defmodule CMDC.Agent.State do
  # 内部模块 — `CMDC.Agent` gen_statem 运行时状态。API 不保证稳定。
  # 外部读 Agent 状态请用 `CMDC.status/1`。
  @moduledoc false

  @type status :: :idle | :running | :streaming | :executing_tools

  @type t :: %__MODULE__{
          # ── Identity ──────────────────────────────────────────────────
          session_id: String.t(),
          model: String.t(),
          working_dir: String.t(),
          config: CMDC.Config.t() | map(),
          status: status(),

          # ── Conversation ──────────────────────────────────────────────
          blueprint_system_prompt: String.t(),
          messages: [CMDC.Message.t()],

          # ── Plugin Pipeline ───────────────────────────────────────────
          plugins: [{module(), term()}],
          plugin_states: %{module() => term()},

          # ── Tool registry ─────────────────────────────────────────────
          tools: [module()],
          disabled_tools: [String.t()],

          # ── Tool execution ────────────────────────────────────────────
          # 第三元素 started_at_ms 用于 status/1 暴露 + duration_ms 计算
          pending_tool_tasks: %{reference() => {Task.t(), map(), integer()}},
          tool_results: [{map(), term()}],

          # ── Streaming accumulator（每 turn 重置）─────────────────────
          current_text: String.t(),
          current_tool_calls: [map()],
          current_thinking: String.t() | nil,
          message_started: boolean(),
          tag_buffers: %{atom() => String.t()},
          tool_call_arg_buffers: %{non_neg_integer() => iodata()},

          # ── Stream transport ──────────────────────────────────────────
          streaming_resp: term() | nil,
          stream_task_pid: pid() | nil,

          # ── Stream health ─────────────────────────────────────────────
          last_chunk_at: integer() | nil,
          stream_errored: false | term(),
          stall_count: non_neg_integer(),

          # ── Token & cost tracking ─────────────────────────────────────
          # 内部 token_usage 仍使用 map 兼容存量代码（含上下文窗口元数据）;
          # 公开 API（事件/status）通过 `CMDC.TokenUsage.from_state_token_map/3` 转 struct。
          token_usage: %{
            prompt_tokens: non_neg_integer(),
            completion_tokens: non_neg_integer(),
            total_tokens: non_neg_integer(),
            context_window: non_neg_integer(),
            current_context_tokens: non_neg_integer()
          },
          turn_count: non_neg_integer(),
          tool_call_count: non_neg_integer(),
          cost_usd: float(),
          cached_tokens: non_neg_integer() | nil,

          # ── Loop detection ────────────────────────────────────────────
          # 最近 N 次工具调用的 hash 序列，供 ToolRunner 检测重复模式
          tool_call_hashes: [binary()],

          # ── Context relay ─────────────────────────────────────────────
          sandbox: module() | nil,
          subagents: [map()],
          todos: [map()],
          memory_contents: %{String.t() => String.t()},
          user_data: map(),

          # ── Resilience ────────────────────────────────────────────────
          retry_count: non_neg_integer(),
          max_retries: pos_integer(),
          retry_base_delay_ms: pos_integer(),
          retry_max_delay_ms: pos_integer(),
          overflow_detected: boolean(),

          # ── Interaction ───────────────────────────────────────────────
          pending_messages: [String.t()],

          # ── Steering（中段软中断）────────────────────────────────────
          steering_queue: [
            %{ref: reference(), text: String.t(), queued_at: integer()}
          ],

          # ── Monitors ─────────────────────────────────
          # 通过 CMDC.monitor/1 登记的观察者，Agent terminate 时广播
          # {:cmdc_down, ref, session_id, structured_reason}
          monitors: %{reference() => pid()},

          # 记录"预期结构化退出原因"，terminate 时优先使用此值覆盖 raw reason。
          # 典型来源：plugin abort / max_turns / provider_timeout 等内部已知分支。
          exit_reason: term() | nil,

          # ── PromptMode ─────────────────────────────
          # 系统提示词模式 :full | :task | :minimal | :none
          # 由 Options.prompt_mode 透传，SubAgent 默认 :task
          prompt_mode: CMDC.Options.prompt_mode(),

