defmodule MoundHuntersWeb.Plugs.BoundsCheck do
  @moduledoc """
  Plug to validate that coordinates are within Ohio boundaries.
  Applies to tile requests but not to geometry sharing API.
  """
  import Plug.Conn
  require Logger

  def init(opts), do: opts

  def call(conn, _opts) do
    # Skip bounds check for non-tile endpoints
    if skip_bounds_check?(conn.request_path) do
      conn
    else
      check_bounds(conn)
    end
  end

  defp skip_bounds_check?(path) do
    # Skip bounds check for geometry API and static files
    String.starts_with?(path, "/api/share") or
      String.starts_with?(path, "/static/") or
      path == "/"
  end

  defp check_bounds(conn) do
    cond do
      # Check query params for tile request
      conn.query_params["lat"] != nil and conn.query_params["lng"] != nil ->
        check_query_params(conn)

      # For tile file serving, we assume tiles in storage are valid
      # (they were validated when created)
      String.starts_with?(conn.request_path, "/tiles/") ->
        conn

      true ->
        conn
    end
  end

  defp check_query_params(conn) do
    with {:ok, lat} <- parse_float(conn.query_params["lat"]),
         {:ok, lng} <- parse_float(conn.query_params["lng"]),
         :ok <- MoundHunters.Boundary.check_bounds(lat, lng) do
      conn
    else
      {:error, :invalid_number} ->
        send_error(conn, 400, "Invalid coordinate format")

      {:error, reason} ->
        send_error(conn, 400, reason)
    end
  end

  defp parse_float(str) when is_binary(str) do
    case Float.parse(str) do
      {num, ""} -> {:ok, num}
      _ -> {:error, :invalid_number}
    end
  end

  defp parse_float(_), do: {:error, :invalid_number}

  defp send_error(conn, status, message) do
    Logger.warning("Bounds check failed: #{message}")

    conn
    |> put_private(:error_message, message)
    |> put_resp_content_type("application/json")
    |> send_resp(status, Jason.encode!(%{error: message}))
    |> halt()
  end
end