#pragma once

/**
 * air quality sensor
 * https://sensirion.com/media/documents/984E0DD5/61644B8B/Sensirion_Gas_Sensors_Datasheet_SGP30.pdf
 */
template <typename I2C> class SGP30 {
	
private:

	I2C& i2c;
	static constexpr const uint8_t ADDR = 0x58;
	static constexpr const char* NAME = "SGP30";
	
	static constexpr const uint16_t CMD_IAQ_INIT = 0x2003;
	static constexpr const uint16_t CMD_IAQ_MEASURE = 0x2008;
	static constexpr const uint16_t CMD_GET_SERIAL = 0x3682;


public:

	SGP30(I2C& i2c) : i2c(i2c) {
		
	}
	
	void init() {
		sendCommand(CMD_IAQ_INIT);
	}		
		
	/** is the device present on the bus? */
	bool isPresent() {
		return i2c.query(ADDR);
	}
	

	struct Result {
		uint16_t co2e;
		uint16_t tvoc;
	};
		
	/** should be called ~ every second */	
	Result measure() {
		
		sendCommand(CMD_IAQ_MEASURE);
		vTaskDelay(100 / portTICK_PERIOD_MS);
		
		uint8_t tmp[6];
		i2c.readRaw(ADDR, 6, tmp);
		
		Result res;
		res.co2e = (tmp[0]<<8) | (tmp[1]<<0);
		res.tvoc = (tmp[3]<<8) | (tmp[4]<<0);
		return res;
		
	}
	
	void getSerial() {
		
		struct Serial {
			uint8_t v1[2];
			uint8_t crc1;
			uint8_t v2[2];
			uint8_t crc2;
			uint8_t v3[2];
			uint8_t crc3;
		} serial;
		
		sendCommand(CMD_GET_SERIAL);
		uint8_t tmp[9];
		i2c.readRaw(ADDR, 9, &serial);
		/*
		uint8_t a = calcCRC(tmp+0, 2);
		uint8_t b = calcCRC(tmp+3, 2);
		uint8_t c = calcCRC(tmp+6, 2);

		printf("%d %d %d %d\n", tmp[0], tmp[1], tmp[2], a);
		printf("%d %d %d %d\n", tmp[3], tmp[4], tmp[5], b);
		printf("%d %d %d %d\n", tmp[6], tmp[7], tmp[8], c);
		*/
	}
		
		
private:

	void sendCommand(uint16_t cmd) {
		uint8_t tmp[2];
		tmp[0] = cmd >> 8;
		tmp[1] = cmd >> 0;
		i2c.writeRaw(ADDR, 2, tmp);
	}
	
	static uint8_t calcCRC(const uint8_t* data, uint8_t len) {
		uint8_t crc = 0xff;
		for (uint8_t i = 0; i < len; i++) {
			crc ^= data[i];
			for (uint8_t j = 0; j < 8; j++) {
				if ((crc & 0x80) != 0) {
					crc = (uint8_t)((crc << 1) ^ 0x31);
				} else {
					crc <<= 1;
				}
			}
		}
		return crc;
	}

	
};