#include <memory>
#include <variant>

// for clangd
#include "../include/build_visitor.hpp"
#include "../include/parse_token_types.hpp"
#include "../include/error_handling.hpp"

namespace interpreter {

void SetPosition(BaseNode& base_node, parser::ParseTree::Node& parse_node) {
  base_node.start_position = parse_node.GetStartPoint();
  base_node.end_position = parse_node.GetEndPoint();
}

// Sources -----------------
void BuildVisitor::Visit(SourceFile* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;
  size_t statement_count = parse_node.NamedChildCount();

  node->statements.resize(statement_count);

  for (size_t i = 0; i < statement_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);
    Visit(node->statements[i]);
  }

  current_node_ = parse_node;
}

// Namespaces, partitions -----------------

void BuildVisitor::Visit(NamespaceSources* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;
  size_t statement_count = parse_node.NamedChildCount();

  node->statements.resize(statement_count);

  for (size_t i = 0; i < statement_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);
    Visit(node->statements[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(Namespace* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.ChildCount();

  if (child_count > 3) { // "namespace", ["var"/"const",] type, scope
    std::string modifier = parse_node.NthChild(1).GetValue();
    if (modifier == "const") {
      node->modifier = utils::ClassInternalsModifier::Const;
    } else if (modifier == "var") {
      node->modifier = utils::ClassInternalsModifier::Var;
    } else {
      error_handling::HandleInternalError("Can't parse namespace modifier",
                                          "BuildVisitor.Namespace",
                                          &node->base);
    }
  } else {
    node->modifier = utils::ClassInternalsModifier::Static;
  }

  node->type = parse_node.ChildByFieldName("type").GetValue();

  current_node_ = parse_node.ChildByFieldName("scope");
  Visit(&node->scope);

  current_node_ = parse_node;
}

// Definitions -----------------

void BuildVisitor::Visit(ImportStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t excluded_child_count = 0;

  if (parse_node.NthChild(0).GetValue() == "use") {
    node->name = parse_node.ChildByFieldName("name").GetValue();
    ++excluded_child_count;
  }

  StringLiteral module_name;
  current_node_ = parse_node.ChildByFieldName("module_name");
  Visit(&module_name);
  node->module_name = module_name.value;
  ++excluded_child_count;

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > excluded_child_count) {
    node->symbols.resize(child_count - excluded_child_count);

    for (size_t i = 0; i < child_count - excluded_child_count; ++i) {
        node->symbols[i] = parse_node.NthNamedChild(i + excluded_child_count).GetValue();
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(AliasDefinitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  std::string modifier = parse_node.NthChild(0).GetValue();
  if (modifier == "alias") {
    node->modifier = utils::AliasModifier::Alias;
  } else if (modifier == "type") {
    node->modifier = utils::AliasModifier::Type;
  } else if (modifier == "let") {
    node->modifier = utils::AliasModifier::Let;
  }

  node->type = parse_node.ChildByFieldName("type").GetValue();

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 2) {
    node->parameters.resize(child_count - 2);

    for (size_t i = 0; i + 2 < child_count; ++i) {
        node->parameters[i] = parse_node.NthNamedChild(i + 1).GetValue();
    }
  }

  current_node_ = parse_node.ChildByFieldName("value");
  node->value = std::make_unique<TypeExpression>();
  Visit(node->value.get());

  current_node_ = parse_node;
}

void BuildVisitor::Visit(VariableDefinitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  std::string modifier = parse_node.NthChild(0).GetValue();
  if (modifier == "const") {
    node->modifier = utils::IsConstModifier::Const;
  } else if (modifier == "var") {
    node->modifier = utils::IsConstModifier::Var;
  } else {
    // error
  }

  current_node_ = parse_node.ChildByFieldName("name");
  Visit(node->name);

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  std::string assignment_modifier = parse_node.NthChild(2).GetValue();
  if (assignment_modifier == "=") {
    node->assignment_modifier = utils::AssignmentModifier::Assign;
  } else if (assignment_modifier == "<-") {
    node->assignment_modifier = utils::AssignmentModifier::Move;
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(FunctionDeclaration* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  // ['decl'] ['interface'] name
  if (parse_node.NthChild(0).GetValue() == "decl") {
    node->is_in_interface = (parse_node.NthChild(1).GetValue() == "interface");
  } else {
    node->is_in_interface = false;
  }

  node->name = parse_node.ChildByFieldName("name").GetValue();

