Enhanced ADT system

enhanced-adt.ex

defmodule EnhancedADT do
  @moduledoc """
  Enhanced ADT system combining the best of both worlds:
  - Complete type system from ADT
  - Advanced recursion and state management from BenBen
  - Powerful fold/bend operations
  """

  defmacro __using__(_opts) do
    quote do
      import EnhancedADT.DSL
      import EnhancedADT.Fold
      import EnhancedADT.Bend
      import EnhancedADT.Recursion
    end
  end
end

defmodule EnhancedADT.DSL do
  @moduledoc """
  Enhanced DSL for defining algebraic data types with recursion markers
  """

  @doc """
  Enhanced sum type definition with recursion support
  
  ## Example
  ```elixir
  defsum Tree(a) do
    Leaf(a)
    Node(rec(Tree(a)), rec(Tree(a)))  # rec() marks recursive fields
  end
  ```
  """
  defmacro defsum(name_and_params, do: variants) do
    {name, params} = case name_and_params do
      {name, _, params} when is_list(params) -> {name, params}
      name when is_atom(name) -> {name, []}
    end
    
    variant_list = extract_variants(variants)
    
    quote do
      defmodule unquote(name) do
        @type_params unquote(params)
        @variants unquote(variant_list)
        
        # Generate constructor functions
        unquote_splicing(generate_constructors(variant_list))
        
        # Generate type definition
        unquote(generate_type_def(name, params, variant_list))
        
        # Generate pattern matching helpers
        unquote(generate_matchers(variant_list))
        
        # Generate enhanced fold function with recursion support
        unquote(generate_enhanced_fold_function(name, variant_list))
        
        # Generate metadata for recursion analysis
        def __recursive_fields__ do
          unquote(analyze_recursive_fields(variant_list))
        end
      end
    end
  end

  @doc """
  Enhanced product type with computed fields and lenses
  """
  defmacro defproduct(name, do: fields) do
    field_list = extract_fields(fields)
    
    quote do
      defmodule unquote(name) do
        @enforce_keys unquote(Enum.map(field_list, fn {name, _type, _opts} -> name end))
        defstruct unquote(Enum.map(field_list, fn {name, _type, opts} -> 
          {name, Keyword.get(opts, :default)}
        end))
        
        @type t :: %__MODULE__{
          unquote_splicing(
            Enum.map(field_list, fn {name, type, _opts} ->
              {name, type}
            end)
          )
        }
        
        # Generate constructor with validation
        def new(attrs \\ []) do
          struct = struct(__MODULE__, attrs)
          validate!(struct)
          struct
        end
        
        # Generate lenses for functional updates
        unquote_splicing(generate_lenses(field_list))
        
        # Generate validators
        unquote(generate_validators(field_list))
        
        # Generate computed fields
        unquote_splicing(generate_computed_fields(field_list))
      end
    end
  end

  # Mark recursive fields
  defmacro rec(type) do
    quote do: {:rec, unquote(type)}
  end

  # Helper functions
  defp extract_variants({:__block__, _, variants}), do: variants
  defp extract_variants(single_variant), do: [single_variant]

  defp extract_fields({:__block__, _, fields}), do: Enum.map(fields, &parse_field/1)
  defp extract_fields(single_field), do: [parse_field(single_field)]

  defp parse_field({:::, _, [{name, _, _}, type]}) do
    {name, type, []}
  end
  defp parse_field({name, _, _}) when is_atom(name) do
    {name, quote(do: any()), []}
  end
  # Support for field options: name :: type, opt1: val1, opt2: val2
  defp parse_field({:when, _, [{:::, _, [{name, _, _}, type]}, opts]}) do
    {name, type, extract_field_options(opts)}
  end

  defp extract_field_options({:__block__, _, opts}), do: opts
  defp extract_field_options(single_opt), do: [single_opt]

  defp generate_constructors(variants) do
    Enum.map(variants, fn
      {name, _, nil} ->
        quote do
          def unquote(name)(), do: {unquote(name)}
        end
      {name, _, []} ->
        quote do
          def unquote(name)(), do: {unquote(name)}
        end
      {name, _, args} when is_list(args) ->
        clean_args = Enum.map(args, &clean_recursive_marker/1)
        quote do
          def unquote(name)(unquote_splicing(clean_args)), do: {unquote(name), unquote_splicing(clean_args)}
        end
      name when is_atom(name) ->
        quote do
          def unquote(name)(), do: {unquote(name)}
        end
    end)
  end

  defp clean_recursive_marker({:rec, _, [arg]}), do: arg
  defp clean_recursive_marker(arg), do: arg

  defp analyze_recursive_fields(variants) do
    Enum.map(variants, fn
      {name, _, args} when is_list(args) ->
        recursive_positions = 
          args
          |> Enum.with_index()
          |> Enum.filter(fn 
            {{:rec, _, _}, _} -> true
            _ -> false
          end)
          |> Enum.map(&elem(&1, 1))
        
