/*

WIFI MODULE

Original code based on JustWifi, Wifi Manager for ESP8266 (GPLv3+)
Copyright (C) 2016-2019 by Xose Pérez <xose dot perez at gmail dot com>

Modified for ESPurna
Copyright (C) 2021 by Maxim Prokhorov <prokhorov dot max at outlook dot com>

*/

#include "wifi.h"
#include "wifi_config.h"

#include "telnet.h"
#include "ws.h"

#include <AddrList.h>

#if WIFI_AP_CAPTIVE_SUPPORT
#include <DNSServer.h>
#endif

#include <algorithm>
#include <array>
#include <queue>
#include <vector>

// -----------------------------------------------------------------------------
// SETTINGS
// -----------------------------------------------------------------------------

namespace settings {
namespace internal {

template<>
wifi::StaMode convert(const String& value) {
    return convert<bool>(value)
        ? wifi::StaMode::Enabled
        : wifi::StaMode::Disabled;
}

template<>
wifi::ApMode convert(const String& value) {
    switch (value.toInt()) {
    case 0:
        return wifi::ApMode::Disabled;
    case 1:
        return wifi::ApMode::Enabled;
    case 2:
        return wifi::ApMode::Fallback;
    }

    return wifi::build::softApMode();
}

template <>
WiFiSleepType_t convert(const String& value) {
    switch (value.toInt()) {
    case 2:
        return WIFI_MODEM_SLEEP;
    case 1:
        return WIFI_LIGHT_SLEEP;
    case 0:
        return WIFI_NONE_SLEEP;
    }

    return wifi::build::sleep();
}

template <>
IPAddress convert(const String& value) {
    IPAddress out;
    out.fromString(value);
    return out;
}

// XXX: "(IP unset)" when not set, no point saving these :/

String serialize(const IPAddress& ip) {
    return ip.isSet() ? ip.toString() : emptyString;
}

} // namespace internal
} // namespace settings

// -----------------------------------------------------------------------------
// INTERNAL
// -----------------------------------------------------------------------------

namespace wifi {

// XXX: esp8266 Arduino API inclues pseudo-modes and is not directly convertible
// into the SDK constants. Provide a constexpr version of the enum, since the code never
// actually uses `WiFi::mode(...)` directly, *but* opmode is retrieved using the SDK function.

constexpr uint8_t OpmodeNull { NULL_MODE };
constexpr uint8_t OpmodeSta { STATION_MODE };
constexpr uint8_t OpmodeAp { SOFTAP_MODE };
constexpr uint8_t OpmodeApSta { OpmodeSta | OpmodeAp };

using Mac = std::array<uint8_t, 6>;
using Macs = std::vector<Mac>;

enum class ScanError {
    None,
    AlreadyScanning,
    System,
    NoNetworks
};

enum class Action {
    StationConnect,
    StationContinueConnect,
    StationTryConnectBetter,
    StationDisconnect,
    AccessPointFallback,
    AccessPointFallbackCheck,
    AccessPointStart,
    AccessPointStop,
    TurnOff,
    TurnOn
};

using Actions = std::list<Action>;
using ActionsQueue = std::queue<Action, Actions>;

enum class State {
    Boot,
    Connect,
    TryConnectBetter,
    Connected,
    Idle,
    Init,
    Timeout,
    Fallback,
    WaitScan,
    WaitScanWithoutCurrent,
    WaitConnected
};

namespace internal {

// Module actions are controled in a serialzed manner, when internal loop is done with the
// current task and is free to take up another one. Allow to toggle OFF for the whole module,
// discarding any actions involving an active WiFi. Default is ON

bool enabled { true };
ActionsQueue actions;

} // namespace internal

uint8_t opmode() {
    return wifi_get_opmode();
}

bool enabled() {
    return internal::enabled;
}

void enable() {
    internal::enabled = true;
}

void disable() {
    internal::enabled = false;
}

void action(Action value) {
    switch (value) {
    case Action::StationConnect:
    case Action::StationTryConnectBetter:
    case Action::StationContinueConnect:
    case Action::StationDisconnect:
    case Action::AccessPointFallback:
    case Action::AccessPointFallbackCheck:
    case Action::AccessPointStart:
    case Action::AccessPointStop:
        if (!enabled()) {
            return;
        }
        break;
    case Action::TurnOff:
    case Action::TurnOn:
        break;
    }

    internal::actions.push(value);
}

ActionsQueue& actions() {
    return internal::actions;
}

// ::forceSleepBegin() remembers the previous mode and ::forceSleepWake() calls station connect when it has STA in it :/
// while we *do* set opmode to 0 to avoid this uncertainty, preper to call wake through SDK instead of the Arduino wrapper
//
// 0xFFFFFFF is a magic number per the NONOS API reference, 3.7.5 wifi_fpm_do_sleep:
// > If sleep_time_in_us is 0xFFFFFFF, the ESP8266 will sleep till be woke up as below:
// > • If wifi_fpm_set_sleep_type is set to be LIGHT_SLEEP_T, ESP8266 can wake up by GPIO.
// > • If wifi_fpm_set_sleep_type is set to be MODEM_SLEEP_T, ESP8266 can wake up by wifi_fpm_do_wakeup.
//
// In our case, wake-up is software driven, so the MODEM sleep is the only choice available.
// This version can *only* work from CONT context, since the only consumer atm is wifi::Action handler
// TODO(esp32): Null mode turns off radio, no need for these

bool sleep() {
    if ((opmode() == ::wifi::OpmodeNull) && (wifi_fpm_get_sleep_type() == NONE_SLEEP_T)) {
        wifi_fpm_set_sleep_type(MODEM_SLEEP_T);
        yield();
        wifi_fpm_open();
        yield();
        if (0 == wifi_fpm_do_sleep(0xFFFFFFF)) {
            delay(10);
            return true;
        }
    }

    return false;
}

bool wakeup() {
    if (wifi_fpm_get_sleep_type() != NONE_SLEEP_T) {
        wifi_fpm_do_wakeup();
        wifi_fpm_close();
        delay(10);
        return true;
    }

    return false;
}

namespace debug {

String error(wifi::ScanError error) {
    const __FlashStringHelper* ptr { nullptr };

    switch (error) {
    case wifi::ScanError::AlreadyScanning:
        ptr = F("Scan already in progress");
        break;
    case wifi::ScanError::System:
        ptr = F("Could not start the scan");
        break;
    case wifi::ScanError::NoNetworks:
        ptr = F("No networks");
        break;
    case wifi::ScanError::None:
        ptr = F("OK");
        break;
    }

    return ptr;
}

String ip(const IPAddress& addr) {
    return addr.toString();
}

String ip(ip4_addr_t addr) {
    String out;
    out.reserve(16);

    bool delim { false };
    for (int byte = 0; byte < 4; ++byte) {
        if (delim) {
            out += '.';
        }
        out += ip4_addr_get_byte_val(addr, byte);
        delim = true;
    }

    return out;
}

String mac(const wifi::Mac& mac) {
    String out;
    out.reserve(18);

    bool delim { false };
    char buffer[3] = {0};
    for (auto& byte : mac) {
        hexEncode(&byte, 1, buffer, sizeof(buffer));
        if (delim) {
            out += ':';
        }
        out += buffer;
        delim = true;
    }

    return out;
}

String authmode(AUTH_MODE mode) {
    const __FlashStringHelper* ptr { F("UNKNOWN") };

    switch (mode) {
    case AUTH_OPEN:
        ptr = F("OPEN");
        break;
    case AUTH_WEP:
        ptr = F("WEP");
        break;
    case AUTH_WPA_PSK:
        ptr = F("WPAPSK");
        break;
    case AUTH_WPA2_PSK:
        ptr = F("WPA2PSK");
        break;
    case AUTH_WPA_WPA2_PSK:
        ptr = F("WPAWPA2-PSK");
        break;
    case AUTH_MAX:
        break;
    }

    return ptr;
}

String opmode(uint8_t mode) {
    const __FlashStringHelper* ptr { nullptr };

    switch (mode) {
    case ::wifi::OpmodeApSta:
        ptr = F("AP+STA");
        break;
    case ::wifi::OpmodeSta:
        ptr = F("STA");
        break;
    case ::wifi::OpmodeAp:
        ptr = F("AP");
        break;
    case ::wifi::OpmodeNull:
        ptr = F("NULL");
        break;
    }

    return ptr;
}

} // namespace debug

namespace settings {

void migrate(int version) {
    if (version && (version < 5)) {
        moveSetting("apmode", "wifiApMode");
    }
}

decltype(millis()) garpInterval() {
    return getSetting("wifiGarpIntvl", secureRandom(wifi::build::garpIntervalMin(), wifi::build::garpIntervalMax()));
}

float txPower() {
    return getSetting("wifiTxPwr", wifi::build::outputDbm());
}