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 2) {
    node->parameters.resize(child_count - 2);
    for (size_t i = 0; i + 2 < child_count; ++i) {
        current_node_ = parse_node.NthNamedChild(i + 1);
        node->parameters[i] = std::make_unique<AnnotatedAbstractType>();
        Visit(node->parameters.back().get());
    }
  }

  current_node_ = parse_node.ChildByFieldName("type");
  node->type = std::make_unique<FunctionType>();
  Visit(node->type.get());

  current_node_ = parse_node;
}

void BuildVisitor::Visit(FunctionDefinitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("definition");
  node->definition = std::make_unique<FunctionDefinition>();
  Visit(node->definition.get());

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeDefinitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  std::string modifier = parse_node.NthChild(0).GetValue();
  if (modifier == "class") {
    node->modifier = utils::ClassModifier::Class;
  } else if (modifier == "struct") {
    node->modifier = utils::ClassModifier::Struct;
  }

  node->is_in_interface = (parse_node.NthChild(1).GetValue() == "interface");

  current_node_ = parse_node.ChildByFieldName("definition");
  node->definition = std::make_unique<TypeDefinition>();
  Visit(node->definition.get());

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(AbstractTypeDefinitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  std::string modifier = parse_node.NthChild(0).GetValue();
  if (modifier == "basic") {
    node->modifier = utils::AbstractTypeModifier::Basic;
  } else if (modifier == "abstract") {
    node->modifier = utils::AbstractTypeModifier::Abstract;
  }

  current_node_ = parse_node.ChildByFieldName("type");
  node->type = std::make_unique<AnnotatedType>();
  Visit(node->type.get());

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeclassDefinitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("definition");
  node->definition = std::make_unique<TypeDefinition>();
  Visit(node->definition.get());

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->requirements.reserve(child_count - 1);

    for (size_t i = 0; i + 1 < child_count; ++i) {
        current_node_ = parse_node.NthNamedChild(i + 1);

        std::string modifier_name = current_node_.PreviousSibling().GetValue();
        utils::ClassInternalsModifier modifier;
        if (modifier_name == "const") {
          modifier = utils::ClassInternalsModifier::Const;
        } else if (modifier_name == "var") {
          modifier = utils::ClassInternalsModifier::Var;
        } else {
          modifier = utils::ClassInternalsModifier::Static;
        }
        node->requirements.push_back({modifier,
                                      std::make_unique<FunctionDeclaration>()});
        Visit(node->requirements.back().second.get());
    }

  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(PartitionStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  std::string partition_modifier = parse_node.NthChild(0).GetValue();

  if (partition_modifier == "exec") {
    node->modifier = utils::PartitionModifier::Exec;
  } else if (partition_modifier == "test") {
    node->modifier = utils::PartitionModifier::Test;
  } else {
    // error
  }

  current_node_ = parse_node.ChildByFieldName("name");
  Visit(&node->name);

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  current_node_ = parse_node;
}

//

void BuildVisitor::Visit(NamespaceStatement& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::AliasDefinitionStatement) { // optimize ??
    node = std::make_unique<AliasDefinitionStatement>();
    Visit(std::get<std::unique_ptr<AliasDefinitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::FunctionDeclaration) {
    node = std::make_unique<FunctionDeclaration>();
    Visit(std::get<std::unique_ptr<FunctionDeclaration>>(node).get());
  } else if (current_node_type == parser::tokens::FunctionDefinitionStatement) {
    node = std::make_unique<FunctionDefinitionStatement>();
    Visit(std::get<std::unique_ptr<FunctionDefinitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::TypeDefinitionStatement) {
    node = std::make_unique<TypeDefinitionStatement>();
    Visit(std::get<std::unique_ptr<TypeDefinitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::PartitionStatement) {
    node = std::make_unique<PartitionStatement>();
    Visit(std::get<std::unique_ptr<PartitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::Namespace) {
    node = std::make_unique<Namespace>();
    Visit(std::get<std::unique_ptr<Namespace>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(SourceStatement& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::ImportStatement) { // optimize ??
    node = std::make_unique<ImportStatement>();
    Visit(std::get<std::unique_ptr<ImportStatement>>(node).get());
  } else if (current_node_type == parser::tokens::AbstractTypeDefinitionStatement) { // optimize ??
    node = std::make_unique<AbstractTypeDefinitionStatement>();
    Visit(std::get<std::unique_ptr<AbstractTypeDefinitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::TypeclassDefinitionStatement) {
    node = std::make_unique<TypeclassDefinitionStatement>();
    Visit(std::get<std::unique_ptr<TypeclassDefinitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::NamespaceStatement) {
    node = std::make_unique<NamespaceStatement>();
    Visit(*std::get<std::unique_ptr<NamespaceStatement>>(node));
  } else {
    // error
  }

  current_node_ = parse_node;
}

// Definition parts

void BuildVisitor::Visit(FunctionDefinition* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->name = parse_node.ChildByFieldName("name").GetValue();