        {name, recursive_positions}
      
      {name, _, _} -> {name, []}
      name when is_atom(name) -> {name, []}
    end)
    |> Enum.into(%{})
  end

  defp generate_enhanced_fold_function(name, variants) do
    quote do
      def fold(value, handlers, opts \\ []) do
        state = Keyword.get(opts, :state)
        mode = Keyword.get(opts, :mode, :bottom_up)
        
        case mode do
          :bottom_up -> fold_bottom_up(value, handlers, state)
          :top_down -> fold_top_down(value, handlers, state)
          :stateful -> fold_stateful(value, handlers, state)
        end
      end
      
      defp fold_bottom_up(value, handlers, state) do
        # Process recursive fields first, then apply handler
        case value do
          unquote_splicing(generate_bottom_up_cases(variants))
          _ -> raise "Invalid #{unquote(name)} value: #{inspect(value)}"
        end
      end
      
      defp fold_top_down(value, handlers, state) do
        # Apply handler first, then process recursive fields
        case value do
          unquote_splicing(generate_top_down_cases(variants))
          _ -> raise "Invalid #{unquote(name)} value: #{inspect(value)}"
        end
      end
      
      defp fold_stateful(value, handlers, initial_state) do
        # Thread state through the computation
        case value do
          unquote_splicing(generate_stateful_cases(variants))
          _ -> raise "Invalid #{unquote(name)} value: #{inspect(value)}"
        end
      end
    end
  end

  defp generate_bottom_up_cases(variants) do
    Enum.map(variants, fn
      {name, _, nil} ->
        quote do
          {unquote(name)} -> 
            handler = Map.get(handlers, unquote(name), fn -> nil end)
            if state, do: {handler.(), state}, else: handler.()
        end
      {name, _, []} ->
        quote do
          {unquote(name)} -> 
            handler = Map.get(handlers, unquote(name), fn -> nil end)
            if state, do: {handler.(), state}, else: handler.()
        end
      {name, _, args} when is_list(args) ->
        # Generate pattern with proper variable binding
        vars = Enum.with_index(args) |> Enum.map(fn {_, i} -> Macro.var(:"arg#{i}", nil) end)
        recursive_positions = get_recursive_positions(args)
        
        quote do
          {unquote(name), unquote_splicing(vars)} ->
            # Process recursive fields first
            processed_args = unquote(generate_recursive_processing(vars, recursive_positions))
            handler = Map.get(handlers, unquote(name), fn _ -> nil end)
            
            if state do
              {result, new_state} = handler.(processed_args, state)
              {result, new_state}
            else
              handler.(processed_args)
            end
        end
      name when is_atom(name) ->
        quote do
          {unquote(name)} -> 
            handler = Map.get(handlers, unquote(name), fn -> nil end)
            if state, do: {handler.(), state}, else: handler.()
        end
    end)
  end

  defp get_recursive_positions(args) do
    args
    |> Enum.with_index()
    |> Enum.filter(fn 
      {{:rec, _, _}, _} -> true
      _ -> false
    end)
    |> Enum.map(&elem(&1, 1))
  end

  defp generate_recursive_processing(vars, recursive_positions) do
    Enum.map(Enum.with_index(vars), fn {var, i} ->
      if i in recursive_positions do
        quote do
          if state do
            {processed, new_state} = fold_bottom_up(unquote(var), handlers, state)
            state = new_state
            processed
          else
            fold_bottom_up(unquote(var), handlers, nil)
          end
        end
      else
        var
      end
    end)
  end

  defp generate_top_down_cases(variants) do
    # Similar to bottom_up but handler is applied first
    # Implementation similar to generate_bottom_up_cases but with different order
    []
  end

  defp generate_stateful_cases(variants) do
    # Similar to bottom_up but with explicit state threading
    # Implementation similar to generate_bottom_up_cases but with state management
    []
  end

  defp generate_lenses(fields) do
    Enum.map(fields, fn {name, _type, _opts} ->
      quote do
        def unquote(:"lens_#{name}")() do
          {
            fn struct -> Map.get(struct, unquote(name)) end,
            fn struct, value -> Map.put(struct, unquote(name), value) end
          }
        end
        
        def unquote(:"update_#{name}")(struct, func) do
          {getter, setter} = unquote(:"lens_#{name}")()
          current = getter.(struct)
          setter.(struct, func.(current))
        end
      end
    end)
  end

  defp generate_validators(fields) do
    quote do
      defp validate!(struct) do
        # Add validation logic here
        struct
      end
    end
  end

  defp generate_computed_fields(fields) do
    # Generate computed field functions
    []
  end