WiFiSleepType_t sleep() {
    return getSetting("wifiSleep", wifi::build::sleep());
}

bool scanNetworks() {
    return getSetting("wifiScan", wifi::build::scanNetworks());
}

int8_t scanRssiThreshold() {
    return getSetting("wifiScanRssi", wifi::build::scanRssiThreshold());
}

String hostname() {
    return getSetting("hostname", getIdentifier());
}

wifi::StaMode staMode() {
    return getSetting("wifiStaMode", wifi::build::staMode());
}

IPAddress staIp(size_t index) {
    return ::settings::internal::convert<IPAddress>(
        getSetting({"ip", index}, wifi::build::ip(index)));
}

String staSsid(size_t index) {
    return getSetting({"ssid", index}, wifi::build::ssid(index));
}

String staPassphrase(size_t index) {
    return getSetting({"pass", index}, wifi::build::passphrase(index));
}

IPAddress staGateway(size_t index) {
    return ::settings::internal::convert<IPAddress>(
        getSetting({"gw", index}, wifi::build::gateway(index)));
}

IPAddress staMask(size_t index) {
    return ::settings::internal::convert<IPAddress>(
        getSetting({"mask", index}, wifi::build::mask(index)));
}

IPAddress staDns(size_t index) {
    return ::settings::internal::convert<IPAddress>(
        getSetting({"dns", index}, wifi::build::dns(index)));
}

bool softApCaptive() {
    return getSetting("wifiApCaptive", wifi::build::softApCaptive());
}

wifi::ApMode softApMode() {
    return getSetting("wifiApMode", wifi::build::softApMode());
}

String softApSsid() {
    return getSetting("wifiApSsid", wifi::build::hasSoftApSsid()
        ? wifi::build::softApSsid()
        : hostname());
}

String softApPassphrase() {
    return getSetting("wifiApPass", wifi::build::hasSoftApPassphrase()
        ? wifi::build::softApPassphrase()
        : getAdminPass());
}

int8_t softApChannel() {
    return getSetting("wifiApChannel", wifi::build::softApChannel());
}

wifi::Mac softApLease(size_t index) {
    wifi::Mac lease { 0u, 0u, 0u, 0u, 0u, 0u };

    auto value = getSetting({"wifiApLease", index});
    if (12 == value.length()) {
        hexDecode(value.c_str(), value.length(), lease.data(), lease.size());
    }

    return lease;
}

} // namespace settings

// We are guaranteed to have '\0' when <32 b/c the SDK zeroes out the data
// But, these are byte arrays, not C strings. When ssid_len is available, use it.
// When not, we are still expecting the <32 arrays to have '\0' at the end and we manually
// set the 32'nd char to '\0' to prevent conversion issues

namespace {

String convertSsid(const softap_config& config) {
    String ssid;
    ssid.concat(reinterpret_cast<const char*>(config.ssid), config.ssid_len);
    return ssid;
}

String convertSsid(const bss_info& info) {
    String ssid;
    ssid.concat(reinterpret_cast<const char*>(info.ssid), info.ssid_len);
    return ssid;
}

String convertSsid(const station_config& config) {
    constexpr size_t SsidSize { sizeof(softap_config::ssid) };

    const char* ptr { reinterpret_cast<const char*>(config.ssid) };
    char ssid[SsidSize + 1];
    std::copy(ptr, ptr + SsidSize, ssid);
    ssid[SsidSize] = '\0';

    return ssid;
}

template <typename T, size_t PassphraseSize = sizeof(T::password)>
String convertPassphrase(const T& config) {
    const char* ptr { reinterpret_cast<const char*>(config.password) };

    char passphrase[PassphraseSize + 1];
    std::copy(ptr, ptr + PassphraseSize, passphrase);
    passphrase[PassphraseSize] = '\0';

    return passphrase;
}

template <typename T>
wifi::Mac convertBssid(const T& info) {
    wifi::Mac mac;
    std::copy(info.bssid, info.bssid + 6, mac.begin());
    return mac;
}

} // namespace

struct Info {
    Info() = default;
    Info(const Info&) = default;
    Info(Info&&) = default;

    Info(wifi::Mac&& bssid, AUTH_MODE authmode, int8_t rssi, uint8_t channel) :
        _bssid(std::move(bssid)),
        _authmode(authmode),
        _rssi(rssi),
        _channel(channel)
    {}

    explicit Info(const bss_info& info) :
        _bssid(convertBssid(info)),
        _authmode(info.authmode),
        _rssi(info.rssi),
        _channel(info.channel)
    {}

    Info& operator=(const Info&) = default;
    Info& operator=(Info&&) = default;

    Info& operator=(const bss_info& info) {
        _bssid = convertBssid(info);
        _authmode = info.authmode;
        _channel = info.channel;
        _rssi = info.rssi;
        return *this;
    }

    explicit operator bool() const {
        return _rssi != 0 && _channel != 0;
    }

    bool operator<(const Info& rhs) const {
        return _rssi < rhs._rssi;
    }

    bool operator>(const Info& rhs) const {
        return _rssi > rhs._rssi;
    }

    const wifi::Mac& bssid() const {
        return _bssid;
    }

    AUTH_MODE authmode() const {
        return _authmode;
    }

    int8_t rssi() const {
        return _rssi;
    }

    uint8_t channel() const {
        return _channel;
    }

private:
    //Mac _bssid {{ 0u, 0u, 0u, 0u, 0u, 0u }}; // TODO: gcc4 can't figure out basic aggregate, replace when using gcc10 builds
    Mac _bssid {};
    AUTH_MODE _authmode { AUTH_OPEN };
    int8_t _rssi { 0 };
    uint8_t _channel { 0u };
};

struct SsidInfo {
    SsidInfo() = delete;

    explicit SsidInfo(const bss_info& info) :
        _ssid(convertSsid(info)),
        _info(info)
    {}

    SsidInfo(String&& ssid, wifi::Info&& info) :
        _ssid(std::move(ssid)),
        _info(std::move(info))
    {}

    const String& ssid() const {
        return _ssid;
    }

    const wifi::Info& info() const {
        return _info;
    }

    // decreasing order by rssi (default sort() order is increasing)
    bool operator<(const SsidInfo& rhs) const {
        if (!_info.rssi()) {
            return false;
        }

        return info() > rhs.info();
    }

private:
    String _ssid;
    wifi::Info _info;
};

using SsidInfos = std::forward_list<SsidInfo>;

// Note that lwip config allows up to 3 DNS servers. But, most of the time we use DHCP.
// TODO: ::dns(size_t index)? how'd that look with settings?

struct IpSettings {
    IpSettings() = default;
    IpSettings(const IpSettings&) = default;
    IpSettings(IpSettings&&) = default;

