defmodule SyntropyWeb.GraphViewModel do
  @moduledoc false

  alias Syntropy.{ClusterInfo, HistoryStore}

  @type graph_node :: %{
          id: String.t(),
          name: String.t(),
          perspective: String.t(),
          position: float(),
          temporary: boolean(),
          selected: boolean(),
          active: boolean(),
          current: boolean()
        }

  @type graph_edge :: %{
          source: String.t(),
          target: String.t(),
          weight: float(),
          interactions: non_neg_integer()
        }

  @type meta :: %{
          ranked_agent_ids: [String.t()],
          task_id: String.t() | nil,
          proposal_id: String.t() | nil,
          node_id: String.t(),
          timestamp: String.t() | nil,
          trigger_kind: String.t()
        }

  @type graph :: %{
          mode: String.t(),
          snapshot_id: String.t() | nil,
          nodes: [graph_node()],
          edges: [graph_edge()],
          meta: meta()
        }

  @spec from_live([map()], keyword()) :: graph()
  def from_live(agents, opts \\ []) do
    selected_agent_ids = Keyword.get(opts, :selected_agent_ids, [])
    active_agent_ids = Keyword.get(opts, :active_agent_ids, [])
    focused_agent_id = Keyword.get(opts, :focused_agent_id)

    %{
      mode: "live",
      snapshot_id: nil,
      nodes: build_nodes(agents, selected_agent_ids, active_agent_ids, focused_agent_id),
      edges: build_edges(agents),
      meta: %{
        ranked_agent_ids: Enum.map(agents, &agent_runtime_id/1),
        task_id: Keyword.get(opts, :task_id),
        proposal_id: Keyword.get(opts, :proposal_id),
        node_id: Syntropy.node_id(),
        timestamp: nil,
        trigger_kind: "live"
      }
    }
  end

  @spec from_replay(HistoryStore.snapshot(), keyword()) :: graph()
  def from_replay(snapshot, opts \\ []) do
    selected_agent_ids = Keyword.get(opts, :selected_agent_ids, [])
    focused_agent_id = Keyword.get(opts, :focused_agent_id)

    %{
      mode: "replay",
      snapshot_id: snapshot.id,
      nodes: build_nodes(snapshot.agents, selected_agent_ids, [], focused_agent_id),
      edges: build_edges(snapshot.agents),
      meta: %{
        ranked_agent_ids: snapshot.ranked_agent_ids,
        task_id: snapshot.task_id,
        proposal_id: snapshot.proposal_id,
        node_id: Map.get(snapshot, :node_id, "local"),
        timestamp: DateTime.to_iso8601(snapshot.inserted_at),
        trigger_kind: snapshot.trigger_kind
      }
    }
  end

  @spec to_json(graph()) :: String.t()
  def to_json(graph) do
    Jason.encode!(graph)
  end

  @doc """
  Derives the runtime ids of the agents a task result selected.

  Prefers the enriched `selected_agents` export, falls back to the selection
  trace, and finally to raw `selected_agent_ids`.
  """
  @spec task_selected_runtime_ids(map() | nil) :: [String.t()]
  def task_selected_runtime_ids(nil), do: []

  def task_selected_runtime_ids(task_result) do
    cond do
      is_list(Map.get(task_result, :selected_agents)) and task_result.selected_agents != [] ->
        Enum.map(task_result.selected_agents, &Map.get(&1, :runtime_id, &1.id))

      is_list(Map.get(task_result, :selection_trace)) and task_result.selection_trace != [] ->
        task_result.selection_trace
        |> Enum.filter(& &1.selected)
        |> Enum.map(&Map.get(&1, :runtime_id, &1.agent_id))

      true ->
        task_result
        |> Map.get(:selected_agent_ids, [])
        |> Enum.map(&runtime_identifier_or_local/1)
    end
  end

  defp build_nodes(agents, selected_agent_ids, active_agent_ids, focused_agent_id) do
    selected_set = MapSet.new(selected_agent_ids)
    active_set = MapSet.new(active_agent_ids)

    Enum.map(agents, fn agent ->
      runtime_id = agent_runtime_id(agent)