          # ── Dynamic System Context（Planning 插件持续注入）─
          # Plugin 可通过 emit {:update_system_context, key, text_or_nil} 动态
          # 向 system prompt 末尾追加段落；text=nil 表示删除该 key。
          # 典型用途：Planning plugin 把 Plan 的 progress 实时注入，让 LLM 每
          # 轮都能感知计划推进状态。
          dynamic_context_sections: %{atom() => String.t()},

          # ── After-turn marker ─────────────────────
          # idle → running 时记录起始快照（messages 长度 + token_usage 快照 +
          # 起始时间），用于在 finish / finalize_abort 触发 `:after_turn`
          # Plugin hook 时计算 diff payload。
          # `nil` 表示当前不在 prompt cycle 中（idle 起始或已被 emit 清空）。
          turn_start_marker:
            %{
              messages_offset: non_neg_integer(),
              token_usage_snapshot: map(),
              cost_usd_snapshot: float(),
              started_at_ms: integer()
            }
            | nil,

          # ── Lifecycle ─────────────────────────────────────────────────
          started_at: integer()
        }

  @enforce_keys [:session_id, :model, :working_dir]
  # credo:disable-for-next-line Credo.Check.Warning.StructFieldAmount
  defstruct [
    # Identity
    :session_id,
    :model,
    :working_dir,
    config: %{},
    status: :idle,

    # Conversation
    blueprint_system_prompt: "",
    messages: [],

    # Plugin Pipeline
    plugins: [],
    plugin_states: %{},

    # Tool registry
    tools: [],
    disabled_tools: [],

    # Tool execution
    pending_tool_tasks: %{},
    tool_results: [],

    # Streaming accumulator
    current_text: "",
    current_tool_calls: [],
    current_thinking: nil,
    message_started: false,
    tag_buffers: %{},
    tool_call_arg_buffers: %{},

    # Stream transport
    streaming_resp: nil,
    stream_task_pid: nil,

    # Stream health
    last_chunk_at: nil,
    stream_errored: false,
    stall_count: 0,

    # Token & cost tracking
    token_usage: %{
      prompt_tokens: 0,
      completion_tokens: 0,
      total_tokens: 0,
      context_window: 0,
      current_context_tokens: 0
    },
    turn_count: 0,
    tool_call_count: 0,
    cost_usd: 0.0,
    cached_tokens: nil,

    # Loop detection
    tool_call_hashes: [],

    # Context relay
    sandbox: nil,
    subagents: [],
    todos: [],
    memory_contents: %{},
    user_data: %{},

    # Resilience
    retry_count: 0,
    max_retries: 3,
    retry_base_delay_ms: 2_000,
    retry_max_delay_ms: 60_000,
    overflow_detected: false,

    # Interaction
    pending_messages: [],

    # Steering
    steering_queue: [],

    # Monitors
    monitors: %{},
    exit_reason: nil,

    # PromptMode
    prompt_mode: :full,

    # Dynamic System Context
    dynamic_context_sections: %{},

    # After-turn marker
    turn_start_marker: nil,

    # Lifecycle
    started_at: 0
  ]

  @max_hash_history 20
  @default_max_steering_queue 3

  # ==========================================================================
  # Public API — 构造
  # ==========================================================================

  @doc """
  从 keyword list 构建 State struct。

  供 Agent.init/1 使用，自动设置 started_at 时间戳。

  ## 示例

      state = State.new(session_id: "abc", model: "anthropic:claude-sonnet-4-5", working_dir: ".")
  """
  @spec new(keyword()) :: t()
  def new(opts) when is_list(opts) do
    struct!(__MODULE__, Keyword.put_new(opts, :started_at, System.system_time(:millisecond)))
  end

  # ==========================================================================
  # Public API — 状态映射
  # ==========================================================================

  @doc "映射 status 字段为 gen_statem 状态名称。"
  @spec state_name(t()) :: status()
  def state_name(%__MODULE__{status: status})
      when status in [:idle, :running, :streaming, :executing_tools],
      do: status

  # ==========================================================================
  # Public API — 消息操作
  # ==========================================================================

