/**
 * \file dcftime.c
 * \brief Decoder for DCF-77 time signals
 * \author Ronald Schaten & Thomas Stegemann
 * \version $Id: dcftime.c,v 1.1 2007/01/02 21:30:40 rschaten Exp $
 *
 * License: See documentation.
 */

#include "boole.h"
#include "dcftime.h"

// TODO: define and use meaningful states for certain situations (valid time, no values received, etc.)
// TODO: find correct start of the seconds. ATM the clock is running late by one second
// TODO: check if it is possible to give DCF_RATE as parameter for init()

typedef unsigned int dcf_sample; /**< number of the current sample */
typedef unsigned int dcf_sizetype; /**< used for the size of a month */

const dcf_sample dcf_second_samples = (DCF_RATE); /**< number of samples per second */
/** dcf signal between 30ms and 130ms => dcf logic false (lower value) */
const dcf_sample dcf_logic_false_min = (DCF_RATE)*3/100;
/** dcf signal between 30ms and 130ms => dcf logic false (upper value) */
const dcf_sample dcf_logic_false_max = (DCF_RATE)*13/100;
/** dcf signal between 140ms and 230ms => dcf logic true (lower value) */
const dcf_sample dcf_logic_true_min = (DCF_RATE)*14/100;
/** dcf signal between 140ms and 230ms => dcf logic true (upper value) */
const dcf_sample dcf_logic_true_max = (DCF_RATE)*23/100;
/** duration between begin of dcf second (== begin of signal), should be 1 * second +/- 3% (lower value) */
const dcf_sample dcf_second_tolerance_min = (DCF_RATE) - (DCF_RATE)*3/100;
/** duration between begin of dcf second (== begin of signal), should be 1 * second +/- 3% (upper value) */
const dcf_sample dcf_second_tolerance_max = (DCF_RATE) + (DCF_RATE)*3/100;

/** definition of logical signal states */
enum dcf_logic_signal_enum {
    dcf_signal_no, /**< no signal */
    dcf_signal_false, /**< 'false' signal */
    dcf_signal_true, /**< 'true' signal */
    dcf_signal_invalid /**< invalid signal */
};
/** definition of logical signal states */
typedef enum dcf_logic_signal_enum dcf_logic_signal;

/** format of the received data, filled during reception */
struct dcf_receiving_data_struct {
    dcf_date date; /**< date */
    dcf_time time; /**< time */
    boolean parity; /**< parity of the received data */
    boolean is_valid; /**< data is valid */
    dcf_logic_signal current_signal; /**< logical state of the received data */
    dcf_sample low_samples; /**< counts low signal samples per second */
    dcf_sample high_samples; /**< counts high signal samples per second */
};
/** definition of the received data, filled during reception */
typedef struct dcf_receiving_data_struct dcf_receiving_data;

/** format of the DCF data.
 * dcf_current_datetime() and dcf_sample() may be called from different contexts. To avoid changing the current_datetime while it is read:
 * if use_first_current_datetime is true: dcf_current_datetime reads current_datetime[0] and dcf_sample changes current_datetime[1]
 * if use_first_current_datetime is false: vice versa
 */
struct dcf_data_struct {
  dcf_datetime current_datetime[2]; /**< two full datasets */
  boolean use_first_current_datetime; /**< flag if the first or the second dataset is used */
  dcf_sample current_datetime_sample; /**< number of the current sample */
  dcf_receiving_data receiving_data; /**< data being filled */
};

/*
  global data
*/

static struct dcf_data_struct dcf_data; /**< full set of received dcf data */

/*
  dcf_time
*/

/**
 * Initialize a dcf_time value.
 * \param pTime: pointer to a dcf_time variable
 */
static void dcf_time_init(dcf_time * pTime) {
    pTime->second = 0;
    pTime->minute = 0;
    pTime->hour = 0;
    pTime->is_dst = False;
}

/**
 * Increment a time-value by one second.
 * \param pTime: pointer to a dcf_time variable
 * \return True if the date has to be incremented, too. Otherwise False.
 */
static boolean dcf_time_inc(dcf_time * pTime) {
    ++(pTime->second);
    if (pTime->second == 60) {
        pTime->second = 0;
        ++(pTime->minute);
        if (pTime->minute == 60) {
            pTime->minute = 0;
            ++(pTime->hour);
            if (pTime->hour == 24) {
                pTime->hour = 0;
                return True;    /* overflow => increment date */
            }
        }
    }
    return False;
}

/**
 * Check if a time-value makes sense.
 * \param pTime: pointer to a dcf_time variable
 * \return True if the time is logically correct. Otherwise False.
 */
static boolean dcf_time_is_valid(dcf_time * pTime) {
    return (pTime->second <= 60)
        && (pTime->minute <= 60)
        && (pTime->hour <= 24);
}

