cmdc

defmodule CMDC.Memory.ETS do
  @moduledoc """
  基于 ETS 的内存 Memory 实现。

  适用于开发、测试或对持久化无要求的场景。进程退出后数据丢失。
  ETS 表类型为 `:set`，以 entry id 为 key，entry map 为 value。

  文本搜索采用关键词包含匹配（大小写不敏感），未来可升级为向量检索。

  ## 使用方式

      {:ok, mem} = CMDC.Memory.ETS.new(:agent_memory)
      :ok = CMDC.Memory.ETS.store(mem, "s1", %{content: "任务完成", outcome: :success})
      {:ok, results} = CMDC.Memory.ETS.search(mem, "任务", limit: 5)
      {:ok, all} = CMDC.Memory.ETS.list(mem)
      :ok = CMDC.Memory.ETS.delete(mem, "s1")
  """

  @behaviour CMDC.Memory

  @type store :: atom()

  # ==========================================================================
  # Public API
  # ==========================================================================

  @doc """
  创建或获取一个 ETS Memory 表。

  若同名表已存在，直接返回 `{:ok, name}`，不报错。
  第二参数 `opts` 保留扩展（当前未使用）。
  """
  @spec new(atom(), keyword()) :: {:ok, store()}
  def new(name, _opts \\ []) when is_atom(name) do
    case :ets.info(name) do
      :undefined ->
        :ets.new(name, [:set, :public, :named_table])
        {:ok, name}

      _ ->
        {:ok, name}
    end
  end

  # ==========================================================================
  # CMDC.Memory callbacks
  # ==========================================================================

  @impl true
  @spec store(store(), CMDC.Memory.entry_id(), map()) :: :ok | {:error, term()}
  def store(store, id, data) when is_binary(id) and is_map(data) do
    entry =
      data
      |> Map.put(:id, id)
      |> Map.put_new(:inserted_at, DateTime.utc_now())

    :ets.insert(store, {id, entry})
    :ok
  end

  @impl true
  @spec search(store(), String.t(), CMDC.Memory.search_opts()) ::
          {:ok, [CMDC.Memory.entry()]} | {:error, term()}
  def search(store, query, opts \\ []) when is_binary(query) do
    limit = Keyword.get(opts, :limit, 10)
    order = Keyword.get(opts, :order, :desc)
    filters = Keyword.get(opts, :filters, [])
    query_lower = String.downcase(query)

    results =
      store
      |> :ets.tab2list()
      |> Enum.map(fn {_id, entry} -> entry end)
      |> Enum.filter(&entry_matches?(&1, query_lower))
      |> apply_filters(filters)
      |> sort_by_inserted_at(order)
      |> Enum.take(limit)

    {:ok, results}
  end

  @impl true
  @spec similarity_search(store(), String.t(), CMDC.Memory.search_opts()) ::
          {:ok, [map()]} | {:error, term()}
  def similarity_search(store, query, opts \\ []) when is_binary(query) do
    limit = Keyword.get(opts, :limit, 5)
    filters = Keyword.get(opts, :filters, [])
    query_lower = String.downcase(query)

    results =
      store
      |> :ets.tab2list()
      |> Enum.map(fn {_id, entry} -> entry end)
      |> Enum.filter(&entry_matches?(&1, query_lower))
      |> apply_filters(filters)
      |> sort_by_inserted_at(:desc)
      |> Enum.take(limit)

    {:ok, results}
  end

  @impl true
  @spec list(store()) :: {:ok, [CMDC.Memory.entry()]} | {:error, term()}
  def list(store) do
    entries =
      store
      |> :ets.tab2list()
      |> Enum.map(fn {_id, entry} -> entry end)
      |> sort_by_inserted_at(:desc)

    {:ok, entries}
  end

  @impl true
  @spec delete(store(), CMDC.Memory.entry_id()) :: :ok | {:error, term()}
  def delete(store, id) when is_binary(id) do
    :ets.delete(store, id)
    :ok
  end

  # ==========================================================================
  # 私有辅助
  # ==========================================================================

  defp entry_matches?(%{content: content}, query_lower) when is_binary(content) do
    String.contains?(String.downcase(content), query_lower)
  end

  defp entry_matches?(_entry, _query_lower), do: false

  defp apply_filters(entries, []), do: entries

  defp apply_filters(entries, filters) do
    Enum.filter(entries, fn entry ->
      Enum.all?(filters, fn {key, val} -> Map.get(entry, key) == val end)
    end)
  end

  defp sort_by_inserted_at(entries, :asc),
    do: Enum.sort_by(entries, & &1[:inserted_at], {:asc, DateTime})

  defp sort_by_inserted_at(entries, _desc),
    do: Enum.sort_by(entries, & &1[:inserted_at], {:desc, DateTime})
end