  @doc "向消息历史头部追加一条消息（反序存储：最新在前）。"
  @spec append_message(t(), CMDC.Message.t()) :: t()
  def append_message(%__MODULE__{} = state, %CMDC.Message{} = msg) do
    %{state | messages: [msg | state.messages]}
  end

  @doc "向消息历史批量追加多条消息。"
  @spec append_messages(t(), [CMDC.Message.t()]) :: t()
  def append_messages(%__MODULE__{} = state, msgs) when is_list(msgs) do
    %{state | messages: Enum.reverse(msgs) ++ state.messages}
  end

  # ==========================================================================
  # Public API — 流式累积重置
  # ==========================================================================

  @doc "重置每个 turn 的流式累积字段（在新 turn 开始时调用）。"
  @spec reset_stream_fields(t()) :: t()
  def reset_stream_fields(%__MODULE__{} = state) do
    %{
      state
      | current_text: "",
        current_tool_calls: [],
        current_thinking: nil,
        message_started: false,
        tag_buffers: %{},
        tool_call_arg_buffers: %{},
        last_chunk_at: nil,
        stream_errored: false,
        stream_task_pid: nil,
        stall_count: 0
    }
  end

  # ==========================================================================
  # Public API — Plugin 状态同步
  # ==========================================================================

  @doc "从 Plugin.Pipeline 的执行结果中同步 plugin_states 回 State。"
  @spec sync_plugin_states(t(), map()) :: t()
  def sync_plugin_states(%__MODULE__{} = state, pipeline_result) do
    new_plugins =
      Enum.map(state.plugins, fn {mod, _old_state} ->
        {mod, Map.get(pipeline_result.plugin_states, mod, %{})}
      end)

    %{state | plugins: new_plugins, plugin_states: pipeline_result.plugin_states}
  end

  # ==========================================================================
  # Public API — Context 构建
  # ==========================================================================

  @doc """
  构建当前 State 对应的 Context 快照（只读，传给 Plugin/Tool）。

  将 State 内部字段映射到 Context 的公共接口：
  - `turn_count` → `turn`
  - `token_usage.total_tokens` → `total_tokens`
  - `cost_usd` → `cost_usd`
  - `sandbox`、`subagents`、`todos`、`memory_contents`、`user_data` 直接透传
  """
  @spec to_context(t()) :: CMDC.Context.t()
  def to_context(%__MODULE__{} = state) do
    %CMDC.Context{
      session_id: state.session_id,
      working_dir: state.working_dir,
      model: state.model,
      sandbox: state.sandbox,
      tools: state.tools,
      subagents: state.subagents,
      config: state.config,
      todos: state.todos,
      memory_contents: state.memory_contents,
      user_data: state.user_data,
      turn: state.turn_count,
      total_tokens: state.token_usage.total_tokens,
      cost_usd: state.cost_usd,
      last_assistant_reply: last_assistant_reply(state)
    }
  end

  # 从 state.messages（头部最新）中取最后一条 assistant 文本回复
  defp last_assistant_reply(%__MODULE__{messages: messages}) do
    Enum.find_value(messages, nil, fn
      %{role: :assistant, content: c} when is_binary(c) and c != "" -> c
      _ -> nil
    end)
  end

  # ==========================================================================
  # Public API — 计数器
  # ==========================================================================

  @doc "增加 turn_count 计数。"
  @spec increment_turn(t()) :: t()
  def increment_turn(%__MODULE__{turn_count: n} = state) do
    %{state | turn_count: n + 1}
  end

  @doc "增加 tool_call_count 计数。"
  @spec increment_tool_calls(t(), non_neg_integer()) :: t()
  def increment_tool_calls(%__MODULE__{tool_call_count: n} = state, delta \\ 1) do
    %{state | tool_call_count: n + delta}
  end

  # ==========================================================================
  # Public API — Turn marker
  # ==========================================================================

  @doc """
  在 prompt cycle 起始处（idle → running）记录快照。

  如果当前已存在 marker（理论上不应发生，例如未消费的 cycle），保留旧 marker
  不覆盖，避免漏算上一次 prompt cycle 的 diff。
  """
  @spec mark_turn_start(t()) :: t()
  def mark_turn_start(%__MODULE__{turn_start_marker: m} = state) when is_map(m), do: state

  def mark_turn_start(%__MODULE__{} = state) do
    marker = %{
      messages_offset: length(state.messages),
      token_usage_snapshot: state.token_usage,
      cost_usd_snapshot: state.cost_usd,
      started_at_ms: System.system_time(:millisecond)
    }