/*
  dcf_date
*/

/**
 * Initialize a dcf_date value.
 * \param pDate: pointer to a dcf_date variable
 */
static void dcf_date_init(dcf_date * pDate) {
    pDate->dayofweek = dcf_sunday;
    pDate->dayofmonth = 1;
    pDate->month = dcf_january;
    pDate->year = 0;
}

/**
 * Calculate the number of days in a month.
 * \param pDate: pointer to a dcf_time variable
 * \return The number of days in the given month.
 */
static dcf_sizetype dcf_date_days_in_month(dcf_date * pDate) {
    switch (pDate->month) {
        case dcf_february:
            if (pDate->year % 4 != 0)
                return 28;          /* year not divisible by 4 */
            else if (pDate->year != 0)
                return 29;          /* year divisible by 4 and not divisible by 100 */
            else if (((pDate->dayofmonth % 7) + 1) != pDate->dayofweek)
                return 28;          /* year divisible by 100 and not divisible by 400 */
            else
                return 29;          /* year divisible by 400 */
            /*
              if year is divisble by 400 (eg year 2000) the 1st february is a tuesday (== 2 (== 1+1))
              if year divided by 400 remains 100 1st February is a monday
              if year divided by 400 remains 200 1st February is a saturday
              if year divided by 400 remains 300 1st February is a thursday
              this repeats every 400 years, because 400 year are 3652425/25 day
                which is 7*521775/25, therefore divisible by 7
                which means every 400 years the day of week are the same
              ! dayofmonth and dayofweek must be synchronized to get the right value
            */
        case dcf_april:
        case dcf_june:
        case dcf_september:
        case dcf_november:
            return 30;
        default:
            return 31;
    }
}

/**
 * Increment a date-value by one day.
 * \param pDate: pointer to a dcf_date variable
 */
static void dcf_date_inc(dcf_date * pDate) {
    ++(pDate->dayofweek);
    if (pDate->dayofweek == 8) {
        pDate->dayofweek = 1;
    }

    ++(pDate->dayofmonth);
    if (pDate->dayofmonth == (dcf_date_days_in_month(pDate) + 1)) {
        pDate->dayofmonth = 1;
        ++(pDate->month);
        if (pDate->month == 13) {
            pDate->month = 1;
            ++(pDate->year);
            if (pDate->year == 100) {
                pDate->year = 0;
            }
        }
    }
}

/**
 * Check if a date-value makes sense.
 * \param pDate: pointer to a dcf_date variable
 * \return True if the date is logically correct. Otherwise False.
 */
static boolean dcf_date_is_valid(dcf_date * pDate) {
    return (1 <= pDate->dayofweek)
        && (pDate->dayofweek <= 7)
        && (1 <= pDate->dayofmonth)
        && (pDate->dayofmonth <= dcf_date_days_in_month(pDate))
        && (1 <= pDate->month)
        && (pDate->month <= 12)
        && (pDate->year <= 99);
}

/*
  dcf_datetime
*/
/**
 * Initialize a dcf_datetime value.
 * \param pDatetime: pointer to a dcf_datetime variable
 */
static void dcf_datetime_init(dcf_datetime * pDatetime) {
    pDatetime->is_valid = False;
    pDatetime->has_signal = False;
    dcf_time_init(&(pDatetime->time));
    dcf_date_init(&(pDatetime->date));
}

/**
 * Increment a datetime-value by one second.
 * \param pDatetime: pointer to a dcf_datetime variable
 */
static void dcf_datetime_inc(dcf_datetime * pDatetime) {
    if (dcf_time_inc(&(pDatetime->time))) {
        dcf_date_inc(&(pDatetime->date));
    }
}

/*
  dcf_receiving_data
*/

/**
 * Initialize a dcf_receiving_data value.
 * \param pReceive: pointer to a dcf_receiving_data variable
 */
static void dcf_receiving_data_init(dcf_receiving_data * pReceive) {
    pReceive->current_signal = dcf_signal_no;
    pReceive->parity = False;
    pReceive->is_valid = True;
    pReceive->low_samples = 0;
    pReceive->high_samples = 0;
    dcf_time_init(&(pReceive->time));
    dcf_date_init(&(pReceive->date));
}

