defmodule Planck.Headless do
  @moduledoc """
  The headless core of the Planck coding agent.

  `planck_headless` owns configuration, loads resources at startup (tools,
  skills, teams, compactor), and manages session lifecycles. UIs depend on
  this module; they are rendering surfaces only and never call `planck_agent`
  directly.

  See the design specs in the `specs/` directory of the repository.
  """

  require Logger

  alias Planck.Agent
  alias Planck.Agent.{AgentSpec, BuiltinTools, Message, Session, Skill, SkillUsage, Team, Tools}
  alias Planck.Headless.{Config, DefaultPrompt, ResourceStore, SessionName, SidecarManager}
  alias Planck.Headless.Config.{EnvBinding, JsonBinding}

  @type session_id :: String.t()

  # ---------------------------------------------------------------------------
  # Config
  # ---------------------------------------------------------------------------

  @doc "Return the resolved configuration."
  @spec config() :: Config.t()
  def config, do: Config.get()

  # ---------------------------------------------------------------------------
  # Sessions
  # ---------------------------------------------------------------------------

  @doc """
  Start a new session. Returns `{:ok, session_id}`.

  ## Options

  - `template:` — team alias, path to a TEAM.json directory, or `nil` for the
    default dynamic team (lone orchestrator built from config defaults).
  - `name:` — session name; auto-generated as `<adjective>-<noun>` if absent.
  - `cwd:` — working directory for the session (default: `File.cwd!()`).
  - `tools:` — extra `Planck.Agent.Tool.t()` list available only for this
    session. These shadow registered and built-in tools of the same name.
  """
  @spec start_session(keyword()) :: {:ok, session_id()} | {:error, term()}
  def start_session(opts \\ []) do
    template = Keyword.get(opts, :template)
    cwd = Keyword.get(opts, :cwd, File.cwd!())
    user_name = Keyword.get(opts, :name)
    session_tools = Keyword.get(opts, :tools, [])

    with {:ok, team} <- resolve_team(template),
         {:ok, session_name} <- resolve_name(user_name),
         {:ok, session_id} <- create_session(session_name, cwd),
         {:ok, team_id} <- materialize_team(session_id, team, cwd, session_tools: session_tools),
         :ok <-
           save_metadata(
             session_id,
             template,
             session_name,
             cwd,
             team_id,
             agent_ids(team_id),
             team.description
           ) do
      {:ok, session_id}
    end
  end

  @doc """
  Resume a session by session_id or by name. Reconstructs the team, restores
  message history, and injects a recovery context if prior work was in-flight.
  """
  @spec resume_session(String.t(), keyword()) :: {:ok, session_id()} | {:error, term()}
  def resume_session(id_or_name, _opts \\ []) do
    sessions_dir = Config.sessions_dir!() |> Path.expand()

    with {:ok, session_id, session_name} <- locate_session(sessions_dir, id_or_name),
         {:ok, _pid} <- reopen_session(session_id, session_name, sessions_dir),
         {:ok, metadata} <- Session.get_metadata(session_id),
         {:ok, team} <- resolve_team(metadata["team_alias"]),
         prev_ids = decode_agent_ids(Map.get(metadata, "agent_ids")),
         {:ok, team_id} <-
           materialize_team(session_id, team, metadata["cwd"] || File.cwd!(),
             prev_ids: prev_ids,
             metadata: metadata
           ),
         :ok <- reconstruct_dynamic_workers(session_id, team_id, team),
         :ok <-
           save_metadata(
             session_id,
             metadata["team_alias"],
             session_name,
             metadata["cwd"] || File.cwd!(),
             team_id,
             agent_ids(team_id),
             metadata["team_description"]
           ),
         :ok <- maybe_inject_recovery(session_id, team_id) do
      {:ok, session_id}
    end
  end

  @doc """
  Close a session. Stops the agent team and the session GenServer.
  The SQLite file is retained for later resumption.
  """
  @spec close_session(session_id()) :: :ok | {:error, term()}
  def close_session(session_id) do
    with {:ok, team_id} <- read_team_id(session_id) do
      stop_team(team_id)
      Session.stop(session_id)
      :ok
    end
  end

  @doc """
  Close a session and permanently delete its SQLite file from disk.

  Stops all running agents and the Session GenServer if active, then removes
  the `.db` file. This operation is irreversible.
  """
  @spec delete_session(session_id()) :: :ok
  def delete_session(session_id) do
    # Stop running processes if active — best-effort, ignore any errors
    try do
      close_session(session_id)
    rescue
      _ -> :ok
    end

    sessions_dir = Config.sessions_dir!() |> Path.expand()

    case Session.find_by_id(sessions_dir, session_id) do
      {:ok, path, _name} ->
        File.rm(path)
        :ok

      {:error, _} ->
        :ok
    end
  end

  @doc """
  Edit a previous user message: rewind the orchestrator to strictly before the
  given DB row id (truncates both the SQLite session and in-memory history via
  `Planck.Agent.rewind_to_message/2`), then re-prompt with `new_text`.
  """
  @spec rewind_to_message(session_id(), pos_integer(), String.t()) ::
          :ok | {:error, term()}
  def rewind_to_message(session_id, db_id, new_text) do
    with {:ok, team_id} <- read_team_id(session_id),
         {:ok, orch_pid} <- find_orchestrator(team_id) do
      Agent.rewind_to_message(orch_pid, db_id)
      Agent.prompt(orch_pid, new_text)
    end
  end

  @doc "Send a user prompt to the orchestrator of a session."
  @spec prompt(session_id(), String.t()) :: :ok | {:error, term()}
  def prompt(session_id, text) do
    with {:ok, team_id} <- read_team_id(session_id),
         {:ok, pid} <- find_orchestrator(team_id) do
      Agent.prompt(pid, text)
    end
  end

  @doc """
  Nudge the orchestrator to act on its existing message history without adding
  a new user message. Used after session resume when a recovery context is
  already present and just needs to be acted upon.