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->arguments.resize(child_count - 1);
    for (size_t i = 0; i + 1 < child_count; ++i) {
      node->arguments[i] = parse_node.NthNamedChild(i + 1).GetValue();
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeDefinition* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("type");
  node->type = std::make_unique<AnnotatedType>();
  Visit(node->type.get());

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    for (size_t i = 0; i + 1 < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i + 1);
      node->parameters.push_back(std::make_unique<AnnotatedAbstractType>());
      Visit(node->parameters.back().get());
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(AnyAnnotatedType* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->type = parse_node.ChildByFieldName("type").GetValue();

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->typeclasses.resize(child_count - 1);

    for (size_t i = 0; i + 1 < child_count; ++i) {
        current_node_ = parse_node.NthNamedChild(i + 1);
        node->typeclasses[i] = std::make_unique<ParametrizedTypeclass>();
        Visit(node->typeclasses[i].get());
    }
  }

  current_node_ = parse_node;
}

// Flow control -----------------

void BuildVisitor::Visit(TypeConstructorPatternParameter* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->name.value() = parse_node.ChildByFieldName("name").GetValue();
  }

  current_node_ = parse_node.ChildByFieldName("value"),
  Visit(node->value);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeConstructorPattern* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("constructor");
  node->constructor = std::make_unique<TypeExpression>();
  Visit(node->constructor.get());

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->parameters.resize(child_count - 1);

    for (size_t i = 0; i + 1 < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i + 1);
      Visit(&node->parameters[i]);
    }
  }

  current_node_ = parse_node;
}


void BuildVisitor::Visit(Pattern& node) { // <-> ScopedPattern
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::NameIdentifier) { // optimize ??
    node = std::make_unique<NameIdentifier>(current_node_.GetValue());
    // Visit(std::get<std::unique_ptr<NameIdentifier>>(node).get());
  } else if (current_node_type == parser::tokens::Literal) {
    node = std::make_unique<Literal>();
    Visit(*std::get<std::unique_ptr<Literal>>(node));
  } else if (current_node_type == parser::tokens::TypeConstructorPattern) {
    node = std::make_unique<TypeConstructorPattern>();
    Visit(std::get<std::unique_ptr<TypeConstructorPattern>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(MatchCase* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    std::string prefix = parse_node.NthChild(2).GetValue();

    if (child_count > 2 || prefix == "?") {
      current_node_ = parse_node.ChildByFieldName("condition");
      node->condition.emplace();
      Visit(node->condition.value());
    }

    if (child_count > 2 || prefix == "->") {
      current_node_ = parse_node.ChildByFieldName("statement");
      node->statement.emplace();
      Visit(node->statement.value());
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(Match* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->is_consuming_value = (parse_node.NthChild(1).GetValue() == "<-");

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  size_t child_count = parse_node.NamedChildCount();

  // if (child_count > 1) { // always true (repeat1)
  node->matches.resize(child_count - 1);

  for (size_t i = 0; i + 1 < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i + 1);
      Visit(&node->matches[i]);
  }
  // }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(Condition* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.NamedChildCount();

  node->conditions.resize(child_count / 2);
  node->statements.resize((child_count + 1) / 2);

  for (size_t i = 0; i < child_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);

    if (i % 2 == 0 && i / 2 < node->conditions.size()) {
      Visit(node->conditions[i / 2]);
    } else {
      Visit(node->statements[i / 2]);
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(DoWhileLoop* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("statement");
  Visit(node->statement);

  current_node_ = parse_node.ChildByFieldName("condition");
  Visit(node->condition);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(WhileLoop* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("condition");
  Visit(node->condition);

  current_node_ = parse_node.ChildByFieldName("statement");
  Visit(node->statement);

  current_node_ = parse_node;
}
void BuildVisitor::Visit(ForLoop* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  if (parse_node.ChildCount() < 7) { // no "var" node
    node->variable_modifier = utils::IsConstModifier::Const;
  } else {
    node->variable_modifier = utils::IsConstModifier::Var;
  }

  current_node_ = parse_node.ChildByFieldName("variable");
  Visit(node->variable);

  current_node_ = parse_node.ChildByFieldName("interval");
  Visit(node->interval);

