// SPDX-License-Identifier: GPL-3.0-or-later
/**
 * @file cmdLine.h
 * @brief Command line option parsing
 * 
 * (C) 2012-2016, 2019, Pascal Monasse <pascal.monasse@enpc.fr>
 */

#ifndef CMDLINE_H
#define CMDLINE_H

#include <vector>
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <sstream>
#include <cassert>

/// Base class for option/switch
class Option {
public:
    char c; ///< Option letter (eg 's' for -s), 0 if you want only a long name
    bool used; ///< Does the command line use that option?
    std::string longName; ///< Optional long name (eg "switch" for --switch)
    std::string desc; ///< Description

    /// Constructor with short name/long name
    Option(char d, std::string name)
    : c(d), used(false), longName(name) {}
    virtual ~Option() {}
    const std::string& doc() const { return desc; }
    virtual void print(std::ostream& str) const {
        if(c)
            str << '-' << c << (longName.empty()? "": ", ");
        else
            str << "    "; // For alignment
        if(! longName.empty())
            str << "--" << longName;
    }
    Option& doc(const std::string& description)
    { desc=description; return *this;}
    virtual bool check(int& argc, char* argv[])=0; ///< Option found at argv[0]?
    virtual Option* clone() const=0; ///< Copy
    /// Print value of option
    virtual std::string printValue() const { return std::string(); }
};

/// Option on/off is called a switch
class OptionSwitch : public Option {
public:
    /// Constructor with short name/long name (optional)
    OptionSwitch(char c, std::string name="")
    : Option(c,name) {}
    /// Find switch in argv[0]
    bool check(int& argc, char* argv[]) {
        if(std::string("-")+c==argv[0] ||
           (!longName.empty() && std::string("--")+longName==argv[0])) {
            used = true;
            std::rotate(argv, argv+1, argv+argc);
            argc -= 1;
            return true;
        } else if(std::string(argv[0]).find(std::string("-")+c)==0) {
            used = true; // Handle multiple switches in single option
            std::rotate(argv[0]+1, argv[0]+2,
                        argv[0]+std::string(argv[0]).size()+1);
            return true;
        }
        return false;
    }
    /// Copy
    Option* clone() const {
        return new OptionSwitch(*this);
    }
};

/// Option with an argument of type T, which must be readable by operator>>
template <class T>
class OptionField : public Option {
public:
    /// Constructor. The result with be stored in variable @field.
    OptionField(char c, T& field, std::string name="")
    : Option(c,name), _field(field) {}
    /// Find option in argv[0] and argument in argv[1]. Throw an exception
    /// (type std::string) if the argument cannot be read.
    bool check(int& argc, char* argv[]) {
        std::string param; int arg=0;
        if(std::string("-")+c==argv[0] ||
           (!longName.empty() && std::string("--")+longName==argv[0])) {
            if(argc<=1)
                throw std::string("Option ")
                    +argv[0]+" requires argument";
            param=argv[1]; arg=2;
        } else if(std::string(argv[0]).find(std::string("-")+c)==0) {
            param=argv[0]+2; arg=1;
        } else if(!longName.empty() &&
                  std::string(argv[0]).find(std::string("--")+longName+'=')==0){
            size_t size=(std::string("--")+longName+'=').size();
            param=std::string(argv[0]).substr(size); arg=1;
        }
        if(arg>0) {
            if(! read_param(param))
                throw std::string("Unable to interpret ")
                    +param+" as argument of "+argv[0];
            used = true;
            std::rotate(argv, argv+arg, argv+argc);
            argc -= arg;
            return true;
        }
        return false;
    }
    /// Decode the string as template type T
    bool read_param(const std::string& param) {
        std::stringstream str(param); char unused;
        return !((str >> _field).fail() || !(str>>unused).fail());
    }
    /// Indicate that an argument is required
    void print(std::ostream& str) const {
        Option::print(str);
        str << (longName.empty()? ' ': '=') << "ARG";
    }
    std::string printValue() const {
        std::stringstream s;
        s << _field;
        return s.str();
    }
    /// Copy
    Option* clone() const {
        return new OptionField<T>(*this);
    }
private:
    T& _field; ///< Reference to variable where to store the value
};

