extern crate stm32f103xx;
use ::i2c::{I2C, TransDir};

const DS3231_ADDR: u8 = 0b1101000;
const DS3231_REG_SEC: u8 = 0x00;

pub struct DS3231<'a> {
    i2c: I2C<'a>
}

pub struct Date {
    second: u8,
    minute: u8,
    hour: u8,
    day: u8,
    date: u8,
    month: u8,
    year: u8
}

impl<'a> DS3231<'a> {
    pub fn new(i2c_reg: &'a stm32f103xx::i2c1::RegisterBlock) -> DS3231<'a> {
        DS3231{i2c: I2C::new(i2c_reg)}
    }

    fn bcd2dec(bcd: u8) -> u8 {
        (bcd >> 4) * 10 + (bcd & 0x0f)
    }

    fn dec2bcd(dec: u8) -> u8 {
        ((dec / 10) << 4) | (dec % 10)
    }

    pub fn read_fulldate(&self) -> Date {
        let mut buf: [u8; 7] = [0; 7];
        let i2c = &self.i2c;
        i2c.conf_ack(true); /* enable ack */
        i2c.start(true, true); /* start condition (for writing reg addr) */
        i2c.send_addr(DS3231_ADDR, TransDir::TRANSMITTER, true);
        i2c.send(DS3231_REG_SEC, true);
        /* restart condition (for reading val from the reg addr) */
        i2c.start(true, true);
        i2c.send_addr(DS3231_ADDR, TransDir::RECEIVER, true);
        for i in 0..6 {
            buf[i] = i2c.recv(true);
        }
        i2c.conf_ack(false); /* disable ack (send nack) */
        buf[6] = i2c.recv(true);
        i2c.stop(true);
        Date{second: DS3231::bcd2dec(buf[0]),
             minute: DS3231::bcd2dec(buf[1]),
             hour: DS3231::bcd2dec(buf[2]),
             day: DS3231::bcd2dec(buf[3]),
             date: DS3231::bcd2dec(buf[4]),
             month: DS3231::bcd2dec(buf[5]),
             year: DS3231::bcd2dec(buf[6])}
    }

    pub fn write_fulldate(&self, date: &Date) {
        let i2c = &self.i2c;
        let buf: [u8; 7] = [DS3231::dec2bcd(date.second),
                            DS3231::dec2bcd(date.minute),
                            DS3231::dec2bcd(date.hour),
                            DS3231::dec2bcd(date.day),
                            DS3231::dec2bcd(date.date),
                            DS3231::dec2bcd(date.month),
                            DS3231::dec2bcd(date.year)];
        i2c.conf_ack(true);
        i2c.start(true, true); /* start condition for writing */
        i2c.send_addr(DS3231_ADDR, TransDir::TRANSMITTER, true);
        i2c.send(DS3231_REG_SEC, true);
        for i in 0..7 {
            i2c.send(buf[i], true);
        }
        i2c.stop(true);
    }
}