// Brandling Safari dedicated server.
//   safari_server [--port 27420] [--name "Brandling Safari"] [--db <path>] [--seed N] [--zone meadow]
//                 [--roster <path>] [--manifest <path>] [--day-minutes 30] [--hour H]
//                 [--weather clear|cloudy|rain|storm|fog]

#include "Database.h"
#include "Game.h"
#include "Log.h"
#include "Net.h"

#include <algorithm>
#include <atomic>
#include <chrono>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <string>

#if defined(_WIN32)
#include <iostream>
#include <mutex>
#include <thread>
#else
#include <poll.h>
#include <unistd.h>
#endif

using namespace bs;

namespace {

std::atomic<bool> gStop{false};

void onSignal(int) { gStop = true; }

std::string defaultDbPath() {
    std::string base;
    if (const char* x = std::getenv("XDG_DATA_HOME"); x && *x) base = x;
#if defined(_WIN32)
    else if (const char* a = std::getenv("APPDATA"); a && *a) base = a;
#endif
    else if (const char* h = std::getenv("HOME"); h && *h) base = std::string(h) + "/.local/share";
    else base = ".";
    return base + "/brandling-safari/world.db";
}

// Non-blocking stdin lines for the console. POSIX polls fd 0 from the tick loop (a reader thread
// blocked inside stdio would deadlock glibc's exit-time stream flush); Windows uses a detached
// reader thread with a process-lifetime queue.
class ConsoleInput {
public:
    bool pop(std::string& out) {
#if defined(_WIN32)
        static bool started = false;
        if (!started) {
            started = true;
            std::thread([] {
                std::string line;
                while (std::getline(std::cin, line)) {
                    std::lock_guard<std::mutex> lock(mutex());
                    queue().push_back(line);
                }
            }).detach();
        }
        std::lock_guard<std::mutex> lock(mutex());
        if (queue().empty()) return false;
        out = std::move(queue().front());
        queue().pop_front();
        return true;
#else
        while (open_) {
            pollfd p{0, POLLIN, 0};
            if (::poll(&p, 1, 0) <= 0 || !(p.revents & (POLLIN | POLLHUP))) break;
            char buf[512];
            ssize_t n = ::read(0, buf, sizeof buf);
            if (n <= 0) {
                open_ = false;  // EOF (or error): no console, keep serving
                break;
            }
            pending_.append(buf, size_t(n));
        }
        size_t nl = pending_.find('\n');
        if (nl == std::string::npos) return false;
        out = pending_.substr(0, nl);
        pending_.erase(0, nl + 1);
        return true;
#endif
    }

private:
#if defined(_WIN32)
    static std::mutex& mutex() { static std::mutex m; return m; }
    static std::deque<std::string>& queue() { static std::deque<std::string> q; return q; }
#else
    bool open_ = true;
    std::string pending_;
#endif
};

void usage() {
    std::printf(
        "usage: safari_server [--port N] [--name NAME] [--db PATH] [--seed N] [--zone meadow]\n"
        "                     [--roster PATH] [--manifest PATH] [--day-minutes M] [--hour H]\n"
        "                     [--weather clear|cloudy|rain|storm|fog]\n");
}

}  // namespace

int main(int argc, char** argv) {
    uint16_t port = kDefaultPort;
    GameConfig cfg;
    std::string dbPath = defaultDbPath();
    std::string rosterPath = std::string(BS_ASSET_DIR) + "/creatures/roster.json";
    std::string manifestPath = std::string(BS_ASSET_DIR) + "/characters/manifest.json";
    bool seedGiven = false;

