nix/src/libutil/error.hh

#ifndef error_hh
#define error_hh

#include "ansicolor.hh"
#include <string>
#include <optional>
#include <iostream>
#include <iomanip>

#include <boost/format.hpp>

namespace nix {

typedef enum  
  { elWarning
  , elError
  } ErrLevel;

class ColumnRange { 
  public:
    unsigned int start;
    unsigned int len;
};

class ErrorInfo;

class ErrLine { 
  public:
    int lineNumber;
    optional<ColumnRange> columnRange;
    optional<string> prevLineOfCode;
    string errLineOfCode;
    optional<string> nextLineOfCode;
};

class NixCode { 
  public:
    optional<string> nixFile;
    optional<ErrLine> errLine;

    ErrLine& ensureErrLine() 
    { 
      if (!this->errLine.has_value())
         this->errLine = optional(ErrLine());
      return *this->errLine; 
    }
};

// -------------------------------------------------
// ErrorInfo.

// Forward friend class declarations.  "builder classes"
template <class T>
class AddName;

template <class T>
class AddDescription;

template <class T>
class AddNixCode;

template <class T>
class AddNixFile;

template <class T>
class AddErrLine;

template <class T> 
class AddLineNumber;

template <class T> 
class AddColumnRange;

template <class T> 
class AddLOC;

// The error info class itself.
class ErrorInfo { 
  public:
    ErrLevel level;
    string name;
    string description;
    optional<NixCode> nixCode;
    optional<string> hint;
    ErrorInfo& GetEI() { return *this; }

    static optional<string> programName;

    // give these access to the private constructor, 
    // when they are direct descendants (children but not grandchildren).
    friend AddName<ErrorInfo>;
    friend AddDescription<ErrorInfo>;
    friend AddNixCode<ErrorInfo>;
    friend AddNixFile<ErrorInfo>;
    friend AddErrLine<ErrorInfo>;
    friend AddLineNumber<ErrorInfo>;
    friend AddColumnRange<ErrorInfo>;
    friend AddLOC<ErrorInfo>;
    
    NixCode& ensureNixCode() 
    { 
      if (!this->nixCode.has_value())
         this->nixCode = optional(NixCode());
      return *this->nixCode; 
    }
  protected:
    // constructor is protected, so only the builder classes can create an ErrorInfo.
    ErrorInfo(ErrLevel level) { this->level = level; }
};

// Init as error
class EIError : public ErrorInfo
{
  protected:
    EIError() : ErrorInfo(elError) {}
};

// Init as warning
class EIWarning : public ErrorInfo
{
  protected:
    EIWarning() : ErrorInfo(elWarning) {}
};

// Builder class definitions.
template <class T>
class AddName : private T
{
  public:
    T& name(const std::string &name){
      GetEI().name = name;
      return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

template <class T>
class AddDescription : private T 
{
  public:
    T& description(const std::string &description){
      GetEI().description = description;
      return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

template <class T> 
class AddNixFile : private T
{
  public:
    T& nixFile(string filename) { 
     GetEI().ensureNixCode().nixFile = filename;
     return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

template <class T> 
class AddLineNumber : private T
{
  public:
    T& lineNumber(int lineNumber) { 
      GetEI().ensureNixCode().ensureErrLine().lineNumber = lineNumber;
      return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

template <class T> 
class AddColumnRange : private T
{
  public:
    T& columnRange(unsigned int start, unsigned int len) { 
      GetEI().ensureNixCode().ensureErrLine().columnRange = { start, len };
      return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

template <class T> 
class AddLOC : private T
{
  public:
    T& linesOfCode(optional<string> prevloc, string loc, optional<string> nextloc) { 
      GetEI().ensureNixCode().ensureErrLine().prevLineOfCode = prevloc;
      GetEI().ensureNixCode().ensureErrLine().errLineOfCode = loc;
      GetEI().ensureNixCode().ensureErrLine().nextLineOfCode = nextloc;
      return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

template <class T>
class yellowify
{
public:
    yellowify(T &s) : value(s) {}
    T &value;
};

template <class T>
std::ostream& operator<<(std::ostream &out, const yellowify<T> &y)
{
  return out << ANSI_YELLOW << y.value << ANSI_NORMAL;
}

// hint format shows templated values in yellow.
class hintfmt 
{
  public:
    hintfmt(string format) :fmt(format) {}
    template<class T>
      hintfmt& operator%(const T &value) { fmt % yellowify(value); return *this; }

    template <typename U>
    friend class AddHint;
  private:
    format fmt;
      
};

template <class T> 
class AddHint : private T
{
  public:
    T& hint(hintfmt &hfmt) {
      GetEI().hint = optional(hfmt.fmt.str());
      return *this;
    }
    T& nohint() {
      GetEI().hint = std::nullopt;
      return *this;
    }
  protected:
    ErrorInfo& GetEI() { return T::GetEI(); }
};

// --------------------------------------------------------
// error types

typedef AddName<
        AddDescription<
        AddHint<
        EIError>>> ProgramError;

typedef AddName<
        AddDescription<
        AddHint<
        EIWarning>>> ProgramWarning;

typedef AddName<
        AddDescription<
        AddNixFile<
        AddLineNumber<
        AddColumnRange<
        AddLOC<
        AddHint<
        EIError>>>>>>> NixLangError;

typedef AddName<
        AddDescription<
        AddNixFile<
        AddLineNumber<
        AddColumnRange<
        AddLOC<
        AddHint<
        EIWarning>>>>>>> NixLangWarning;


// --------------------------------------------------------
// error printing

// just to cout for now.
void printErrorInfo(ErrorInfo &einfo);

}

#endif