  current_node_ = parse_node.ChildByFieldName("statement");
  Visit(node->statement);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(LoopLoop* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("statement");
  Visit(node->statement);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(FlowControl& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::Match) { // optimize ??
    node = std::make_unique<Match>();
    Visit(std::get<std::unique_ptr<Match>>(node).get());
  } else if (current_node_type == parser::tokens::Condition) {
    node = std::make_unique<Condition>();
    Visit(std::get<std::unique_ptr<Condition>>(node).get());
  } else if (current_node_type == parser::tokens::DoWhileLoop) {
    node = std::make_unique<DoWhileLoop>();
    Visit(std::get<std::unique_ptr<DoWhileLoop>>(node).get());
  } else if (current_node_type == parser::tokens::WhileLoop) {
    node = std::make_unique<WhileLoop>();
    Visit(std::get<std::unique_ptr<WhileLoop>>(node).get());
  } else if (current_node_type == parser::tokens::ForLoop) {
    node = std::make_unique<ForLoop>();
    Visit(std::get<std::unique_ptr<ForLoop>>(node).get());
  } else if (current_node_type == parser::tokens::LoopLoop) {
    node = std::make_unique<LoopLoop>();
    Visit(std::get<std::unique_ptr<LoopLoop>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

// Statements, expressions, blocks, etc. -----------------

void BuildVisitor::Visit(BlockStatement& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::Expression) { // optimize ??
    node = std::make_unique<Expression>();
    Visit(*std::get<std::unique_ptr<Expression>>(node));
  } else if (current_node_type == parser::tokens::VariableDefinitionStatement) {
    node = std::make_unique<VariableDefinitionStatement>();
    Visit(std::get<std::unique_ptr<VariableDefinitionStatement>>(node).get());
  } else if (current_node_type == parser::tokens::FlowControl) {
    node = std::make_unique<FlowControl>();
    Visit(*std::get<std::unique_ptr<FlowControl>>(node));
  } else if (current_node_type == parser::tokens::PrefixedExpression) {
    node = std::make_unique<PrefixedExpression>();
    Visit(*std::get<std::unique_ptr<PrefixedExpression>>(node));
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(Block* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;
  size_t statement_count = parse_node.NamedChildCount();

  node->statements.resize(statement_count);

  for (size_t i = 0; i < statement_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i);
      Visit(node->statements[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(SubExpressionToken& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::NameExpression) {
    node = std::make_unique<NameExpression>();
    Visit(std::get<std::unique_ptr<NameExpression>>(node).get());
  } else if (current_node_type == parser::tokens::ScopedStatement) {
    node = std::make_unique<ScopedStatement>();
    Visit(std::get<std::unique_ptr<ScopedStatement>>(node).get());
  } if (current_node_type == parser::tokens::AccessExpression) {
    node = std::make_unique<AccessExpression>();
    Visit(std::get<std::unique_ptr<AccessExpression>>(node).get());
  } else if (current_node_type == parser::tokens::Literal) {
    node = std::make_unique<Literal>();
    Visit(*std::get<std::unique_ptr<Literal>>(node));
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(SubExpression& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::FunctionCallExpression) { // optimize ??
    node = std::make_unique<FunctionCallExpression>();
    Visit(std::get<std::unique_ptr<FunctionCallExpression>>(node).get());
  } else if (current_node_type == parser::tokens::BinaryOperatorExpression) {
    node = std::make_unique<FunctionCallExpression>();
    VisitBinaryOperatorExpression(std::get<std::unique_ptr<FunctionCallExpression>>(node).get());
  } else if (current_node_type == parser::tokens::SubExpressionToken) {
    node = std::make_unique<SubExpressionToken>();
    Visit(*std::get<std::unique_ptr<SubExpressionToken>>(node));
  } else if (current_node_type == parser::tokens::ReferenceExpression) {
    node = std::make_unique<ReferenceExpression>();
    Visit(std::get<std::unique_ptr<ReferenceExpression>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(PrefixedExpression& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::ReturnExpression) { // optimize ??
    node = std::make_unique<ReturnExpression>();
    Visit(std::get<std::unique_ptr<ReturnExpression>>(node).get());
  } else if (current_node_type == parser::tokens::LoopControlExpression) {
    node = std::make_unique<LoopControlExpression>();
    Visit(*std::get<std::unique_ptr<LoopControlExpression>>(node));
  } else if (current_node_type == parser::tokens::Block) {
    node = std::make_unique<Block>();
    Visit(std::get<std::unique_ptr<Block>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(Expression& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::LambdaFunction) { // optimize ??
    node = std::make_unique<LambdaFunction>();
    Visit(std::get<std::unique_ptr<LambdaFunction>>(node).get());
  } else if (current_node_type == parser::tokens::TypeConstructor) {
    node = std::make_unique<TypeConstructor>();
    Visit(std::get<std::unique_ptr<TypeConstructor>>(node).get());
  } else if (current_node_type == parser::tokens::PrefixedExpression) {
    node = std::make_unique<PrefixedExpression>();
    Visit(*std::get<std::unique_ptr<PrefixedExpression>>(node));
  } else if (current_node_type == parser::tokens::SubExpression) {
    node = std::make_unique<SubExpression>();
    Visit(*std::get<std::unique_ptr<SubExpression>>(node));
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(SuperExpression& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::FlowControl) { // optimize ??
    node = std::make_unique<FlowControl>();
    Visit(*std::get<std::unique_ptr<FlowControl>>(node));
  } else if (current_node_type == parser::tokens::TupleExpression) {
    node = std::make_unique<TupleExpression>();
    Visit(std::get<std::unique_ptr<TupleExpression>>(node).get());
  } else if (current_node_type == parser::tokens::VariantExpression) {
    node = std::make_unique<VariantExpression>();
    Visit(std::get<std::unique_ptr<VariantExpression>>(node).get());
  } else if (current_node_type == parser::tokens::ArrayExpression) {
    node = std::make_unique<ArrayExpression>();
    Visit(std::get<std::unique_ptr<ArrayExpression>>(node).get());
  } else if (current_node_type == parser::tokens::Expression) {
    node = std::make_unique<Expression>();
    Visit(*std::get<std::unique_ptr<Expression>>(node));
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(ScopedStatement* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("statement");
  Visit(node->statement);

