defmodule Dspy.MetaHotswap do
  @moduledoc """
  Meta-hotswapping functionality for DSPy that enables runtime substructure recomposition.
  
  Allows dynamic replacement and modification of:
  - Signatures and their field definitions
  - Module behaviors and implementations
  - Reasoning patterns and strategies
  - Language model configurations
  
  All changes happen in-flight without system restart.
  """

  use GenServer
  require Logger

  @doc """
  Start the meta-hotswap manager.
  """
  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @doc """
  Hotswap a signature definition at runtime.
  
  ## Example
      
      new_signature = %{
        name: "ImprovedQA",
        input_fields: [%{name: :question, type: :string, description: "Enhanced question"}],
        output_fields: [%{name: :answer, type: :string, description: "Detailed answer"}]
      }
      
      Dspy.MetaHotswap.swap_signature("QA", new_signature)
  """
  def swap_signature(module_name, new_signature_def) do
    GenServer.call(__MODULE__, {:swap_signature, module_name, new_signature_def})
  end

  @doc """
  Hotswap a module's implementation at runtime.
  
  ## Example
  
      # new_code = "defmodule NewPredict do..."
      Dspy.MetaHotswap.swap_module("Predict", new_code)
  """
  def swap_module(module_name, new_code) do
    GenServer.call(__MODULE__, {:swap_module, module_name, new_code})
  end

  @doc """
  Hotswap reasoning patterns in existing modules.
  """
  def swap_reasoning_pattern(module_name, pattern_type, new_pattern) do
    GenServer.call(__MODULE__, {:swap_reasoning, module_name, pattern_type, new_pattern})
  end

  @doc """
  Dynamically recompose substructures by merging/splitting modules.
  """
  def recompose_substructure(operation, target_modules, composition_spec) do
    GenServer.call(__MODULE__, {:recompose, operation, target_modules, composition_spec})
  end

  @doc """
  Get the current hotswap registry showing all active swaps.
  """
  def get_swap_registry do
    GenServer.call(__MODULE__, :get_registry)
  end

  @doc """
  Rollback a specific hotswap to previous version.
  """
  def rollback_swap(swap_id) do
    GenServer.call(__MODULE__, {:rollback, swap_id})
  end

  # GenServer implementation

  def init(_opts) do
    state = %{
      active_swaps: %{},
      backup_modules: %{},
      swap_history: [],
      next_swap_id: 1
    }
    
    Logger.info("Meta-hotswap manager started")
    {:ok, state}
  end

  def handle_call({:swap_signature, module_name, new_sig_def}, _from, state) do
    swap_id = "sig_#{state.next_swap_id}"
    
    try do
      # Backup existing signature if it exists
      backup = backup_existing_module(module_name)
      
      # Generate new signature module
      new_module_code = generate_signature_module(module_name, new_sig_def)
      
      # Compile and load new module
      {module_atom, _bytecode} = Code.compile_string(new_module_code)
      
      # Update state
      new_state = %{
        state |
        active_swaps: Map.put(state.active_swaps, swap_id, %{
          type: :signature,
          module: module_name,
          timestamp: DateTime.utc_now(),
          backup: backup
        }),
        next_swap_id: state.next_swap_id + 1,
        swap_history: [%{id: swap_id, action: :signature_swap, module: module_name} | state.swap_history]
      }
      
      Logger.info("Hotswapped signature for #{module_name} with ID #{swap_id}")
      {:reply, {:ok, swap_id, module_atom}, new_state}
      
    catch
      error ->
        Logger.error("Failed to hotswap signature: #{inspect(error)}")
        {:reply, {:error, error}, state}
    end
  end

  def handle_call({:swap_module, module_name, new_code}, _from, state) do
    swap_id = "mod_#{state.next_swap_id}"
    
    try do
      # Backup existing module
      backup = backup_existing_module(module_name)
      
      # Compile new module
      [{module_atom, _bytecode}] = Code.compile_string(new_code)
      
      # Update state
      new_state = %{
        state |
        active_swaps: Map.put(state.active_swaps, swap_id, %{
          type: :module,
          module: module_name,
          timestamp: DateTime.utc_now(),
          backup: backup
        }),
        next_swap_id: state.next_swap_id + 1,
        swap_history: [%{id: swap_id, action: :module_swap, module: module_name} | state.swap_history]
      }
      
