#include <stdio.h>
#include <string.h>
#include "pico/stdlib.h"
#include "hardware/i2c.h"

#define PICO_I2C_SDA_PIN 20
#define PICO_I2C_SCL_PIN 21

#define DS1307_ADDR 0x68
#define DS1307_REG_SECONDS 0x00
#define DS1307_REG_MINUTES 0x01
#define DS1307_REG_HOURS 0x02
#define DS1307_REG_DAYOFWEEK 0x03
#define DS1307_REG_DAY 0x04
#define DS1307_REG_MONTH 0x05
#define DS1307_REG_YEAR 0x06

uint8_t bcd_to_dec(uint8_t val) {
    return (val >> 4) * 10 + (val & 0x0F);
}

uint8_t dec_to_bcd(uint8_t val) {
    return ((val / 10) << 4) + (val % 10);
}

int main() {
    stdio_init_all();
    // Initialize I2C0 at 100kHz
    i2c_init(i2c_default, 100 * 1000);
    gpio_set_function(PICO_I2C_SDA_PIN, GPIO_FUNC_I2C);
    gpio_set_function(PICO_I2C_SCL_PIN, GPIO_FUNC_I2C);
    gpio_pull_up(PICO_I2C_SDA_PIN);
    gpio_pull_up(PICO_I2C_SCL_PIN);

    /* // --- Set Time (Optional - uncomment to set the time once) ---
    uint8_t set_data[] = {
        DS1307_REG_SECONDS, // Start writing from seconds register
        dec_to_bcd(0),      // Seconds
        dec_to_bcd(55),     // Minutes
        dec_to_bcd(13),     // Hours (24-hour format)
        dec_to_bcd(5),      // Day of Week (1–7, Sunday=1)
        dec_to_bcd(2),      // Day
        dec_to_bcd(11),     // Month
        dec_to_bcd(2025 - 2000) // Year (last two digits)
    };
    i2c_write_blocking(i2c_default, DS1307_ADDR, set_data, sizeof(set_data), false);
    */

    while (true) {
        uint8_t read_data[7];
        uint8_t reg_addr = DS1307_REG_SECONDS;

        // Write the register address to start reading from
        i2c_write_blocking(i2c_default, DS1307_ADDR, &reg_addr, 1, true);
        i2c_read_blocking(i2c_default, DS1307_ADDR, read_data, 7, false); // Read 7 bytes (seconds to year)

        uint8_t seconds = bcd_to_dec(read_data[0] & 0x7F);  // Mask CH bit
        uint8_t minutes = bcd_to_dec(read_data[1]);
        uint8_t hours = bcd_to_dec(read_data[2] & 0x3F);    // Mask 12/24-hour bit
        uint8_t day_of_week = bcd_to_dec(read_data[3]);
        uint8_t day = bcd_to_dec(read_data[4]);
        uint8_t month = bcd_to_dec(read_data[5]);
        uint16_t year = bcd_to_dec(read_data[6]) + 2000;    // Add 2000 for full year

        printf("Time: %02d:%02d:%02d, Date: %02d/%02d/%04d (Day %d)\n",
               hours, minutes, seconds, day, month, year, day_of_week);

        sleep_ms(1000); // Read every second
    }

    return 0;
}