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

  alias Microwaveprop.Weather.NexradCache

  setup do
    NexradCache.clear()
    :ok
  end

  describe "fetch/1" do
    test "returns :miss when nothing is cached" do
      assert NexradCache.fetch(~U[2026-04-12 12:00:00Z]) == :miss
    end

    test "returns cached pixels + width after put" do
      NexradCache.put(~U[2026-04-12 12:00:00Z], <<1, 2, 3, 4>>, 2)
      assert {:ok, <<1, 2, 3, 4>>, 2} = NexradCache.fetch(~U[2026-04-12 12:00:00Z])
    end

    test "isolates entries by timestamp" do
      NexradCache.put(~U[2026-04-12 12:00:00Z], <<1>>, 1)
      NexradCache.put(~U[2026-04-12 12:05:00Z], <<2>>, 1)

      assert {:ok, <<1>>, 1} = NexradCache.fetch(~U[2026-04-12 12:00:00Z])
      assert {:ok, <<2>>, 1} = NexradCache.fetch(~U[2026-04-12 12:05:00Z])
    end
  end

  describe "prune_older_than/1" do
    test "removes entries with a timestamp strictly before the cutoff" do
      NexradCache.put(~U[2026-04-12 11:50:00Z], <<1>>, 1)
      NexradCache.put(~U[2026-04-12 12:00:00Z], <<2>>, 1)

      NexradCache.prune_older_than(~U[2026-04-12 11:55:00Z])

      assert NexradCache.fetch(~U[2026-04-12 11:50:00Z]) == :miss
      assert {:ok, <<2>>, 1} = NexradCache.fetch(~U[2026-04-12 12:00:00Z])
    end

    test "keeps entries equal to the cutoff" do
      NexradCache.put(~U[2026-04-12 12:00:00Z], <<1>>, 1)
      NexradCache.prune_older_than(~U[2026-04-12 12:00:00Z])
      assert {:ok, <<1>>, 1} = NexradCache.fetch(~U[2026-04-12 12:00:00Z])
    end
  end

  describe "size cap" do
    test "evicts the oldest-by-timestamp entries once the cap is exceeded" do
      # Insert 25 entries; max is 20, so 5 oldest get dropped.
      base = ~U[2026-04-12 00:00:00Z]

      for i <- 1..25 do
        ts = DateTime.add(base, i * 300, :second)
        NexradCache.put(ts, <<i>>, 1)
      end

      # The 5 oldest (i = 1..5) should have been evicted.
      for i <- 1..5 do
        ts = DateTime.add(base, i * 300, :second)
        assert NexradCache.fetch(ts) == :miss
      end

      # The most recent 20 should still be present.
      for i <- 6..25 do
        ts = DateTime.add(base, i * 300, :second)
        assert {:ok, <<^i>>, 1} = NexradCache.fetch(ts)
      end
    end
  end
end