  current_node_ = parse_node;
}

// Operators

void BuildVisitor::VisitBinaryOperatorExpression(FunctionCallExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->is_binary_operator_expression = true;
  node->arguments.resize(2);

  current_node_ = parse_node.ChildByFieldName("left_expression");
  Visit(node->arguments[0]);

  node->name = parse_node.ChildByFieldName("operator_name").GetValue();

  { // remove operator precedence markers
    size_t operator_size = 0;
    for (; operator_size < node->name.size() && node->name[operator_size] != '.'; ++operator_size) {}
    node->precedence = utils::MaxOperatorPrecedence - (node->name.size() - operator_size);
    node->name = node->name.substr(0, operator_size);
  }

  current_node_ = parse_node.ChildByFieldName("right_expression");
  Visit(node->arguments[1]);

  // ??
  for (size_t i = 0; i < node->arguments.size(); ++i) {
    if (std::holds_alternative<std::unique_ptr<FunctionCallExpression>>(node->arguments[i])) {
      FunctionCallExpression* argument_node = std::get<std::unique_ptr<FunctionCallExpression>>(node->arguments[i]).get();
      if (argument_node->is_binary_operator_expression
          && argument_node->precedence.has_value()
          && argument_node->precedence.value() >= node->precedence.value()) {
        error_handling::HandleParsingError("Operators can't be chained (left argument)", node->base.start_position, node->base.end_position);
      }
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(ReferenceExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.ChildCount();

  if (child_count > 1) {
    node->references.resize(child_count - 1);
    for (size_t i = 0; i + 1 < child_count; ++i) {
      std::string reference = parse_node.NthChild(i).GetValue();
      if (reference == "^") {
        node->references[i] = utils::ReferenceModifier::Reference;
      } else if (reference == "~") {
        node->references[i] = utils::ReferenceModifier::Dereference;
      } else if (reference == "@") {
        node->references[i] = utils::ReferenceModifier::UniqueReference; // TODO: rename to move ??
      }
    }
  }

  current_node_ = parse_node.ChildByFieldName("expression");
  node->expression = std::make_unique<ScopedStatement>();
  Visit(node->expression.get());

  current_node_ = parse_node;
}

void BuildVisitor::Visit(AccessExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  current_node_ = parse_node.ChildByFieldName("name");
  node->name = std::make_unique<NameExpression>();
  Visit(node->name.get());

  current_node_ = parse_node.ChildByFieldName("id");
  Visit(node->id);

  current_node_ = parse_node;
}

// Other expressions

void BuildVisitor::Visit(FunctionCallExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t excluded_child_count = 0;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::SubExpressionToken) {
    node->prefix = std::make_unique<SubExpressionToken>();
    Visit(*std::get<std::unique_ptr<SubExpressionToken>>(node->prefix.value()));
    ++excluded_child_count;
  } else if (current_node_type == parser::tokens::TypeExpression) {
    node->prefix = std::make_unique<TypeExpression>();
    Visit(std::get<std::unique_ptr<TypeExpression>>(node->prefix.value()).get());
    ++excluded_child_count;
  } else {
    // no prefix
  }

  node->name = parse_node.ChildByFieldName("name").GetValue();
  ++excluded_child_count;

