// This document implements some function to interact with an 
// Raspberry Pi 4 and some external components.
// Used components: DS18B20, and LED and a push button.

// libgpiod is used for the communication with the GPIOs
#include <gpiod.h>
#include <stdio.h>
#include <unistd.h>  // For sleep()
#include <fcntl.h>


#define GPIO_CHIP    "gpiochip0"
#define LED_GPIO_PIN     18
#define BUTTON_GPIO_PIN  22
#define LED_BLINK_TIME   1  // Blink delay in seconds
#define SENSOR_PATH   "/sys/bus/w1/devices/28-000000306565/temperature"  // DS18B20 sensor address

// function to set the LED state by passing the pin and state
void set_led(int pin, int state) {
    struct gpiod_chip *chip;
    struct gpiod_line *line;

    chip = gpiod_chip_open_by_name(GPIO_CHIP);
    if (!chip) {
        perror("Failed to open GPIO chip");
        return;
    }

    line = gpiod_chip_get_line(chip, pin);
    if (!line) {
        perror("Failed to get GPIO line");
        gpiod_chip_close(chip);
        return;
    }

    if (gpiod_line_request_output(line, "gpio-led", 0) < 0) {
        perror("Failed to request line as output");
        gpiod_chip_close(chip);
        return;
    }

    // Set the LED state
    gpiod_line_set_value(line, state);

    // Release the GPIO line and chip
    gpiod_line_release(line);
    gpiod_chip_close(chip);
}

// function to blink the LED by passing the pin, number of blinks and the delay
void blink_led(int pin, int time, int delay) {
    for (int i = 0; i < time; i++) {
        set_led(pin, 1);
        sleep(delay);
        set_led(pin, 0);
        sleep(delay);
    }
}

float read_temperature() {
	int fd;
	float temperature;
    char buf[16];  // Large enough to hold the temperature string

    fd = open(SENSOR_PATH, O_RDONLY);
    if (fd == -1) {
        perror("Failed to open temperature file");
        return -1;  // Return an error indicator
    }

    ssize_t numRead = read(fd, buf, sizeof(buf) - 1);
    if (numRead == -1) {
        perror("Failed to read temperature file");
        close(fd);
        return -1;  // Return an error indicator
    }

    buf[numRead] = '\0';  // Null-terminate the string
    temperature = atof(buf) / 1000;  // Convert the string to an integer
    close(fd);

    return temperature;
}

// funciton to read button status
int read_button(int pin) {
    struct gpiod_chip *chip;
    struct gpiod_line *line;
    int value;

    chip = gpiod_chip_open_by_name(GPIO_CHIP);
    if (!chip) {
        perror("Failed to open GPIO chip");
        return -1;
    }

    line = gpiod_chip_get_line(chip, pin);
    if (!line) {
        perror("Failed to get GPIO line");
        gpiod_chip_close(chip);
        return -1;
    }

    if (gpiod_line_request_input(line, "gpio-button") < 0) {
        perror("Failed to request line as input");
        gpiod_chip_close(chip);
        return -1;
    }

    value = gpiod_line_get_value(line);

    // Release the GPIO line and chip
    gpiod_line_release(line);
    gpiod_chip_close(chip);

    return value;
}

int main(void) {
//    printf("Temperature: %.2f\n", read_temperature(SENSOR_ADDRESS));
//    blink_led(LED_GPIO_PIN, 5, LED_BLINK_TIME);
//	printf("Temperature: %.2f\n", read_temperature());
    //	check button status and sleep for a second
    while(1){
        printf("Button status: %d\n", read_button(BUTTON_GPIO_PIN));
        sleep(1);
    }
    return 0;
}