defmodule Dspy.StructuredDecomposition do
  @moduledoc """
  Structured decomposition system with LLMs for self-scaffolding code generation.

  Similar to the Python self-scaffolding OpenAPI agent, this module provides:
  - Dynamic schema generation and validation
  - Endpoint discovery and automatic route generation  
  - LLM-powered task decomposition and execution
  - Full Elixir ecosystem access for self-modification
  """

  use Dspy.Module
  alias Dspy.{Signature, LM, Prediction}

  defstruct [
    :base_signature,
    :decomposition_strategy,
    :schema_generator,
    :endpoint_discoverer,
    :execution_engine,
    :max_decomposition_depth,
    :validation_enabled,
    :self_modification_enabled
  ]

  @type t :: %__MODULE__{
          base_signature: Signature.t(),
          decomposition_strategy: atom(),
          schema_generator: module(),
          endpoint_discoverer: module(),
          execution_engine: module(),
          max_decomposition_depth: non_neg_integer(),
          validation_enabled: boolean(),
          self_modification_enabled: boolean()
        }

  # === CORE DECOMPOSITION SIGNATURES ===

  defmodule TaskDecompositionSignature do
    @moduledoc """
    Signature for decomposing complex tasks into manageable subtasks.

    Analyzes complex tasks and creates execution plans with dependencies,
    required schemas, endpoints, and code generation specifications.
    """
    use Dspy.Signature

    input_field(:complex_task, :string, "Complex task requiring decomposition")
    input_field(:context, :json, "Context information including schemas, endpoints, capabilities")
    input_field(:decomposition_depth, :number, "Current decomposition depth")
    input_field(:available_modules, :json, "Available Elixir modules and functions")

    output_field(:subtasks, :json, "Array of decomposed subtasks with dependencies")
    output_field(:execution_plan, :json, "Detailed execution plan with ordering")
    output_field(:required_schemas, :json, "Schemas that need to be generated")
    output_field(:required_endpoints, :json, "Endpoints that need to be created")
    output_field(:code_generation_tasks, :json, "Code generation tasks with specifications")
    output_field(:validation_strategy, :string, "Strategy for validating the decomposition")
  end

  defmodule SchemaGenerationSignature do
    @moduledoc """
    Signature for generating dynamic schemas and data structures.

    Creates Elixir structs, protocols, or behaviours with validation rules
    and type specifications based on input specifications.
    """
    use Dspy.Signature

    input_field(:schema_specification, :json, "Specification for the schema to generate")
    input_field(:target_format, :string, "Target format (struct, protocol, behaviour, etc.)")
    input_field(:validation_rules, :json, "Validation rules and constraints")
    input_field(:existing_schemas, :json, "Existing schemas to reference or extend")

    output_field(:generated_code, :code, "Generated Elixir code for the schema")
    output_field(:dependencies, :json, "Required dependencies and imports")
    output_field(:validation_code, :code, "Code for validating instances of this schema")
    output_field(:example_usage, :code, "Example usage code")
    output_field(:tests, :code, "Generated tests for the schema")
  end

  defmodule EndpointGenerationSignature do
    @moduledoc """
    Signature for generating HTTP endpoints and routing configuration.

    Creates complete endpoint implementations including routes, controllers,
    middleware, and documentation based on specifications.
    """
    use Dspy.Signature

    input_field(:endpoint_specification, :json, "Specification for the endpoint to generate")
    input_field(:routing_strategy, :string, "Routing strategy (Phoenix, Plug, custom)")
    input_field(:request_schema, :json, "Request schema specification")
    input_field(:response_schema, :json, "Response schema specification")
    input_field(:middleware_requirements, :json, "Required middleware and plugs")

    output_field(:endpoint_code, :code, "Generated endpoint implementation code")
    output_field(:router_code, :code, "Router configuration code")
    output_field(:controller_code, :code, "Controller implementation if needed")
    output_field(:middleware_code, :code, "Custom middleware implementations")
    output_field(:documentation, :string, "Generated documentation for the endpoint")
  end

  defmodule CodeExecutionSignature do
    @moduledoc """
    Signature for executing generated code and tracking runtime modifications.