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > excluded_child_count) {
    bool parameters_ended = false;

    for (size_t i = 0; i + excluded_child_count < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i + excluded_child_count);

      if (current_node_.GetType() != parser::tokens::TypeExpression) {
        parameters_ended = true;
      }

      if (!parameters_ended) {
        node->parameters.push_back(std::make_unique<TypeExpression>());
        Visit(node->parameters.back().get());
      } else {
        node->arguments.push_back(std::make_unique<SubExpressionToken>());
        Visit(*std::get<std::unique_ptr<SubExpressionToken>>(node->arguments.back()));
      }
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TupleExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t expressions_count = parse_node.NamedChildCount();

  node->expressions.resize(expressions_count);

  for (size_t i = 0; i < expressions_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);
    Visit(node->expressions[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(VariantExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t expressions_count = parse_node.NamedChildCount();

  node->expressions.resize(expressions_count);

  for (size_t i = 0; i < expressions_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);
    Visit(node->expressions[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(ReturnExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->is_from_definition = (parse_node.NthChild(0).GetValue() == "return"); // "return" to return from definition and "bring" to return from block

  current_node_ = parse_node.ChildByFieldName("expression");
  Visit(node->expression);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeConstructorParameter* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->name = parse_node.ChildByFieldName("name").GetValue();

    std::string assignment_modifier = current_node_.NextSibling().GetValue();
    if (assignment_modifier == "=") {
      node->asignment_modifier = utils::AssignmentModifier::Assign;
    } else if (assignment_modifier == "<-") {
      node->asignment_modifier = utils::AssignmentModifier::Move;
    }
  }

  current_node_ = parse_node.ChildByFieldName("value");
  Visit(node->value);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeConstructor* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->is_allocated_on_heap = (parse_node.NthChild(1).GetValue() == "@");

  current_node_ = parse_node.ChildByFieldName("constructor");
  node->constructor = std::make_unique<TypeExpression>();
  Visit(node->constructor.get());

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->parameters.resize(child_count - 1);

    for (size_t i = 0; i + 1 < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i + 1);
      Visit(&node->parameters[i]);
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(LambdaFunction* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    bool parameters_ended = false;

    for (size_t i = 0; i + 1 < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i);

      if (current_node_.GetType() != parser::tokens::AnnotatedAbstractType) {
        parameters_ended = true;
      }

      if (!parameters_ended) {
        node->parameters.push_back(std::make_unique<AnnotatedAbstractType>());
        Visit(node->parameters.back().get());
      } else {
        node->arguments.emplace_back();
        node->arguments.back() = current_node_.GetValue();
      }
    }
  }

  current_node_ = parse_node.ChildByFieldName("expression");
  Visit(node->expression);

  current_node_ = parse_node;
}

void BuildVisitor::Visit(ArrayExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t elements_count = parse_node.NamedChildCount();

  node->elements.resize(elements_count);

  for (size_t i = 0; i < elements_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);
    Visit(node->elements[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(LoopControlExpression& node) {
  std::string value = current_node_.NthChild(0).GetValue();

  if (value == "break") {
    node = LoopControlExpression::Break;
  } else if (value == "continue") {
    node = LoopControlExpression::Continue;
  } else {
    // error
  }
}

// Name

void BuildVisitor::Visit(PartitionName* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->path.resize(child_count - 1);
    for (size_t i = 0; i + 1 < child_count; ++i) {
      node->path[i] = parse_node.NthNamedChild(i).GetValue();
    }
  }

  node->path.push_back(parse_node.ChildByFieldName("name").GetValue());

  current_node_ = parse_node;
}

void BuildVisitor::Visit(NameExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.NamedChildCount();

  node->names.resize(child_count);
  for (size_t i = 0; i < child_count; ++i) {
    node->names[i] = parse_node.NthNamedChild(i).GetValue();
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TupleName* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t names_count = parse_node.NamedChildCount();

  node->names.resize(names_count);

  for (size_t i = 0; i < names_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i);
      node->names[i] = std::make_unique<AnnotatedName>();
      Visit(node->names[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(VariantName* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t names_count = parse_node.NamedChildCount();

  node->names.resize(names_count);

  for (size_t i = 0; i < names_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i);
      node->names[i] =std::make_unique<AnnotatedName>();
      Visit(node->names[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(AnnotatedName* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->name = parse_node.ChildByFieldName("name").GetValue();