  Returns `:ok` if the orchestrator was nudged, `{:error, reason}` otherwise.
  """
  @spec nudge(session_id()) :: :ok | {:error, term()}
  def nudge(session_id) do
    with {:ok, team_id} <- read_team_id(session_id),
         {:ok, pid} <- find_orchestrator(team_id) do
      Agent.nudge(pid)
    end
  end

  @doc """
  List all sessions on disk — active and inactive — with their id, name, and
  whether they are currently running.
  """
  @spec list_sessions() ::
          [%{session_id: String.t(), name: String.t(), active: boolean()}]
  def list_sessions do
    sessions_dir = Config.sessions_dir!() |> Path.expand()

    sessions_dir
    |> Path.join("*.db")
    |> Path.wildcard()
    |> Enum.sort_by(&File.stat!(&1).ctime, :desc)
    |> Enum.map(fn path ->
      [id, name] = path |> Path.basename(".db") |> String.split("_", parts: 2)
      %{session_id: id, name: name, active: session_active?(id)}
    end)
  end

  @spec session_active?(String.t()) :: boolean()
  defp session_active?(session_id) do
    case Session.whereis(session_id) do
      {:ok, _pid} -> true
      {:error, :not_found} -> false
    end
  end

  # ---------------------------------------------------------------------------
  # Teams
  # ---------------------------------------------------------------------------

  @doc "List all registered teams with alias, name, and description."
  @spec list_teams() ::
          [%{alias: String.t(), name: String.t() | nil, description: String.t() | nil}]
  def list_teams do
    ResourceStore.get().teams
    |> Enum.map(fn {team_alias, team} ->
      %{alias: team_alias, name: team.name, description: team.description}
    end)
  end

  @doc "Look up a team by alias."
  @spec get_team(String.t()) :: {:ok, Planck.Agent.Team.t()} | {:error, :not_found}
  def get_team(team_alias) do
    case Map.fetch(ResourceStore.get().teams, team_alias) do
      {:ok, team} -> {:ok, team}
      :error -> {:error, :not_found}
    end
  end

  # ---------------------------------------------------------------------------
  # Resources
  # ---------------------------------------------------------------------------

  @doc "Return models available for use (providers with API keys configured)."
  @spec available_models() :: [Planck.AI.Model.t()]
  def available_models, do: ResourceStore.get().available_models

  @doc """
  Register a local-node tool globally. Available to all new sessions.

  If a tool with the same name is already registered it is replaced.
  Registered tools shadow sidecar tools and built-ins of the same name.
  See the tool-shadowing guide for details.
  """
  @spec register_tool(Planck.Agent.Tool.t()) :: :ok
  def register_tool(tool), do: ResourceStore.register_tool(tool)

  @doc "Remove a globally registered tool by name. No-op if not found."
  @spec unregister_tool(String.t()) :: :ok
  def unregister_tool(name), do: ResourceStore.unregister_tool(name)

  @doc """
  Persist a provider entry to the JSON config and API key to `.env`, then
  reload resources.

  Options:
  - `:id` (required) — provider key written to `providers` map (e.g. `"anthropic"`, `"nvidia"`)
  - `:type` (required) — `"anthropic"`, `"openai"`, or `"google"`
  - `:base_url` — for OpenAI-compatible endpoints
  - `:identifier` — uppercase tag for env var derivation (`"NVIDIA"` → `NVIDIA_API_KEY`)
  - `:has_api_key` — set `false` for keyless local servers; default `true`
  - `:api_key` — written to `<scope>/.env`
  - `:scope` — `:local` (default, `.planck/`) or `:global` (`~/.planck/`)
  """
  @spec configure_provider(keyword()) :: :ok | {:error, term()}
  def configure_provider(opts) do
    id = Keyword.fetch!(opts, :id)
    type = Keyword.fetch!(opts, :type)
    scope = Keyword.get(opts, :scope, :local)
    api_key = Keyword.get(opts, :api_key)
    base_url = Keyword.get(opts, :base_url)
    identifier = Keyword.get(opts, :identifier)
    has_api_key = Keyword.get(opts, :has_api_key, true)

    config_path = Keyword.get(opts, :config_file) || config_path_for(scope)
    env_path = Keyword.get(opts, :env_file) || env_path_for(scope)

    entry =
      %{"type" => type}
      |> maybe_put("base_url", base_url)
      |> maybe_put("identifier", identifier)
      |> then(fn m -> if has_api_key, do: m, else: Map.put(m, "has_api_key", false) end)

    config_update = %{"providers" => %{id => entry}}

    effective_api_key = if has_api_key, do: api_key, else: nil

    with :ok <- ensure_config_dir(config_path),
         :ok <- update_json_config(config_path, config_update),
         :ok <- maybe_write_provider_api_key(env_path, type, effective_api_key, identifier) do
      reload_resources()
    end
  end

  @doc """
  Persist a model entry to the JSON config, then reload resources so the new
  model is immediately available.