    %{state | turn_start_marker: marker}
  end

  @doc """
  消费 marker，返回 `{after_turn_payload | nil, state_with_marker_cleared}`。

  - `outcome :: :finished | :aborted`
  - `abort_reason` 仅在 `:aborted` 时非 nil

  payload 字段：

  - `:outcome` — `:finished | :aborted`
  - `:abort_reason` — `term() | nil`
  - `:messages_diff` — 本轮 prompt cycle 内新增的消息（按时间顺序）
  - `:token_usage_diff` — `%CMDC.TokenUsage{}` 本轮增量
  - `:duration_ms` — 本轮总耗时
  - `:started_at_ms` / `:ended_at_ms` — 起止时间戳

  marker 为 `nil` 时返回 `{nil, state}`（Plugin 不会触发 `:after_turn`）。
  """
  @spec consume_turn_marker(t(), :finished | :aborted, term() | nil) ::
          {map() | nil, t()}
  def consume_turn_marker(%__MODULE__{turn_start_marker: nil} = state, _outcome, _reason),
    do: {nil, state}

  def consume_turn_marker(
        %__MODULE__{turn_start_marker: marker} = state,
        outcome,
        abort_reason
      )
      when outcome in [:finished, :aborted] do
    ended_at_ms = System.system_time(:millisecond)
    messages_diff = diff_messages_since(state.messages, marker.messages_offset)
    snap = marker.token_usage_snapshot

    token_usage_diff = %CMDC.TokenUsage{
      prompt_tokens: state.token_usage.prompt_tokens - Map.get(snap, :prompt_tokens, 0),
      completion_tokens:
        state.token_usage.completion_tokens - Map.get(snap, :completion_tokens, 0),
      total_tokens: state.token_usage.total_tokens - Map.get(snap, :total_tokens, 0),
      cost_usd: state.cost_usd - marker.cost_usd_snapshot,
      cached_tokens: nil
    }

    payload = %{
      outcome: outcome,
      abort_reason: abort_reason,
      messages_diff: messages_diff,
      token_usage_diff: token_usage_diff,
      started_at_ms: marker.started_at_ms,
      ended_at_ms: ended_at_ms,
      duration_ms: max(ended_at_ms - marker.started_at_ms, 0)
    }

    {payload, %{state | turn_start_marker: nil}}
  end

  defp diff_messages_since(messages, offset) when is_list(messages) and is_integer(offset) do
    take = max(length(messages) - offset, 0)

    messages
    |> Enum.take(take)
    |> Enum.reverse()
  end

  # ==========================================================================
  # Public API — Token & Cost 追踪
  # ==========================================================================

  @doc """
  更新 token_usage，累加新的 usage 数据。

  `new_usage` 接受 plain map 或 `%CMDC.TokenUsage{}` struct（自动取共有字段）。
  Anthropic 的 cache_read_input_tokens 通过 `:cached_tokens` 字段累加到顶层
  `state.cached_tokens`（独立于 token_usage map，保持向后兼容）。
  """
  @spec update_token_usage(t(), map() | CMDC.TokenUsage.t()) :: t()
  def update_token_usage(%__MODULE__{token_usage: current} = state, new_usage) do
    merged = %{
      prompt_tokens: current.prompt_tokens + Map.get(new_usage, :prompt_tokens, 0),
      completion_tokens: current.completion_tokens + Map.get(new_usage, :completion_tokens, 0),
      total_tokens: current.total_tokens + Map.get(new_usage, :total_tokens, 0),
      context_window: Map.get(new_usage, :context_window, current.context_window),
      current_context_tokens:
        Map.get(new_usage, :current_context_tokens, current.current_context_tokens)
    }

    new_cached =
      case Map.get(new_usage, :cached_tokens) do
        n when is_integer(n) -> (state.cached_tokens || 0) + n
        _ -> state.cached_tokens
      end

