#include "sem/func.h"

#include <cstring>
#include <stdexcept>
#include <string>

#include "utils/Log.h"
#include <cmath>   // 提供 ldexp

namespace {

// 解析十六进制浮点字面量，支持 0xH.Hp±E 格式
double ParseHexFloat(const std::string& str) {
    const char* s = str.c_str();
    if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) s += 2;

    double significand = 0.0;
    bool have_dot = false;
    double dot_scale = 1.0 / 16.0;

    while (*s && *s != 'p' && *s != 'P') {
        if (*s == '.') {
            have_dot = true;
            ++s;
            continue;
        }
        int digit = -1;
        if (*s >= '0' && *s <= '9') digit = *s - '0';
        else if (*s >= 'a' && *s <= 'f') digit = *s - 'a' + 10;
        else if (*s >= 'A' && *s <= 'F') digit = *s - 'A' + 10;
        if (digit >= 0) {
            if (have_dot) {
                significand += digit * dot_scale;
                dot_scale /= 16.0;
            } else {
                significand = significand * 16 + digit;
            }
        }
        ++s;
    }

    int exponent = 0;
    if (*s == 'p' || *s == 'P') {
        ++s;
        int sign = 1;
        if (*s == '-') { sign = -1; ++s; }
        else if (*s == '+') { ++s; }
        exponent = 0;
        while (*s >= '0' && *s <= '9') {
            exponent = exponent * 10 + (*s - '0');
            ++s;
        }
        exponent *= sign;
    }

    return ldexp(significand, exponent);
}

} // anonymous namespace

namespace sem {

// Truncate double to float32 precision (mimics C float arithmetic)
static double ToFloat32(double v) {
  float f = static_cast<float>(v);
  return static_cast<double>(f);
}

// 编译时求值常量表达式
ConstValue EvaluateConstExp(SysYParser::ConstExpContext& ctx) {
  return EvaluateExp(*ctx.addExp());
}

// 求值表达式
ConstValue EvaluateExp(SysYParser::AddExpContext& ctx) {
  ConstValue result = EvaluateMulExp(*ctx.mulExp(0));
  for (size_t i = 1; i < ctx.mulExp().size(); ++i) {
    ConstValue rhs = EvaluateMulExp(*ctx.mulExp(i));
    if (ctx.AddOp(i-1)->getText() == "+") {
      result = AddValues(result, rhs);
    } else {
      result = SubValues(result, rhs);
    }
  }
  return result;
}

// 求值乘法表达式
ConstValue EvaluateMulExp(SysYParser::MulExpContext& ctx) {
  ConstValue result = EvaluateUnaryExp(*ctx.unaryExp(0));
  for (size_t i = 1; i < ctx.unaryExp().size(); ++i) {
    ConstValue rhs = EvaluateUnaryExp(*ctx.unaryExp(i));
    std::string op = ctx.MulOp(i-1)->getText();
    if (op == "*") {
      result = MulValues(result, rhs);
    } else if (op == "/") {
      if (IsZero(rhs)) {
        throw std::runtime_error(FormatError("sema", "除零错误"));
      }
      result = DivValues(result, rhs);
    } else if (op == "%") {
      if (IsZero(rhs)) {
        throw std::runtime_error(FormatError("sema", "取模除零错误"));
      }
      result = ModValues(result, rhs);
    }
  }
  return result;
}

// 求值一元表达式
ConstValue EvaluateUnaryExp(SysYParser::UnaryExpContext& ctx) {
  if (ctx.unaryOp()) {
    ConstValue operand = EvaluateUnaryExp(*ctx.unaryExp());
    std::string op = ctx.unaryOp()->getText();
    if (op == "-") {
      return NegValue(operand);
    } else if (op == "!") {
      return NotValue(operand);
    } else {
      return operand; // "+" 操作符
    }
  } else if (ctx.primaryExp()) {
    return EvaluatePrimaryExp(*ctx.primaryExp());
  } else {
    throw std::runtime_error(FormatError("sema", "非法常量表达式"));
  }
}