  # ... other helper functions from original ADT ...
  defp generate_type_def(name, params, variants) do
    type_variants = Enum.map(variants, fn
      {variant_name, _, nil} -> {variant_name}
      {variant_name, _, []} -> {variant_name}
      {variant_name, _, args} when is_list(args) ->
        clean_args = Enum.map(args, &clean_recursive_marker/1)
        quote do: {unquote(variant_name), unquote_splicing(clean_args)}
      variant_name when is_atom(variant_name) -> {variant_name}
    end)
    
    if params == [] do
      quote do
        @type t :: unquote({:|, [], type_variants})
      end
    else
      quote do
        @type t(unquote_splicing(params)) :: unquote({:|, [], type_variants})
      end
    end
  end

  defp generate_matchers(variants) do
    Enum.map(variants, fn
      {name, _, nil} ->
        quote do
          def unquote(:"is_#{name}")({unquote(name)}), do: true
          def unquote(:"is_#{name}")(_), do: false
        end
      {name, _, []} ->
        quote do
          def unquote(:"is_#{name}")({unquote(name)}), do: true
          def unquote(:"is_#{name}")(_), do: false
        end
      {name, _, _args} ->
        quote do
          def unquote(:"is_#{name}")({unquote(name), _}), do: true
          def unquote(:"is_#{name}")(_), do: false
        end
      name when is_atom(name) ->
        quote do
          def unquote(:"is_#{name}")({unquote(name)}), do: true
          def unquote(:"is_#{name}")(_), do: false
        end
    end)
  end
end

defmodule EnhancedADT.Fold do
  @moduledoc """
  Enhanced fold operations with BenBen-like power
  """

  @doc """
  Powerful fold with automatic recursion handling
  
  ## Example
  ```elixir
  fold tree, state: 0, mode: :bottom_up do
    Leaf(x) -> x
    Node(left, right) -> left + right
  end
  ```
  """
  defmacro fold(value, opts \\ [], do: clauses) do
    state = Keyword.get(opts, :state)
    mode = Keyword.get(opts, :mode, :bottom_up)
    
    cases = extract_fold_cases(clauses)
    handlers = generate_handler_map(cases)
    
    if state do
      quote do
        result = unquote(value).__struct__.fold(
          unquote(value), 
          unquote(handlers), 
          state: unquote(state),
          mode: unquote(mode)
        )
        result
      end
    else
      quote do
        unquote(value).__struct__.fold(
          unquote(value), 
          unquote(handlers), 
          mode: unquote(mode)
        )
      end
    end
  end

  @doc """
  Stateful fold with explicit state threading
  """
  defmacro fold_with_state(value, initial_state, do: clauses) do
    cases = extract_fold_cases(clauses)
    handlers = generate_stateful_handler_map(cases)
    
    quote do
      unquote(value).__struct__.fold(
        unquote(value),
        unquote(handlers),
        state: unquote(initial_state),
        mode: :stateful
      )
    end
  end

  @doc """
  Parallel fold for independent computations
  """
  defmacro fold_parallel(value, do: clauses) do
    # Implementation for parallel processing
    quote do
      # Parallel fold implementation
      fold(unquote(value), mode: :parallel, do: unquote(clauses))
    end
  end

  defp extract_fold_cases({:__block__, _, clauses}), do: clauses
  defp extract_fold_cases(single_clause), do: [single_clause]

  defp generate_handler_map(cases) do
    handlers = Enum.map(cases, fn
      {:->, _, [[{name, _, args}], body]} when is_list(args) ->
        {name, quote(do: fn unquote(args) -> unquote(body) end)}
      {:->, _, [[{name, _, _}], body]} ->
        {name, quote(do: fn -> unquote(body) end)}
      {:->, _, [[name], body]} when is_atom(name) ->
        {name, quote(do: fn -> unquote(body) end)}
    end)
    
    quote do: %{unquote_splicing(handlers)}
  end

  defp generate_stateful_handler_map(cases) do
    handlers = Enum.map(cases, fn
      {:->, _, [[{name, _, args}], body]} when is_list(args) ->
        {name, quote(do: fn unquote(args), state -> {unquote(body), state} end)}
      {:->, _, [[{name, _, _}], body]} ->
        {name, quote(do: fn state -> {unquote(body), state} end)}
      {:->, _, [[name], body]} when is_atom(name) ->
        {name, quote(do: fn state -> {unquote(body), state} end)}
    end)
    
    quote do: %{unquote_splicing(handlers)}
  end
end

defmodule EnhancedADT.Bend do
  @moduledoc """
  Enhanced bend operations with fork support
  """