    IpSettings& operator=(const IpSettings&) = default;
    IpSettings& operator=(IpSettings&&) = default;

    template <typename Ip, typename Gateway, typename Netmask, typename Dns>
    IpSettings(Ip&& ip, Gateway&& gateway, Netmask&& netmask, Dns&& dns) :
        _ip(std::forward<Ip>(ip)),
        _gateway(std::forward<Gateway>(gateway)),
        _netmask(std::forward<Netmask>(netmask)),
        _dns(std::forward<Dns>(dns))
    {}

    const IPAddress& ip() const {
        return _ip;
    }

    const IPAddress& gateway() const {
        return _gateway;
    }

    const IPAddress& netmask() const {
        return _netmask;
    }

    const IPAddress& dns() const {
        return _dns;
    }

    explicit operator bool() const {
        return _ip.isSet()
            && _gateway.isSet()
            && _netmask.isSet()
            && _dns.isSet();
    }

private:
    IPAddress _ip;
    IPAddress _gateway;
    IPAddress _netmask;
    IPAddress _dns;
};

struct StaNetwork {
    Mac bssid;
    String ssid;
    String passphrase;
    int8_t rssi;
    uint8_t channel;
};

struct SoftApNetwork {
    Mac bssid;
    String ssid;
    String passphrase;
    uint8_t channel;
    AUTH_MODE authmode;
};

struct Network {
    Network() = delete;
    Network(const Network&) = default;
    Network(Network&&) = default;

    Network& operator=(Network&&) = default;

    template <typename Ssid>
    explicit Network(Ssid&& ssid) :
        _ssid(std::forward<Ssid>(ssid))
    {}

    template <typename Ssid, typename Passphrase>
    Network(Ssid&& ssid, Passphrase&& passphrase) :
        _ssid(std::forward<Ssid>(ssid)),
        _passphrase(std::forward<Passphrase>(passphrase))
    {}

    template <typename Ssid, typename Passphrase, typename Settings>
    Network(Ssid&& ssid, Passphrase&& passphrase, Settings&& settings) :
        _ssid(std::forward<Ssid>(ssid)),
        _passphrase(std::forward<Passphrase>(passphrase)),
        _ipSettings(std::forward<Settings>(settings))
    {}

    // TODO(?): in case SDK API is used directly, this also could use an authmode field
    // Arduino wrapper sets WPAPSK minimum by default, so one use-case is to set it to WPA2PSK

    Network(Network&& other, wifi::Mac bssid, uint8_t channel) :
        _ssid(std::move(other._ssid)),
        _passphrase(std::move(other._passphrase)),
        _ipSettings(std::move(other._ipSettings)),
        _bssid(bssid),
        _channel(channel)
    {}

    bool dhcp() const {
        return !_ipSettings;
    }

    const String& ssid() const {
        return _ssid;
    }

    const String& passphrase() const {
        return _passphrase;
    }

    const IpSettings& ipSettings() const {
        return _ipSettings;
    }

    const wifi::Mac& bssid() const {
        return _bssid;
    }

    uint8_t channel() const {
        return _channel;
    }

private:
    String _ssid;
    String _passphrase;
    IpSettings _ipSettings;

    Mac _bssid {};
    uint8_t _channel { 0u };
};

using Networks = std::list<Network>;

// -----------------------------------------------------------------------------
// STATION
// -----------------------------------------------------------------------------

namespace sta {

constexpr auto ConnectionInterval = wifi::build::staConnectionInterval();
constexpr auto ConnectionRetries = wifi::build::staConnectionRetries();
constexpr auto ReconnectionInterval = wifi::build::staReconnectionInterval();

uint8_t channel() {
    return wifi_get_channel();
}

int8_t rssi() {
    return wifi_station_get_rssi();
}

// Note that authmode is a spefific threshold selected by the Arduino WiFi.begin()
// (ref. Arduino ESP8266WiFi default, which is AUTH_WPA_WPA2_PSK in the current 3.0.0)
// Also, it is not really clear whether `wifi_get_channel()` will work correctly in the future versions,
// since the API seems to be related to the promiscuous WiFi (aka sniffer), but it does return the correct values.

wifi::Info info(const station_config& config) {
    return wifi::Info{
        convertBssid(config),
        config.threshold.authmode,
        rssi(),
        channel()};
}

wifi::Info info() {
    station_config config{};
    wifi_station_get_config(&config);
    return info(config);
}

wifi::IpSettings ipsettings() {
    return {
        WiFi.localIP(),
        WiFi.gatewayIP(),
        WiFi.subnetMask(),
        WiFi.dnsIP()};
}

wifi::Mac bssid() {
    station_config config{};
    wifi_station_get_config(&config);

    return convertBssid(config);
}

wifi::StaNetwork current(const station_config& config) {
    return {
        convertBssid(config),
        convertSsid(config),
        convertPassphrase(config),
        rssi(),
        channel()};
}

wifi::StaNetwork current() {
    station_config config{};
    wifi_station_get_config(&config);
    return current(config);
}

#if WIFI_GRATUITOUS_ARP_SUPPORT
namespace garp {
namespace internal {

Ticker timer;
bool wait { false };
decltype(millis()) interval { wifi::build::garpIntervalMin() };

} // namespace internal

bool send() {
    bool result { false };

    for (netif* interface = netif_list; interface != nullptr; interface = interface->next) {
        if (
            (interface->flags & NETIF_FLAG_ETHARP)
            && (interface->hwaddr_len == ETHARP_HWADDR_LEN)
            && (!ip4_addr_isany_val(*netif_ip4_addr(interface)))
            && (interface->flags & NETIF_FLAG_LINK_UP)
            && (interface->flags & NETIF_FLAG_UP)
        ) {
            etharp_gratuitous(interface);
            result = true;
        }
    }

    return result;
}

bool wait() {
    if (internal::wait) {
        return true;
    }

    internal::wait = true;
    return false;
}

void stop() {
    internal::timer.detach();
}

void start(decltype(millis()) ms) {
    internal::timer.attach_ms(ms, []() {
        internal::wait = false;
    });
}

} // namespace garp
#endif

namespace scan {

using SsidInfosPtr = std::shared_ptr<wifi::SsidInfos>;

using Success = std::function<void(bss_info*)>;
using Error = std::function<void(wifi::ScanError)>;

struct Task {
    Task() = delete;

    template <typename S, typename E>
    Task(S&& success, E&& error) :
        _success(std::forward<S>(success)),
        _error(std::forward<E>(error))
    {}

    void success(bss_info* info) {
        _success(info);
    }

    void error(wifi::ScanError error) {
        _error(error);
    }

private:
    Success _success;
    Error _error;
};

using TaskPtr = std::unique_ptr<Task>;

namespace internal {

TaskPtr task;

void stop() {
    task = nullptr;
}

// STATUS comes from c_types.h, and it seems this is the only place that uses it
// instead of some ESP-specific type.

void complete(void* result, STATUS status) {
    if (status) { // aka anything but OK / 0
        task->error(wifi::ScanError::System);
        stop();
        return;
    }

    size_t networks { 0ul };
    bss_info* head = reinterpret_cast<bss_info*>(result);
    for (bss_info* it = head; it; it = STAILQ_NEXT(it, next), ++networks) {
        task->success(it);
    }

    if (!networks) {
        task->error(wifi::ScanError::NoNetworks);
    }

    stop();
}

} // namespace internal

bool start(Success&& success, Error&& error) {
    if (internal::task) {
        error(wifi::ScanError::AlreadyScanning);
        return false;
    }

    // Note that esp8266 callback only reports the resulting status and will (always?) timeout all by itself
    // Default values are an active scan with some unspecified channel times.
    // (zeroed out scan_config struct or simply nullptr)

    // For example, c/p config from the current esp32 Arduino Core wrapper which are close to the values mentioned here:
    // https://github.com/espressif/ESP8266_NONOS_SDK/issues/103#issuecomment-383440370
    // Which could be useful if scanning needs to be more aggressive or switched into PASSIVE scan type