    Executes code in a controlled environment, tracking created modules,
    runtime modifications, and validation results.
    """
    use Dspy.Signature

    input_field(:execution_plan, :json, "Execution plan from decomposition")
    input_field(:generated_code, :code, "Generated code to execute")
    input_field(:execution_context, :json, "Execution context and environment")
    input_field(:dependency_order, :json, "Order of dependencies to execute")

    output_field(:execution_results, :json, "Results from code execution")
    output_field(:created_modules, :json, "Modules that were created/modified")
    output_field(:runtime_modifications, :json, "Runtime modifications made to the system")
    output_field(:validation_results, :json, "Results of validation checks")
    output_field(:next_steps, :json, "Recommended next steps or iterations")
  end

  # === MAIN DECOMPOSITION INTERFACE ===

  def new(base_signature, opts \\ []) do
    %__MODULE__{
      base_signature: base_signature,
      decomposition_strategy: Keyword.get(opts, :strategy, :recursive),
      schema_generator: Keyword.get(opts, :schema_generator, __MODULE__.SchemaGenerator),
      endpoint_discoverer: Keyword.get(opts, :endpoint_discoverer, __MODULE__.EndpointDiscoverer),
      execution_engine: Keyword.get(opts, :execution_engine, __MODULE__.ExecutionEngine),
      max_decomposition_depth: Keyword.get(opts, :max_depth, 5),
      validation_enabled: Keyword.get(opts, :validation, true),
      self_modification_enabled: Keyword.get(opts, :self_modification, true)
    }
  end

  @impl true
  def forward(decomposer, inputs) do
    with {:ok, task_analysis} <- analyze_task_complexity(inputs),
         {:ok, decomposition_plan} <- create_decomposition_plan(decomposer, task_analysis),
         {:ok, execution_results} <- execute_decomposition_plan(decomposer, decomposition_plan),
         {:ok, validation_results} <- validate_results(decomposer, execution_results) do
      # Create structured prediction with all results
      prediction_attrs = %{
        task_analysis: task_analysis,
        decomposition_plan: decomposition_plan,
        execution_results: execution_results,
        validation_results: validation_results,
        created_artifacts: extract_created_artifacts(execution_results),
        runtime_state: capture_runtime_state()
      }

      prediction = Prediction.new(prediction_attrs)
      {:ok, prediction}
    else
      {:error, reason} -> {:error, reason}
    end
  end

  # === TASK ANALYSIS ===

  defp analyze_task_complexity(inputs) do
    complexity_signature = TaskDecompositionSignature.new()

    analysis_inputs = %{
      complex_task: Map.get(inputs, :task, ""),
      context: build_context_info(),
      decomposition_depth: 0,
      available_modules: discover_available_modules()
    }

    case LM.generate_structured_output(complexity_signature, analysis_inputs) do
      {:ok, analysis} -> {:ok, analysis}
      {:error, reason} -> {:error, {:task_analysis_failed, reason}}
    end
  end

  defp build_context_info do
    %{
      current_modules: Application.spec(:dspy, :modules) || [],
      loaded_applications: Application.loaded_applications(),
      available_schemas: discover_existing_schemas(),
      runtime_capabilities: %{
        self_modification: true,
        dependency_modification: true,
        hot_code_reloading: true,
        distributed_execution: Node.alive?()
      }
    }
  end

  defp discover_available_modules do
    # Discover all available modules in the current environment
    :code.all_loaded()
    |> Enum.map(fn {module, _} ->
      %{
        name: module,
        exports:
          try do
            module.__info__(:functions)
          rescue
            _ -> []
          end,
        attributes:
          try do
            module.__info__(:attributes)
          rescue
            _ -> []
          end
      }
    end)
  end

  defp discover_existing_schemas do
    # Discover existing schemas, structs, and protocols
    :code.all_loaded()
    |> Enum.filter(fn {module, _} ->
      try do
        module.__info__(:attributes)[:__struct__] != nil or
          module.__info__(:attributes)[:protocol] != nil
      rescue
        _ -> false
      end
    end)
    |> Enum.map(fn {module, _} ->
      %{
        module: module,
        type:
          cond do
            function_exported?(module, :__struct__, 0) -> :struct
            function_exported?(module, :__protocol__, 1) -> :protocol
            true -> :unknown
          end
      }
    end)
  end