  @doc """
  Powerful unfold with fork semantics
  
  ## Example
  ```elixir
  bend from: 10 do
    n when n > 0 -> Tree.Node(fork(n-1), fork(n-1))
    0 -> Tree.Leaf(0)
  end
  ```
  """
  defmacro bend(opts, do: clauses) do
    seed = Keyword.get(opts, :from)
    cases = extract_bend_cases(clauses)
    
    quote do
      EnhancedADT.Bend.unfold_with_fork(unquote(seed), fn value ->
        case value do
          unquote_splicing(cases)
        end
      end)
    end
  end

  @doc """
  Fork operation for parallel unfold branches
  """
  defmacro fork(expr) do
    quote do: {:fork, unquote(expr)}
  end

  @doc """
  Unfold with fork support
  """
  def unfold_with_fork(seed, generator) do
    case generator.(seed) do
      {:fork, next_seed} ->
        unfold_with_fork(next_seed, generator)
      
      {tag, {:fork, arg1}, {:fork, arg2}} ->
        {tag, unfold_with_fork(arg1, generator), unfold_with_fork(arg2, generator)}
      
      {tag, {:fork, arg}} ->
        {tag, unfold_with_fork(arg, generator)}
      
      {tag, args} when is_list(args) ->
        processed_args = Enum.map(args, fn
          {:fork, arg} -> unfold_with_fork(arg, generator)
          arg -> arg
        end)
        List.to_tuple([tag | processed_args])
      
      {tag} -> {tag}
      result -> result
    end
  end

  defp extract_bend_cases({:__block__, _, clauses}), do: clauses
  defp extract_bend_cases(single_clause), do: [single_clause]
end

defmodule EnhancedADT.Recursion do
  @moduledoc """
  Advanced recursion utilities
  """

  @doc """
  Automatic memoization for recursive functions
  """
  defmacro memo_fold(value, do: clauses) do
    quote do
      memo_table = :ets.new(:memo_table, [:set, :private])
      
      try do
        result = memo_fold_impl(unquote(value), memo_table, unquote(clauses))
        result
      after
        :ets.delete(memo_table)
      end
    end
  end

  def memo_fold_impl(value, memo_table, clauses) do
    # Implementation of memoized fold
    case :ets.lookup(memo_table, value) do
      [{^value, result}] -> result
      [] ->
        result = fold(value, do: clauses)
        :ets.insert(memo_table, {value, result})
        result
    end
  end

  @doc """
  Zipper for navigating recursive structures
  """
  def zipper(value) do
    %{
      focus: value,
      path: [],
      modified: false
    }
  end

  def move_down(zipper, index) do
    # Implementation for moving down in the structure
    zipper
  end

  def move_up(zipper) do
    # Implementation for moving up in the structure
    zipper
  end

  def modify(zipper, func) do
    # Implementation for modifying the current focus
    %{zipper | focus: func.(zipper.focus), modified: true}
  end
end

# Enhanced examples
defmodule EnhancedADT.Examples do
  use EnhancedADT

  # Tree with recursion markers
  defsum Tree(a) do
    Leaf(a)
    Node(rec(Tree(a)), rec(Tree(a)))
  end

  # Maybe with enhanced operations
  defsum Maybe(a) do
    Some(a)
    None
  end

  # Enhanced product type with computed fields
  defproduct Person do
    first_name :: String.t()
    last_name :: String.t()
    age :: integer()
    # computed field would be generated
  end

  # Usage examples
  def tree_sum(tree) do
    fold tree, mode: :bottom_up do
      Leaf(x) -> x
      Node(left, right) -> left + right
    end
  end

  def tree_sum_with_depth(tree) do
    fold_with_state tree, 0 do
      Leaf(x) -> {x, state + 1}
      Node(left, right) -> {left + right, state + 1}
    end
  end

  def generate_perfect_tree(depth) do
    bend from: depth do
      n when n > 0 -> Tree.Node(fork(n-1), fork(n-1))
      0 -> Tree.Leaf(0)
    end
  end

  def memoized_fibonacci_tree(n) do
    memo_fold generate_perfect_tree(n) do
      Leaf(x) -> x
      Node(left, right) -> left + right
    end
  end
end