  Options:
  - `:id` (required) — user alias (e.g. `"sonnet"`)
  - `:model` (required) — provider model identifier (e.g. `"claude-sonnet-4-6"`)
  - `:provider` (required) — key referencing an entry in the `providers` map
  - `:scope` — `:local` (default, `.planck/`) or `:global` (`~/.planck/`)
  - `:default` — set as `default_model` (default: `true`)
  - `:params` — inference parameters map (e.g. `%{"temperature" => 0.7}`)
  """
  @spec configure_model(keyword()) :: :ok | {:error, term()}
  def configure_model(opts) do
    id = Keyword.fetch!(opts, :id)
    model_id = Keyword.fetch!(opts, :model)
    provider = Keyword.fetch!(opts, :provider)
    scope = Keyword.get(opts, :scope, :local)
    set_default = Keyword.get(opts, :default, true)
    params = Keyword.get(opts, :params)

    config_path = Keyword.get(opts, :config_file) || config_path_for(scope)

    entry =
      %{"id" => id, "model" => model_id, "provider" => provider}
      |> maybe_put("params", params)

    config_update =
      if set_default,
        do: %{"default_model" => id, "models" => [entry]},
        else: %{"models" => [entry]}

    with :ok <- ensure_config_dir(config_path),
         :ok <- update_json_config(config_path, config_update) do
      reload_resources()
    end
  end

  @doc """
  Reload tools, skills, teams, and the compactor from disk.
  In-flight sessions keep their original resources.
  """
  @spec reload_resources() :: :ok
  def reload_resources do
    JsonBinding.invalidate()
    EnvBinding.invalidate()
    # Clear Skogsra's own persistent_term caches for every key that reads from
    # the JSON or .env bindings, so the next access re-resolves from disk.
    Config.reload_default_provider()
    Config.reload_default_model()
    Config.reload_providers()
    Config.reload_models()
    Config.reload_locale()
    Config.reload_sessions_dir()
    Config.reload_skills_dirs()
    Config.reload_teams_dirs()
    Config.reload_sidecar()
    Config.reload_anthropic_api_key()
    Config.reload_openai_api_key()
    Config.reload_google_api_key()
    ResourceStore.reload()
  end

  # ---------------------------------------------------------------------------
  # Private — session lifecycle
  # ---------------------------------------------------------------------------

  @spec locate_session(Path.t(), String.t()) ::
          {:ok, String.t(), String.t()} | {:error, term()}
  defp locate_session(sessions_dir, id_or_name) do
    with {:error, :not_found} <- Session.find_by_id(sessions_dir, id_or_name),
         {:ok, _path, id} <- Session.find_by_name(sessions_dir, id_or_name) do
      {:ok, id, id_or_name}
    else
      {:ok, _path, name} ->
        {:ok, id_or_name, name}

      {:error, :not_found} ->
        {:error, {:session_not_found, id_or_name}}
    end
  end

  @spec reopen_session(String.t(), String.t(), Path.t()) ::
          {:ok, pid()} | {:error, term()}
  defp reopen_session(session_id, session_name, sessions_dir) do
    case Session.whereis(session_id) do
      {:ok, pid} ->
        {:ok, pid}

      {:error, :not_found} ->
        Session.start(session_id, name: session_name, dir: sessions_dir)
    end
  end

  @spec create_session(String.t(), Path.t()) :: {:ok, String.t()} | {:error, term()}
  defp create_session(session_name, _cwd) do
    session_id = generate_id()
    sessions_dir = Config.sessions_dir!() |> Path.expand()

    case Session.start(session_id, name: session_name, dir: sessions_dir) do
      {:ok, _pid} -> {:ok, session_id}
      {:error, reason} -> {:error, {:session_start_failed, reason}}
    end
  end

  @spec save_metadata(
          String.t(),
          term(),
          String.t(),
          Path.t(),
          String.t(),
          map(),
          String.t() | nil
        ) :: :ok
  defp save_metadata(session_id, template, session_name, cwd, team_id, agent_id_map, description) do
    team_alias =
      case template do
        nil -> nil
        alias when is_binary(alias) -> alias
      end

    Session.save_metadata(session_id, %{
      "team_alias" => team_alias,
      "team_description" => description,
      "team_id" => team_id,
      "session_name" => session_name,
      "cwd" => cwd,
      "agent_ids" => Jason.encode!(agent_id_map)
    })
  end

  # Build a name → id map for all agents in a team, keyed by their display name.
  # Used to preserve agent IDs across session resumes.
  @spec agent_ids(String.t()) :: %{String.t() => String.t()}
  defp agent_ids(team_id) do
    Registry.lookup(Planck.Agent.Registry, {team_id, :member})
    |> Map.new(fn {_pid, meta} -> {meta.name || meta.type, meta.id} end)
  end

  @spec decode_agent_ids(String.t() | nil) :: %{String.t() => String.t()}
  defp decode_agent_ids(nil), do: %{}

  defp decode_agent_ids(json) do
    case Jason.decode(json) do
      {:ok, map} -> map
      _ -> %{}
    end
  end

  @spec read_team_id(String.t()) :: {:ok, String.t()} | {:error, term()}
  defp read_team_id(session_id) do
    with {:ok, meta} <- Session.get_metadata(session_id) do
      case meta["team_id"] do
        nil -> {:error, :team_id_not_found}
        team_id -> {:ok, team_id}
      end
    end
  end

  @spec resolve_name(String.t() | nil) :: {:ok, String.t()} | {:error, term()}
  defp resolve_name(nil) do
    sessions_dir = Config.sessions_dir!() |> Path.expand()

    case SessionName.generate(sessions_dir) do
      {:ok, name} -> {:ok, name}
      {:error, :exhausted} -> {:error, :session_name_exhausted}
    end
  end

  defp resolve_name(name) do
    case SessionName.sanitize(name) do
      {:ok, sanitized} -> {:ok, sanitized}
      {:error, :invalid} -> {:error, {:invalid_session_name, name}}
    end
  end

