module Assistant
  Error = Class.new(StandardError)

  REGISTRY = {
    "builtin" => Assistant::Builtin,
    "external" => Assistant::External
  }.freeze

  # Statement Vault + provenance tools, for users who opted into preview features
  # in Settings -> Preferences. They back the wealth agent-harness workflow
  # documented in docs/llm-guides/wealth-agent-harness.md.
  PREVIEW_FUNCTION_CLASSES = [
    Function::UploadAccountStatement,
    Function::ListAccountStatements,
    Function::GetAccountStatement,
    Function::GetStatementCoverage,
    Function::RecordValuation
  ].freeze

  class << self
    def for_chat(chat)
      implementation_for(chat).for_chat(chat)
    end

    def config_for(chat)
      raise Error, "chat is required" if chat.blank?
      Assistant::Builtin.config_for(chat)
    end

    def available_types
      REGISTRY.keys
    end

    # The single registry behind both the builtin chat and the /mcp endpoint's
    # tools/list — a function class added here is immediately callable by an
    # external agent, so pass the user to keep preview tools out of the default
    # surface.
    def function_classes(user = nil)
      classes = [
        Function::GetTransactions,
        Function::GetAccounts,
        Function::GetHoldings,
        Function::GetBalanceSheet,
        Function::GetIncomeStatement,
        Function::GetBudget,
        Function::ImportBankStatement,
        Function::SearchFamilyFiles,
        Function::CreateGoal,
        Function::GetTags,
        Function::CreateTag,
        Function::UpdateTag,
        Function::GetCategories,
        Function::CreateCategory,
        Function::UpdateCategory,
        Function::UpdateTransaction,
        Function::UpdateBudget
      ]

      classes += PREVIEW_FUNCTION_CLASSES if user&.preview_features_enabled?
      classes
    end

    private

      def implementation_for(chat)
        raise Error, "chat is required" if chat.blank?
        type = ENV["ASSISTANT_TYPE"].presence || chat.user&.family&.assistant_type.presence || "builtin"
        REGISTRY.fetch(type) { REGISTRY["builtin"] }
      end
  end
end