  # === DECOMPOSITION PLANNING ===

  defp create_decomposition_plan(decomposer, task_analysis) do
    case decomposer.decomposition_strategy do
      :recursive -> create_recursive_plan(decomposer, task_analysis)
      :parallel -> create_parallel_plan(decomposer, task_analysis)
      :hybrid -> create_hybrid_plan(decomposer, task_analysis)
      _ -> {:error, {:unknown_strategy, decomposer.decomposition_strategy}}
    end
  end

  defp create_recursive_plan(decomposer, task_analysis) do
    # Create a recursive decomposition plan
    plan = %{
      strategy: :recursive,
      max_depth: decomposer.max_decomposition_depth,
      execution_phases: [
        %{
          phase: :schema_generation,
          tasks: task_analysis.required_schemas,
          dependencies: []
        },
        %{
          phase: :endpoint_generation,
          tasks: task_analysis.required_endpoints,
          dependencies: [:schema_generation]
        },
        %{
          phase: :code_execution,
          tasks: task_analysis.code_generation_tasks,
          dependencies: [:schema_generation, :endpoint_generation]
        },
        %{
          phase: :validation,
          tasks: [%{type: :validate_all, scope: :global}],
          dependencies: [:code_execution]
        }
      ]
    }

    {:ok, plan}
  end

  defp create_parallel_plan(_decomposer, task_analysis) do
    # Create a parallel execution plan for independent tasks
    independent_tasks = identify_independent_tasks(task_analysis)
    dependent_tasks = identify_dependent_tasks(task_analysis)

    plan = %{
      strategy: :parallel,
      parallel_groups: [
        %{
          group: :independent_schemas,
          tasks: filter_tasks(independent_tasks, :schema),
          can_run_parallel: true
        },
        %{
          group: :independent_endpoints,
          tasks: filter_tasks(independent_tasks, :endpoint),
          can_run_parallel: true,
          depends_on: [:independent_schemas]
        },
        %{
          group: :dependent_tasks,
          tasks: dependent_tasks,
          can_run_parallel: false,
          depends_on: [:independent_schemas, :independent_endpoints]
        }
      ]
    }

    {:ok, plan}
  end

  defp create_hybrid_plan(decomposer, task_analysis) do
    # Hybrid approach: parallel where possible, recursive for complex dependencies
    {:ok, recursive_plan} = create_recursive_plan(decomposer, task_analysis)
    {:ok, parallel_plan} = create_parallel_plan(decomposer, task_analysis)

    # Merge the strategies intelligently
    plan = %{
      strategy: :hybrid,
      execution_phases: recursive_plan.execution_phases,
      parallel_opportunities: parallel_plan.parallel_groups
    }

    {:ok, plan}
  end

  # === EXECUTION ENGINE ===

  defp execute_decomposition_plan(decomposer, plan) do
    case plan.strategy do
      :recursive -> execute_recursive_plan(decomposer, plan)
      :parallel -> execute_parallel_plan(decomposer, plan)
      :hybrid -> execute_hybrid_plan(decomposer, plan)
    end
  end

  defp execute_recursive_plan(decomposer, plan) do
    results = %{
      completed_phases: [],
      generated_artifacts: [],
      execution_log: [],
      runtime_modifications: []
    }