    for (int i = 1; i < argc; ++i) {
        std::string a = argv[i];
        auto next = [&]() -> std::string {
            if (i + 1 >= argc) {
                std::fprintf(stderr, "missing value for %s\n", a.c_str());
                std::exit(2);
            }
            return argv[++i];
        };
        if (a == "--port") port = uint16_t(std::atoi(next().c_str()));
        else if (a == "--name") cfg.serverName = next().substr(0, 64);
        else if (a == "--db") dbPath = next();
        else if (a == "--seed") cfg.seed = uint32_t(std::strtoul(next().c_str(), nullptr, 10)), seedGiven = true;
        else if (a == "--zone") cfg.zoneId = next();
        else if (a == "--roster") rosterPath = next();
        else if (a == "--manifest") manifestPath = next();
        else if (a == "--day-minutes") cfg.dayMinutes = std::max(0.1f, std::strtof(next().c_str(), nullptr));
        else if (a == "--hour") cfg.hour = std::clamp(std::strtof(next().c_str(), nullptr), 0.0f, 23.999f);
        else if (a == "--weather") {
            Weather w;
            std::string v = next();
            if (!parseWeather(v, w)) {
                std::fprintf(stderr, "unknown weather '%s'\n", v.c_str());
                return 2;
            }
            cfg.weather = int(w);
        } else if (a == "--help" || a == "-h") {
            usage();
            return 0;
        } else {
            std::fprintf(stderr, "unknown argument '%s'\n", a.c_str());
            usage();
            return 2;
        }
    }

    std::string err;
    Roster roster;
    if (!roster.load(rosterPath, &err)) {
        std::fprintf(stderr, "roster: %s\n", err.c_str());
        return 1;
    }
    CharacterManifest manifest;
    if (!manifest.load(manifestPath, &err)) {
        std::fprintf(stderr, "manifest: %s\n", err.c_str());
        return 1;
    }
    Database db;
    if (!db.open(dbPath, &err)) {
        std::fprintf(stderr, "database %s: %s\n", dbPath.c_str(), err.c_str());
        return 1;
    }
    // The zone seed is part of the world: keep the first one unless --seed overrides it.
    std::string saved;
    if (!seedGiven && db.getWorld("seed", saved)) cfg.seed = uint32_t(std::strtoul(saved.c_str(), nullptr, 10));
    db.setWorld("seed", std::to_string(cfg.seed));
    Zone zone;
    if (!zone.generate(cfg.zoneId, cfg.seed)) {
        std::fprintf(stderr, "unknown zone '%s'\n", cfg.zoneId.c_str());
        return 1;
    }

    if (!net::initialize()) {
        std::fprintf(stderr, "enet initialization failed\n");
        return 1;
    }
    {
        net::Host host;
        if (!host.listen(port, 32)) {
            std::fprintf(stderr, "cannot listen on UDP port %u\n", unsigned(port));
            net::shutdown();
            return 1;
        }
        net::Beacon beacon;
        bool lan = beacon.open(kDiscoveryPort);

        Game game(host, db, zone, roster, manifest, cfg);
        logf("\"%s\" listening on UDP %u (LAN discovery %s), db %s", cfg.serverName.c_str(), unsigned(port),
             lan ? "on" : "unavailable", dbPath.c_str());
        logf("type 'help' for console commands");

        std::signal(SIGINT, onSignal);
        std::signal(SIGTERM, onSignal);
        ConsoleInput input;

        using Clock = std::chrono::steady_clock;
        const auto step = std::chrono::duration_cast<Clock::duration>(std::chrono::duration<double>(kTickDt));
        auto next = Clock::now();
        bool running = true;
        while (running && !gStop) {
            auto now = Clock::now();
            uint32_t waitMs = 0;
            if (next > now)
                waitMs = uint32_t(std::chrono::duration_cast<std::chrono::milliseconds>(next - now).count());
            net::Event ev;
            bool got = host.poll(ev, waitMs);
            while (got) {
                switch (ev.type) {
                    case net::Event::Connect: game.onConnect(ev.peer); break;
                    case net::Event::Disconnect: game.onDisconnect(ev.peer); break;
                    case net::Event::Receive: game.onReceive(ev.peer, ev.data); break;
                    default: break;
                }
                got = host.poll(ev, 0);
            }
            std::string line;
            while (running && input.pop(line)) running = game.console(line);

            now = Clock::now();
            int steps = 0;
            while (now >= next && steps < 5) {
                game.tick();
                next += step;
                ++steps;
            }
            if (now - next > std::chrono::seconds(1)) next = now;  // fell far behind: drop the backlog
            beacon.poll(port, cfg.serverName, game.playerCount());
            host.flush();
        }
        logf("shutting down, saving...");
        game.saveAll();
        host.flush();
    }
    db.close();
    net::shutdown();
    logf("bye");
    return 0;
}