/*
 * file: statusclient.ino
 * desc: This file is part of the Krautspace Doorstatus project. It's the
 * main file for a client, who deals with the input from a reed sensor and
 * push these values to a server. The code is make to run on a NodeMCU with
 * ESP8266 chip. 
 */

#include <time.h>
#include <ESP8266WiFi.h>
#include <WiFiClientSecure.h>

#include "certs.h"
#include "config.h"
#include "credentials.h"

// cpp23 utility
namespace cpp23 {
    template <typename Enum>
    constexpr std::underlying_type_t<Enum> to_underlying(Enum e) noexcept { return static_cast<std::underlying_type_t<Enum>>(e);}
}

// defining some constants
enum : uint8_t {
    LED_PIN = 16, // D0 - GPIO 16
    REED_PIN = 2 // D4 - GPIO 2
};

enum class door_state {
    closed = 0,
    open = 1
};

// defining some globals
static inline door_state current_door_state = door_state::closed;
constexpr static inline std::array<char const[2], 2> state_str {{"0", "1"}};

// initializing 
static inline BearSSL::X509List const ca_certs { CA_CERTS };
static inline BearSSL::X509List const client_cert { CLIENT_CERT };
static inline BearSSL::PrivateKey const client_key { CLIENT_KEY };

void blink_led(uint8_t blink_count, uint8_t delay_time) {
    /*
     * zur ausgabe von meldungen blinkt die interne led.
     * erfolgreichesmeldungen werden durch kurze blinkzeichen angezeigt,
     * fehlermeldungen sind durch eine lange sequenz gekennzeichnet.
     * Signale:
     * status der tür hat sich geändert:      2x kurz
     * änderung erfolgreich gesendet:         5x kurz
     * es konnte keine wifi aufgebaut werden: 3x lang
     * senden des status fehlgeschlagen:      5x lang
     *
     * param 1: integer
     * param 2: integer
     */
    for (; blink_count; --blink_count) {
        digitalWrite(LED_PIN, LOW);
        delay(delay_time);
        digitalWrite(LED_PIN, HIGH);
        delay(delay_time);
    }
}

void init_serial() {
    /*  
     *  set baudrate and debug modus
     */
    Serial.begin(BAUD_RATE);
    Serial.setDebugOutput(DEBUG);
    Serial.println("\n[Srl] Serial interface initialized");
}

void init_pins() {
    /*
     * set gpio for reed sensor and led
     */
    pinMode(REED_PIN, INPUT_PULLUP);
    pinMode(LED_PIN, OUTPUT);
    digitalWrite(LED_PIN, HIGH);
    Serial.println("[Pin] LED and REED sensor initialized");
}

void init_wifi() {
    WiFi.begin(SSID, PSK);
    Serial.println("[WiFi] Wifi initialized");
    
    while (WiFi.status() != WL_CONNECTED) {
        Serial.println("[WiFi] Error: Failed to connect");
        blink_led(3, 500);
    }
    
    Serial.printf("[WiFi] Connected to %s\n", WiFi.SSID());
    Serial.print("[WiFi] IP: ");
    Serial.println(WiFi.localIP());
    
    set_clock();
}

door_state read_door_state() {
    /* 
     *  die initialisierung des reed-switch-pins mit pullup bewirkt, dass am pin
     *  3,3 volt anliegen. die verbindung des pins mit GND sorgt dafür,
     *  dass die spannung "abfließen" kann. dadurch hat der pin dann den
     *  status 'low'.
     *  geschlossene tür -> reed geschlossen -> low
     *  geöffnete tür -> reed offen -> high
     */
    return (digitalRead(REED_PIN) == HIGH) ? door_state::open : door_state::closed;
}

void set_clock() {
    /*
     * We need time for certificate authorization
     */
    configTime(TZ_STRING, NTP_URL);

    Serial.print("[Clock] Waiting for NTP time sync");
    time_t now = time(nullptr);
    for (; now < 16 * 3600; now = time(nullptr)) { // 16 hours
        delay(500);
        Serial.print(".");
    }
    Serial.println("");
    struct tm timeinfo;
    gmtime_r(&now, &timeinfo);
    Serial.printf("[Clock] Current time: %s\n", asctime(&timeinfo));
}

bool send_status(door_state state) {
    /*
     * Inits wifi (if needed) and send the status
     */
    char const* const status = state_str[cpp23::to_underlying(state)];

    BearSSL::WiFiClientSecure client;
    client.setTrustAnchors(&ca_certs);
    client.setClientRSACert(&client_cert, &client_key);

    Serial.println("[Ctx] SSL Context initialized");
    Serial.printf("[Send] Connect to %s:%i\n", SERVER_URL, SERVER_PORT); 
    
    if (!client.connect(SERVER_URL, SERVER_PORT)) {
        Serial.println("[Send] Can't connect to server");
        Serial.printf("[Send] SSL Error: %d\n", client.getLastSSLError());
        client.stop();
        return false;
    }

    Serial.println("[Send] Connection successful established");
    Serial.printf("[Send] Send status: %s\n", status);
    client.write(status);
    client.stop();

    return true;
}

void setup() {

    /*
     * things to do once at boot time
     */
    init_serial();
    init_pins();
    init_wifi();
}

void loop() {

    /*
     * things are running in a endless loop
     */
    door_state new_door_state = read_door_state();
    if (new_door_state != current_door_state) {
        Serial.printf("[Loop] Status has changed to %i\n", new_door_state);
        blink_led(2, 100);
        if (send_status(new_door_state)) {
            current_door_state = new_door_state;
            blink_led(5, 100);
        } else {
            blink_led(5, 500);
        }
    }

    delay(FREQUENCY);
}