defmodule Microwaveprop.Weather.HrdpsClientTest do
  use ExUnit.Case, async: false

  alias Microwaveprop.Weather.HrdpsClient

  describe "nearest_hrdps_cycle/1" do
    test "snaps to the start of the current 6-hour cycle" do
      assert HrdpsClient.nearest_hrdps_cycle(~U[2026-04-29 13:45:00Z]) == ~U[2026-04-29 12:00:00Z]
      assert HrdpsClient.nearest_hrdps_cycle(~U[2026-04-29 19:00:00Z]) == ~U[2026-04-29 18:00:00Z]
      assert HrdpsClient.nearest_hrdps_cycle(~U[2026-04-29 00:30:00Z]) == ~U[2026-04-29 00:00:00Z]
    end

    test "rounds DOWN" do
      assert HrdpsClient.nearest_hrdps_cycle(~U[2026-04-29 11:59:00Z]) == ~U[2026-04-29 06:00:00Z]
    end

    test "stays same when exactly on a cycle boundary" do
      assert HrdpsClient.nearest_hrdps_cycle(~U[2026-04-29 12:00:00Z]) == ~U[2026-04-29 12:00:00Z]
    end
  end

  describe "grib_url/3" do
    test "builds surface 2m temperature URL with date-prefixed datamart path" do
      assert HrdpsClient.grib_url(:tmp_2m, ~U[2026-04-29 12:00:00Z], 0) ==
               "https://dd.weather.gc.ca/20260429/WXO-DD/model_hrdps/continental/2.5km/12/000/" <>
                 "20260429T12Z_MSC_HRDPS_TMP_AGL-2m_RLatLon0.0225_PT000H.grib2"
    end

    test "pads forecast hour to three digits" do
      assert String.contains?(HrdpsClient.grib_url(:tmp_2m, ~U[2026-04-29 12:00:00Z], 24), "PT024H.grib2")
    end

    test "uses MSC level slug for pressure-level temperature" do
      assert String.contains?(HrdpsClient.grib_url(:tmp_850mb, ~U[2026-04-29 12:00:00Z], 0), "MSC_HRDPS_TMP_ISBL_0850_")
    end

    test "raises on unknown variable" do
      assert_raise ArgumentError, ~r/unknown HRDPS variable/, fn ->
        HrdpsClient.grib_url(:not_a_real_var, ~U[2026-04-29 12:00:00Z], 0)
      end
    end
  end

  describe "variables/0" do
    test "covers the surface set" do
      vars = HrdpsClient.variables()

      for v <- [:tmp_2m, :depr_2m, :pres_sfc, :ugrd_10m, :vgrd_10m, :tcdc_sfc, :hpbl_sfc] do
        assert v in vars
      end
    end

    test "covers the grid pressure-level set" do
      vars = HrdpsClient.variables()

      for var_kind <- [:tmp, :depr, :hgt], level <- [1000, 950, 900, 850, 800, 750, 700] do
        assert String.to_existing_atom("#{var_kind}_#{level}mb") in vars
      end
    end
  end

  describe "concat_grib_binaries/1" do
    test "byte-concatenates GRIB2 records" do
      a = <<"GRIB", 1::24, 2::8, 0::8*100>>
      b = <<"GRIB", 1::24, 2::8, 1::8*200>>
      assert HrdpsClient.concat_grib_binaries([a, b]) == a <> b
    end

    test "returns empty binary for empty list" do
      assert HrdpsClient.concat_grib_binaries([]) == <<>>
    end
  end

  describe "build_profile_from_extracted/1" do
    test "translates extracted data into profile shape" do
      extracted = %{
        "TMP:2 m above ground" => 285.15,
        "DPT:2 m above ground" => 280.15,
        "PRES:surface" => 100_000.0,
        "HPBL:surface" => 800.0,
        "UGRD:10 m above ground" => 3.0,
        "VGRD:10 m above ground" => 1.0,
        "TCDC:surface" => 50.0,
        "TMP:850 mb" => 275.0,
        "DPT:850 mb" => 270.0,
        "HGT:850 mb" => 1500.0
      }

      profile = HrdpsClient.build_profile_from_extracted(extracted)

      assert_in_delta profile.surface_temp_c, 12.0, 0.01
      assert_in_delta profile.surface_dewpoint_c, 7.0, 0.01
      assert profile.surface_pressure_mb == 1000.0
      assert profile.hpbl_m == 800.0
      assert profile.cloud_cover_pct == 50.0
    end
  end