// 求值基本表达式
ConstValue EvaluatePrimaryExp(SysYParser::PrimaryExpContext& ctx) {
  if (ctx.exp()) {
    return EvaluateExp(*ctx.exp()->addExp());
  } else if (ctx.lVar()) {
    // 处理变量引用：向上遍历 AST 找到对应的常量定义并求值
    auto* ident = ctx.lVar()->Ident();
    if (!ident) {
      throw std::runtime_error(FormatError("sema", "非法变量引用"));
    }
    std::string name = ident->getText();
    // 向上遍历 AST 找到作用域内的 constDef
    antlr4::ParserRuleContext* scope =
        dynamic_cast<antlr4::ParserRuleContext*>(ctx.lVar()->parent);
    while (scope) {
      // 检查当前作用域中的所有 constDecl
      for (auto* tree_child : scope->children) {
        auto* child = dynamic_cast<antlr4::ParserRuleContext*>(tree_child);
        if (!child) continue;
        auto* block_item = dynamic_cast<SysYParser::BlockItemContext*>(child);
        if (block_item && block_item->decl()) {
          auto* decl = block_item->decl();
          if (decl->constDecl()) {
            for (auto* def : decl->constDecl()->constDef()) {
              if (def->Ident() && def->Ident()->getText() == name) {
                if (def->constInitVal() && def->constInitVal()->constExp()) {
                  ConstValue cv = EvaluateConstExp(*def->constInitVal()->constExp());
                  bool decl_is_int = decl->constDecl()->bType() &&
                                     decl->constDecl()->bType()->Int();
                  if (decl_is_int) {
                    cv.is_int = true;
                    cv.int_val = static_cast<long long>(static_cast<int>(cv.float_val));
                    cv.float_val = static_cast<double>(cv.int_val);
                  }
                  return cv;
                }
              }
            }
          }
        }
        // compUnit 级别的 constDecl
        auto* decl = dynamic_cast<SysYParser::DeclContext*>(child);
        if (decl && decl->constDecl()) {
          for (auto* def : decl->constDecl()->constDef()) {
            if (def->Ident() && def->Ident()->getText() == name) {
              if (def->constInitVal() && def->constInitVal()->constExp()) {
                ConstValue cv = EvaluateConstExp(*def->constInitVal()->constExp());
                // If declared as int, truncate to integer
                bool decl_is_int = decl->constDecl()->bType() &&
                                   decl->constDecl()->bType()->Int();
                if (decl_is_int) {
                  cv.is_int = true;
                  cv.int_val = static_cast<long long>(static_cast<int>(cv.float_val));
                  cv.float_val = static_cast<double>(cv.int_val);
                }
                return cv;
              }
            }
          }
        }
      }
      scope = dynamic_cast<antlr4::ParserRuleContext*>(scope->parent);
    }
    // 未找到常量定义，返回 0
    ConstValue val;
    val.is_int = true;
    val.int_val = 0;
    val.float_val = 0.0;
    return val;
  } else if (ctx.number()) {
    // 处理数字字面量
    auto* int_const = ctx.number()->IntConst();
    auto* float_const = ctx.number()->FloatConst();
    
    ConstValue val;
    if (int_const) {
      val.is_int = true;
      val.int_val = std::stoll(int_const->getText(), nullptr, 0);
      val.float_val = static_cast<double>(val.int_val);
    } else if (float_const) {
      val.is_int = false;
      std::string text = float_const->getText();
      if (text.size() >= 2 && (text[1] == 'x' || text[1] == 'X')) {
        val.float_val = ToFloat32(ParseHexFloat(text));
      } else {
        val.float_val = ToFloat32(std::stod(text));
      }
      val.int_val = static_cast<long long>(val.float_val);
    } else {
      throw std::runtime_error(FormatError("sema", "非法数字字面量"));
    }
    return val;
  } else {
    throw std::runtime_error(FormatError("sema", "非法基本表达式"));
  }
}

// 辅助函数：检查值是否为零
bool IsZero(const ConstValue& val) {
  if (val.is_int) {
    return val.int_val == 0;
  } else {
    return val.float_val == 0.0;
  }
}

// 辅助函数：加法
ConstValue AddValues(const ConstValue& lhs, const ConstValue& rhs) {
  ConstValue result;
  if (lhs.is_int && rhs.is_int) {
    result.is_int = true;
    result.int_val = lhs.int_val + rhs.int_val;
    result.float_val = static_cast<double>(result.int_val);
  } else {
    result.is_int = false;
    double l = lhs.is_int ? lhs.int_val : lhs.float_val;
    double r = rhs.is_int ? rhs.int_val : rhs.float_val;
    result.float_val = ToFloat32(l + r);
    result.int_val = static_cast<long long>(result.float_val);
  }
  return result;
}

// 辅助函数：减法
ConstValue SubValues(const ConstValue& lhs, const ConstValue& rhs) {
  ConstValue result;
  if (lhs.is_int && rhs.is_int) {
    result.is_int = true;
    result.int_val = lhs.int_val - rhs.int_val;
    result.float_val = static_cast<double>(result.int_val);
  } else {
    result.is_int = false;
    double l = lhs.is_int ? lhs.int_val : lhs.float_val;
    double r = rhs.is_int ? rhs.int_val : rhs.float_val;
    result.float_val = ToFloat32(l - r);
    result.int_val = static_cast<long long>(result.float_val);
  }
  return result;
}

// 辅助函数：乘法
ConstValue MulValues(const ConstValue& lhs, const ConstValue& rhs) {
  ConstValue result;
  if (lhs.is_int && rhs.is_int) {
    result.is_int = true;
    result.int_val = lhs.int_val * rhs.int_val;
    result.float_val = static_cast<double>(result.int_val);
  } else {
    result.is_int = false;
    double l = lhs.is_int ? lhs.int_val : lhs.float_val;
    double r = rhs.is_int ? rhs.int_val : rhs.float_val;
    result.float_val = ToFloat32(l * r);
    result.int_val = static_cast<long long>(result.float_val);
  }
  return result;
}