  @spec resolve_team(term()) :: {:ok, Team.t()} | {:error, term()}
  defp resolve_team(nil), do: build_dynamic_team()

  defp resolve_team(alias) when is_binary(alias) do
    case get_team(alias) do
      {:ok, team} ->
        {:ok, team}

      {:error, :not_found} ->
        expanded = Path.expand(alias)

        if File.dir?(expanded) do
          Team.load(expanded)
        else
          {:error, {:team_not_found, alias}}
        end
    end
  end

  @spec build_dynamic_team() :: {:ok, Team.t()} | {:error, term()}
  defp build_dynamic_team do
    model_alias = Config.default_model!()

    if is_nil(model_alias) do
      {:error,
       {:no_default_model_configured,
        "Set default_model in ~/.planck/config.json or via PLANCK_DEFAULT_MODEL"}}
    else
      store = ResourceStore.get()

      case Enum.find(store.available_models, &(&1.id == model_alias)) do
        nil ->
          {:error,
           {:default_model_not_available,
            "Model #{inspect(model_alias)} not found — check providers and models in config"}}

        model ->
          orchestrator =
            AgentSpec.new(
              type: "orchestrator",
              provider: model.provider,
              model_id: model.id,
              base_url: model.base_url,
              system_prompt: DefaultPrompt.orchestrator(),
              tools: builtin_tool_names() ++ Enum.map(store.tools, & &1.name),
              skills: Enum.map(store.skills, & &1.name)
            )

          {:ok, Team.dynamic(orchestrator)}
      end
    end
  end

  # ---------------------------------------------------------------------------
  # Private — team materialization
  # ---------------------------------------------------------------------------

  @spec materialize_team(String.t(), Team.t(), Path.t(), keyword()) ::
          {:ok, String.t()} | {:error, term()}
  defp materialize_team(session_id, team, cwd, opts) do
    prev_ids = Keyword.get(opts, :prev_ids, %{})
    metadata = Keyword.get(opts, :metadata, %{})
    session_tools = Keyword.get(opts, :session_tools, [])

    ctx = %{
      prev_ids: prev_ids,
      metadata: metadata,
      session_tools: session_tools,
      team_name: team.alias || "default"
    }

    store = ResourceStore.get()
    team_id = generate_id()

    orch_spec = Enum.find(team.members, &(&1.type == "orchestrator"))
    workers = Enum.reject(team.members, &(&1.type == "orchestrator"))
    orchestrator_id = Map.get(prev_ids, orch_spec.name || orch_spec.type, generate_id())

    with {:ok, _} <-
           start_orchestrator(session_id, team_id, orchestrator_id, orch_spec, store, cwd, ctx),
         :ok <- start_workers(session_id, team_id, orchestrator_id, workers, store, cwd, ctx) do
      {:ok, team_id}
    end
  end

  @spec start_orchestrator(
          String.t(),
          String.t(),
          String.t(),
          AgentSpec.t(),
          ResourceStore.t(),
          Path.t(),
          %{
            metadata: map(),
            session_tools: [Planck.Agent.Tool.t()],
            prev_ids: map(),
            team_name: String.t() | nil
          }
        ) :: {:ok, pid()} | {:error, term()}
  defp start_orchestrator(session_id, team_id, orchestrator_id, spec, store, cwd, ctx) do
    %{metadata: metadata, session_tools: session_tools} = ctx

    skill_opts =
      build_skill_opts(ctx.team_name, spec.name, spec.type, store.skills, cwd)

    default_tools = if spec.tools == [], do: builtins(), else: []

    base_opts =
      AgentSpec.to_start_opts(spec,
        tool_pool:
          builtins() ++
            store.tools ++
            store.registered_tools ++ skill_discovery_tools(store.skills),
        tools: default_tools,
        skill_pool: store.skills,
        skill_refresh_fn: fn -> ResourceStore.get().skills end,
        on_skill_use: skill_opts[:on_skill_use],
        team_id: team_id,
        session_id: session_id,
        available_models: store.available_models
      )

    resolved = base_opts[:tools]

    full_tools =
      Tools.orchestrator_tools(
        session_id,
        team_id,
        store.available_models,
        resolved,
        store.skills,
        cwd
      ) ++
        Tools.worker_tools(team_id, nil) ++
        skill_discovery_tools(store.skills) ++
        resolved ++
        store.registered_tools ++
        session_tools

    system_prompt = Tools.prepend_agents_md(base_opts[:system_prompt], cwd)
    {usage, cost} = load_agent_usage(metadata, orchestrator_id)

    opts =
      base_opts
      |> Keyword.put(:id, orchestrator_id)
      |> Keyword.put(:cwd, cwd)
      |> Keyword.put(:tools, full_tools)
      |> Keyword.put(:system_prompt, system_prompt)
      |> Keyword.put(:compactor, resolve_hook_module(spec.compactor))
      |> Keyword.put(:prompt_hook, resolve_hook_module(spec.prompt_hook))
      |> Keyword.put(:turn_end_hook, resolve_hook_module(spec.turn_end_hook))
      |> Keyword.put(:sidecar_node, SidecarManager.node())
      |> Keyword.put(:team_name, ctx.team_name)
      |> Keyword.put(:ranked_skill_names, skill_opts[:ranked_skill_names])
      |> Keyword.put(:top_skills, skill_opts[:top_skills])
      |> Keyword.put(:skill_pool, skill_opts[:skill_pool])
      |> Keyword.put(:usage, usage)
      |> Keyword.put(:cost, cost)

    start_agent(opts)
  end

  @spec start_workers(
          String.t(),
          String.t(),
          String.t(),
          [AgentSpec.t()],
          ResourceStore.t(),
          Path.t(),
          %{
            prev_ids: map(),
            metadata: map(),
            session_tools: [Planck.Agent.Tool.t()],
            team_name: String.t() | nil
          }
        ) :: :ok | {:error, term()}
  defp start_workers(session_id, team_id, orchestrator_id, workers, store, cwd, ctx) do
    %{prev_ids: prev_ids, metadata: metadata, session_tools: session_tools} = ctx

