#include "DHT.h"
#include <ESP8266WiFi.h>
#include <ModbusIP_ESP8266.h>
#include "config.h"
#include "LittleFS.h"

// network

IPAddress my_ip(MY_IP);
IPAddress gateway(MY_GW);
IPAddress subnet(MY_NET);
IPAddress sensor_ip(SENSOR_IP);

// After how much time without connection we will 
// reboot (in millis)
#define NON_CONNECTED_REBOOT_TIMEOUT 60000 

// dht sensor
#define DHTPIN D6
#define DHTTYPE AM2301
DHT dht(DHTPIN, DHTTYPE);
#define DHT_UPDATE_INTERVAL 500

// relay
#define RELAY_PIN D1
#define T_UPDATE_INTERVAL 500

// external t
#define EXTERNAL_UPDATE_INTERVAL 1000

// logic consts

// deviation from target t allowed (in degrees multiplied by 100)
#define T_HYSTERESIS 150
// timeout to switch from external to internal temperature data (in milliseconds)
#define SWITCH_TO_INTERNAL_TIMEOUT 50000

// modbus consts and works
#define TCP_PORT 15000

#define MODE_AUTO 0
#define MODE_MANUAL 1

#define REGISTER_MODE 0
#define REGISTER_CUR_STATE 1
#define REGISTER_RELAY_TEMP 2
#define REGISTER_OVERHEAT 3
#define REGISTER_OVERRIDE_STATE 4
// desired temperature
#define REGISTER_TARGET_T 5
// temperature from internal sensor
#define REGISTER_INTERNAL_T 6
// temperatur from external sensor (received via modbus-tcp)
#define REGISTER_EXTERNAL_T 7

// critical relay temp (degrees multiplied by 100)
#define CRITICAL_T 6000

ModbusIP mb;

char id[64];


int cur_mode = MODE_AUTO;
int cur_state = 0;
int relay_t = 0;
int overheat = 0;
int override_state = 0;
int target_t = 0;
int internal_t = 0;
int external_t = 0;

void LoadState()
{
	File f = LittleFS.open("/target_t.txt", "r");
	if (!f) return;
	String s = f.readStringUntil('\n');
	target_t = atoi(s.c_str());
	f.close();
}

void SaveState()
{
	File f = LittleFS.open("/target_t.txt", "w");
	if (!f) return;
	f.println(target_t);
	f.close();
}

void setup() 
{
	if (!LittleFS.begin())
	{
		Serial.println("Unable to mount the filesystem");
		ESP.restart();
	}
	LoadState();
	pinMode(DHTPIN, INPUT);
	pinMode(RELAY_PIN, OUTPUT);
	dht.begin();
	Serial.begin(115200);
	Serial.println("Initialised...");

	WiFi.mode(WIFI_STA);
	WiFi.config(my_ip, gateway, subnet);
	WiFi.setAutoReconnect(true);
	WiFi.begin(WIFI_NAME, WIFI_PASS);
	Serial.print("Connecting");
	unsigned long start = millis();
	while (WiFi.status() != WL_CONNECTED)
	{
		delay(500);
		Serial.print(".");
		if (millis() - start > NON_CONNECTED_REBOOT_TIMEOUT)
		{
			ESP.restart();
		}
	}
	Serial.println();

	Serial.print("Connected, IP address: ");
	Serial.println(WiFi.localIP());
	uint8_t macAddr[6];
	WiFi.macAddress(macAddr);
	sprintf(id, "%02x:%02x:%02x:%02x:%02x:%02x", macAddr[0], macAddr[1], macAddr[2], macAddr[3], macAddr[4], macAddr[5]);
	Serial.printf("Connected, mac address: %s\n", id);
	
	mb.server(15000);
	mb.addHreg(REGISTER_MODE, cur_mode);
	mb.addHreg(REGISTER_CUR_STATE, cur_state);
	mb.addHreg(REGISTER_RELAY_TEMP, relay_t);
	mb.addHreg(REGISTER_OVERHEAT, overheat);
	mb.addHreg(REGISTER_OVERRIDE_STATE, override_state);
	mb.addHreg(REGISTER_TARGET_T, target_t);
	mb.addHreg(REGISTER_INTERNAL_T, internal_t);
	mb.addHreg(REGISTER_EXTERNAL_T, external_t);
}

//////////////////////////////////////////////////////////////////
// thermistor (relay temperature)
//////////////////////////////////////////////////////////////////
#define THERMISTORPIN A0
#define THERMISTORNOMINAL 10000
#define TEMPERATURENOMINAL 25
#define NUMSAMPLES 5
#define BCOEFFICIENT 3950
#define SERIESRESISTOR 10000

unsigned long last_relay_update = 0;

void UpdateRelayT()
{
	float average = 0;
	for (int i = 0; i < NUMSAMPLES; i++) 
	{
		average += analogRead(THERMISTORPIN);
		delay(10);
	}
	average /= NUMSAMPLES;
	average = 1023 / average - 1;
	average = SERIESRESISTOR / average;
	float steinhart;
	steinhart = average / THERMISTORNOMINAL; // (R/Ro)
	steinhart = log(steinhart); // ln(R/Ro)
	steinhart /= BCOEFFICIENT; // 1/B * ln(R/Ro)
	steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
	steinhart = 1.0 / steinhart; // инвертируем
	steinhart -= 273.15; // конвертируем в градусы по Цельсию
	relay_t = int(steinhart * 100);
	last_relay_update = millis();
}