    //scan_config config{};
    //config.scan_type = WIFI_SCAN_TYPE_ACTIVE;
    //config.scan_time.active.min = 100;
    //config.scan_time.active.max = 300;

    if (wifi_station_scan(nullptr, &internal::complete)) {
        internal::task = std::make_unique<Task>(std::move(success), std::move(error));
        return true;
    }

    error(wifi::ScanError::System);
    return false;
}

// Alternative to the stock WiFi method, where we wait for the task to finish before returning
bool wait(Success&& success, Error&& error) {
    auto result = start(std::move(success), std::move(error));
    while (internal::task) {
        delay(100);
    }

    return result;
}

// Another alternative to the stock WiFi method, return a shared Info list
// Caller is expected to wait for the scan to complete before using the contents
SsidInfosPtr ssidinfos() {
    auto infos = std::make_shared<wifi::SsidInfos>();

    start(
        [infos](bss_info* found) {
            wifi::SsidInfo pair(*found);
            infos->remove_if([&](const wifi::SsidInfo& current) {
                return (current.ssid() == pair.ssid()) && (current.info() < pair.info());
            });
            infos->emplace_front(std::move(pair));
        },
        [infos](wifi::ScanError) {
            infos->clear();   
        });

    return infos;
}

} // namespace scan

bool enabled() {
    return wifi::opmode() & wifi::OpmodeSta;
}

// XXX: WiFi.disconnect() also implicitly disables STA mode *and* erases the current STA config

void disconnect() {
    if (enabled()) {
        wifi_station_disconnect();
    }
}

// Some workarounds for built-in WiFi management:
// - don't *intentionally* perist current SSID & PASS even when persistance is disabled from the Arduino Core side.
// while this seems like a good idea in theory, we end up with a bunch of async actions coming our way.
// - station disconnect events are linked with the connection routine as well, single WiFi::begin() may trigger up to
// 3 events (as observed with `WiFi::waitForConnectResult()`) before the connection loop stops further attempts
// - explicit OPMODE changes to both notify the userspace when the change actually happens (alternative is SDK event, but it is SYS context),
// since *all* STA & AP start-up methods will implicitly change the mode (`WiFi.begin()`, `WiFi.softAP()`, `WiFi.config()`)

void enable() {
    if (WiFi.enableSTA(true)) {
        disconnect();
        ETS_UART_INTR_DISABLE();
        wifi_station_set_reconnect_policy(false);
        if (wifi_station_get_auto_connect()) {
            wifi_station_set_auto_connect(false);
        }
        ETS_UART_INTR_ENABLE();
        return;
    }

    // `std::abort()` calls are the to ensure the mode actually changes, but it should be extremely rare
    // it may be also wise to add these for when the mode is already the expected one,
    // since we should enforce mode changes to happen *only* through the configuration loop
    abort();
}

void disable() { 
    if (!WiFi.enableSTA(false)) {
        abort();
    }
}

namespace connection {
namespace internal {

struct Task {
    using Iterator = wifi::Networks::iterator;

    Task() = delete;
    Task(const Task&) = delete;
    Task(Task&&) = delete;

    explicit Task(String&& hostname, Networks&& networks, int retries) :
        _hostname(std::move(hostname)),
        _networks(std::move(networks)),
        _begin(_networks.begin()),
        _end(_networks.end()),
        _current(_begin),
        _retries(retries),
        _retry(_retries)
    {}

    bool empty() const {
        return _networks.empty();
    }

    size_t count() const {
        return _networks.size();
    }

    bool done() const {
        return _current == _end;
    }

    bool next() {
        if (!done()) {
            if (_retry-- < 0) {
                _retry = _retries;
                _current = std::next(_current);
            }
            return !done();
        }

        return false;
    }

    // Sanity checks for SSID & PASSPHRASE lengths are performed by the WiFi.begin()
    // (or, failing connection, if we ever use raw SDK API)

    bool connect() const {
        if (!done() && wifi::sta::enabled()) {
            wifi::sta::disconnect();
            auto& network = *_current;
            if (!network.dhcp()) {
                auto& ipsettings = network.ipSettings();
                if (!WiFi.config(ipsettings.ip(), ipsettings.gateway(), ipsettings.netmask(), ipsettings.dns())) {
                    return false;
                }
            }

            // Only the STA cares about the hostname setting
            // esp8266 specific Arduino-specific - this sets lwip internal structs related to the DHCPc
            WiFi.hostname(_hostname);

            if (network.channel()) {
                WiFi.begin(network.ssid(), network.passphrase(),
                        network.channel(), network.bssid().data());
            } else {
                WiFi.begin(network.ssid(), network.passphrase());
            }

            return true;
        }

        return false;
    }

    Networks& networks() {
        return _networks;
    }

    void reset() {
        _begin = _networks.begin();
        _end = _networks.end();
        _current = _begin;
        _retry = _retries;
    }

    // Since after sort() the ssid<->info pairs will be in a proper order, look up the known network and move it to the front aka 'head'
    // Continue after shifting the 'head' element one element further, b/c we also a guaranteed that ssid<->info pairs are unique
    // Authmode comparison is pretty lenient, so only requirement is availability of the passphrase text.

    // Does not invalidate iterators, since the elements are swapped in-place, but we still need to reset to initial state.

    void sort(scan::SsidInfosPtr&& ptr) {
        auto& pairs = *ptr;
        pairs.sort();

        auto begin = _networks.begin();
        auto end = _networks.end();

        auto head = begin;

        for (auto& pair : pairs) {
            for (auto network = head; (head != end) && (network != end); ++network) {
                if (pair.ssid() != (*network).ssid()) {
                    continue;
                }

                auto& info = pair.info();
                if ((*network).passphrase().length()
                        && (info.authmode() == AUTH_OPEN)) {
                    continue;
                }
                
                *network = wifi::Network(std::move(*network), info.bssid(), info.channel());
                if (network != head) {
                    std::swap(*network, *head);
                }
                ++head;
                break;
            }
        }

        reset();
    }

    // Allow to remove the currently used network right from the scan routine
    // Only makes sense when wifi::Network's bssid exist, either after sort() or if loaded from settings

    bool filter(const wifi::Info& info) {
        _networks.remove_if([&](const wifi::Network& network) {
            return network.bssid() == info.bssid();
        });
        reset();
        return !done();
    }


private:
    String _hostname;
    Networks _networks;
    Iterator _begin;
    Iterator _end;
    Iterator _current;

    const int _retries;
    int _retry;
};

station_status_t last { STATION_IDLE };
bool connected { false };

Ticker timer;
bool persist { false };
bool lock { false };

using TaskPtr = std::unique_ptr<Task>;
TaskPtr task;

} // namespace internal

bool locked() {
    return internal::lock;
}

void unlock() {
    internal::lock = false;
}

void lock() {
    internal::lock = true;
}

void persist(bool value) {
    internal::persist = value;
}

bool persist() {
    return internal::persist;
}

void stop() {
    if (!locked()) {
        internal::task.reset();
        internal::timer.detach();
    }
}

bool started() {
    return static_cast<bool>(internal::task);
}

void start(String&& hostname, Networks&& networks, int retries) {
    if (!locked()) {
        internal::task = std::make_unique<internal::Task>(
            std::move(hostname),
            std::move(networks),
            retries);
        internal::timer.detach();
    }
}

void schedule(decltype(millis()) ms, wifi::Action next) {
    internal::timer.once_ms(ms, [next]() {
        wifi::action(next);
        unlock();
    });
    lock();
}

void continued() {
    schedule(wifi::sta::ConnectionInterval, wifi::Action::StationContinueConnect);
}

void initial() {
    schedule(wifi::sta::ReconnectionInterval, wifi::Action::StationConnect);
}

bool next() {
    return internal::task->next();
}

bool connect() {
    return internal::task->connect();
}

bool filter(const wifi::Info& info) {
    return internal::task->filter(info);
}

void sort(scan::SsidInfosPtr&& infos) {
    internal::task->sort(std::move(infos));
}

station_status_t last() {
    return internal::last;
}

// Note that `wifi_station_get_connect_status()` only makes sence when something is setting `wifi_set_event_handler_cb(...)`
// *and*, it should only be expected to work when STA is not yet connected. After a successful connection, we should track the network interface and / or SDK events.
// Events are already enabled in the Arduino Core (and heavily wired through-out it, so we can't override b/c only one handler is allowed).

