// 极简语义分析：只检查变量是否先声明再使用。
#include "sem/Sema.h"

#include <stdexcept>
#include <string>
#include <unordered_set>

#include "ast/AstNodes.h"
#include "sem/SymbolTable.h"

namespace {

class SemaVisitor {
 public:
  explicit SemaVisitor(SymbolTable& table) : table_(table) {}

  void CheckBlock(const ast::Block& block) {
    for (const auto& decl : block.varDecls) {
      table_.Add(decl->name);
      if (decl->init) CheckExpr(*decl->init);
    }
    for (const auto& stmt : block.stmts) {
      if (auto ret = dynamic_cast<ast::ReturnStmt*>(stmt.get())) {
        CheckExpr(*ret->value);
      }
    }
  }

  void CheckExpr(const ast::Expr& expr) {
    if (auto var = dynamic_cast<const ast::VarExpr*>(&expr)) {
      if (!table_.Contains(var->name)) {
        throw std::runtime_error("使用了未定义的变量: " + var->name);
      }
    } else if (auto bin = dynamic_cast<const ast::BinaryExpr*>(&expr)) {
      CheckExpr(*bin->lhs);
      CheckExpr(*bin->rhs);
    }
  }

 private:
  SymbolTable& table_;
};

}  // namespace

std::shared_ptr<ast::CompUnit> RunSema(std::shared_ptr<ast::CompUnit> ast) {
  if (!ast || !ast->func || !ast->func->body) return ast;
  SymbolTable table;
  SemaVisitor visitor(table);
  visitor.CheckBlock(*ast->func->body);
  return ast;
}