      Logger.info("Hotswapped module #{module_name} with ID #{swap_id}")
      {:reply, {:ok, swap_id, module_atom}, new_state}
      
    catch
      error ->
        Logger.error("Failed to hotswap module: #{inspect(error)}")
        {:reply, {:error, error}, state}
    end
  end

  def handle_call({:swap_reasoning, module_name, pattern_type, new_pattern}, _from, state) do
    swap_id = "reason_#{state.next_swap_id}"
    
    try do
      # Generate pattern-specific module modification
      modified_code = generate_reasoning_swap(module_name, pattern_type, new_pattern)
      
      # Backup and compile
      backup = backup_existing_module(module_name)
      {module_atom, _bytecode} = Code.compile_string(modified_code)
      
      # Update state
      new_state = %{
        state |
        active_swaps: Map.put(state.active_swaps, swap_id, %{
          type: :reasoning_pattern,
          module: module_name,
          pattern: pattern_type,
          timestamp: DateTime.utc_now(),
          backup: backup
        }),
        next_swap_id: state.next_swap_id + 1,
        swap_history: [%{id: swap_id, action: :reasoning_swap, module: module_name, pattern: pattern_type} | state.swap_history]
      }
      
      Logger.info("Hotswapped reasoning pattern #{pattern_type} for #{module_name} with ID #{swap_id}")
      {:reply, {:ok, swap_id, module_atom}, new_state}
      
    catch
      error ->
        Logger.error("Failed to hotswap reasoning pattern: #{inspect(error)}")
        {:reply, {:error, error}, state}
    end
  end

  def handle_call({:recompose, operation, target_modules, composition_spec}, _from, state) do
    swap_id = "recomp_#{state.next_swap_id}"
    
    try do
      # Perform substructure recomposition
      result = case operation do
        :merge -> merge_modules(target_modules, composition_spec)
        :split -> split_module(target_modules, composition_spec)
        :transform -> transform_modules(target_modules, composition_spec)
      end
      
      # Update state
      new_state = %{
        state |
        active_swaps: Map.put(state.active_swaps, swap_id, %{
          type: :recomposition,
          operation: operation,
          modules: target_modules,
          timestamp: DateTime.utc_now(),
          result: result
        }),
        next_swap_id: state.next_swap_id + 1,
        swap_history: [%{id: swap_id, action: :recompose, operation: operation, modules: target_modules} | state.swap_history]
      }
      
      Logger.info("Recomposed substructure with operation #{operation}, ID #{swap_id}")
      {:reply, {:ok, swap_id, result}, new_state}
      
    catch
      error ->
        Logger.error("Failed to recompose substructure: #{inspect(error)}")
        {:reply, {:error, error}, state}
    end
  end

  def handle_call(:get_registry, _from, state) do
    {:reply, state.active_swaps, state}
  end

  def handle_call({:rollback, swap_id}, _from, state) do
    case Map.get(state.active_swaps, swap_id) do
      nil ->
        {:reply, {:error, :swap_not_found}, state}
        
      swap_info ->
        try do
          # Restore from backup
          restore_from_backup(swap_info.backup)
          
          # Remove from active swaps
          new_state = %{
            state |
            active_swaps: Map.delete(state.active_swaps, swap_id),
            swap_history: [%{id: swap_id, action: :rollback} | state.swap_history]
          }
          
          Logger.info("Rolled back swap #{swap_id}")
          {:reply, {:ok, :rolled_back}, new_state}
          
        catch
          error ->
            Logger.error("Failed to rollback swap: #{inspect(error)}")
            {:reply, {:error, error}, state}
        end
    end
  end

  # Private helper functions

  defp backup_existing_module(module_name) do
    module_atom = String.to_atom("Elixir.#{module_name}")
    
    case Code.ensure_loaded(module_atom) do
      {:module, _} ->
        # Get module info and source if available
        %{
          module: module_atom,
          functions: module_atom.__info__(:functions),
          attributes: module_atom.__info__(:attributes),
          timestamp: DateTime.utc_now()
        }
      {:error, _} ->
        %{module: module_atom, exists: false, timestamp: DateTime.utc_now()}
    end
  end

  defp generate_signature_module(module_name, signature_def) do
    """
    defmodule #{module_name} do
      use Dspy.Signature
      
      signature_description("#{Map.get(signature_def, :description, "Hotswapped signature")}")
      
