american-regional-reanalysis/access/3-hourly/201006/20100615/narr-a_221_20100615_1200_000.grb"
    end

    test "uses zero-padded HHMM for off-hour analyses" do
      vt = ~U[2010-06-15 03:00:00Z]

      assert NarrClient.url_for(vt) ==
               "https://www.ncei.noaa.gov/data/north-american-regional-reanalysis/access/3-hourly/201006/20100615/narr-a_221_20100615_0300_000.grb"
    end

    test "raises ArgumentError on non-3-hourly hours" do
      assert_raise ArgumentError, fn ->
        NarrClient.url_for(~U[2010-06-15 13:00:00Z])
      end
    end

    test "raises ArgumentError when minutes are non-zero" do
      assert_raise ArgumentError, fn ->
        NarrClient.url_for(~U[2010-06-15 12:30:00Z])
      end
    end
  end

  describe "url_for_inventory/1" do
    test "swaps .grb for .inv" do
      vt = ~U[2010-06-15 12:00:00Z]

      assert NarrClient.url_for_inventory(vt) ==
               "https://www.ncei.noaa.gov/data/north-american-regional-reanalysis/access/3-hourly/201006/20100615/narr-a_221_20100615_1200_000.inv"
    end
  end

  describe "snap_to_analysis_hour/1" do
    test "rounds down to the nearest 3-hourly NARR slot" do
      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 13:42:00Z]) ==
               ~U[2010-06-15 12:00:00Z]

      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 14:30:00Z]) ==
               ~U[2010-06-15 12:00:00Z]

      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 15:00:00Z]) ==
               ~U[2010-06-15 15:00:00Z]

      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 23:59:59Z]) ==
               ~U[2010-06-15 21:00:00Z]

      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 00:00:00Z]) ==
               ~U[2010-06-15 00:00:00Z]

      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 02:00:00Z]) ==
               ~U[2010-06-15 00:00:00Z]
    end

    test "preserves the date when snapping doesn't cross midnight" do
      assert NarrClient.snap_to_analysis_hour(~U[2010-06-15 05:17:42Z]) ==
               ~U[2010-06-15 03:00:00Z]
    end

    test "snaps minutes and seconds to zero" do
      snapped = NarrClient.snap_to_analysis_hour(~U[2010-06-15 13:42:37Z])
      assert snapped.minute == 0
      assert snapped.second == 0
      assert snapped.microsecond == {0, 0}
    end
  end

  describe "parse_inventory/2" do
    @fixture_path "test/fixtures/narr/narr-a_221_20100615_1200_000.inv"
    @fixture_file_size 56_221_430

    test "parses the spike fixture inventory into an offset/length index" do
      inv = File.read!(@fixture_path)

      {:ok, index} = NarrClient.parse_inventory(inv, @fixture_file_size)

      # Record 288: TMP @ 2 m above gnd, offset 37836396, next record at 37967364.
      assert {37_836_396, 130_968} = index[{"TMP", "2 m above gnd"}]

      # Record 15: HPBL at surface — length is positive and computed from next record.
      assert {1_940_538, len_hpbl} = index[{"HPBL", "sfc"}]
      assert len_hpbl > 0

      # Record 202: TMP at 850 mb — pressure-level record present in the index.
      assert {_off_850, _len_850} = index[{"TMP", "850 mb"}]

      # Record 317: PWAT at atmos col.
      assert {_off_pwat, _len_pwat} = index[{"PWAT", "atmos col"}]

      # Last record in the file (423): length is computed against file_size.
      assert {56_042_950, last_len} = index[{"WVVFLX", "atmos col"}]
      assert last_len == @fixture_file_size - 56_042_950
      assert last_len > 0
    end

    test "returns an empty index for empty input" do
      assert {:ok, %{}} = NarrClient.parse_inventory("", 0)
    end

    test "ignores blank lines and trailing whitespace" do
      inv = """
      1:0:D=2010061512:MSLET:MSL:kpds=130,102,0:anl:winds in grid direction:"Mean sea level pressure [Pa]

      2:166602:D=2010061512:PRMSL:MSL:kpds=2,102,0:anl:winds in grid direction:"Pressure reduced to MSL [Pa]

      """

      {:ok, index} = NarrClient.parse_inventory(inv, 333_204)

      assert {0, 166_602} = index[{"MSLET", "MSL"}]
      assert {166_602, 166_602} = index[{"PRMSL", "MSL"}]
    end
  end

  describe "fetch_inventory/1" do
    @fixture_path "test/fixtures/narr/narr-a_221_20100615_1200_000.inv"
    @fixture_file_size 56_221_430

    test "fetches the .inv body and the .grb HEAD content-length, then parses" do
      inv_body = File.read!(@fixture_path)

      Req.Test.stub(NarrClient, fn conn ->
        cond do
          String.ends_with?(conn.request_path, ".inv") and conn.method == "GET" ->
            Plug.Conn.send_resp(conn, 200, inv_body)

          String.ends_with?(conn.request_path, ".grb") and conn.method == "HEAD" ->
            conn
            |> Plug.Conn.put_resp_header("content-length", Integer.to_string(@fixture_file_size))
            |> Plug.Conn.send_resp(200, "")

          true ->
            Plug.Conn.send_resp(conn, 500, "unexpected #{conn.method} #{conn.request_path}")
        end
      end)

      assert {:ok, index} = NarrClient.fetch_inventory(~U[2010-06-15 12:00:00Z])

      # Matches the parse_inventory spot-check for the same fixture.
      assert {37_836_396, 130_968} = index[{"TMP", "2 m above gnd"}]
      assert {56_042_950, last_len} = index[{"WVVFLX", "atmos col"}]
      assert last_len == @fixture_file_size - 56_042_950
    end

    test "returns {:error, _} when the inv fetch fails" do
      Req.Test.stub(NarrClient, fn conn ->
        if String.ends_with?(conn.request_path, ".inv") do
          Plug.Conn.send_resp(conn, 404, "not found")
        else
          Plug.Conn.send_resp(conn, 200, "")
        end
      end)

      assert {:error, _reason} = NarrClient.fetch_inventory(~U[2010-06-15 12:00:00Z])
    end

    test "returns {:error, _} when the grb HEAD fails" do
      inv_body = File.read!(@fixture_path)

      Req.Test.stub(NarrClient, fn conn ->
        cond do
          String.ends_with?(conn.request_path, ".inv") ->
            Plug.Conn.send_resp(conn, 200, inv_body)

          String.ends_with?(conn.request_path, ".grb") ->
            Plug.Conn.send_resp(conn, 500, "server error")

          true ->
            Plug.Conn.send_resp(conn, 500, "unexpected")
        end
      end)

      assert {:error, _reason} = NarrClient.fetch_inventory(~U[2010-06-15 12:00:00Z])
    end
  end
end