    %{state | token_usage: merged, cached_tokens: new_cached}
  end

  @doc """
  更新累计成本（USD）。

  在每轮 stream_done 后由 Agent 调用，基于 token 使用量和模型定价计算。
  """
  @spec update_cost(t(), float()) :: t()
  def update_cost(%__MODULE__{cost_usd: current} = state, delta_usd)
      when is_number(delta_usd) do
    %{state | cost_usd: current + delta_usd}
  end

  # ==========================================================================
  # Public API — 循环检测
  # ==========================================================================

  @doc """
  记录一次工具调用 hash，用于 ToolRunner 循环检测。

  保留最近 #{@max_hash_history} 条记录，超出时截断最旧的。
  """
  @spec record_tool_call_hash(t(), binary()) :: t()
  def record_tool_call_hash(%__MODULE__{tool_call_hashes: hashes} = state, hash)
      when is_binary(hash) do
    updated = [hash | hashes] |> Enum.take(@max_hash_history)
    %{state | tool_call_hashes: updated}
  end

  @doc "返回循环检测 hash 历史的最大保留数。"
  @spec max_hash_history() :: pos_integer()
  def max_hash_history, do: @max_hash_history

  # ==========================================================================
  # Public API — Steering（中段软中断）
  # ==========================================================================

  @typedoc "Steering queue 中的单条记录。"
  @type steering_entry :: %{ref: reference(), text: String.t(), queued_at: integer()}

  @doc """
  向 `:steering_queue` 末尾追加一条 steering 记录。

  Queue 上限由 `state.config[:max_steering_queue]` 控制（缺省 #{@default_max_steering_queue}）。
  溢出时丢弃**最旧**一条（FIFO 截断），保证总长不超 limit。
  """
  @spec enqueue_steering(t(), reference(), String.t()) :: t()
  def enqueue_steering(%__MODULE__{} = state, ref, text)
      when is_reference(ref) and is_binary(text) do
    entry = %{ref: ref, text: text, queued_at: System.system_time(:millisecond)}
    limit = max_steering_queue(state)

    new_queue =
      (state.steering_queue ++ [entry])
      |> Enum.take(-limit)

    %{state | steering_queue: new_queue}
  end

  @doc """
  一次性取出 `:steering_queue` 中的全部记录并清空。

  返回 `{entries, state}`，`entries` 为按时间顺序排列的 list（最早在前）。
  Steering 注入下一 turn 时由 ToolRunner.inject_steering 调用。
  """
  @spec drain_steering(t()) :: {[steering_entry()], t()}
  def drain_steering(%__MODULE__{steering_queue: queue} = state) do
    {queue, %{state | steering_queue: []}}
  end

  @doc """
  返回 `:steering_queue` 已满（达到 max_steering_queue 上限）。

  调用方在 enqueue 之前用此判断决定是否拒绝新 steer。
  """
  @spec steering_queue_full?(t()) :: boolean()
  def steering_queue_full?(%__MODULE__{} = state) do
    length(state.steering_queue) >= max_steering_queue(state)
  end

  @doc """
  返回当前 state 的 `max_steering_queue` 配置（无配置时回落到默认值 #{@default_max_steering_queue}）。
  """
  @spec max_steering_queue(t()) :: pos_integer()
  def max_steering_queue(%__MODULE__{config: config}) do
    case config_get(config, :max_steering_queue) do
      n when is_integer(n) and n > 0 -> n
      _ -> @default_max_steering_queue
    end
  end

  @doc """
  返回当前 state 的 `interrupt_immune_tools` 白名单（缺省即 Options 默认值）。
  """
  @spec interrupt_immune_tools(t()) :: [String.t()]
  def interrupt_immune_tools(%__MODULE__{config: config}) do
    case config_get(config, :interrupt_immune_tools) do
      list when is_list(list) -> list
      _ -> []
    end
  end

  # 兼容 config 为 map / Config struct / nil 三种形态。
  defp config_get(%CMDC.Config{} = config, key), do: Map.get(config, key)
  defp config_get(config, key) when is_map(config), do: Map.get(config, key)
  defp config_get(_, _), do: nil
end