  if (parse_node.NamedChildCount() > 1) {
    current_node_ = parse_node.ChildByFieldName("type");
    node->type.emplace();
    Visit(node->type.value());

    current_node_ = parse_node;
  }
}

void BuildVisitor::Visit(AnyName& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::AnnotatedName) {
    node = std::make_unique<AnnotatedName>();
    Visit(std::get<std::unique_ptr<AnnotatedName>>(node).get());
  } else if (current_node_type == parser::tokens::TupleName) {
    node = std::make_unique<TupleName>();
    Visit(std::get<std::unique_ptr<TupleName>>(node).get());
  } else if (current_node_type == parser::tokens::VariantName) {
    node = std::make_unique<VariantName>();
    Visit(std::get<std::unique_ptr<VariantName>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

// Type, typeclass, etc. -----------------

// Type

void BuildVisitor::Visit(FunctionType* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t types_count = parse_node.NamedChildCount();

  node->types.resize(types_count);

  for (size_t i = 0; i < types_count; ++i) {
    current_node_ = parse_node.NthNamedChild(i);
    Visit(node->types[i]);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TupleType* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t current_child = 0;

  current_node_ = parse_node.NthNamedChild(current_child);

  if (parse_node.NthChild(0).GetValue() != "&") {
    node->type = current_node_.GetValue();

    ++current_child;
    current_node_ = parse_node.NthNamedChild(current_child);
  }

  while (current_child < parse_node.NamedChildCount()) {
    node->entities.emplace_back();

    if (current_node_.GetType() == parser::tokens::NameIdentifier) {
      node->entities.back().first = current_node_.GetValue();

      ++current_child;
      current_node_ = parse_node.NthNamedChild(current_child);
    }

    node->entities.back().second = std::make_unique<ExtendedScopedAnyType>();
    Visit(node->entities.back().second.get());

    ++current_child;
    current_node_ = parse_node.NthNamedChild(current_child);
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(VariantType* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t excluded_child_count = 0;

  size_t child_count = parse_node.NamedChildCount();

  if (parse_node.NthChild(0).GetValue() != "|") {
    node->type = parse_node.NthNamedChild(0).GetValue();

    ++excluded_child_count;
  }


  node->constructors.resize(child_count - excluded_child_count);
  for (size_t i = 0; i < node->constructors.size(); ++i) {
    current_node_ = parse_node.NthNamedChild(i + excluded_child_count);

    std::string current_node_type = current_node_.GetType();

    if (current_node_type == parser::tokens::Constructor) {
      node->constructors[i] = current_node_.GetValue();
    } else if (current_node_type == parser::tokens::TupleType) {
      node->constructors[i] = std::make_unique<TupleType>();
      Visit(std::get<std::unique_ptr<TupleType>>(node->constructors[i]).get());
    } else {
      // error
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(TypeExpression* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t excluded_child_count = 0;

  size_t child_count = parse_node.NamedChildCount();

  current_node_ = parse_node.ChildByFieldName("type");
  Visit(&node->type);
  ++excluded_child_count;

  current_node_ = current_node_.NextSibling();

  if (!current_node_.IsNull()) {
    current_node_ = current_node_.NextSibling();
    if (!current_node_.IsNull()) {
      NumberLiteral literal;
      Visit(&literal);
      node->array_size = literal.value;
      ++excluded_child_count;
    } else {
      node->array_size = 0;
    }
  }

  if (child_count > excluded_child_count) {
    node->path.resize(child_count - excluded_child_count);

    for (size_t i = 0; i + excluded_child_count < child_count; ++i) {
        current_node_ = parse_node.NthNamedChild(i);
        Visit(&node->path[i]);
    }
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(AnyType& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::TypeExpression) {
    node = std::make_unique<TypeExpression>();
    Visit(std::get<std::unique_ptr<TypeExpression>>(node).get());
  } else if (current_node_type == parser::tokens::TupleType) {
    node = std::make_unique<TupleType>();
    Visit(std::get<std::unique_ptr<TupleType>>(node).get());
  } else if (current_node_type == parser::tokens::VariantType) {
    node = std::make_unique<VariantType>();
    Visit(std::get<std::unique_ptr<VariantType>>(node).get());
  } else if (current_node_type == parser::tokens::FunctionType) {
    node = std::make_unique<FunctionType>();
    Visit(std::get<std::unique_ptr<FunctionType>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

void BuildVisitor::Visit(ExtendedScopedAnyType* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  size_t child_count = parse_node.ChildCount();

