// 编译期常量求值与常量初始化展开。
#pragma once

#include <cstdint>
#include <string>
#include <unordered_map>
#include <vector>

#include "SysYParser.h"
#include "sem/SymbolTable.h"

struct ConstValue {
  SymbolDataType type = SymbolDataType::Unknown;
  int64_t int_value = 0;
  double float_value = 0.0;
  bool bool_value = false;

  static ConstValue FromInt(int64_t value);
  static ConstValue FromFloat(double value);
  static ConstValue FromBool(bool value);

  bool IsScalar() const;
  bool IsNumeric() const;
  int64_t AsInt() const;
  double AsFloat() const;
  bool AsBool() const;
};

struct ConstArrayValue {
  SymbolDataType elem_type = SymbolDataType::Unknown;
  std::vector<int64_t> dims;
  std::vector<ConstValue> elements;
};

class ConstEvalContext {
 public:
  ConstEvalContext();

  void EnterScope();
  void ExitScope();

  bool DefineScalar(const std::string& name, ConstValue value);
  bool DefineArray(const std::string& name, ConstArrayValue value);

  const ConstValue* LookupScalar(const std::string& name) const;
  const ConstArrayValue* LookupArray(const std::string& name) const;

 private:
  struct Binding {
    bool is_array = false;
    ConstValue scalar;
    ConstArrayValue array;
  };

  using Scope = std::unordered_map<std::string, Binding>;

  const Binding* LookupBinding(const std::string& name) const;

  std::vector<Scope> scopes_;
};

class ConstEvaluator {
 public:
  ConstEvaluator(const SymbolTable& table, const ConstEvalContext& ctx);

  ConstValue EvaluateConstExp(SysYParser::ConstExpContext& ctx) const;
  ConstValue EvaluateExp(SysYParser::ExpContext& ctx) const;

  // 数组维度必须是正整数。
  int64_t EvaluateArrayDim(SysYParser::ConstExpContext& ctx) const;

  // 展平 const 初始化列表，结果按行优先顺序存放。
  std::vector<ConstValue> EvaluateConstInitList(
      SysYParser::ConstInitValContext& init, SymbolDataType elem_type,
      const std::vector<int64_t>& dims) const;

 private:
  const SymbolTable& table_;
  const ConstEvalContext& ctx_;
};