    Enum.reduce_while(workers, :ok, fn spec, :ok ->
      base_opts =
        AgentSpec.to_start_opts(spec,
          tool_pool:
            builtins() ++
              store.tools ++ store.registered_tools ++ skill_discovery_tools(store.skills),
          skill_pool: store.skills,
          skill_refresh_fn: fn -> ResourceStore.get().skills end,
          team_id: team_id,
          session_id: session_id,
          available_models: store.available_models
        )

      resolved = base_opts[:tools]
      worker_id = Map.get(prev_ids, spec.name, base_opts[:id])
      sender = %{id: worker_id, name: spec.name}
      {usage, cost} = load_agent_usage(metadata, worker_id)
      system_prompt = Tools.prepend_agents_md(base_opts[:system_prompt], cwd)

      skill_opts =
        build_skill_opts(ctx.team_name, spec.name, spec.type, store.skills, cwd)

      opts =
        base_opts
        |> Keyword.put(:id, worker_id)
        |> Keyword.put(:cwd, cwd)
        |> Keyword.put(
          :tools,
          Tools.worker_tools(team_id, orchestrator_id, sender) ++
            resolved ++ store.registered_tools ++ session_tools
        )
        |> Keyword.put(:system_prompt, system_prompt)
        |> Keyword.put(:delegator_id, orchestrator_id)
        |> Keyword.put(:compactor, resolve_hook_module(spec.compactor))
        |> Keyword.put(:prompt_hook, resolve_hook_module(spec.prompt_hook))
        |> Keyword.put(:turn_end_hook, resolve_hook_module(spec.turn_end_hook))
        |> Keyword.put(:sidecar_node, SidecarManager.node())
        |> Keyword.put(:team_name, ctx.team_name)
        |> Keyword.put(:ranked_skill_names, skill_opts[:ranked_skill_names])
        |> Keyword.put(:top_skills, skill_opts[:top_skills])
        |> Keyword.put(:skill_pool, skill_opts[:skill_pool])
        |> Keyword.put(:usage, usage)
        |> Keyword.put(:cost, cost)

      case start_agent(opts) do
        {:ok, _pid} -> {:cont, :ok}
        {:error, reason} -> {:halt, {:error, reason}}
      end
    end)
  end

  @spec resolve_hook_module(String.t() | nil) :: module() | nil
  defp resolve_hook_module(nil), do: nil
  defp resolve_hook_module(name), do: :"Elixir.#{name}"

  @spec build_skill_opts(String.t(), String.t(), String.t(), [Skill.t()], Path.t()) :: keyword()
  defp build_skill_opts(team_name, agent_name, agent_type, skills, cwd) do
    top_n = Config.top_skills!()

    ranked = SkillUsage.ranked_names(cwd, team_name, agent_name, skills, top_n)

    [
      ranked_skill_names: ranked,
      top_skills: top_n,
      skill_pool: skills,
      on_skill_use: fn _agent_id, skill_name ->
        SkillUsage.record_use(cwd, team_name, agent_name, agent_type, skill_name)
      end,
      skill_index_refresh_fn: fn ->
        current = ResourceStore.get().skills

        new_ranked = SkillUsage.ranked_names(cwd, team_name, agent_name, current, top_n)

        {current, new_ranked}
      end
    ]
  end

  # list_skills is opt-in: agents declare "list_skills" in their TEAM.json tools
  # array to get autonomous skill discovery. load_skill is injected automatically
  # by AgentSpec.to_start_opts when skill_pool is non-empty.
  @spec skill_discovery_tools([Skill.t()]) :: [Planck.Agent.Tool.t()]
  defp skill_discovery_tools([]), do: []

  defp skill_discovery_tools(skills) do
    base = Skill.list_skills_tool(skills)

    execute_fn =
      fn _agent_id, _id, _args ->
        current = ResourceStore.get().skills

        entries =
          Enum.map_join(current, "\n", fn %Skill{name: name, description: desc} ->
            "- **#{name}**: #{desc}"
          end)

        if entries == "", do: {:ok, "No skills available."}, else: {:ok, entries}
      end

    [%{base | execute_fn: execute_fn}]
  end

  @spec load_agent_usage(map(), String.t()) ::
          {%{input_tokens: non_neg_integer(), output_tokens: non_neg_integer()}, float()}
  defp load_agent_usage(metadata, agent_id) do
    with json when not is_nil(json) <- Map.get(metadata, "agent_usage:#{agent_id}"),
         {:ok, %{"input_tokens" => i, "output_tokens" => o, "cost" => c}} <- Jason.decode(json) do
      {%{input_tokens: i, output_tokens: o}, c}
    else
      _ -> {%{input_tokens: 0, output_tokens: 0}, 0.0}
    end
  end

  @spec start_agent(keyword()) :: {:ok, pid()} | {:error, term()}
  defp start_agent(opts) do
    case DynamicSupervisor.start_child(Planck.Agent.AgentSupervisor, {Planck.Agent, opts}) do
      {:ok, pid} -> {:ok, pid}
      {:error, reason} -> {:error, {:agent_start_failed, reason}}
    end
  end

