#ifndef regex_hh_INCLUDED
#define regex_hh_INCLUDED

#include "string.hh"
#include "regex_vm.hh"
#include "ref_ptr.hh"

namespace Kakoune
{

// Regex that keeps track of its string representation
class Regex
{
public:
    Regex() = default;

    explicit Regex(StringView re, RegexCompileFlags flags = RegexCompileFlags::None);
    bool empty() const { return m_str.empty(); }
    bool operator==(const Regex& other) const { return m_str == other.m_str; }

    const String& str() const { return m_str; }

    size_t mark_count() const { return m_impl->save_count / 2 - 1; }
    int named_capture_index(StringView name) const;

    static constexpr const char* option_type_name = "regex";

    const CompiledRegex* impl() const { return m_impl.get(); }

private:
    struct Impl : RefCountable, CompiledRegex {};

    RefPtr<Impl> m_impl;
    String m_str;
};

template<typename Iterator>
struct MatchResults
{
    struct SubMatch : std::pair<Iterator, Iterator>
    {
        SubMatch() = default;
        SubMatch(Iterator begin, Iterator end)
            : std::pair<Iterator, Iterator>{begin, end}, matched{static_cast<bool>(begin)}
        {}

        bool matched = false;
    };

    struct iterator
    {
        using difference_type = size_t;
        using value_type = SubMatch;
        using pointer = SubMatch*;
        using reference = SubMatch;
        using iterator_category = std::bidirectional_iterator_tag;
        using It = typename Vector<Iterator, MemoryDomain::Regex>::const_iterator;

        iterator() = default;
        iterator(It it) : m_it{std::move(it)} {}

        iterator& operator--() { m_it += 2; return *this; }
        iterator& operator++() { m_it += 2; return *this; }
        SubMatch operator*() const { return {*m_it, *(m_it+1)}; }

        friend bool operator==(const iterator& lhs, const iterator& rhs) = default;
    private:

        It m_it;
    };

    MatchResults() = default;
    MatchResults(Vector<Iterator, MemoryDomain::Regex> values) : m_values{std::move(values)} {}

    iterator begin() const { return iterator{m_values.begin()}; }
    iterator cbegin() const { return iterator{m_values.cbegin()}; }
    iterator end() const { return iterator{m_values.end()}; }
    iterator cend() const { return iterator{m_values.cend()}; }

    size_t size() const { return m_values.size() / 2; }
    bool empty() const { return m_values.empty(); }

    SubMatch operator[](size_t i) const
    {
        return i * 2 < m_values.size() ?
            SubMatch{m_values[i*2], m_values[i*2+1]} : SubMatch{};
    }

    friend bool operator==(const MatchResults& lhs, const MatchResults& rhs) = default;

    void swap(MatchResults& other)
    {
        m_values.swap(other.m_values);
    }

    Vector<Iterator, MemoryDomain::Regex>& values() { return m_values; }

private:
    Vector<Iterator, MemoryDomain::Regex> m_values;
};

inline RegexExecFlags match_flags(bool bol, bool eol, bool bow, bool eow)
{
    return (bol ? RegexExecFlags::None : RegexExecFlags::NotBeginOfLine) |
           (eol ? RegexExecFlags::None : RegexExecFlags::NotEndOfLine) |
           (bow ? RegexExecFlags::None : RegexExecFlags::NotBeginOfWord) |
           (eow ? RegexExecFlags::None : RegexExecFlags::NotEndOfWord);
}

struct NoopIdle
{
    void operator()() {}
};

template<typename It, typename IdleFunc = NoopIdle>
bool regex_match(It begin, It end, const Regex& re, IdleFunc&& idle_func = {})
{
    ThreadedRegexVM<It, RegexMode::Forward | RegexMode::AnyMatch | RegexMode::NoSaves> vm{*re.impl()};
    return vm.exec(begin, end, begin, end, RegexExecFlags::None, idle_func);
}

template<typename It, typename IdleFunc = NoopIdle>
bool regex_match(It begin, It end, MatchResults<It>& res, const Regex& re, IdleFunc&& idle_func = {})
{
    res.values().clear();
    ThreadedRegexVM<It, RegexMode::Forward> vm{*re.impl()};
    if (vm.exec(begin, end, begin, end, RegexExecFlags::None, idle_func))
    {
        std::copy(vm.captures().begin(), vm.captures().end(), std::back_inserter(res.values()));
        return true;
    }
    return false;
}

template<typename It, typename IdleFunc = NoopIdle>
bool regex_search(It begin, It end, It subject_begin, It subject_end, const Regex& re,
                  RegexExecFlags flags = RegexExecFlags::None, IdleFunc&& idle_func = {})
{
    ThreadedRegexVM<It, RegexMode::Forward | RegexMode::Search | RegexMode::AnyMatch | RegexMode::NoSaves> vm{*re.impl()};
    return vm.exec(begin, end, subject_begin, subject_end, flags, idle_func);
}

