lix/src/libutil/error.hh

#ifndef error_hh
#define error_hh

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

#include "types.hh"

namespace nix
{

typedef enum {
    elWarning,
    elError
} ErrLevel;

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

class ErrorInfo;

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

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

    ErrLine& ensureErrLine()
    {
        if (!this->errLine.has_value())
            this->errLine = std::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 AddPos;

template <class T>
class AddLOC;

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

    static std::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 AddPos<ErrorInfo>;
    friend AddLOC<ErrorInfo>;

    NixCode& ensureNixCode()
    {
        if (!this->nixCode.has_value())
            this->nixCode = std::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 AddPos : private T
{
public:
    template <class P>
    T& pos(const P &aPos)
    {
        GetEI().ensureNixCode().nixFile = aPos.file;
        GetEI().ensureNixCode().ensureErrLine().lineNumber = aPos.line;
        GetEI().ensureNixCode().ensureErrLine().columnRange = { .start = aPos.column, .len = 1 };
        return *this;
    }
protected:
    ErrorInfo& GetEI()
    {
        return T::GetEI();
    }
};

template <class T>
class AddLOC : private T
{
public:
    T& linesOfCode(std::optional<string> prevloc, string loc, std::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();
    }
};


// ----------------------------------------------------------------
// format for hints.  same as fmt, except templated values
// are always in yellow.

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;
}

class hintformat
{
public:
    hintformat(string format) :fmt(format)
    {
        fmt.exceptions(boost::io::all_error_bits ^ boost::io::too_many_args_bit);
    }
    template<class T>
    hintformat& operator%(const T &value)
    {
        fmt % yellowify(value);
        return *this;
    }

    std::string str() const
    {
        return fmt.str();
    }

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

};

template<typename... Args>
inline hintformat hintfmt(const std::string & fs, const Args & ... args)
{
    hintformat f(fs);
    formatHelper(f, args...);
    return f;
}

// the template layer for adding a hint.
template <class T>
class AddHint : private T
{
public:
    T& hint(const hintformat &hf)
    {
        GetEI().hint = std::optional(hf.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<
        AddPos<
        AddLOC<
        AddHint<
        EIError>>>>> NixLangError;

typedef AddName<
        AddDescription<
        AddPos<
        AddLOC<
        AddHint<
        EIWarning>>>>> NixLangWarning;


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

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

}

#endif