bool wait() {
    internal::last = wifi_station_get_connect_status();
    bool out { false };

    switch (internal::last) {
    case STATION_CONNECTING:
        out = true;
        break;
    case STATION_GOT_IP:
        internal::connected = true;
        break;
    case STATION_IDLE:
    case STATION_NO_AP_FOUND:
    case STATION_CONNECT_FAIL:
    case STATION_WRONG_PASSWORD:
        break;
    }

    return out;
}

// TODO(Core 2.7.4): `WiFi.isConnected()` is a simple `wifi_station_get_connect_status() == STATION_GOT_IP`,
// Meaning, it will never detect link up / down updates when AP silently kills the connection or something else unexpected happens.
// Running JustWiFi with autoconnect + reconnect enabled, it silently avoided the issue b/c the SDK reconnect routine disconnected the STA,
// causing our state machine to immediatly cancel it (since `WL_CONNECTED != WiFi.status()`) and then try to connect again using it's own loop.
// We could either (* is used currently):
// - (*) listen for the SDK event through the `WiFi.onStationModeDisconnected()`
// - ( ) poll NETIF_FLAG_LINK_UP for the lwip's netif, since the SDK will bring the link down on disconnection
//   find the `interface` in the `netif_list`, where `interface->num == STATION_IF`
// - ( ) use lwip's netif event system from the recent Core, track UP and DOWN for a specific interface number
//   this one is probably only used internally, thus should be treated as a private API
// - ( ) poll whether `wifi_get_ip_info(STATION_IF, &ip);` is set to something valid
//   (tuple of ip, gw and mask)
// - ( ) poll `WiFi.localIP().isSet()`
//   (will be unset when the link is down)

// placing status into a simple bool to avoid extracting ip info every time someone needs to check the connection

bool connected() {
    return internal::connected;
}

bool connecting() {
    return static_cast<bool>(internal::task);
}

bool lost() {
    static bool last { internal::connected };

    bool out { false };
    if (internal::connected != last) {
        last = internal::connected;
        if (!last) {
            if (persist() && !connecting()) {
                schedule(wifi::sta::ConnectionInterval * wifi::sta::ConnectionRetries, wifi::Action::StationConnect);
            }
            out = true;
        }
    }

    return out;
}

} // namespace connection

bool connected() {
    return connection::connected();
}

bool connecting() {
    return connection::connecting();
}

bool scanning() {
    return static_cast<bool>(scan::internal::task);
}

// TODO: generic onEvent is deprecated on esp8266 in favour of the event-specific
// methods returning 'cancelation' token. Right now it is a basic shared_ptr with an std function inside of it.
// esp32 only has a generic onEvent, but event names are not compatible with the esp8266 version.

void init() {
    static auto status = WiFi.onStationModeDisconnected([](const WiFiEventStationModeDisconnected& src) { // aka const auto&
        connection::internal::connected = false;
    });
    disconnect();
    disable();
}

void toggle() {
    auto current = enabled();
    connection::persist(!current);
    wifi::action(current
        ? wifi::Action::StationDisconnect
        : wifi::Action::StationConnect);
}

namespace scan {
namespace periodic {
namespace internal {

constexpr int8_t Checks { wifi::build::scanRssiChecks() };
constexpr decltype(millis()) CheckInterval { wifi::build::scanRssiCheckInterval() };

int8_t threshold { wifi::build::scanRssiThreshold() };
int8_t counter { Checks };
Ticker timer;

void task() {
    if (!wifi::sta::connected()) {
        counter = Checks;
        return;
    }

    auto rssi = wifi::sta::rssi();
    if (rssi > threshold) {
        counter = Checks;
    } else if (rssi < threshold) {
        if (counter < 0) {
            return;
        }

        if (!--counter) {
            wifi::action(wifi::Action::StationTryConnectBetter);
        }
    }
}

void start() {
    counter = Checks;
    timer.attach_ms(CheckInterval, task);
}

void stop() {
    counter = Checks;
    timer.detach();
}

} // namespace internal

void threshold(int8_t value) {
    internal::threshold = value;
}

int8_t threshold() {
    return internal::threshold;
}

void stop() {
    internal::stop();
}

void start() {
    internal::start();
}

bool check() {
    if (internal::counter <= 0) {
        internal::counter = internal::Checks;
        return true;
    }

    return false;
}

bool enabled() {
    return internal::timer.active();
}

} // namespace periodic
} // namespace scan
} // namespace sta

// -----------------------------------------------------------------------------
// ACCESS POINT
// -----------------------------------------------------------------------------

namespace ap {

static constexpr size_t LeasesMax { 4u };

namespace internal {

#if WIFI_AP_CAPTIVE_SUPPORT
bool captive { wifi::build::softApCaptive() };
DNSServer dns;
#endif

#if WIFI_AP_LEASES_SUPPORT
wifi::Macs leases;
#endif

} // namespace internal

#if WIFI_AP_CAPTIVE_SUPPORT

void captive(bool value) {
    internal::captive = value;
}

bool captive() {
    return internal::captive;
}

void dnsLoop() {
    internal::dns.processNextRequest();
}

#endif

void enable() {
    if (!WiFi.enableAP(true)) {
        abort();
    }
}

void disable() {
    if (!WiFi.enableAP(false)) {
        abort();
    }
}

bool enabled() {
    return wifi::opmode() & WIFI_AP;
}

void toggle() {
    wifi::action(wifi::ap::enabled()
        ? wifi::Action::AccessPointStop
        : wifi::Action::AccessPointStart);
}

#if WIFI_AP_LEASES_SUPPORT

void setupLeases() {
    for (auto& lease : internal::leases) {
        wifi_softap_add_dhcps_lease(lease.data());
    }
}

void clearLeases() {
    internal::leases.clear();
}

template <typename T>
void lease(T&& mac) {
    if (internal::leases.size() < LeasesMax) {
        internal::leases.push_back(std::forward<T>(mac));
    }
}

#endif

void stop() {
#if WIFI_AP_CAPTIVE_SUPPORT
    internal::dns.stop();
#endif
    WiFi.softAPdisconnect();
}

void start(String&& ssid, String&& passphrase, uint8_t channel) {
    if (!enabled()) {
        return;
    }

    if (!ssid.length()) {
        disable();
        return;
    }

#if WIFI_AP_LEASES_SUPPORT
    // Default amount of stations is 4, which we use here b/c softAp is called without arguments.
    // When chaging the number below, update LeasesMax / use it as the 5th param
    // (4th is `hidden` SSID)
    setupLeases();
#endif
    // TODO: softAP() implicitly enables AP mode
    enable();
    WiFi.softAP(ssid, passphrase, channel);

#if WIFI_AP_CAPTIVE_SUPPORT
    if (internal::captive) { 
        internal::dns.setErrorReplyCode(DNSReplyCode::NoError);
        internal::dns.start(53, "*", WiFi.softAPIP());
    } else {
        internal::dns.stop();
    }
#endif
}

wifi::SoftApNetwork current() {
    softap_config config{};
    wifi_softap_get_config(&config);

    wifi::Mac mac;
    WiFi.softAPmacAddress(mac.data());

    return {
        mac,
        convertSsid(config),
        convertPassphrase(config),
        config.channel,
        config.authmode};
}

void init() {
    disable();
}

uint8_t stations() {
    return WiFi.softAPgetStationNum();
}

namespace fallback {
namespace internal {

bool enabled { false };
decltype(millis()) timeout { wifi::build::softApFallbackTimeout() };
Ticker timer;