template<typename It, RegexMode mode = RegexMode::Forward, typename IdleFunc = NoopIdle>
bool regex_search(It begin, It end, It subject_begin, It subject_end,
                  MatchResults<It>& res, const Regex& re,
                  RegexExecFlags flags = RegexExecFlags::None,
                  IdleFunc&& idle_func = {})
{
    res.values().clear();
    ThreadedRegexVM<It, mode | RegexMode::Search> vm{*re.impl()};
    if (vm.exec(begin, end, subject_begin, subject_end, flags, idle_func))
    {
        std::move(vm.captures().begin(), vm.captures().end(), std::back_inserter(res.values()));
        return true;
    }
    return false;
}

template<typename It, typename IdleFunc = NoopIdle>
bool backward_regex_search(It begin, It end, It subject_begin, It subject_end,
                           MatchResults<It>& res, const Regex& re,
                           RegexExecFlags flags = RegexExecFlags::None,
                           IdleFunc&& idle_func = {})
{
    return regex_search<It, RegexMode::Backward>(begin, end, subject_begin, subject_end, res, re, flags, idle_func);
}

enum class Quoting;
String option_to_string(const Regex& re, Quoting quoting);
Regex option_from_string(Meta::Type<Regex>, StringView str);

template<typename Iterator, RegexMode mode = RegexMode::Forward,
         typename VmArg = const Regex, typename IdleFunc = NoopIdle>
struct RegexIterator
{
    static_assert(has_direction(mode));
    static constexpr bool forward = mode & RegexMode::Forward;
    using ValueType = MatchResults<Iterator>;
    struct Sentinel{};
    struct It
    {
        It(RegexIterator& base) : m_base(base), m_valid{m_base.next()} {}

        const ValueType& operator*() const { kak_assert(m_valid); return m_base.m_results; }
        const ValueType* operator->() const { kak_assert(m_valid); return &m_base.m_results; }

        It& operator++() { m_valid = m_base.next(); return *this; }
        bool operator==(Sentinel) const { return not m_valid; }

        RegexIterator& m_base;
        bool m_valid;
    };

    RegexIterator(Iterator begin, Iterator end,
                  Iterator subject_begin, Iterator subject_end,
                  VmArg& vm_arg, RegexExecFlags flags = RegexExecFlags::None,
                  IdleFunc idle_func = {})
        : m_vm{make_vm(vm_arg)}, m_next_pos{forward ? begin : end},
          m_begin{std::move(begin)}, m_end{std::move(end)},
          m_subject_begin{std::move(subject_begin)}, m_subject_end{std::move(subject_end)},
          m_flags{flags}, m_idle_func{idle_func} {}

    RegexIterator(const Iterator& begin, const Iterator& end,
                  VmArg& vm_arg, RegexExecFlags flags = RegexExecFlags::None,
                  IdleFunc idle_func = {})
        : RegexIterator{begin, end, begin, end, vm_arg, flags, idle_func} {}

    It begin() { return {*this}; }
    Sentinel end() const { return {}; }

private:
    bool next()
    {
        auto additional_flags = RegexExecFlags::None;
        if (m_results.size() and m_results[0].first == m_results[0].second)
            additional_flags |= RegexExecFlags::NotInitialNull;

        if (not m_vm.exec(forward ? m_next_pos : m_begin, forward ? m_end : m_next_pos,
                          m_subject_begin, m_subject_end, m_flags | additional_flags,
                          m_idle_func))
            return false;

        m_results.values().clear();
        std::move(m_vm.captures().begin(), m_vm.captures().end(), std::back_inserter(m_results.values()));
        m_next_pos = forward ? m_results[0].second : m_results[0].first;
        kak_assert(forward ? (m_next_pos <= m_end) : (m_next_pos >= m_begin));
        return true;
    }

    using RegexVM = ThreadedRegexVM<Iterator, mode | RegexMode::Search>;
    static RegexVM& make_vm(RegexVM& vm) { return vm; }
    static RegexVM make_vm(const Regex& regex) { return {*regex.impl()}; }

    decltype(make_vm(std::declval<VmArg&>())) m_vm;
    MatchResults<Iterator> m_results;
    Iterator m_next_pos{};
    const Iterator m_begin{};
    const Iterator m_end{};
    const Iterator m_subject_begin{};
    const Iterator m_subject_end{};
    const RegexExecFlags m_flags = RegexExecFlags::None;
    IdleFunc m_idle_func;
};

}

#endif // regex_hh_INCLUDED
