#include "snote_thread.hpp"

#include "irc_parse_thread.hpp"
#include "connection.hpp"

#include <cstring>
#include <cstdlib>
#include <stdexcept>
#include <utility>
#include <regex>

namespace {

struct SnotePattern
{
    SnotePattern(SnoteTag tag, char const* expression, unsigned flags = 0)
    : tag{tag}
    , expression{expression}
    , flags{flags}
    , regex{expression, std::regex_constants::ECMAScript | std::regex_constants::optimize}
    {
    }

    SnoteTag tag;
    char const* expression;
    unsigned flags;
    std::regex regex;
};

SnotePattern const patterns[] =
{
    {SnoteTag::ClientConnecting,
     R"(^Client connecting: ([^ ]+) \(([^@ ]+)@([^) ]+)\) \[(.*)\] \{([^ ]*)\} <([^ ]*)> \[(.*)\]$)"},

    {SnoteTag::ClientExiting,
     R"(^Client exiting: ([^ ]+) \(([^@ ]+)@([^) ]+)\) \[(.*)\] \[(.*)\]$)"},
};

auto setup_database() -> std::unique_ptr<hs_database_t, SnoteThread::DbDeleter>
{
    std::vector<char const*> expressions;
    std::vector<unsigned> flags;
    std::vector<unsigned> ids;

    expressions.reserve(std::size(patterns));
    flags.reserve(std::size(patterns));
    ids.reserve(std::size(patterns));

    unsigned id = 0;

    for (auto const& pattern : patterns)
    {
        expressions.push_back(pattern.expression);
        flags.push_back(pattern.flags);
        ids.push_back(id++);
    }

    hs_database_t* db;
    hs_compile_error *error;

    switch (hs_compile_multi(expressions.data(), flags.data(), ids.data(), expressions.size(), HS_MODE_BLOCK, nullptr, &db, &error))
    {
        case HS_COMPILER_ERROR:
        {
            std::string msg = error->message;
            hs_free_compile_error(error);
            throw std::runtime_error{std::move(msg)};
        }
        case HS_SUCCESS:
            break;
        default:
            abort();
    }
    return std::unique_ptr<hs_database_t, SnoteThread::DbDeleter>{db};
}

} // namespace

auto SnoteThread::start(Connection& connection) -> std::shared_ptr<SnoteThread>
{
    auto thread = std::make_shared<SnoteThread>();

    thread->db_ = setup_database();

    hs_scratch_t* scratch = nullptr;
    if (HS_SUCCESS != hs_alloc_scratch(thread->db_.get(), &scratch))
    {
        abort();
    }
    thread->scratch_ = std::unique_ptr<hs_scratch_t, ScratchDeleter>{scratch};

    static char const* const prefix = "*** Notice -- ";
    connection.add_listener<IrcMsgEvent>([&connection, thread](IrcMsgEvent& event)
    {
        auto& args = event.irc.args;
        if (IrcCommand::NOTICE == event.command
         && "*" == args[0]
         && args[1].starts_with(prefix))
        {
            event.handled_ = true;
            auto message = args[1].substr(strlen(prefix));
            unsigned int match_id = -1;
            auto const scan_result = hs_scan(thread->db_.get(), message.data(), message.size(), 0, thread->scratch_.get(),
                [](unsigned int id, unsigned long long from, unsigned long long to, unsigned int flags, void *context) -> int
                {
                    int* const match_id = static_cast<int*>(context);
                    *match_id = id;
                    return 1; // stop scanning
                }
            , &match_id);

            if (scan_result != HS_SUCCESS && scan_result != HS_SCAN_TERMINATED)
            {
                abort();
            }

            if (match_id != -1)
            {
                auto& pattern = patterns[match_id];
                std::match_results<std::string_view::const_iterator> results;                
                if (not std::regex_match(message.begin(), message.end(), results, pattern.regex))
                {
                    // something went wrong - hyperscan disagrees with std::regex
                    abort();
                }

                std::vector<std::string_view> parts;
                for (auto const sub : results)
                {
                    parts.push_back(std::string_view{sub.first, sub.second});
                }
                connection.make_event<SnoteEvent>(pattern.tag, std::move(parts));
            }
        }
    });

    return thread;
}