    Enum.reduce_while(plan.execution_phases, results, fn phase, acc ->
      case execute_phase(decomposer, phase, acc) do
        {:ok, phase_results} ->
          updated_acc = %{
            acc
            | completed_phases: [phase.phase | acc.completed_phases],
              generated_artifacts: acc.generated_artifacts ++ phase_results.artifacts,
              execution_log: acc.execution_log ++ phase_results.log_entries,
              runtime_modifications: acc.runtime_modifications ++ phase_results.modifications
          }

          {:cont, updated_acc}

        {:error, reason} ->
          {:halt, {:error, {:phase_execution_failed, phase.phase, reason}}}
      end
    end)
    |> case do
      %{} = results -> {:ok, results}
      {:error, reason} -> {:error, reason}
    end
  end

  defp execute_parallel_plan(decomposer, plan) do
    # Execute parallel groups using Task.async_stream
    plan.parallel_groups
    |> Enum.reduce({:ok, %{completed_groups: [], all_artifacts: []}}, fn group, acc ->
      case acc do
        {:ok, state} ->
          case execute_parallel_group(decomposer, group, state) do
            {:ok, group_results} ->
              {:ok,
               %{
                 completed_groups: [group.group | state.completed_groups],
                 all_artifacts: state.all_artifacts ++ group_results.artifacts
               }}
          end

        {:error, _} = error ->
          error
      end
    end)
  end

  defp execute_hybrid_plan(decomposer, plan) do
    # Execute parallel opportunities first, then fall back to recursive for dependencies
    with {:ok, parallel_results} <-
           execute_parallel_opportunities(decomposer, plan.parallel_opportunities),
         {:ok, recursive_results} <-
           execute_remaining_phases(decomposer, plan.execution_phases, parallel_results) do
      merged_results = merge_execution_results(parallel_results, recursive_results)
      {:ok, merged_results}
    else
      {:error, reason} -> {:error, reason}
    end
  end

  # === PHASE EXECUTION ===

  defp execute_phase(decomposer, phase, context) do
    case phase.phase do
      :schema_generation ->
        execute_schema_generation_phase(decomposer, phase.tasks, context)

      :endpoint_generation ->
        execute_endpoint_generation_phase(decomposer, phase.tasks, context)

      :code_execution ->
        execute_code_execution_phase(decomposer, phase.tasks, context)

      :validation ->
        execute_validation_phase(decomposer, phase.tasks, context)

      _ ->
        {:error, {:unknown_phase, phase.phase}}
    end
  end

  defp execute_schema_generation_phase(decomposer, tasks, context) do
    results = %{artifacts: [], log_entries: [], modifications: []}

    Enum.reduce_while(tasks, results, fn task, acc ->
      schema_inputs = %{
        schema_specification: task,
        target_format: Map.get(task, :format, "struct"),
        validation_rules: Map.get(task, :validation, %{}),
        existing_schemas: context.generated_artifacts
      }

      case generate_schema(decomposer.schema_generator, schema_inputs) do
        {:ok, schema_result} ->
          # Execute the generated schema code
          case execute_generated_code(schema_result.generated_code) do
            {:ok, execution_result} ->
              updated_acc = %{
                acc
                | artifacts: [schema_result | acc.artifacts],
                  log_entries: [log_schema_generation(task, schema_result) | acc.log_entries],
                  modifications: [execution_result | acc.modifications]
              }

              {:cont, updated_acc}

            {:error, reason} ->
              {:halt, {:error, {:schema_execution_failed, task, reason}}}
          end

        {:error, reason} ->
          {:halt, {:error, {:schema_generation_failed, task, reason}}}
      end
    end)
    |> case do
      %{} = results -> {:ok, results}
      {:error, reason} -> {:error, reason}
    end
  end

  defp execute_endpoint_generation_phase(decomposer, tasks, context) do
    results = %{artifacts: [], log_entries: [], modifications: []}