} // namespace internal

void enable() {
    internal::enabled = true;
}

void disable() {
    internal::enabled = false;
}

bool enabled() {
    return internal::enabled;
}

void remove() {
    internal::timer.detach();
}

bool scheduled() {
    return internal::timer.active();
}

void check();

void schedule() {
    internal::timer.once_ms(internal::timeout, check);
}

void check() {
    if (wifi::ap::enabled()
        && wifi::sta::connected()
        && !wifi::ap::stations())
    {
        remove();
        wifi::action(wifi::Action::AccessPointStop);
        return;
    }

    schedule();
}

} // namespace fallback
} // namespace ap

// -----------------------------------------------------------------------------
// SETTINGS
// -----------------------------------------------------------------------------

namespace settings {

wifi::Networks networks() {
    wifi::Networks out;
    for (size_t id = 0; id < wifi::build::NetworksMax; ++id) {
        auto ssid = wifi::settings::staSsid(id);
        if (!ssid.length()) {
            break;
        }

        auto pass = wifi::settings::staPassphrase(id);
        auto ip = staIp(id);
        if (ip.isSet()) {
            out.emplace_back(std::move(ssid), std::move(pass),
                wifi::IpSettings{std::move(ip), staGateway(id), staMask(id), staDns(id)});
        } else {
            out.emplace_back(std::move(ssid), std::move(pass));
        }
    }

    auto leftover = std::unique(out.begin(), out.end(), [](const wifi::Network& lhs, const wifi::Network& rhs) {
        return lhs.ssid() == rhs.ssid();
    });
    out.erase(leftover, out.end());

    return out;
}

void configure() {
    auto ap_mode = wifi::settings::softApMode();
    if (wifi::ApMode::Fallback == ap_mode) {
        wifi::ap::fallback::enable();
    } else {
        wifi::ap::fallback::disable();
        wifi::ap::fallback::remove();
        wifi::action((ap_mode == wifi::ApMode::Enabled)
                ? wifi::Action::AccessPointStart
                : wifi::Action::AccessPointStop);
    }

#if WIFI_AP_CAPTIVE_SUPPORT
    wifi::ap::captive(wifi::settings::softApCaptive());
#endif
#if WIFI_AP_LEASES_SUPPORT
    wifi::ap::clearLeases();
    for (size_t index = 0; index < wifi::ap::LeasesMax; ++index) {
        wifi::ap::lease(wifi::settings::softApLease(index));
    }
#endif

    auto sta_enabled = (wifi::StaMode::Enabled == wifi::settings::staMode());
    wifi::sta::connection::persist(sta_enabled);
    wifi::action(sta_enabled
        ? wifi::Action::StationConnect
        : wifi::Action::StationDisconnect);

    wifi::sta::scan::periodic::threshold(wifi::settings::scanRssiThreshold());

#if WIFI_GRATUITOUS_ARP_SUPPORT
    wifi::sta::garp::start(wifi::settings::garpInterval());
#endif

    WiFi.setSleepMode(wifi::settings::sleep());
    WiFi.setOutputPower(wifi::settings::txPower());
}

} // namespace settings

// -----------------------------------------------------------------------------
// TERMINAL
// -----------------------------------------------------------------------------

namespace terminal {

#if TERMINAL_SUPPORT

void init() {

    terminalRegisterCommand(F("WIFI.STATIONS"), [](const ::terminal::CommandContext& ctx) {
        size_t stations { 0ul };
        for (auto* it = wifi_softap_get_station_info(); it; it = STAILQ_NEXT(it, next), ++stations) {
            ctx.output.printf_P(PSTR("%s %s\n"),
                wifi::debug::mac(convertBssid(*it)).c_str(),
                wifi::debug::ip(it->ip).c_str());
        }

        wifi_softap_free_station_info();

        if (!stations) {
            terminalError(ctx, F("No stations connected"));
            return;
        }

        terminalOK(ctx);
    });

    terminalRegisterCommand(F("NETWORK"), [](const ::terminal::CommandContext& ctx) {
        for (auto& addr : addrList) {
            ctx.output.printf_P(PSTR("%s%d %4s %6s "),
                addr.ifname().c_str(),
                addr.ifnumber(),
                addr.ifUp() ? "up" : "down",
                addr.isLocal() ? "local" : "global");

#if LWIP_IPV6
            if (addr.isV4()) {
#endif
                ctx.output.printf_P(PSTR("ip %s gateway %s mask %s\n"),
                    wifi::debug::ip(addr.ipv4()).c_str(),
                    wifi::debug::ip(addr.gw()).c_str(),
                    wifi::debug::ip(addr.netmask()).c_str());
#if LWIP_IPV6
            } else {
                // TODO: ip6_addr[...] array is included in the list
                // we'll just see another entry
                // TODO: routing info is not attached to the netif :/
                // ref. nd6.h (and figure out what it does)
                ctx.output.printf_P(PSTR("ip %s\n"),
                    wifi::debug::ip(netif->ip6_addr[i]).c_str());
            }
#endif

        }

        for (int n = 0; n < DNS_MAX_SERVERS; ++n) {
            auto ip = IPAddress(dns_getserver(n));
            if (!ip.isSet()) {
                break;
            }
            ctx.output.printf_P(PSTR("dns %s\n"), wifi::debug::ip(ip).c_str());
        }
    });

    terminalRegisterCommand(F("WIFI"), [](const ::terminal::CommandContext& ctx) {
        const auto mode = wifi::opmode();
        ctx.output.printf_P(PSTR("OPMODE: %s\n"), wifi::debug::opmode(mode).c_str());

        if (mode & OpmodeAp) {
            auto current = wifi::ap::current();

            ctx.output.printf_P(PSTR("SoftAP: bssid %s channel %hhu auth %s ssid \"%s\" passphrase \"%s\"\n"),
                wifi::debug::mac(current.bssid).c_str(),
                current.channel,
                wifi::debug::authmode(current.authmode).c_str(),
                current.ssid.c_str(),
                current.passphrase.c_str());
        }

        if (mode & OpmodeSta) {
            if (wifi::sta::connected()) {
                station_config config{};
                wifi_station_get_config(&config);

                auto network = wifi::sta::current(config);
                ctx.output.printf_P(PSTR("STA: bssid %s rssi %hhd channel %hhu ssid \"%s\"\n"),
                    wifi::debug::mac(network.bssid).c_str(),
                    network.rssi, network.channel, network.ssid.c_str());
            } else {
                ctx.output.println(F("STA: disconnected"));
            }
        }

        terminalOK(ctx);
    });

    terminalRegisterCommand(F("WIFI.RESET"), [](const ::terminal::CommandContext& ctx) {
        wifiDisconnect();
        wifi::settings::configure();
        terminalOK(ctx);
    });

    terminalRegisterCommand(F("WIFI.STA"), [](const ::terminal::CommandContext& ctx) {
        wifi::sta::toggle();
        terminalOK(ctx);
    });

    terminalRegisterCommand(F("WIFI.AP"), [](const ::terminal::CommandContext& ctx) {
        wifi::ap::toggle();
        terminalOK(ctx);
    });

    terminalRegisterCommand(F("WIFI.SCAN"), [](const ::terminal::CommandContext& ctx) {
        wifi::sta::scan::wait(
            [&](bss_info* info) {
                ctx.output.printf_P(PSTR("BSSID: %s AUTH: %11s RSSI: %3hhd CH: %2hhu SSID: %s\n"),
                    wifi::debug::mac(convertBssid(*info)).c_str(),
                    wifi::debug::authmode(info->authmode).c_str(),
                    info->rssi,
                    info->channel,
                    convertSsid(*info).c_str()
                );
            },
            [&](wifi::ScanError error) {
                terminalError(ctx, wifi::debug::error(error));
            }
        );
    });

