cmdc

defmodule CMDC.Agent.SystemPrompt do
  @moduledoc """
  系统提示词组装器 — 编译 Agent 最终的 system prompt。

  ## 组装层级（从底到顶）

  1. **BasePrompt** — 核心行为准则 + 可用工具列表
  2. **用户 system_prompt** — Blueprint 或直接传入的自定义指令
  3. **Blueprint Identity** — name / purpose（若有 Blueprint 配置）
  4. **Skills 列表** — 渐进式技能清单（name + description）
  5. **Memory 内容** — AGENTS.md 等持久记忆内容

  ## PromptMode 门控（v0.2 Phase 10B）

  通过 `state.prompt_mode` 控制注入哪些段落：

  | 模式 | user_prompt | BasePrompt | Identity | Skills | Memory |
  |------|-------------|-----------|----------|--------|--------|
  | `:full`（默认）| ✓ | 完整 `BasePrompt.build/1` | ✓ | ✓ | ✓ |
  | `:task`      | ✓ | 精简 `BasePrompt.for_mode(:task)` | ✓ | ✗ | ✗ |
  | `:minimal`   | ✓ | 仅 tools 名称列表 | ✓ | ✗ | ✗ |
  | `:none`      | ✓ | ✗ | ✗ | ✗ | ✗ |

  `:task` 模式相比 `:full` 典型省 30-50% system prompt token。

  ## 用法

      prompt = CMDC.Agent.SystemPrompt.build(state)

  ## 与旧项目的差异

  - 新增 Skills 注入（对标 DeepAgents SkillsMiddleware）
  - 新增 Memory 注入（对标 DeepAgents MemoryMiddleware）
  - BasePrompt 独立模块化（旧项目直接硬编码在 SystemPrompt 中）
  - Blueprint Identity 信息从 config 中提取
  """

  alias CMDC.Agent.{BasePrompt, State}

  require Logger

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

  @doc """
  从 Agent State 编译完整的系统提示词。

  按 `state.prompt_mode` 门控：各模式注入的段落见模块 @moduledoc 表格。
  空段自动跳过，段间用双换行分隔。
  """
  @spec build(State.t()) :: String.t()
  def build(%State{prompt_mode: mode} = state) when mode in [:full, :task, :minimal, :none] do
    state
    |> sections_for(mode)
    |> Enum.reject(&(is_nil(&1) or &1 == ""))
    |> Enum.join("\n\n")
  end

  def build(%State{} = state), do: build(%{state | prompt_mode: :full})

  # ==========================================================================
  # 模式段落选择
  # ==========================================================================

  defp sections_for(state, :full) do
    [
      build_user_prompt(state),
      build_base_prompt(state, :full),
      build_blueprint_identity(state),
      build_skills_section(state),
      build_memory_section(state),
      build_dynamic_sections(state)
    ]
  end

  defp sections_for(state, :task) do
    [
      build_user_prompt(state),
      build_base_prompt(state, :task),
      build_blueprint_identity(state),
      build_dynamic_sections(state)
    ]
  end

  defp sections_for(state, :minimal) do
    [
      build_user_prompt(state),
      build_base_prompt(state, :minimal),
      build_blueprint_identity(state),
      build_dynamic_sections(state)
    ]
  end

  defp sections_for(state, :none) do
    [build_user_prompt(state)]
  end

  # ==========================================================================
  # 层 1: 用户自定义 system_prompt
  # ==========================================================================

  defp build_user_prompt(%State{blueprint_system_prompt: prompt})
       when is_binary(prompt) and prompt != "" do
    prompt
  end

  defp build_user_prompt(_state), do: nil

  # ==========================================================================
  # 层 2: BasePrompt + 工具列表（按 prompt_mode 精简）
  # ==========================================================================

  defp build_base_prompt(%State{tools: tools}, :full), do: BasePrompt.build(tools)
  defp build_base_prompt(%State{tools: tools}, mode), do: BasePrompt.for_mode(tools, mode)

  # ==========================================================================
  # 层 3: Blueprint Identity（从 config 中提取）
  # ==========================================================================

  defp build_blueprint_identity(%State{config: config}) when is_map(config) do
    blueprint = Map.get(config, :blueprint)
    build_identity_from_blueprint(blueprint)
  end

  defp build_blueprint_identity(_state), do: nil

  defp build_identity_from_blueprint(nil), do: nil

  defp build_identity_from_blueprint(blueprint) when is_map(blueprint) do
    bp = if is_struct(blueprint), do: Map.from_struct(blueprint), else: blueprint
    name = bp[:name]
    purpose = bp[:purpose] || bp[:description]

    case {name, purpose} do
      {nil, _} -> nil
      {_, nil} -> nil
      {n, p} -> "## Agent Identity\n\nYou are **#{n}**: #{p}"
    end
  end

  defp build_identity_from_blueprint(_), do: nil

  # ==========================================================================
  # 层 4: Skills 列表（支持 Selector 智能筛选）
  # ==========================================================================

  defp build_skills_section(%State{config: config} = state) when is_map(config) do
    skills = Map.get(config, :skills, [])

    if is_list(skills) and skills != [] do
      selected = maybe_select_skills(skills, config, state)

      if selected != [] do
        CMDC.Skill.to_prompt_snippet(selected)
      else
        nil
      end
    else
      nil
    end
  end

  defp build_skills_section(_state), do: nil

  defp maybe_select_skills(skills, config, state) do
    selector = Map.get(config, :skill_selector)

    if is_atom(selector) and not is_nil(selector) do
      query = extract_latest_user_query(state)
      ctx = build_selector_context(state)

      try do
        selector.select(skills, query, ctx)
      rescue
        e ->
          Logger.warning(
            "[SystemPrompt] Skill Selector #{inspect(selector)} 失败: #{Exception.message(e)}，回退全量注入"
          )

          skills
      end
    else
      skills
    end
  end

  defp extract_latest_user_query(%State{messages: messages}) do
    messages
    |> Enum.find(fn msg -> msg.role == :user end)
    |> case do
      %{content: content} when is_binary(content) -> content
      _ -> ""
    end
  end

  defp build_selector_context(%State{} = state) do
    %CMDC.Context{
      session_id: state.session_id,
      working_dir: state.working_dir,
      model: state.model,
      sandbox: state.sandbox,
      todos: Map.get(state, :todos, []),
      memory_contents: Map.get(state, :memory_contents, %{}),
      user_data: Map.get(state, :user_data, %{}),
      turn: state.turn_count,
      total_tokens: get_in(state.token_usage, [:total_tokens]) || 0,
      cost_usd: state.cost_usd
    }
  end

  # ==========================================================================
  # 层 5: Memory 内容
  # ==========================================================================

  defp build_memory_section(%State{memory_contents: contents})
       when is_map(contents) and map_size(contents) > 0 do
    entries =
      contents
      |> Enum.sort_by(fn {name, _} -> name end)
      |> Enum.map_join("\n\n", fn {name, content} ->
        "<agent_memory name=\"#{name}\">\n#{content}\n</agent_memory>"
      end)

    "## Agent Memory\n\n#{entries}"
  end

  defp build_memory_section(_state), do: nil

  # ==========================================================================
  # 层 6: Dynamic System Context（v0.3 Phase 11D — Plugin 动态注入）
  # ==========================================================================

  defp build_dynamic_sections(%State{dynamic_context_sections: sections})
       when is_map(sections) and map_size(sections) > 0 do
    sections
    |> Enum.sort_by(fn {k, _} -> to_string(k) end)
    |> Enum.map_join("\n\n", fn {_k, content} -> content end)
  end

  defp build_dynamic_sections(_state), do: nil
end