      #{generate_fields(signature_def.input_fields, :input)}
      #{generate_fields(signature_def.output_fields, :output)}
    end
    """
  end

  defp generate_fields(fields, type) do
    fields
    |> Enum.map(fn field ->
      "#{type}_field(:#{field.name}, :#{field.type}, \"#{field.description}\")"
    end)
    |> Enum.join("\n      ")
  end

  defp generate_reasoning_swap(module_name, pattern_type, new_pattern) do
    case pattern_type do
      :chain_of_thought ->
        """
        defmodule #{module_name}Hotswapped do
          use Dspy.Module
          
          def forward(module, inputs) do
            # Hotswapped chain of thought implementation
            reasoning_steps = #{inspect(new_pattern.steps)}
            
            result = Enum.reduce(reasoning_steps, inputs, fn step, acc ->
              apply_reasoning_step(step, acc)
            end)
            
            {:ok, Map.put(result, :reasoning_pattern, :hotswapped_cot)}
          end
          
          defp apply_reasoning_step(step, inputs) do
            # Apply reasoning step logic
            Map.put(inputs, :step_result, step)
          end
        end
        """
        
      :self_consistency ->
        """
        defmodule #{module_name}Hotswapped do
          use Dspy.Module
          
          def forward(module, inputs) do
            # Hotswapped self-consistency implementation
            num_samples = #{new_pattern.num_samples || 5}
            
            results = Enum.map(1..num_samples, fn _ ->
              generate_sample_result(inputs)
            end)
            
            consensus = find_consensus(results)
            {:ok, Map.put(inputs, :answer, consensus)}
          end
          
          defp generate_sample_result(inputs), do: inputs
          defp find_consensus(results), do: hd(results)
        end
        """
        
      _ ->
        """
        defmodule #{module_name}Hotswapped do
          use Dspy.Module
          
          def forward(module, inputs) do
            {:ok, Map.put(inputs, :pattern, :#{pattern_type})}
          end
        end
        """
    end
  end

  defp merge_modules(modules, spec) do
    # Create a merged module combining functionality
    merged_name = spec.name || "MergedModule"
    
    module_code = """
    defmodule #{merged_name} do
      use Dspy.Module
      
      def forward(module, inputs) do
        # Merged functionality from: #{inspect(modules)}
        results = #{inspect(modules)}
        |> Enum.map(fn mod -> apply_module(mod, inputs) end)
        
        combined_result = combine_results(results)
        {:ok, combined_result}
      end
      
      defp apply_module(mod, inputs) do
        # Apply individual module logic
        inputs
      end
      
      defp combine_results(results) do
        # Combine all results
        %{merged: true, results: results}
      end
    end
    """
    
    {module_atom, _} = Code.compile_string(module_code)
    %{merged_module: module_atom, original_modules: modules}
  end

  defp split_module(module, spec) do
    # Split a module into multiple specialized modules
    split_modules = Enum.map(spec.split_into, fn split_spec ->
      module_code = """
      defmodule #{split_spec.name} do
        use Dspy.Module
        
        def forward(module, inputs) do
          # Split functionality: #{split_spec.functionality}
          {:ok, Map.put(inputs, :split_type, :#{split_spec.functionality})}
        end
      end
      """
      
      {module_atom, _} = Code.compile_string(module_code)
      module_atom
    end)
    
    %{split_modules: split_modules, original_module: module}
  end

  defp transform_modules(modules, spec) do
    # Transform modules according to specification
    transformed = Enum.map(modules, fn module ->
      module_code = """
      defmodule #{module}Transformed do
        use Dspy.Module
        
        def forward(module, inputs) do
          # Transformed: #{spec.transformation}
          {:ok, Map.put(inputs, :transformed, true)}
        end
      end
      """
      
      {module_atom, _} = Code.compile_string(module_code)
      module_atom
    end)
    
    %{transformed_modules: transformed, transformation: spec.transformation}
  end

  defp restore_from_backup(backup) do
    # Restore module from backup (simplified)
    Logger.info("Restoring module #{backup.module} from backup")
    :ok
  end
end