/**
 * Calculate the time and date while the bits are received.
 * \param signal: True if the received bit is 200ms, False if the bit is 100ms.
 */
static void dcf_logic(boolean signal) {
    dcf_data.receiving_data.parity ^= signal;
    switch (dcf_data.receiving_data.time.second) {
        case 16: dcf_data.receiving_data.parity = True;                                       break;
        case 17: dcf_data.receiving_data.time.is_dst = signal;                                break;
        case 18: if(dcf_data.receiving_data.parity) dcf_data.receiving_data.is_valid = False; break;
        case 19: dcf_data.receiving_data.parity = True;                                       break;
        case 20: if(!signal)                        dcf_data.receiving_data.is_valid = False; break;
        case 21: dcf_data.receiving_data.time.minute =      signal ?  1 : 0;                  break;
        case 22: dcf_data.receiving_data.time.minute +=     signal ?  2 : 0;                  break;
        case 23: dcf_data.receiving_data.time.minute +=     signal ?  4 : 0;                  break;
        case 24: dcf_data.receiving_data.time.minute +=     signal ?  8 : 0;                  break;
        case 25: dcf_data.receiving_data.time.minute +=     signal ? 10 : 0;                  break;
        case 26: dcf_data.receiving_data.time.minute +=     signal ? 20 : 0;                  break;
        case 27: dcf_data.receiving_data.time.minute +=     signal ? 40 : 0;                  break;
        case 28: if(dcf_data.receiving_data.parity) dcf_data.receiving_data.is_valid = False; break;
        case 29: dcf_data.receiving_data.time.hour =        signal ?  1 : 0;                  break;
        case 30: dcf_data.receiving_data.time.hour +=       signal ?  2 : 0;                  break;
        case 31: dcf_data.receiving_data.time.hour +=       signal ?  4 : 0;                  break;
        case 32: dcf_data.receiving_data.time.hour +=       signal ?  8 : 0;                  break;
        case 33: dcf_data.receiving_data.time.hour +=       signal ? 10 : 0;                  break;
        case 34: dcf_data.receiving_data.time.hour +=       signal ? 20 : 0;                  break;
        case 35: if(dcf_data.receiving_data.parity) dcf_data.receiving_data.is_valid = False; break;
        case 36: dcf_data.receiving_data.date.dayofmonth =  signal ?  1 : 0;                  break;
        case 37: dcf_data.receiving_data.date.dayofmonth += signal ?  2 : 0;                  break;
        case 38: dcf_data.receiving_data.date.dayofmonth += signal ?  4 : 0;                  break;
        case 39: dcf_data.receiving_data.date.dayofmonth += signal ?  8 : 0;                  break;
        case 40: dcf_data.receiving_data.date.dayofmonth += signal ? 10 : 0;                  break;
        case 41: dcf_data.receiving_data.date.dayofmonth += signal ? 20 : 0;                  break;
        case 42: dcf_data.receiving_data.date.dayofweek =   signal ?  1 : 0;                  break;
        case 43: dcf_data.receiving_data.date.dayofweek +=  signal ?  2 : 0;                  break;
        case 44: dcf_data.receiving_data.date.dayofweek +=  signal ?  4 : 0;                  break;
        case 45: dcf_data.receiving_data.date.month =       signal ?  1 : 0;                  break;
        case 46: dcf_data.receiving_data.date.month +=      signal ?  2 : 0;                  break;
        case 47: dcf_data.receiving_data.date.month +=      signal ?  4 : 0;                  break;
        case 48: dcf_data.receiving_data.date.month +=      signal ?  8 : 0;                  break;
        case 49: dcf_data.receiving_data.date.month +=      signal ? 10 : 0;                  break;
        case 50: dcf_data.receiving_data.date.year =        signal ?  1 : 0;                  break;
        case 51: dcf_data.receiving_data.date.year +=       signal ?  2 : 0;                  break;
        case 52: dcf_data.receiving_data.date.year +=       signal ?  4 : 0;                  break;
        case 53: dcf_data.receiving_data.date.year +=       signal ?  8 : 0;                  break;
        case 54: dcf_data.receiving_data.date.year +=       signal ? 10 : 0;                  break;
        case 55: dcf_data.receiving_data.date.year +=       signal ? 20 : 0;                  break;
        case 56: dcf_data.receiving_data.date.year +=       signal ? 40 : 0;                  break;
        case 57: dcf_data.receiving_data.date.year +=       signal ? 80 : 0;                  break;
        case 58: if(dcf_data.receiving_data.parity) dcf_data.receiving_data.is_valid = False; break;
    }
    ++(dcf_data.receiving_data.time.second);
}