  # ---------------------------------------------------------------------------
  # Private — session helpers
  # ---------------------------------------------------------------------------

  @spec stop_team(String.t()) :: :ok
  defp stop_team(team_id) do
    Planck.Agent.Registry
    |> Registry.lookup({team_id, :member})
    |> Enum.each(fn {pid, _} ->
      DynamicSupervisor.terminate_child(Planck.Agent.AgentSupervisor, pid)
    end)
  end

  @spec find_orchestrator(String.t()) :: {:ok, pid()} | {:error, :orchestrator_not_found}
  defp find_orchestrator(team_id) do
    case Registry.lookup(Planck.Agent.Registry, {team_id, "orchestrator"}) do
      [{pid, _} | _] -> {:ok, pid}
      [] -> {:error, :orchestrator_not_found}
    end
  end

  # After the base team is materialised, replay any spawn_agent calls that
  # completed during the original session but are not part of the base team.
  # This reconstructs dynamic workers added at runtime by the orchestrator.
  @spec reconstruct_dynamic_workers(String.t(), String.t(), Team.t()) :: :ok
  defp reconstruct_dynamic_workers(session_id, team_id, base_team) do
    with {:ok, all_rows} <- Session.messages(session_id),
         {:ok, orch_pid} <- find_orchestrator(team_id) do
      orch_id = Agent.get_info(orch_pid).id
      messages_by_agent = Enum.group_by(all_rows, & &1.agent_id, & &1.message)
      orch_messages = Map.get(messages_by_agent, orch_id, [])

      # Workers are identified by {type, name}. Name defaults to type when absent,
      # matching AgentSpec.default_name/2 behaviour.
      base_members =
        MapSet.new(base_team.members, fn m -> {m.type, m.name} end)

      store = ResourceStore.get()

      orch_messages
      |> completed_spawn_calls()
      |> Enum.reject(fn {args, _id} ->
        type = args["type"]
        name = args["name"] || type
        MapSet.member?(base_members, {type, name})
      end)
      |> Enum.reverse()
      |> Enum.uniq_by(fn {args, _id} ->
        type = args["type"]
        name = args["name"] || type
        {type, name}
      end)
      |> Enum.each(fn {args, original_id} ->
        start_dynamic_worker(args, session_id, team_id, orch_id, store, original_id)
      end)
    end

    :ok
  end

  # Returns {args, original_worker_id} pairs. The worker ID is extracted from
  # the spawn_agent tool result so it matches the ID under which the worker's
  # messages were stored, restoring history on resume.
  @spec completed_spawn_calls([Planck.Agent.Message.t()]) :: [{map(), String.t() | nil}]
  defp completed_spawn_calls(messages) do
    results_by_id =
      messages
      |> Enum.flat_map(fn msg ->
        Enum.flat_map(msg.content, fn
          {:tool_result, id, result} -> [{id, result}]
          _ -> []
        end)
      end)
      |> Map.new()

    messages
    |> Enum.filter(&(&1.role == :assistant))
    |> Enum.flat_map(&completed_spawn_parts(&1.content, results_by_id))
  end

  @spec completed_spawn_parts([term()], %{String.t() => term()}) :: [{map(), String.t() | nil}]
  defp completed_spawn_parts(content, results_by_id) do
    Enum.flat_map(content, fn
      {:tool_call, id, "spawn_agent", args} -> successful_spawn(Map.get(results_by_id, id), args)
      _ -> []
    end)
  end

  @spec successful_spawn(term(), map()) :: [{map(), String.t()}]
  defp successful_spawn(worker_id, args)
       when is_binary(worker_id) and not is_nil(worker_id) do
    if String.starts_with?(worker_id, "Error"), do: [], else: [{args, worker_id}]
  end

  defp successful_spawn(_result, _args), do: []

  @spec start_dynamic_worker(
          map(),
          String.t(),
          String.t(),
          String.t(),
          ResourceStore.t(),
          String.t() | nil
        ) :: :ok
  defp start_dynamic_worker(args, session_id, team_id, orchestrator_id, store, original_id) do
    case AgentSpec.from_map(args) do
      {:ok, spec} ->
        base_opts =
          AgentSpec.to_start_opts(spec,
            tool_pool:
              builtins() ++
                store.tools ++ store.registered_tools ++ skill_discovery_tools(store.skills),
            skill_pool: store.skills,
            skill_refresh_fn: fn -> ResourceStore.get().skills end,
            team_id: team_id,
            session_id: session_id,
            available_models: store.available_models
          )

        base_opts =
          if original_id, do: Keyword.put(base_opts, :id, original_id), else: base_opts

        dynamic_worker_id = base_opts[:id]
        sender = %{id: dynamic_worker_id, name: spec.name}

        opts =
          base_opts
          |> Keyword.put(
            :tools,
            Tools.worker_tools(team_id, orchestrator_id, sender) ++
              base_opts[:tools]
          )
          |> Keyword.put(:delegator_id, orchestrator_id)
          |> Keyword.put(:compactor, resolve_hook_module(spec.compactor))
          |> Keyword.put(:prompt_hook, resolve_hook_module(spec.prompt_hook))
          |> Keyword.put(:turn_end_hook, resolve_hook_module(spec.turn_end_hook))
          |> Keyword.put(:sidecar_node, SidecarManager.node())
          |> Keyword.put(:team_name, nil)

        case start_agent(opts) do
          {:ok, _} ->
            :ok

          {:error, r} ->
            Logger.warning("[Planck.Headless] could not reconstruct worker: #{inspect(r)}")
        end

      {:error, reason} ->
        Logger.warning("[Planck.Headless] skipping worker reconstruction: #{reason}")
    end

