/*++
  Copyright (c) 2017 Microsoft Corporation

  Module Name:

  <name>

  Abstract:

  <abstract>

  Author:
  Nikolaj Bjorner (nbjorner)
  Lev Nachmanson (levnach)

  Revision History:


  --*/
#pragma once
#include "util/rational.h"
#include "util/lp/monomial.h"

namespace nla {

struct factorization_factory;
typedef unsigned lpvar;

enum class factor_type { VAR, RM }; // RM stands for rooted monomial 

class factor {
    unsigned     m_index;
    factor_type  m_type;
public:
    factor() {}
    explicit factor(unsigned j) : factor(j, factor_type::VAR) {}
    factor(unsigned i, factor_type t) : m_index(i), m_type(t) {}
    unsigned index() const { return m_index; }
    unsigned& index() { return m_index; }
    factor_type type() const { return m_type; }
    factor_type& type() { return m_type; }
    bool is_var() const { return m_type == factor_type::VAR; }
    bool operator==(factor const& other) const {
        return m_index == other.index() && m_type == other.type();
    }
    bool operator!=(factor const& other) const {
        return m_index != other.index() || m_type != other.type();
    }
};


class factorization {
    vector<factor>        m_vars;
    const monomial*       m_mon;
public:
    factorization(const monomial* m): m_mon(m) {
        if (m != nullptr) {
            for(lpvar j : *m)
                m_vars.push_back(factor(j, factor_type::VAR));
        }
    }
    bool is_mon() const { return m_mon != nullptr;}
    bool is_empty() const { return m_vars.empty(); }
    factor operator[](unsigned k) const { return m_vars[k]; }
    size_t size() const { return m_vars.size(); }
    const factor* begin() const { return m_vars.begin(); }
    const factor* end() const { return m_vars.end(); }
    void push_back(factor v) {
        SASSERT(!is_mon());
        m_vars.push_back(v);
    }
    const monomial* mon() const { return m_mon; }
};

struct const_iterator_mon {
    // fields
    svector<bool>                  m_mask;
    const factorization_factory *  m_ff;
    bool                           m_full_factorization_returned;

    // typedefs
    typedef const_iterator_mon self_type;
    typedef factorization value_type;
    typedef int difference_type;
    typedef std::forward_iterator_tag iterator_category;

    void init_vars_by_the_mask(unsigned_vector & k_vars, unsigned_vector & j_vars) const;
            
    bool get_factors(factor& k, factor& j, rational& sign) const;

    factorization operator*() const;
    void advance_mask();
            
    self_type operator++();
    self_type operator++(int);

    const_iterator_mon(const svector<bool>& mask, const factorization_factory *f);
    
    bool operator==(const self_type &other) const;
    bool operator!=(const self_type &other) const;
            
    factorization create_binary_factorization(factor j, factor k) const;
    
    factorization create_full_factorization(const monomial*) const;
};

struct factorization_factory {
    const svector<lpvar>& m_vars;
    const monomial*       m_monomial;
    // returns true if found
    virtual bool find_rm_monomial_of_vars(const svector<lpvar>& vars, unsigned& i) const = 0;
    virtual const monomial* find_monomial_of_vars(const svector<lpvar>& vars) const = 0;
    

    factorization_factory(const svector<lpvar>& vars, const monomial* m) :
        m_vars(vars), m_monomial(m) {
    }

    svector<bool> get_mask() const {
        // we keep the last element always in the first factor to avoid
        // repeating a pair twice, that is why m_mask is shorter by one then m_vars
        
        return
            m_vars.size() != 2?
            svector<bool>(m_vars.size() - 1, false)
            :
            svector<bool>(1, true); // init mask as in the end() since the full iteration will do the job
    }
    
    const_iterator_mon begin() const {
        return const_iterator_mon(get_mask(), this);
    }
    
    const_iterator_mon end() const {
        svector<bool> mask(m_vars.size() - 1, true);
        auto it = const_iterator_mon(mask, this);
        it.m_full_factorization_returned = true;
        return it;
    } 
   
};

}