  if (child_count > 1) {
    node->references.resize(child_count - 1);
    for (size_t i = 0; i + 1 < child_count; ++i) {
      std::string reference = parse_node.NthChild(i).GetValue();
      if (reference == "^") {
        node->references[i] = utils::ReferenceModifier::Reference;
      } else if (reference == "@") {
        node->references[i] = utils::ReferenceModifier::UniqueReference;
      }
    }
  }

  current_node_ = parse_node.ChildByFieldName("type");
  Visit(node->type);

  current_node_ = parse_node;
}

// Typeclass

void BuildVisitor::Visit(ParametrizedTypeclass* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  std::string prefixed_typeclass = parse_node.ChildByFieldName("typeclass").GetValue(); // prefix # removed
  node->typeclass = prefixed_typeclass.substr(1, prefixed_typeclass.size() - 1);

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->parameters.resize(child_count - 1);

    for (size_t i = 0; i + 1 < child_count; ++i) {
        current_node_ = parse_node.NthNamedChild(i + 1);
        node->parameters[i] = std::make_unique<TypeExpression>();
        Visit(node->parameters[i].get());
    }
  }

  current_node_ = parse_node;
}

// Typeclass & Type -----------------


void BuildVisitor::Visit(ParametrizedType* node) {
  SetPosition(node->base, current_node_);

  auto parse_node = current_node_;

  node->type = parse_node.ChildByFieldName("type").GetValue();

  size_t child_count = parse_node.NamedChildCount();

  if (child_count > 1) {
    node->parameters.resize(child_count - 1);

    for (size_t i = 0; i + 1 < child_count; ++i) {
      current_node_ = parse_node.NthNamedChild(i + 1);
      node->parameters[i] = std::make_unique<TypeExpression>();
      Visit(node->parameters[i].get());
    }
  }

  current_node_ = parse_node;
}

// Identifiers, constants, etc. -----------------

// void BuildVisitor::Visit(AnyIdentifier* node) { // std::string
//   *node = current_node_.GetValue();
// }

void BuildVisitor::Visit(FloatNumberLiteral* node) {
  SetPosition(node->base, current_node_);

  node->value = std::stod(current_node_.GetValue());
}

void BuildVisitor::Visit(NumberLiteral* node) {
  SetPosition(node->base, current_node_);

  node->value = std::stoll(current_node_.GetValue());
}

void BuildVisitor::Visit(StringLiteral* node) {
  SetPosition(node->base, current_node_);

  std::string literal = current_node_.GetValue();
  node->value = literal.substr(1, literal.size() - 2);
}

void BuildVisitor::Visit(CharLiteral* node) {
  SetPosition(node->base, current_node_);

  std::string literal = current_node_.GetValue();
  node->value = literal.substr(1, literal.size() - 2).back(); // TODO: special symbols, etc.
}

void BuildVisitor::Visit(UnitLiteral* node) {
  SetPosition(node->base, current_node_);
}

void BuildVisitor::Visit(BoolLiteral* node) {
  SetPosition(node->base, current_node_);

  std::string literal = current_node_.GetValue();
  node->value = (literal == "true"); // always "false" in other way
}

void BuildVisitor::Visit(Literal& node) {
  auto parse_node = current_node_;

  current_node_ = parse_node.NthNamedChild(0);

  std::string current_node_type = current_node_.GetType();

  if (current_node_type == parser::tokens::FloatNumberLiteral) {
    node = std::make_unique<FloatNumberLiteral>();
    Visit(std::get<std::unique_ptr<FloatNumberLiteral>>(node).get());
  } else if (current_node_type == parser::tokens::NumberLiteral) {
    node = std::make_unique<NumberLiteral>();
    Visit(std::get<std::unique_ptr<NumberLiteral>>(node).get());
  } else if (current_node_type == parser::tokens::StringLiteral) {
    node = std::make_unique<StringLiteral>();
    Visit(std::get<std::unique_ptr<StringLiteral>>(node).get());
  } else if (current_node_type == parser::tokens::CharLiteral) {
    node = std::make_unique<CharLiteral>();
    Visit(std::get<std::unique_ptr<CharLiteral>>(node).get());
  } else if (current_node_type == parser::tokens::UnitLiteral) {
    node = std::make_unique<UnitLiteral>();
    Visit(std::get<std::unique_ptr<UnitLiteral>>(node).get());
  } else if (current_node_type == parser::tokens::BoolLiteral) {
    node = std::make_unique<BoolLiteral>();
    Visit(std::get<std::unique_ptr<BoolLiteral>>(node).get());
  } else {
    // error
  }

  current_node_ = parse_node;
}

} // namespace interpreter