cmdc

defmodule CMDC.Agent.Overflow do
  # 内部模块 — LLM provider 上下文溢出检测。API 不保证稳定。
  @moduledoc false

  @overflow_patterns [
    "context_length_exceeded",
    "maximum context length",
    "max_tokens",
    "max_prompt_tokens",
    "too many tokens",
    "prompt is too long",
    "prompt_tokens_exceeded",
    "request too large",
    "context window",
    "token limit",
    "exceeds the limit",
    "input too long",
    "exceeds the model's maximum",
    "reduce the length",
    "maximum number of tokens",
    "content_too_large",
    "string_above_max_length"
  ]

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

  @doc "返回所有溢出错误模式字符串列表。"
  @spec overflow_patterns() :: [String.t()]
  def overflow_patterns, do: @overflow_patterns

  @doc """
  返回 `true` 如果错误字符串匹配已知的上下文窗口溢出模式。

  ## 示例

      iex> CMDC.Agent.Overflow.context_overflow?("context_length_exceeded")
      true

      iex> CMDC.Agent.Overflow.context_overflow?("rate_limit")
      false
  """
  @spec context_overflow?(term()) :: boolean()
  def context_overflow?(reason) do
    text = stringify(reason) |> String.downcase()
    matches_any?(text, @overflow_patterns)
  end

  @doc """
  返回 `true` 如果 input_tokens 超过 context_window。

  ## 示例

      iex> CMDC.Agent.Overflow.usage_overflow?(250_000, 200_000)
      true
  """
  @spec usage_overflow?(non_neg_integer(), pos_integer()) :: boolean()
  def usage_overflow?(input_tokens, context_window)
      when is_integer(input_tokens) and is_integer(context_window) and context_window > 0 do
    input_tokens > context_window
  end

  def usage_overflow?(_input_tokens, _context_window), do: false

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

  defp stringify(reason) when is_binary(reason), do: reason
  defp stringify(reason) when is_atom(reason), do: Atom.to_string(reason)
  defp stringify(reason), do: inspect(reason)

  defp matches_any?(text, patterns) do
    Enum.any?(patterns, &String.contains?(text, &1))
  end
end