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)}, {^sort_dir, q.id}])
      |> limit(^@per_page)
      |> offset(^offset)
      |> Repo.all()
      |> Repo.preload(:user)

    %{
      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
    terms = search |> String.split() |> Enum.map(&String.trim/1) |> Enum.reject(&(&1 == ""))

    case terms do
      [a, b] ->
        pa = "%" <> String.upcase(a) <> "%"
        pb = "%" <> String.upcase(b) <> "%"

        where(
          query,
          [q],
          (ilike(q.station1, ^pa) and ilike(q.station2, ^pb)) or
            (ilike(q.station1, ^pb) and ilike(q.station2, ^pa))
        )

      _ ->
        pattern = "%" <> String.upcase(search) <> "%"
        where(query, [q], ilike(q.station1, ^pattern) or ilike(q.station2, ^pattern))
    end
  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

  # ── Enrichment status queries ────────────────────────────────────

  @enrichable_statuses [:pending, :failed]

  def contacts_needing_enrichment(field, limit \\ 500, extra_filter \\ nil) do
    query =
      Contact
      |> where([q], field(q, ^field) in ^@enrichable_statuses and not is_nil(q.pos1))
      |> order_by([q], asc: q.qso_timestamp)
      |> limit(^limit)

    query = if extra_filter, do: extra_filter.(query), else: query
    Repo.all(query)
  end

  def unprocessed_contacts(limit \\ 500), do: contacts_needing_enrichment(:weather_status, limit)

  def unprocessed_hrrr_contacts(limit \\ 500), do: contacts_needing_enrichment(:hrrr_status, limit)

  def unprocessed_terrain_contacts(limit \\ 500),
    do: contacts_needing_enrichment(:terrain_status, limit, &where(&1, [q], not is_nil(q.pos2)))

  def unprocessed_iemre_contacts(limit \\ 500), do: contacts_needing_enrichment(:iemre_status, limit)

  def set_enrichment_status!(ids, field, status) do
    Contact
    |> where([q], q.id in ^ids and field(q, ^field) != ^status)
    |> Repo.update_all(set: [{field, status}])
  end

  def mark_weather_queued!(ids), do: set_enrichment_status!(ids, :weather_status, :queued)
  def mark_hrrr_queued!(ids), do: set_enrichment_status!(ids, :hrrr_status, :queued)
  def mark_terrain_queued!(ids), do: set_enrichment_status!(ids, :terrain_status, :queued)
  def mark_iemre_queued!(ids), do: set_enrichment_status!(ids, :iemre_status, :queued)

  @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"]

    cond do
      lat1 && lon1 && lat2 && lon2 ->
        mid_lat = (lat1 + lat2) / 2
        mid_lon = (lon1 + lon2) / 2
        [{lat1, lon1}, {mid_lat, mid_lon}, {lat2, lon2}]

      lat1 && lon1 ->
        [{lat1, lon1}]

      true ->
        []
    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
    updates =
      for contact <- contacts,
          is_nil(contact.distance_km) && contact.pos1 && contact.pos2,
          lat1 = contact.pos1["lat"],
          lon1 = contact.pos1["lon"] || contact.pos1["lng"],
          lat2 = contact.pos2["lat"],
          lon2 = contact.pos2["lon"] || contact.pos2["lng"],
          lat1 && lon1 && lat2 && lon2 do
        dist = lat1 |> haversine_km(lon1, lat2, lon2) |> round()
        {contact.id, dist}
      end

    if updates != [] do
      # Build a single UPDATE ... FROM (VALUES ...) statement
      # Ecto.UUID.dump!/1 converts string UUIDs to the 16-byte binary Postgrex expects
      {values_sql, params} =
        updates
        |> Enum.with_index()
        |> Enum.reduce({"", []}, fn {{id, dist}, i}, {sql, params} ->
          frag = "($#{i * 2 + 1}::uuid, $#{i * 2 + 2}::numeric)"
          sep = if sql == "", do: "", else: ", "
          {sql <> sep <> frag, params ++ [Ecto.UUID.dump!(id), dist]}
        end)

      Repo.query!(
        "UPDATE contacts AS c SET distance_km = v.dist FROM (VALUES #{values_sql}) AS v(id, dist) WHERE c.id = v.id",
        params
      )
    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

  @doc """
  Computes pos1/pos2/distance_km from grid squares if missing.
  Returns the updated contact, or the original if already computed or grids are missing.
  """
  def ensure_positions!(contact) do
    needs_pos1 = is_nil(contact.pos1) && contact.grid1
    needs_pos2 = is_nil(contact.pos2) && contact.grid2

    if needs_pos1 || needs_pos2 do
      pos1 = contact.pos1 || latlon_from_grid(contact.grid1)
      pos2 = contact.pos2 || latlon_from_grid(contact.grid2)

      distance =
        if pos1 && pos2 do
          lon1 = pos1["lon"] || pos1["lng"]
          lon2 = pos2["lon"] || pos2["lng"]

          pos1["lat"]
          |> haversine_km(lon1, pos2["lat"], lon2)
          |> round()
          |> Decimal.new()
        else
          contact.distance_km
        end

      changes =
        %{}
        |> then(fn c -> if pos1 && is_nil(contact.pos1), do: Map.put(c, :pos1, pos1), else: c end)
        |> then(fn c -> if pos2 && is_nil(contact.pos2), do: Map.put(c, :pos2, pos2), else: c end)
        |> then(fn c -> if distance && is_nil(contact.distance_km), do: Map.put(c, :distance_km, distance), else: c end)

      if changes == %{} do
        contact
      else
        # Reset unavailable statuses to pending now that positions exist
        new_pos1 = Map.get(changes, :pos1)
        new_pos2 = Map.get(changes, :pos2)

        changes =
          if new_pos1 do
            changes
            |> maybe_reset_status(:hrrr_status, contact.hrrr_status)
            |> maybe_reset_status(:weather_status, contact.weather_status)
            |> maybe_reset_status(:iemre_status, contact.iemre_status)
          else
            changes
          end

        changes =
          if new_pos1 && (new_pos2 || contact.pos2) do
            maybe_reset_status(changes, :terrain_status, contact.terrain_status)
          else
            changes
          end

        contact
        |> Ecto.Changeset.change(changes)
        |> Repo.update!()
      end
    else
      contact
    end
  end

  defp maybe_reset_status(changes, field, :unavailable), do: Map.put(changes, field, :pending)
  defp maybe_reset_status(changes, _field, _status), do: changes

  defp latlon_from_grid(nil), do: nil

  defp latlon_from_grid(grid) do
    case Maidenhead.to_latlon(grid) do
      {:ok, {lat, lon}} ->
        %{"lat" => lat, "lon" => lon}

      _ ->
        # Try truncating to nearest valid even length (e.g. "FN03c" → "FN03")
        truncated = String.slice(grid, 0, div(String.length(grid), 2) * 2)

        case Maidenhead.to_latlon(truncated) do
          {:ok, {lat, lon}} -> %{"lat" => lat, "lon" => lon}
          _ -> nil
        end
    end
  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