////////////////////////////////////////////////////////////////////////
// DHT (internal thermo sensor)
////////////////////////////////////////////////////////////////////////

unsigned long last_dht_update = 0;

void UpdateDHT()
{
	float t = dht.readTemperature();
	internal_t = (int)(t * 100);
	last_dht_update = millis();
}

////////////////////////////////////////////////////////////////////////
// Modbus client (external sensor t)
////////////////////////////////////////////////////////////////////////

#define ANSWER_READ_TIMEOUT 1000

unsigned long last_external_update = 0;
bool was_external_update = false;

WiFiClient client;

#define SENSOR_T_REGISTER 0
uint8_t mb_message[50];
uint8_t mb_answer[50];
int mb_answer_len;

void UpdateExternalT()
{
	if (!client.connect(sensor_ip, SENSOR_PORT))
	{
		Serial.println("Unable to connect to sensor");
		return;
	}
	mb_message[0] = 0; // transaction id
	mb_message[1] = 0;
	mb_message[2] = 0; // protocol id
	mb_message[3] = 0;
	mb_message[4] = 0; // length
	mb_message[5] = 6;
	mb_message[6] = 0; // unit id
	mb_message[7] = 3; // function
	mb_message[8] = (SENSOR_T_REGISTER >> 8) & 0xFF; // address - high
	mb_message[9] = (SENSOR_T_REGISTER) & 0xFF; // address - low
	mb_message[10] = 0; // amount
	mb_message[11] = 1; 
	client.write(mb_message, 12);
	client.flush();
	// read answer (it should be 8 (header) + 1 (amount received bytes) + 2 (actual data)
	mb_answer_len = 0;
	unsigned long start = millis();
	while (millis() - start < ANSWER_READ_TIMEOUT && mb_answer_len < 11)
	{
		int result = client.read();
		if (result != -1)
		{
			mb_answer[mb_answer_len++] = result;
		}
	}
	if (mb_answer_len < 11)
	{
		Serial.println("Too short answer from sensor");
		return;
	}
	external_t = (((int)mb_answer[9]) << 8) | ((int)mb_answer[10]);
	last_external_update = millis();
	was_external_update = true;
}

////////////////////////////////////////////////////////////////////////

int GetCurrentT()
{
	unsigned long current = millis();
	// case when we did not receive external T since device boot
	if (!was_external_update) return internal_t;
	if (current < last_external_update || current - last_external_update < SWITCH_TO_INTERNAL_TIMEOUT)
	{
		return external_t;
	}
	return internal_t;
}

unsigned long last_connected = 0;

void loop() 
{
	unsigned long current = millis();
	int u = 0;
	if (current < last_relay_update || current - last_relay_update >= T_UPDATE_INTERVAL)
	{
		UpdateRelayT();
		u = 1;
	}
	if (current < last_dht_update || current - last_dht_update >= DHT_UPDATE_INTERVAL)
	{
		UpdateDHT();
		u = 1;
	}
	if (current < last_external_update || current - last_external_update >= EXTERNAL_UPDATE_INTERVAL)
	{
		UpdateExternalT();
		u = 1;
	}
	mb.task();
	cur_mode = mb.Hreg(REGISTER_MODE);
	override_state = mb.Hreg(REGISTER_OVERRIDE_STATE);
	target_t = mb.Hreg(REGISTER_TARGET_T);
	int current_t = GetCurrentT();
	if (cur_mode == MODE_AUTO)
	{
		if (current_t < target_t - T_HYSTERESIS)
		{
			cur_state = 1;
		}

		else if (current_t > target_t + T_HYSTERESIS)
		{
			cur_state = 0;
		}
	}
	else
	{
		cur_state = override_state;
	}
	if (relay_t > CRITICAL_T)
	{
		//Serial.printf("Critical overheat, t = %d\n", relay_t);
		cur_state = 0;
		overheat = 1;
	}
	else overheat = 0;
	digitalWrite(RELAY_PIN, cur_state);
	if (u) 
	{
		Serial.printf("State %d Relay t %d Internal t %d External t %d Current t %d Target t %d\n", cur_state, relay_t, internal_t, external_t, current_t, target_t);
		SaveState();
	}
	mb.Hreg(REGISTER_MODE, cur_mode);
	mb.Hreg(REGISTER_RELAY_TEMP, relay_t);
	mb.Hreg(REGISTER_OVERHEAT, overheat);
	mb.Hreg(REGISTER_CUR_STATE, cur_state);
	mb.Hreg(REGISTER_INTERNAL_T, internal_t);
	mb.Hreg(REGISTER_EXTERNAL_T, external_t);
	if (WiFi.status() != WL_CONNECTED)
	{
		WiFi.reconnect();
	}
	else
	{
		last_connected = current;
	}
	if (current < last_connected || current - last_connected > NON_CONNECTED_REBOOT_TIMEOUT)
	{
		SaveState();
		ESP.restart();
	}
}