    Enum.reduce_while(tasks, results, fn task, acc ->
      endpoint_inputs = %{
        endpoint_specification: task,
        routing_strategy: Map.get(task, :routing, "phoenix"),
        request_schema: find_schema_for_task(task, :request, context),
        response_schema: find_schema_for_task(task, :response, context),
        middleware_requirements: Map.get(task, :middleware, [])
      }

      case generate_endpoint(decomposer.endpoint_discoverer, endpoint_inputs) do
        {:ok, endpoint_result} ->
          # Execute the generated endpoint code
          case execute_generated_code(endpoint_result.endpoint_code) do
            {:ok, execution_result} ->
              updated_acc = %{
                acc
                | artifacts: [endpoint_result | acc.artifacts],
                  log_entries: [log_endpoint_generation(task, endpoint_result) | acc.log_entries],
                  modifications: [execution_result | acc.modifications]
              }

              {:cont, updated_acc}

            {:error, reason} ->
              {:halt, {:error, {:endpoint_execution_failed, task, reason}}}
          end

        {:error, reason} ->
          {:halt, {:error, {:endpoint_generation_failed, task, reason}}}
      end
    end)
    |> case do
      %{} = results -> {:ok, results}
      {:error, reason} -> {:error, reason}
    end
  end

  defp execute_code_execution_phase(_decomposer, tasks, context) do
    results = %{artifacts: [], log_entries: [], modifications: []}

    # Use the Program of Thoughts module for code execution
    pot_module = Dspy.ProgramOfThoughts.new(CodeExecutionSignature)

    Enum.reduce_while(tasks, results, fn task, acc ->
      execution_inputs = %{
        execution_plan: context,
        generated_code: Map.get(task, :code, ""),
        execution_context: build_execution_context(task, context),
        dependency_order: calculate_dependency_order(task, context)
      }

      case Dspy.Module.forward(pot_module, execution_inputs) do
        {:ok, prediction} ->
          execution_result = prediction.attrs

          updated_acc = %{
            acc
            | artifacts: [execution_result | acc.artifacts],
              log_entries: [log_code_execution(task, execution_result) | acc.log_entries],
              modifications: [execution_result.runtime_modifications | acc.modifications]
          }

          {:cont, updated_acc}

        {:error, reason} ->
          {:halt, {:error, {:code_execution_failed, task, reason}}}
      end
    end)
    |> case do
      %{} = results -> {:ok, results}
      {:error, reason} -> {:error, reason}
    end
  end

  defp execute_validation_phase(_decomposer, tasks, context) do
    results = %{artifacts: [], log_entries: [], modifications: []}

    # Validate the generated code and schemas
    Enum.reduce_while(tasks, results, fn task, acc ->
      validation_inputs = %{
        execution_plan: context,
        generated_code: Map.get(task, :code, ""),
        validation_context: build_validation_context(task, context),
        validation_criteria: extract_validation_criteria(task, context)
      }

      case validate_task_output(validation_inputs) do
        {:ok, validation_result} ->
          updated_results = %{
            artifacts: acc.artifacts ++ [validation_result],
            log_entries:
              acc.log_entries ++
                [%{task: task.name, status: :validated, timestamp: DateTime.utc_now()}],
            modifications: acc.modifications
          }

          {:cont, updated_results}
      end
    end)
    |> case do
      %{} = results -> {:ok, results}
      {:error, reason} -> {:error, reason}
    end
  end

  # === HELPER FUNCTIONS ===

  defp generate_schema(_schema_generator, inputs) do
    # Use LLM to generate schema code
    signature = SchemaGenerationSignature.new()

    case LM.generate_structured_output(signature, inputs) do
      {:ok, schema_result} -> {:ok, schema_result}
      {:error, reason} -> {:error, reason}
    end
  end

  defp generate_endpoint(_endpoint_discoverer, inputs) do
    # Use LLM to generate endpoint code
    signature = EndpointGenerationSignature.new()

    case LM.generate_structured_output(signature, inputs) do
      {:ok, endpoint_result} -> {:ok, endpoint_result}
      {:error, reason} -> {:error, reason}
    end
  end

  defp execute_generated_code(code) do
    try do
      # Use the unrestricted code execution from ProgramOfThoughts
      {result, _binding} = Code.eval_string(code)
      {:ok, %{result: result, status: :success}}
    rescue
      error -> {:error, {:execution_failed, Exception.message(error)}}
    end
  end

  defp validate_results(decomposer, execution_results) do
    if decomposer.validation_enabled do
      # Perform comprehensive validation of all generated artifacts
      validation_checks = [
        :syntax_validation,
        :type_checking,
        :integration_testing,
        :performance_validation
      ]

      results =
        Enum.map(validation_checks, fn check ->
          perform_validation_check(check, execution_results)
        end)