  describe "build_profile_from_extracted/1 — DEPR fallback" do
    test "derives surface dewpoint from TMP - DEPR when DPT is missing" do
      extracted = %{
        "TMP:2 m above ground" => 290.0,
        "DEPR:2 m above ground" => 5.0,
        "PRES:surface" => 100_000.0
      }

      profile = HrdpsClient.build_profile_from_extracted(extracted)

      assert_in_delta profile.surface_temp_c, 16.85, 0.01
      # 290 - 5 = 285 K = 11.85 C
      assert_in_delta profile.surface_dewpoint_c, 11.85, 0.01
    end

    test "uses TCDC entire-atmosphere when surface variant is missing" do
      extracted = %{
        "TMP:2 m above ground" => 280.0,
        "DPT:2 m above ground" => 275.0,
        "PRES:surface" => 100_000.0,
        "TCDC:entire atmosphere" => 90.0
      }

      profile = HrdpsClient.build_profile_from_extracted(extracted)
      assert profile.cloud_cover_pct == 90.0
    end

    test "returns nil surface scalars when nothing surface-level is in the input" do
      profile = HrdpsClient.build_profile_from_extracted(%{})
      assert profile.surface_temp_c == nil
      assert profile.surface_dewpoint_c == nil
      assert profile.surface_pressure_mb == nil
      assert profile.profile == []
    end

    test "skips a pressure level that is missing HGT" do
      extracted = %{
        "TMP:2 m above ground" => 290.0,
        "DPT:2 m above ground" => 285.0,
        "PRES:surface" => 100_000.0,
        # Level 850 mb has TMP+DPT but no HGT — skipped.
        "TMP:850 mb" => 275.0,
        "DPT:850 mb" => 270.0,
        # Level 700 mb is fully populated.
        "TMP:700 mb" => 265.0,
        "DPT:700 mb" => 260.0,
        "HGT:700 mb" => 3000.0
      }

      profile = HrdpsClient.build_profile_from_extracted(extracted)
      assert length(profile.profile) == 1
      assert hd(profile.profile)["pres"] == 700.0
    end
  end

  describe "cycle_available?/1 (injected http_head)" do
    setup do
      prev = Application.get_env(:microwaveprop, :hrdps_http_head)

      on_exit(fn ->
        if prev,
          do: Application.put_env(:microwaveprop, :hrdps_http_head, prev),
          else: Application.delete_env(:microwaveprop, :hrdps_http_head)
      end)

      :ok
    end

    test "returns true when head returns 200" do
      Application.put_env(:microwaveprop, :hrdps_http_head, fn _url, _opts ->
        {:ok, %{status: 200}}
      end)

      assert HrdpsClient.cycle_available?(~U[2026-04-29 12:00:00Z])
    end

    test "returns false when head returns non-200" do
      Application.put_env(:microwaveprop, :hrdps_http_head, fn _url, _opts ->
        {:ok, %{status: 404}}
      end)

      refute HrdpsClient.cycle_available?(~U[2026-04-29 12:00:00Z])
    end

    test "returns false on transport error" do
      Application.put_env(:microwaveprop, :hrdps_http_head, fn _url, _opts ->
        {:error, :timeout}
      end)

      refute HrdpsClient.cycle_available?(~U[2026-04-29 12:00:00Z])
    end
  end

  describe "fetch_grid/3 with injected http_get" do
    setup do
      prev_get = Application.get_env(:microwaveprop, :hrdps_http_get)
      prev_head = Application.get_env(:microwaveprop, :hrdps_http_head)

      Application.put_env(:microwaveprop, :hrdps_http_head, fn _url, _opts ->
        {:ok, %{status: 200}}
      end)

      on_exit(fn ->
        if prev_get,
          do: Application.put_env(:microwaveprop, :hrdps_http_get, prev_get),
          else: Application.delete_env(:microwaveprop, :hrdps_http_get)

        if prev_head,
          do: Application.put_env(:microwaveprop, :hrdps_http_head, prev_head),
          else: Application.delete_env(:microwaveprop, :hrdps_http_head)
      end)

      :ok
    end

    test "returns error when variable fetch fails" do
      call_count = :counters.new(1, [:atomics])

      Application.put_env(:microwaveprop, :hrdps_http_get, fn _url, _opts ->
        :counters.add(call_count, 1, 1)
        {:error, :timeout}
      end)

      assert {:error, _} = HrdpsClient.fetch_grid([{33.0, -97.0}], ~U[2026-04-29 12:00:00Z])
    end
  end
end