defmodule Microwaveprop.Radio do
  @moduledoc false

  import Ecto.Query

  alias Microwaveprop.Radio.Contact
  alias Microwaveprop.Radio.Maidenhead
  alias Microwaveprop.Repo

  @per_page 20
  @sortable_fields ~w(station1 station2 band mode distance_km qso_timestamp inserted_at)a

  def list_contacts(opts \\ []) do
    page = max(Keyword.get(opts, :page, 1), 1)
    offset = (page - 1) * @per_page
    search = Keyword.get(opts, :search)

    {sort_field, sort_dir} = sort_opts(opts)

    base_query = maybe_search(Contact, search)

    total_entries = Repo.aggregate(base_query, :count)
    total_pages = max(ceil(total_entries / @per_page), 1)

    entries =
      base_query
      |> order_by([q], [{^sort_dir, field(q, ^sort_field)}])
      |> limit(^@per_page)
      |> offset(^offset)
      |> Repo.all()

    %{
      entries: entries,
      grouped_entries: group_reciprocals(entries),
      page: page,
      total_pages: total_pages,
      total_entries: total_entries
    }
  end

  @doc """
  Groups reciprocal contacts (same station pair swapped, same band, same timestamp).
  Returns a list of `{primary, reciprocals}` tuples where reciprocals is
  a (possibly empty) list of matching contacts.
  """
  def group_reciprocals(contacts) do
    {groups, _seen_ids} =
      Enum.reduce(contacts, {[], MapSet.new()}, fn contact, {groups, seen} ->
        if MapSet.member?(seen, contact.id) do
          {groups, seen}
        else
          reciprocals =
            Enum.filter(contacts, fn other ->
              other.id != contact.id and
                not MapSet.member?(seen, other.id) and
                other.band == contact.band and
                reciprocal_pair?(contact, other)
            end)

          new_seen = Enum.reduce(reciprocals, MapSet.put(seen, contact.id), &MapSet.put(&2, &1.id))
          {[{contact, reciprocals} | groups], new_seen}
        end
      end)

    Enum.reverse(groups)
  end

  defp reciprocal_pair?(a, b) do
    same_stations =
      (a.station1 == b.station2 and a.station2 == b.station1) or
        (a.station1 == b.station1 and a.station2 == b.station2)

    same_stations and same_hour?(a.qso_timestamp, b.qso_timestamp)
  end

  defp same_hour?(t1, t2) do
    t1 |> NaiveDateTime.truncate(:second) |> Map.take([:year, :month, :day, :hour]) ==
      t2 |> NaiveDateTime.truncate(:second) |> Map.take([:year, :month, :day, :hour])
  end

  defp maybe_search(query, nil), do: query
  defp maybe_search(query, ""), do: query

  defp maybe_search(query, search) do
    pattern = "%" <> String.upcase(search) <> "%"

    where(query, [q], ilike(q.station1, ^pattern) or ilike(q.station2, ^pattern))
  end

  defp sort_opts(opts) do
    sort_by = Keyword.get(opts, :sort_by, :qso_timestamp)
    sort_order = Keyword.get(opts, :sort_order, :desc)

    field = if sort_by in @sortable_fields, do: sort_by, else: :qso_timestamp
    dir = if sort_order in [:asc, :desc], do: sort_order, else: :desc

    {field, dir}
  end

  def unprocessed_contacts(limit \\ 500) do
    Contact
    |> where([q], q.weather_queued == false and not is_nil(q.pos1))
    |> order_by([q], asc: q.qso_timestamp)
    |> limit(^limit)
    |> Repo.all()
  end

  def mark_weather_queued!(ids) do
    Contact
    |> where([q], q.id in ^ids)
    |> Repo.update_all(set: [weather_queued: true])
  end

  def unprocessed_hrrr_contacts(limit \\ 500) do
    Contact
    |> where([q], q.hrrr_queued == false and not is_nil(q.pos1))
    |> order_by([q], asc: q.qso_timestamp)
    |> limit(^limit)
    |> Repo.all()
  end

  def mark_hrrr_queued!(ids) do
    Contact
    |> where([q], q.id in ^ids)
    |> Repo.update_all(set: [hrrr_queued: true])
  end

  def unprocessed_terrain_contacts(limit \\ 500) do
    Contact
    |> where([q], q.terrain_queued == false and not is_nil(q.pos1) and not is_nil(q.pos2))
    |> order_by([q], asc: q.qso_timestamp)
    |> limit(^limit)
    |> Repo.all()
  end

  def mark_terrain_queued!(ids) do
    Contact
    |> where([q], q.id in ^ids)
    |> Repo.update_all(set: [terrain_queued: true])
  end

  def unprocessed_iemre_contacts(limit \\ 500) do
    Contact
    |> where([q], q.iemre_queued == false and not is_nil(q.pos1))
    |> order_by([q], asc: q.qso_timestamp)
    |> limit(^limit)
    |> Repo.all()
  end

  def mark_iemre_queued!(ids) do
    Contact
    |> where([q], q.id in ^ids)
    |> Repo.update_all(set: [iemre_queued: true])
  end