    :ok
  end

  @spec maybe_inject_recovery(String.t(), String.t()) :: :ok
  defp maybe_inject_recovery(session_id, team_id) do
    with {:ok, orch_pid} <- find_orchestrator(team_id),
         {:ok, all_rows} <- Session.messages(session_id) do
      orch_id = Agent.get_info(orch_pid).id
      messages_by_agent = Enum.group_by(all_rows, & &1.agent_id, & &1.message)
      orch_messages = Map.get(messages_by_agent, orch_id, [])

      in_flight =
        if last_message_is_recovery?(orch_messages),
          do: [],
          else: unfinished_workers(messages_by_agent, orch_id, orch_messages)

      if in_flight != [] do
        Session.append(session_id, orch_id, build_recovery_message(in_flight))
      end
    end

    :ok
  end

  @recovery_marker "Session resumed after interruption."

  @spec last_message_is_recovery?([Planck.Agent.Message.t()]) :: boolean()
  defp last_message_is_recovery?(messages) do
    case List.last(messages) do
      %{role: :user, content: [{:text, text}]} -> String.starts_with?(text, @recovery_marker)
      _ -> false
    end
  end

  @orchestrator_tools ~w(call_agent send_agent spawn_agent)

  @spec has_orchestrator_tool_calls?([Planck.Agent.Message.t()]) :: boolean()
  defp has_orchestrator_tool_calls?(messages) do
    Enum.any?(messages, fn msg ->
      msg.role == :assistant &&
        Enum.any?(msg.content, fn
          {:tool_call, _, name, _} -> name in @orchestrator_tools
          _ -> false
        end)
    end)
  end

  @spec build_recovery_message([{String.t(), String.t()}]) :: Planck.Agent.Message.t()
  defp build_recovery_message(in_flight) do
    lines = Enum.map_join(in_flight, "\n", fn {tool, desc} -> "- #{tool}: #{desc}" end)

    body = """
    #{@recovery_marker} The following tasks were still in progress when the session ended:

    #{lines}

    The workers listed above are idle and waiting for instructions. Before re-delegating, \
    you can ask each of them where they left off — they retain their context and can \
    continue from that point if you see it fit.
    """

    Message.new(:user, [{:text, String.trim(body)}])
  end

  # Find workers (non-orchestrator agent_ids) whose last received task has no
  # respond_agent after it. For each, find the LAST orchestrator tool call
  # (call_agent or send_agent) that matches the worker's pending task text —
  # that determines both the tool type and the target label in the report.
  @spec unfinished_workers(
          %{String.t() => [Planck.Agent.Message.t()]},
          String.t(),
          [Planck.Agent.Message.t()]
        ) :: [{String.t(), String.t()}]
  defp unfinished_workers(messages_by_agent, orch_id, orch_messages) do
    orchestrator_ids =
      MapSet.new(messages_by_agent, fn {id, msgs} ->
        if has_orchestrator_tool_calls?(msgs), do: id, else: nil
      end)
      |> MapSet.delete(nil)
      |> MapSet.put(orch_id)

    messages_by_agent
    |> Enum.reject(fn {id, _} -> MapSet.member?(orchestrator_ids, id) end)
    |> Enum.flat_map(fn {_worker_id, msgs} ->
      task_text = worker_task_text(msgs)
      interaction = last_orchestrator_interaction(task_text, orch_messages)
      pending_interaction_entry(interaction, msgs)
    end)
  end

  @spec pending_interaction_entry(
          {String.t(), String.t(), String.t()} | nil,
          [Planck.Agent.Message.t()]
        ) :: [{String.t(), String.t()}]
  defp pending_interaction_entry(nil, _msgs), do: []

  defp pending_interaction_entry({"call_agent", target, task}, msgs) do
    if worker_answered_ask?(msgs) do
      []
    else
      [{"call_agent", "#{target}: #{truncate(task, 80)}"}]
    end
  end

  defp pending_interaction_entry({"send_agent", target, task}, msgs) do
    if worker_sent_response?(msgs),
      do: [],
      else: [{"send_agent", "#{target} did not complete: #{truncate(task, 80)}"}]
  end

  # Find the LAST call_agent or send_agent call from the orchestrator whose
  # question/task text matches the worker's current pending task text.
  @spec last_orchestrator_interaction(String.t(), [Planck.Agent.Message.t()]) ::
          {String.t(), String.t(), String.t()} | nil
  defp last_orchestrator_interaction(task_text, orch_messages) do
    orch_messages
    |> Enum.filter(&(&1.role == :assistant))
    |> Enum.flat_map(&match_interactions(&1.content, task_text))
    |> List.last()
  end

  @spec match_interactions([term()], String.t()) :: [{String.t(), String.t(), String.t()}]
  defp match_interactions(content, task_text) do
    Enum.flat_map(content, fn
      {:tool_call, _, tool, args} when tool in ["call_agent", "send_agent"] ->
        content_text = args["question"] || args["task"] || ""

        if content_text == task_text do
          [{tool, args["identifier"] || "worker", task_text}]
        else
          []
        end

      _ ->
        []
    end)
  end

  # The worker's last :user message is their current pending task text.
  @spec worker_task_text([Planck.Agent.Message.t()]) :: String.t()
  defp worker_task_text(messages) do
    case Enum.filter(messages, &(&1.role == :user)) |> List.last() do
      nil ->
        ""

      msg ->
        msg.content
        |> Enum.flat_map(fn
          {:text, t} -> [t]
          _ -> []
        end)
        |> Enum.join("")
    end
  end