/// Template specialization to declare a switch like an option, storing result
/// in the variable.
template <>
inline bool OptionField<bool>::check(int& argc, char* argv[]) {
    bool res = OptionSwitch(c,longName).check(argc, argv);
    if(res)
        _field = true;
    return res;
}

/// Specialisation for a switch, no argument to print.
template<>
void OptionField<bool>::print(std::ostream& str) const {
    Option::print(str);    
}

/// Specialisation for a switch, no argument to print.
template<>
std::string OptionField<bool>::printValue() const {
    return Option::printValue();
}

/// Template specialization to be able to take parameter including space.
/// Generic method would do >>_field (stops at space) and signal unused chars.
template <>
inline bool OptionField<std::string>::read_param(const std::string& param) {
    _field = param;
    return true;
}

/// New switch option
OptionSwitch make_switch(char c, std::string name="") {
    return OptionSwitch(c, name);
}

/// New option with argument.
template <class T>
OptionField<T> make_option(char c, T& field, std::string name="") {
    return OptionField<T>(c, field, name);
}

/// Command line parsing
class CmdLine {
    std::vector<Option*> opts;
public:
    std::string prefixDoc; ///< For example, a tabulation for each line of doc
    int alignDoc; ///< Column where option description starts
    bool showDefaults; ///< Show default values of options
    /// Constructor
    CmdLine(): alignDoc(0), showDefaults(true) {}
    /// Destructor
    ~CmdLine() {
        std::vector<Option*>::iterator it=opts.begin();
        for(; it != opts.end(); ++it)
            delete *it;
    }
    /// Add an option
    void add(const Option& opt) {
        opts.push_back( opt.clone() );
    }
    /// Parse of command line acting as a filter. All options are virtually
    /// removed from the command line.
    void process(int& argc, char* argv[]) {
        std::vector<Option*>::iterator it=opts.begin();
        for(; it != opts.end(); ++it)
            (*it)->used = false;
        for(int i=1; i<argc;) {
            if(std::string("--")==argv[i]) { // "--" means stop option parsing
                std::rotate(argv+i, argv+i+1, argv+argc);
                -- argc;
                break;
            }
            bool found=false; // Find option
            for(it=opts.begin(); it != opts.end(); ++it) {
                int n = argc-i;
                found = (*it)->check(n, argv+i);
                if(found) {
                    argc = n+i;
                    break;
                }
            }
            if(! found) { // A negative number is not an option
                if(std::string(argv[i]).size()>1 && argv[i][0] == '-') {
                    std::istringstream str(argv[i]);
                    float v;
                    if(! (str>>v).eof())
                        throw std::string("Unrecognized option ")+argv[i];
                }
                ++i;
            }
        }
    }
    /// Output options.
    void print(std::ostream& str) const {
        std::vector<Option*>::const_iterator it=opts.begin();
        for(; it != opts.end(); ++it) {
            std::stringstream ss;
            ss << prefixDoc;
            (*it)->print(ss);
            ss << ' ';
            std::string d = ss.str();
            str << d;
            if((int)d.size() < alignDoc)
                std::fill_n(std::ostream_iterator<char>(str),
                            alignDoc-d.size(), ' ');
            str << (*it)->desc;
            if(showDefaults && !(*it)->printValue().empty())
                str << " (" << (*it)->printValue() << ')';
            str << std::endl;
        }
    }
    /// Was the option used in last parsing?
    bool used(char c) const {
        std::vector<Option*>::const_iterator it=opts.begin();
        for(; it != opts.end(); ++it)
            if((*it)->c == c)
                return (*it)->used;
        assert(false); // Called with non-existent option, probably a bug
        return false;
    }
};

/// Output possible options.
std::ostream& operator<<(std::ostream& str, const CmdLine& cmd) {
    cmd.print(str);
    return str;
}

#endif