}

} // namespace terminal

#endif

// -----------------------------------------------------------------------------
// WEB
// -----------------------------------------------------------------------------

namespace web {

#if WEB_SUPPORT

bool onKeyCheck(const char * key, JsonVariant& value) {
    if (strncmp(key, "wifi", 4) == 0) return true;
    if (strncmp(key, "ssid", 4) == 0) return true;
    if (strncmp(key, "pass", 4) == 0) return true;
    if (strncmp(key, "ip", 2) == 0) return true;
    if (strncmp(key, "gw", 2) == 0) return true;
    if (strncmp(key, "mask", 4) == 0) return true;
    if (strncmp(key, "dns", 3) == 0) return true;
    return false;
}

void onConnected(JsonObject& root) {
    root["wifiScan"] = wifi::settings::scanNetworks();

    JsonObject& wifi = root.createNestedObject("wifiConfig");
    root["max"] = wifi::build::NetworksMax;

    {
        const char* schema_keys[] = {
            "ssid",
            "pass",
            "ip",
            "gw",
            "mask",
            "dns"
        };

        JsonArray& schema = wifi.createNestedArray("schema");
        schema.copyFrom(schema_keys, sizeof(schema_keys) / sizeof(*schema_keys));
    }

    JsonArray& networks = wifi.createNestedArray("networks");

    // TODO: send build flags as 'original' replacements?
    //       with the current model, removing network from the UI is
    //       equivalent to the factory reset and will silently use the build default
    auto entries = wifi::settings::networks();
    for (auto& entry : entries) {
        JsonArray& network = networks.createNestedArray();

        network.add(entry.ssid());
        network.add(entry.passphrase());

        auto& ipsettings = entry.ipSettings();
        network.add(::settings::internal::serialize(ipsettings.ip()));
        network.add(::settings::internal::serialize(ipsettings.gateway()));
        network.add(::settings::internal::serialize(ipsettings.netmask()));
        network.add(::settings::internal::serialize(ipsettings.dns()));
    }
}

void onScan(uint32_t client_id) {
    if (wifi::sta::scanning()) {
        return;
    }

    wifi::sta::scan::start([client_id](bss_info* found) {
        wifi::SsidInfo result(*found);
        wsPost(client_id, [result](JsonObject& root) {
            JsonArray& scan = root.createNestedArray("scanResult");
            scan.add(result.ssid());

            auto& info = result.info();
            scan.add(info.rssi());
            scan.add(info.authmode());
            scan.add(info.channel());
            scan.add(wifi::debug::mac(info.bssid()));
        });
    },
    [client_id](wifi::ScanError error) {
        wsPost(client_id, [error](JsonObject& root) {
            root["scanError"] = wifi::debug::error(error);
        });
    });
}

void onAction(uint32_t client_id, const char* action, JsonObject&) {
    if (strcmp(action, "scan") == 0) {
        onScan(client_id);
    }
}

#endif

} // namespace web

// -----------------------------------------------------------------------------
// INITIALIZATION
// -----------------------------------------------------------------------------

namespace debug {

String event(wifi::Event value) {
    String out;

    switch (value) {
    case wifi::Event::Initial:
        out = F("Initial");
        break;
    case wifi::Event::Mode: {
        const auto mode = wifi::opmode();
        out = F("Mode changed to ");
        out += wifi::debug::opmode(mode);
        break;
    }
    case wifi::Event::StationInit:
        out = F("Station init");
        break;
    case wifi::Event::StationScan:
        out = F("Scanning");
        break;
    case wifi::Event::StationConnecting:
        out = F("Connecting");
        break;
    case wifi::Event::StationConnected: {
        auto current = wifi::sta::current();
        out += F("Connected to BSSID ");
        out += wifi::debug::mac(current.bssid);
        out += F(" SSID ");
        out += current.ssid;
        break;
    }
    case wifi::Event::StationTimeout:
        out = F("Connection timeout");
        break;
    case wifi::Event::StationDisconnected: {
        auto current = wifi::sta::current();
        out += F("Disconnected from ");
        out += current.ssid;
        break;
    }
    case wifi::Event::StationReconnect:
        out = F("Reconnecting");
        break;
    }

    return out;
}

const char* state(wifi::State value) {
    switch (value) {
    case wifi::State::Boot:
        return "Boot";
    case wifi::State::Connect:
        return "Connect";
    case wifi::State::TryConnectBetter:
        return "TryConnectBetter";
    case wifi::State::Fallback:
        return "Fallback";
    case wifi::State::Connected:
        return "Connected";
    case wifi::State::Idle:
        return "Idle";
    case wifi::State::Init:
        return "Init";
    case wifi::State::Timeout:
        return "Timeout";
    case wifi::State::WaitScan:
        return "WaitScan";
    case wifi::State::WaitScanWithoutCurrent:
        return "WaitScanWithoutCurrent";
    case wifi::State::WaitConnected:
        return "WaitConnected";
    }

    return "";
}

} // namespace debug

namespace internal {

// STA + AP FALLBACK:
// - try connection
// - if ok, stop existing AP
// - if not, keep / start AP
//
// STA:
// - try connection
// - don't do anything on completion
//
// TODO? WPS / SMARTCONFIG + STA + AP FALLBACK
// - same as above
// - when requested, make sure there are no active connections
//   abort when sta connected or ap is connected
// - run autoconf, receive credentials and store in a free settings slot

// TODO: provide a clearer 'unroll' of the current state?

using EventCallbacks = std::forward_list<wifi::EventCallback>;
EventCallbacks callbacks;

void publish(wifi::Event event) {
    for (auto& callback : callbacks) {
        callback(event);
    }
}

void subscribe(wifi::EventCallback callback) {
    callbacks.push_front(callback);
}

namespace {

} // namespace

State handleAction(State& state, Action action) { 
    switch (action) {
    case Action::StationConnect:
        if (!wifi::sta::connecting() && !wifi::sta::connected()) {
            if (!wifi::sta::enabled()) {
                wifi::sta::enable();
                publish(wifi::Event::Mode);
            }

            if (!wifi::sta::connecting()) {
                state = State::Init;
            }
        }
        break;

    case Action::StationContinueConnect:
        if (wifi::sta::connecting() && !wifi::sta::connection::locked()) {
            state = State::Connect;
        }
        break;

    case Action::StationDisconnect:
        if (wifi::sta::connected()) {
            wifi::ap::fallback::remove();
            wifi::sta::disconnect();
        }

        if (wifi::sta::connecting()) { 
            wifi::sta::connection::unlock();
            wifi::sta::connection::stop();
        }

        if (wifi::sta::enabled()) {
            wifi::sta::disable();
            publish(wifi::Event::Mode);
        }
        break;

    case Action::StationTryConnectBetter:
        if (!wifi::sta::connected() || wifi::sta::connecting()) {
            wifi::sta::scan::periodic::stop();
            break;
        }

        if (wifi::sta::scan::periodic::check()) {
            state = State::TryConnectBetter;
        }
        break;

    case Action::AccessPointFallback:
    case Action::AccessPointStart:
        if (!wifi::ap::enabled()) {
            wifi::ap::enable();
            wifi::ap::start(
                wifi::settings::softApSsid(),
                wifi::settings::softApPassphrase(),
                wifi::settings::softApChannel());
            if ((Action::AccessPointFallback == action)
                    && wifi::ap::fallback::enabled()) {
                wifi::ap::fallback::schedule();
            }
        }
        break;

    case Action::AccessPointFallbackCheck:
        if (wifi::ap::fallback::enabled()) {
            wifi::ap::fallback::check();
        }
        break;

    case Action::AccessPointStop:
        if (wifi::ap::enabled()) {
            wifi::ap::fallback::remove();
            wifi::ap::stop();
            wifi::ap::disable();
            publish(wifi::Event::Mode);
        }
        break;

    case Action::TurnOff:
        if (wifi::enabled()) {
            wifi::ap::fallback::remove();
            wifi::ap::stop();
            wifi::ap::disable();
            wifi::sta::scan::periodic::stop();
            wifi::sta::connection::stop();
            wifi::sta::disconnect();
            wifi::sta::disable();
            wifi::disable();
            if (!wifi::sleep()) {
                wifi::action(wifi::Action::TurnOn);
                break;
            }
        }
        break;

    case Action::TurnOn:
        if (!wifi::enabled()) {
            wifi::enable();
            wifi::wakeup();
            wifi::settings::configure();
        }
        break;