  @doc """
  Returns a list of {lat, lon} points along the contact path: pos1, midpoint, pos2.
  Returns [pos1] if pos2 is nil, or [] if pos1 is nil.
  """
  def contact_path_points(%{pos1: nil}), do: []

  def contact_path_points(%{pos1: pos1, pos2: nil}) do
    lat = pos1["lat"]
    lon = pos1["lon"] || pos1["lng"]
    if lat && lon, do: [{lat, lon}], else: []
  end

  def contact_path_points(%{pos1: pos1, pos2: pos2}) do
    lat1 = pos1["lat"]
    lon1 = pos1["lon"] || pos1["lng"]
    lat2 = pos2["lat"]
    lon2 = pos2["lon"] || pos2["lng"]

    if lat1 && lon1 && lat2 && lon2 do
      mid_lat = (lat1 + lat2) / 2
      mid_lon = (lon1 + lon2) / 2
      [{lat1, lon1}, {mid_lat, mid_lon}, {lat2, lon2}]
    else
      [{lat1, lon1}]
    end
  end

  @earth_radius_km 6371.0

  def haversine_km(lat1, lon1, lat2, lon2) do
    dlat = deg_to_rad(lat2 - lat1)
    dlon = deg_to_rad(lon2 - lon1)
    rlat1 = deg_to_rad(lat1)
    rlat2 = deg_to_rad(lat2)

    a =
      :math.sin(dlat / 2) ** 2 +
        :math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2

    2 * @earth_radius_km * :math.asin(:math.sqrt(a))
  end

  def backfill_distances(contacts) do
    Enum.each(contacts, fn contact ->
      if is_nil(contact.distance_km) && contact.pos1 && contact.pos2 do
        lat1 = contact.pos1["lat"]
        lon1 = contact.pos1["lon"] || contact.pos1["lng"]
        lat2 = contact.pos2["lat"]
        lon2 = contact.pos2["lon"] || contact.pos2["lng"]

        if lat1 && lon1 && lat2 && lon2 do
          dist = lat1 |> haversine_km(lon1, lat2, lon2) |> round() |> Decimal.new()

          Contact
          |> where([q], q.id == ^contact.id)
          |> Repo.update_all(set: [distance_km: dist])
        end
      end
    end)
  end

  defp deg_to_rad(deg), do: deg * :math.pi() / 180

  def get_contact!(id) do
    Repo.get!(Contact, id)
  end

  def toggle_flagged_invalid!(contact) do
    contact
    |> Ecto.Changeset.change(flagged_invalid: !contact.flagged_invalid)
    |> Repo.update!()
  end

  def change_contact(contact, attrs \\ %{}) do
    Contact.submission_changeset(contact, attrs)
  end

  def create_contact(attrs) do
    changeset = Contact.submission_changeset(%Contact{}, attrs)

    if changeset.valid? do
      grid1 = Ecto.Changeset.get_change(changeset, :grid1)
      grid2 = Ecto.Changeset.get_change(changeset, :grid2)

      case {Maidenhead.to_latlon(grid1), Maidenhead.to_latlon(grid2)} do
        {{:ok, {lat1, lon1}}, {:ok, {lat2, lon2}}} ->
          distance = lat1 |> haversine_km(lon1, lat2, lon2) |> round() |> Decimal.new()

          changeset
          |> Ecto.Changeset.put_change(:pos1, %{"lat" => lat1, "lon" => lon1})
          |> Ecto.Changeset.put_change(:pos2, %{"lat" => lat2, "lon" => lon2})
          |> Ecto.Changeset.put_change(:distance_km, distance)
          |> Ecto.Changeset.put_change(:user_submitted, true)
          |> Repo.insert()

        _ ->
          changeset = Ecto.Changeset.add_error(changeset, :grid1, "could not resolve grid to coordinates")
          {:error, %{changeset | action: :insert}}
      end
    else
      {:error, %{changeset | action: :insert}}
    end
  end
end