// 辅助函数：除法
ConstValue DivValues(const ConstValue& lhs, const ConstValue& rhs) {
  ConstValue result;
  if (lhs.is_int && rhs.is_int) {
    result.is_int = true;
    result.int_val = lhs.int_val / rhs.int_val;
    result.float_val = static_cast<double>(result.int_val);
  } else {
    result.is_int = false;
    double l = lhs.is_int ? lhs.int_val : lhs.float_val;
    double r = rhs.is_int ? rhs.int_val : rhs.float_val;
    result.float_val = ToFloat32(l / r);
    result.int_val = static_cast<long long>(result.float_val);
  }
  return result;
}

// 辅助函数：取模
ConstValue ModValues(const ConstValue& lhs, const ConstValue& rhs) {
  ConstValue result;
  if (!lhs.is_int || !rhs.is_int) {
    throw std::runtime_error(FormatError("sema", "取模运算只能用于整数"));
  }
  result.is_int = true;
  result.int_val = lhs.int_val % rhs.int_val;
  result.float_val = static_cast<double>(result.int_val);
  return result;
}

// 辅助函数：取负
ConstValue NegValue(const ConstValue& val) {
  ConstValue result;
  result.is_int = val.is_int;
  if (val.is_int) {
    result.int_val = -val.int_val;
    result.float_val = static_cast<double>(result.int_val);
  } else {
    result.float_val = -val.float_val;
    result.int_val = static_cast<long long>(result.float_val);
  }
  return result;
}

// 辅助函数：逻辑非
ConstValue NotValue(const ConstValue& val) {
  ConstValue result;
  result.is_int = true;
  if (val.is_int) {
    result.int_val = !val.int_val;
  } else {
    result.int_val = !val.float_val;
  }
  result.float_val = static_cast<double>(result.int_val);
  return result;
}

// 检查常量初始化器
size_t CheckConstInitVal(SysYParser::ConstInitValContext& ctx, 
                         const std::vector<size_t>& dimensions, 
                         bool is_int, 
                         size_t total_elements) {
  if (ctx.constExp()) {
    // 单个常量值
    // 求值并检查常量表达式
    ConstValue value = EvaluateConstExp(*ctx.constExp());
    
    // 检查类型约束
    if (is_int && !value.is_int) {
      throw std::runtime_error(FormatError("sema", "整型数组的初始化列表中不能出现浮点型常量"));
    }
    
    // 检查值域
    if (is_int) {
      if (value.int_val < INT_MIN || value.int_val > INT_MAX) {
        throw std::runtime_error(FormatError("sema", "整数值超过int类型表示范围"));
      }
    }
    return 1;
  } else if (ctx.L_BRACE()) {
    // 花括号初始化列表
    size_t count = 0;
    auto init_vals = ctx.constInitVal();
    
    for (auto* init_val : init_vals) {
      // 计算剩余维度的总元素个数
      size_t remaining_elements = total_elements;
      if (!dimensions.empty()) {
        remaining_elements = total_elements / dimensions[0];
      }
      
      count += CheckConstInitVal(*init_val, 
                               std::vector<size_t>(dimensions.begin() + 1, dimensions.end()), 
                               is_int, 
                               remaining_elements);
    }
    // 检查总元素个数
    if (count > total_elements) {
      throw std::runtime_error(FormatError("sema", "初始化列表元素个数超过数组大小"));
    }
    return count;
  } else {
    // 空初始化列表
    return 0;
  }
}

// 检查变量初始化器
size_t CheckInitVal(SysYParser::InitValContext& ctx, 
                   const std::vector<size_t>& dimensions, 
                   bool is_int, 
                   size_t total_elements) {
  if (ctx.exp()) {
    // 单个表达式值
    // 检查表达式中的变量引用
    // 这里不需要编译时求值，只需要检查类型约束
    // 类型检查在IR生成阶段进行
    return 1;
  } else if (ctx.L_BRACE()) {
    // 花括号初始化列表
    size_t count = 0;
    auto init_vals = ctx.initVal();
    
    for (auto* init_val : init_vals) {
      // 计算剩余维度的总元素个数
      size_t remaining_elements = total_elements;
      if (!dimensions.empty()) {
        remaining_elements = total_elements / dimensions[0];
      }
      
      count += CheckInitVal(*init_val, 
                          std::vector<size_t>(dimensions.begin() + 1, dimensions.end()), 
                          is_int, 
                          remaining_elements);
    }
    // 检查总元素个数
    if (count > total_elements) {
      throw std::runtime_error(FormatError("sema", "初始化列表元素个数超过数组大小"));
    }
    return count;
  } else {
    // 空初始化列表
    return 0;
  }
}

} // namespace sem