    }

    return state;
}

bool prepareConnection() {
    if (wifi::sta::enabled()) {
        auto networks = wifi::settings::networks();
        if (networks.size()) {
            wifi::sta::connection::start(
                    wifi::settings::hostname(), std::move(networks), wifi::sta::ConnectionRetries);
            return true;
        }
    }

    return false;
}

void loop() {
    static decltype(wifi::sta::scan::ssidinfos()) infos;

    static State state { State::Boot };
    static State last_state { state };

    if (last_state != state) {
        DEBUG_MSG_P(PSTR("[WIFI] State %s -> %s\n"),
            debug::state(last_state),
            debug::state(state));
        last_state = state;
    }

    switch (state) {

    case State::Boot:
        publish(wifi::Event::Initial);
        state = State::Idle;
        break;

    case State::Init: {
        if (!prepareConnection()) {
            state = State::Fallback;
            break;
        }

        wifi::sta::scan::periodic::stop();
        if (wifi::settings::scanNetworks()) {
            infos = wifi::sta::scan::ssidinfos();
            state = State::WaitScan;
            break;
        }
        state = State::Connect;
        break;
    }

    case State::TryConnectBetter:
        if (wifi::settings::scanNetworks() && prepareConnection()) {
            wifi::sta::scan::periodic::stop();
            infos = wifi::sta::scan::ssidinfos();
            state = State::WaitScanWithoutCurrent;
            break;
        }
        state = State::Idle;
        break;

    case State::Fallback:
        publish(wifi::Event::StationReconnect);
        wifi::sta::connection::initial();
        wifi::action(wifi::Action::AccessPointFallback);
        state = State::Idle;
        break;

    case State::WaitScan:
        if (wifi::sta::scanning()) {
            break;
        }

        wifi::sta::connection::sort(std::move(infos));
        state = State::Connect;
        break;

    case State::WaitScanWithoutCurrent:
        if (wifi::sta::scanning()) {
            break;
        }

        wifi::sta::connection::sort(std::move(infos));
        if (wifi::sta::connection::filter(wifi::sta::info())) {
            wifi::sta::disconnect();
            state = State::Connect;
            break;
        }

        state = State::Idle;
        break;

    case State::Connect: {
        if (wifi::sta::connection::connect()) {
            state = State::WaitConnected;
            publish(wifi::Event::StationConnecting);
        } else {
            state = State::Timeout;
        }
        break;
    }

    case State::WaitConnected:
        if (wifi::sta::connection::wait()) {
            break;
        }

        if (wifi::sta::connected()) {
            state = State::Connected;
            break;
        }

        state = State::Timeout;
        break;

    // Current logic closely follows the SDK connection routine with reconnect enabled,
    // and will retry the same network multiple times before giving up.
    case State::Timeout:
        wifi::sta::connection::unlock();
        if (wifi::sta::connecting() && wifi::sta::connection::next()) {
            wifi::sta::connection::continued();
            state = State::Idle;
            publish(wifi::Event::StationTimeout);
        } else {
            wifi::sta::connection::stop();
            state = State::Fallback;
        }
        break;

    case State::Connected:
        infos.reset();
        wifi::sta::connection::unlock();
        wifi::sta::connection::stop();
        if (wifi::settings::scanNetworks()) {
            wifi::sta::scan::periodic::start();
        }
        state = State::Idle;
        publish(wifi::Event::StationConnected);
        break;

    case State::Idle: {
        auto& actions = wifi::actions();
        if (!actions.empty()) {
            state = handleAction(state, actions.front());
            actions.pop();
        }
        break;
    }

    }

    // SDK disconnection event is specific to the phy layer. i.e. it will happen all the same
    // when trying to connect and being unable to find the AP, being forced out by the AP with bad credentials
    // or being disconnected when the wireless signal is lost.
    // Thus, provide a specific connected -> disconnected event specific to the IP network availability.
    if (wifi::sta::connection::lost()) {
        publish(wifi::Event::StationDisconnected);
    }

#if WIFI_AP_CAPTIVE_SUPPORT
    // Captive portal only queues packets and those need to be processed asap
    if (wifi::ap::enabled() && wifi::ap::captive()) {
        wifi::ap::dnsLoop();
    }
#endif
#if WIFI_GRATUITOUS_ARP_SUPPORT
    // ref: https://github.com/xoseperez/espurna/pull/1877#issuecomment-525612546
    // Periodically send out ARP, even if no one asked
    if (wifi::sta::connected() && !wifi::sta::garp::wait()) {
        wifi::sta::garp::send();
    }
#endif
}

// XXX: With Arduino Core 3.0.0, WiFi is asleep on boot
// It will wake up when calling WiFi::mode(...):
// - WiFi.begin(...)
// - WiFi.softAP(...)
// - WiFi.enableSTA(...)
// - WiFi.enableAP(...)
// ref. https://github.com/esp8266/Arduino/pull/7902

void init() {
    WiFi.persistent(false);
    wifi::ap::init();
    wifi::sta::init();
}

} // namespace internal
} // namespace wifi

// -----------------------------------------------------------------------------
// API
// -----------------------------------------------------------------------------

void wifiRegister(wifi::EventCallback callback) {
    wifi::internal::subscribe(callback);
}

bool wifiConnectable() {
    return wifi::ap::enabled();
}

bool wifiConnected() {
    return wifi::sta::connected();
}

IPAddress wifiStaIp() {
    if (wifi::opmode() & wifi::OpmodeSta) {
        return WiFi.localIP();
    }

    return {};
}

String wifiStaSsid() {
    if (wifi::opmode() & wifi::OpmodeSta) {
        auto current = wifi::sta::current();
        return current.ssid;
    }

    return emptyString;
}

void wifiDisconnect() {
    wifi::sta::disconnect();
}

void wifiToggleAp() {
    wifi::ap::toggle();
}

void wifiToggleSta() {
    wifi::sta::toggle();
}

void wifiStartAp() {
    wifi::action(wifi::Action::AccessPointStart);
}

void wifiTurnOff() {
    wifi::action(wifi::Action::TurnOff);
}

void wifiTurnOn() {
    wifi::action(wifi::Action::TurnOn);
}

void wifiApCheck() {
    wifi::action(wifi::Action::AccessPointFallbackCheck);
}

void wifiSetup() {
    wifi::internal::init();
    wifi::settings::migrate(migrateVersion());
    wifi::settings::configure();

#if SYSTEM_CHECK_ENABLED
    if (!systemCheck()) {
        wifi::actions() = wifi::ActionsQueue{};
        wifi::action(wifi::Action::AccessPointStart);
    }
#endif

#if DEBUG_SUPPORT
    wifiRegister([](wifi::Event event) {
        DEBUG_MSG_P(PSTR("[WIFI] %s\n"), wifi::debug::event(event).c_str());
    });
#endif

#if WEB_SUPPORT
    wsRegister()
        .onAction(wifi::web::onAction)
        .onConnected(wifi::web::onConnected)
        .onKeyCheck(wifi::web::onKeyCheck);
#endif

#if TERMINAL_SUPPORT
    wifi::terminal::init();
#endif

    espurnaRegisterLoop(wifi::internal::loop);
    espurnaRegisterReload(wifi::settings::configure);
}