/**
 * Copy the values from receiving_data to current_datetime.
 */
static void dcf_store(void) {
    if ((dcf_data.receiving_data.is_valid)
        && dcf_time_is_valid(&(dcf_data.receiving_data.time))
        && dcf_date_is_valid(&(dcf_data.receiving_data.date))) {
        dcf_data.current_datetime_sample = 0;
        if (dcf_data.use_first_current_datetime) {
            dcf_data.current_datetime[1].time = dcf_data.receiving_data.time;
            dcf_data.current_datetime[1].date = dcf_data.receiving_data.date;
            dcf_data.current_datetime[1].is_valid = True;
            dcf_data.use_first_current_datetime = False;
        } else {
            dcf_data.current_datetime[0].time = dcf_data.receiving_data.time;
            dcf_data.current_datetime[0].date = dcf_data.receiving_data.date;
            dcf_data.current_datetime[0].is_valid = True;
            dcf_data.use_first_current_datetime = True;
        }
    }
}

/**
 * Copy valid time and increment it.
 */
static void dcf_inc(void) {
    if (dcf_data.use_first_current_datetime) {
        dcf_data.current_datetime[1] = dcf_data.current_datetime[0];
        dcf_datetime_inc(&(dcf_data.current_datetime[1]));
        dcf_data.use_first_current_datetime = False;
    } else {
        dcf_data.current_datetime[0] = dcf_data.current_datetime[1];
        dcf_datetime_inc(&(dcf_data.current_datetime[0]));
        dcf_data.use_first_current_datetime = True;
    }
}

/*
  exported functions, documented in header file
*/

void dcf_init(void) {
    dcf_data.use_first_current_datetime = True;
    dcf_data.current_datetime_sample = 0;
    dcf_datetime_init(&(dcf_data.current_datetime[0]));
    dcf_datetime_init(&(dcf_data.current_datetime[1]));
    dcf_receiving_data_init(&(dcf_data.receiving_data));
}

void dcf_signal(boolean signal) {
    if (dcf_data.receiving_data.low_samples > dcf_second_samples) {
        if (dcf_data.receiving_data.time.second == 59) {
            dcf_data.receiving_data.time.second = 0;
            dcf_store();
        } else {
            dcf_data.receiving_data.time.second = 0;
        }
        dcf_data.receiving_data.low_samples = 0;
        dcf_data.receiving_data.is_valid = True;
    }
    /* calculate receiving date time */
    if (signal) {
        dcf_data.receiving_data.low_samples = 0;
        ++(dcf_data.receiving_data.high_samples);
    } else {
        ++(dcf_data.receiving_data.low_samples);
        if (dcf_data.receiving_data.high_samples == 0) {
        } else if (dcf_data.receiving_data.high_samples < dcf_logic_false_min) {
            /* too short signal */
            dcf_data.receiving_data.is_valid = False;
            dcf_data.receiving_data.current_signal = dcf_signal_invalid;
        } else if (dcf_data.receiving_data.high_samples < dcf_logic_false_max) {
            /* short signal, logic 0 */
            dcf_logic(False);
            dcf_data.receiving_data.current_signal = dcf_signal_false;
        } else if (dcf_data.receiving_data.high_samples < dcf_logic_true_min) {
            /* signal cannot be assigned to true or false */
            dcf_data.receiving_data.is_valid = False;
            dcf_data.receiving_data.current_signal = dcf_signal_invalid;
        } else if (dcf_data.receiving_data.high_samples < dcf_logic_true_max) {
            /* long signal, logic 1 */
            dcf_logic(True);
            dcf_data.receiving_data.current_signal = dcf_signal_true;
        } else {
            /* too long signal */
            dcf_data.receiving_data.is_valid = False;
            dcf_data.receiving_data.current_signal = dcf_signal_invalid;
        }
        dcf_data.receiving_data.high_samples = 0;
    }
    /* calculate current date time */
    ++(dcf_data.current_datetime_sample);
    if (dcf_data.current_datetime_sample == dcf_second_samples) {
        dcf_data.current_datetime_sample = 0;
        dcf_inc();
    }
}

dcf_datetime dcf_current_datetime(void) {
    if (dcf_data.use_first_current_datetime) {
        dcf_data.current_datetime[0].has_signal = dcf_data.receiving_data.is_valid;
        return dcf_data.current_datetime[0];
    } else {
        dcf_data.current_datetime[1].has_signal = dcf_data.receiving_data.is_valid;
        return dcf_data.current_datetime[1];
    }
}

const char *dcf_dayofweek_name(dcf_dayofweek dow) {
    switch (dow) {
        case 1:
            return "Mo";
        case 2:
            return "Tu";
        case 3:
            return "We";
        case 4:
            return "Th";
        case 5:
            return "Fr";
        case 6:
            return "Sa";
        case 7:
            return "Su";
        default:
            return "??";
    }
}

const char *dcf_is_dst_name(dcf_is_dst dst) {
    if (dst) {
        return "ST";
    } else {
        return "WT";
    }
}