  @spec truncate(String.t(), non_neg_integer()) :: String.t()
  defp truncate(text, max) do
    if String.length(text) > max,
      do: String.slice(text, 0, max) <> "…",
      else: text
  end

  # send_agent: done when the worker has called respond_agent after the last task.
  @spec worker_sent_response?([Planck.Agent.Message.t()]) :: boolean()
  defp worker_sent_response?(msgs) do
    msgs_after_last_user(msgs)
    |> Enum.any?(fn msg ->
      msg.role == :assistant &&
        Enum.any?(msg.content, fn
          {:tool_call, _, "respond_agent", _} -> true
          _ -> false
        end)
    end)
  end

  # call_agent: done when the worker has produced any assistant turn after the question.
  @spec worker_answered_ask?([Planck.Agent.Message.t()]) :: boolean()
  defp worker_answered_ask?(msgs) do
    msgs_after_last_user(msgs)
    |> Enum.any?(&(&1.role == :assistant))
  end

  @spec msgs_after_last_user([Planck.Agent.Message.t()]) :: [Planck.Agent.Message.t()]
  defp msgs_after_last_user(msgs) do
    case msgs
         |> Enum.with_index()
         |> Enum.filter(fn {m, _} -> m.role == :user end)
         |> List.last() do
      nil -> []
      {_, idx} -> Enum.drop(msgs, idx + 1)
    end
  end

  @spec builtins() :: [Planck.Agent.Tool.t()]
  defp builtins do
    [BuiltinTools.read(), BuiltinTools.write(), BuiltinTools.edit(), BuiltinTools.bash()]
  end

  @spec builtin_tool_names() :: [String.t()]
  defp builtin_tool_names, do: Enum.map(builtins(), & &1.name)

  @spec generate_id() :: String.t()
  defp generate_id do
    :crypto.strong_rand_bytes(8) |> Base.encode16(case: :lower)
  end

  # ---------------------------------------------------------------------------
  # Private — configure_model helpers
  # ---------------------------------------------------------------------------

  @spec config_path_for(:local | :global) :: Path.t()
  defp config_path_for(:local), do: ".planck/config.json"
  defp config_path_for(:global), do: "~/.planck/config.json"

  @spec env_path_for(:local | :global) :: Path.t()
  defp env_path_for(:local), do: ".planck/.env"
  defp env_path_for(:global), do: "~/.planck/.env"

  @spec maybe_put(map(), String.t(), term()) :: map()
  defp maybe_put(map, _key, nil), do: map
  defp maybe_put(map, key, value), do: Map.put(map, key, value)

  @spec ensure_config_dir(Path.t()) :: :ok | {:error, File.posix()}
  defp ensure_config_dir(path) do
    case path |> Path.expand() |> Path.dirname() |> File.mkdir_p() do
      :ok -> :ok
      {:error, reason} -> {:error, reason}
    end
  end

  @spec update_json_config(Path.t(), map()) :: :ok | {:error, term()}
  defp update_json_config(path, update) do
    expanded = Path.expand(path)

    existing =
      case File.read(expanded) do
        {:ok, content} -> Jason.decode!(content)
        {:error, :enoent} -> %{}
      end

    merged =
      Map.merge(existing, update, fn
        "models", old, new -> Enum.uniq_by(new ++ old, & &1["id"])
        "providers", old, new -> Map.merge(old, new)
        _key, _old, new -> new
      end)

    case Jason.encode(merged, pretty: true) do
      {:ok, json} -> File.write(expanded, json)
      error -> error
    end
  end

  @spec maybe_write_provider_api_key(Path.t(), String.t(), String.t() | nil, String.t() | nil) ::
          :ok | {:error, term()}
  defp maybe_write_provider_api_key(_path, _type, key, _id) when key in [nil, ""], do: :ok

  defp maybe_write_provider_api_key(path, type, api_key, identifier) do
    case provider_api_key_env_var(type, identifier) do
      nil -> :ok
      env_var -> write_env_var(path, env_var, api_key)
    end
  end

  @spec provider_api_key_env_var(String.t(), String.t() | nil) :: String.t() | nil
  defp provider_api_key_env_var("anthropic", _), do: "ANTHROPIC_API_KEY"
  defp provider_api_key_env_var("google", _), do: "GOOGLE_API_KEY"
  defp provider_api_key_env_var("openai", id) when is_binary(id) and id != "", do: "#{id}_API_KEY"
  defp provider_api_key_env_var("openai", _), do: "OPENAI_API_KEY"
  defp provider_api_key_env_var(_, _), do: nil

  @spec write_env_var(Path.t(), String.t(), String.t()) :: :ok | {:error, term()}
  defp write_env_var(path, env_var, value) do
    expanded = Path.expand(path)
    :ok = ensure_config_dir(path)

    lines =
      case File.read(expanded) do
        {:ok, content} -> String.split(content, "\n", trim: true)
        {:error, :enoent} -> []
      end

    {found, updated} =
      Enum.reduce(lines, {false, []}, fn line, {found, acc} ->
        upsert_env_line(line, env_var, value, found, acc)
      end)

    final = if found, do: updated, else: ["#{env_var}=#{value}" | updated]
    File.write(expanded, final |> Enum.reverse() |> Enum.join("\n") |> Kernel.<>("\n"))
  end

  @spec upsert_env_line(String.t(), String.t(), String.t(), boolean(), [String.t()]) ::
          {boolean(), [String.t()]}
  defp upsert_env_line(line, env_var, value, found, acc) do
    if String.starts_with?(line, "#{env_var}=") do
      {true, ["#{env_var}=#{value}" | acc]}
    else
      {found, [line | acc]}
    end
  end
end