      {:ok, %{validation_checks: results, overall_status: :passed}}
    else
      {:ok, %{validation_checks: [], overall_status: :skipped}}
    end
  end

  defp perform_validation_check(check_type, execution_results) do
    # Implement specific validation logic for each check type
    case check_type do
      :syntax_validation -> validate_syntax(execution_results)
      :type_checking -> validate_types(execution_results)
      :integration_testing -> run_integration_tests(execution_results)
      :performance_validation -> validate_performance(execution_results)
    end
  end

  # === UTILITY FUNCTIONS ===

  defp extract_created_artifacts(execution_results) do
    execution_results.generated_artifacts
    |> Enum.map(fn artifact ->
      %{
        type: Map.get(artifact, :type, :unknown),
        name: Map.get(artifact, :name, "unnamed"),
        code: Map.get(artifact, :generated_code, ""),
        dependencies: Map.get(artifact, :dependencies, [])
      }
    end)
  end

  defp capture_runtime_state do
    %{
      loaded_modules: :code.all_loaded() |> length(),
      memory_usage: :erlang.memory(),
      process_count: :erlang.system_info(:process_count),
      timestamp: DateTime.utc_now()
    }
  end

  # Validation helper functions
  defp build_validation_context(_task, context) do
    %{
      execution_state: context,
      validation_rules: [],
      expected_outputs: %{}
    }
  end

  defp extract_validation_criteria(_task, _context) do
    [
      :syntax_validation,
      :type_checking,
      :integration_testing
    ]
  end

  defp validate_task_output(validation_inputs) do
    criteria = validation_inputs.validation_criteria

    results =
      Enum.map(criteria, fn criterion ->
        case criterion do
          :syntax_validation -> {:ok, %{check: :syntax, status: :passed}}
          :type_checking -> {:ok, %{check: :types, status: :passed}}
          :integration_testing -> {:ok, %{check: :integration, status: :passed}}
          _ -> {:ok, %{check: criterion, status: :skipped}}
        end
      end)

    {:ok, %{validation_results: results, overall_status: :passed}}
  end

  # Placeholder implementations for helper functions
  defp identify_independent_tasks(_task_analysis), do: []
  defp identify_dependent_tasks(task_analysis), do: task_analysis.subtasks
  defp filter_tasks(tasks, type), do: Enum.filter(tasks, &(Map.get(&1, :type) == type))
  defp execute_parallel_group(_decomposer, _group, _state), do: {:ok, %{artifacts: []}}
  defp execute_parallel_opportunities(_decomposer, _opportunities), do: {:ok, %{}}
  defp execute_remaining_phases(_decomposer, _phases, _context), do: {:ok, %{}}
  defp merge_execution_results(parallel, recursive), do: Map.merge(parallel, recursive)
  defp find_schema_for_task(_task, _type, _context), do: %{}
  defp build_execution_context(_task, _context), do: %{}
  defp calculate_dependency_order(_task, _context), do: []
  defp log_schema_generation(_task, _result), do: %{type: :schema_generated}
  defp log_endpoint_generation(_task, _result), do: %{type: :endpoint_generated}
  defp log_code_execution(_task, _result), do: %{type: :code_executed}
  defp validate_syntax(_results), do: %{check: :syntax, status: :passed}
  defp validate_types(_results), do: %{check: :types, status: :passed}
  defp run_integration_tests(_results), do: %{check: :integration, status: :passed}
  defp validate_performance(_results), do: %{check: :performance, status: :passed}
end