      %{
        id: runtime_id,
        runtime_id: runtime_id,
        node_id: agent_node_id(agent),
        name: agent_name(agent),
        perspective: agent_perspective(agent),
        position: agent_position(agent),
        temporary: agent_temporary?(agent),
        selected: identifier_selected?(selected_set, agent),
        active: identifier_selected?(active_set, agent),
        current: identifier_matches?(focused_agent_id, agent)
      }
    end)
  end

  defp build_edges(agents) do
    agents
    |> Enum.flat_map(fn agent ->
      source = agent_runtime_id(agent)

      Enum.map(agent_connections(agent), fn connection ->
        %{
          source: source,
          target: Map.fetch!(connection, :target_agent_id),
          weight: Map.fetch!(connection, :weight),
          interactions: Map.fetch!(connection, :interactions)
        }
      end)
    end)
    |> Enum.reject(&(&1.source == &1.target))
    |> Enum.reduce(%{}, fn edge, acc ->
      key = Enum.sort([edge.source, edge.target]) |> List.to_tuple()

      Map.update(acc, key, normalize_edge(edge), fn existing ->
        %{
          source: elem(key, 0),
          target: elem(key, 1),
          weight: max(existing.weight, edge.weight),
          interactions: max(existing.interactions, edge.interactions)
        }
      end)
    end)
    |> Map.values()
    |> Enum.sort_by(&{&1.source, &1.target})
  end

  defp normalize_edge(edge) do
    [source, target] = Enum.sort([edge.source, edge.target])
    %{source: source, target: target, weight: edge.weight, interactions: edge.interactions}
  end

  defp agent_runtime_id(agent) do
    case Map.get(agent, :runtime_id) do
      runtime_id when is_binary(runtime_id) and runtime_id != "" -> runtime_id
      _other -> Map.fetch!(agent, :id)
    end
  end

  defp agent_node_id(agent) do
    case Map.get(agent, :node_id, "local") do
      "" -> "local"
      nil -> "local"
      node_id -> node_id
    end
  end

  defp agent_name(agent), do: Map.fetch!(agent, :name)
  defp agent_perspective(agent), do: Map.fetch!(agent, :perspective)
  defp agent_position(agent), do: Map.fetch!(agent, :position)
  defp agent_temporary?(agent), do: Map.fetch!(agent, :temporary)

  defp agent_connections(%{connections: connections} = agent) when is_map(connections) do
    connections
    |> Enum.sort_by(fn {target_id, _value} -> target_id end)
    |> Enum.map(fn {target_id, value} ->
      %{
        target_agent_id: connection_target_id(agent, target_id),
        weight: Map.fetch!(value, :weight),
        interactions: Map.fetch!(value, :interactions)
      }
    end)
  end

  defp agent_connections(%{connections: connections} = agent) when is_list(connections) do
    connections
    |> Enum.map(fn connection ->
      %{
        target_agent_id: connection_target_id(agent, Map.fetch!(connection, :target_agent_id)),
        weight: Map.fetch!(connection, :weight),
        interactions: Map.fetch!(connection, :interactions)
      }
    end)
    |> Enum.sort_by(& &1.target_agent_id)
  end

  defp identifier_selected?(identifier_set, agent) do
    runtime_id = agent_runtime_id(agent)
    local_id = Map.fetch!(agent, :id)

    MapSet.member?(identifier_set, runtime_id) or MapSet.member?(identifier_set, local_id)
  end

  defp identifier_matches?(nil, _agent), do: false

  defp identifier_matches?(identifier, agent) do
    identifier in [agent_runtime_id(agent), Map.fetch!(agent, :id)]
  end

  defp connection_target_id(agent, target_id) when is_binary(target_id) do
    cond do
      String.contains?(target_id, "::") ->
        target_id

      explicit_runtime_id?(agent) ->
        ClusterInfo.runtime_id(target_id, agent_node_id(agent))

      true ->
        target_id
    end
  end

  defp explicit_runtime_id?(agent) do
    case Map.get(agent, :runtime_id) do
      runtime_id when is_binary(runtime_id) and runtime_id != "" -> true
      _other -> false
    end
  end

  defp runtime_identifier_or_local(agent_id) do
    case ClusterInfo.parse_runtime_id(agent_id) do
      {:ok, ref} -> ref.runtime_id
      :error -> agent_id
    end
  end
end