/*
 * Copyright (C) 1995.  Bill Brown <brown@gis.uiuc.edu> & Michael Shapiro
 *
 * This program is free software under the GPL (>=v2)
 * Read the file GPL.TXT coming with GRASS for details.
 */
#include <stdio.h>
#include <string.h>
#include <grass/datetime.h>

  
static int scan_absolute (DateTime *,const char *);
static int more (const char **);
static int minus_sign(const char **);
static int is_bc (const char **);
static int is_relative(const char *);
static int relative_term( const char **,double *,int *,int *, int *);
static int scan_tz (const char *, int *);
static int get_word (const char **, char *);
static char lowercase (char );
static int which_month (const char *, int *);
static int scan_relative (DateTime *, const char *);
static int is_space(char);
static int is_digit(char);
static void skip_space(const char **);
static int get_int ( const char **, int *, int *);
static int get_double ( const char **, double *, int *, int *);


/*!
 * \brief 
 *
 * Convert the ascii string
 * into a DateTime. This determines the mode/from/to based on the string, inits
 * 'dt' and then sets values in 'dt' based on the [???]
 * Returns 0 if 'string' is legal, -1 if not. 
 *
 *  \param dt
 *  \param buf
 *  \return int
 */

int datetime_scan (
    DateTime *dt,
    const char *buf)
  {
      if (is_relative(buf))
      {
	if (scan_relative(dt, buf)) return 0;
	return datetime_error(-1, "Invalid interval datetime format");
    }
    if (scan_absolute(dt, buf)) return 0;
    return datetime_error(-2, "Invalid absolute datetime format");
}

static const char *month_names[] = {
	"jan","feb","mar","apr","may","jun",
	"jul","aug","sep","oct","nov","dec"};

static int scan_absolute (DateTime *dt, const char *buf)
{
    char word[1024];
    int n;
    int ndigits;
    int tz = 0;
    int have_tz = 0;
    int bc = 0;
    int to, fracsec = 0;
    int year, month, day=0, hour, minute;
    double second;
    const char *p;

    p = buf;
    if(!more(&p)) return 0;

    if (!get_int (&p, &n, &ndigits))  /* no day, so must be month, like Jan */
    {
	if (!get_word(&p, word))
	    return 0;
	if (!which_month(word,&month))
	    return 0;
	if (!get_int (&p, &year, &ndigits)) /* year following the month */
	    return 0;
	to = DATETIME_MONTH;
	if (is_bc (&p))
	    bc = 1;
	goto set;
    }

    bc = is_bc(&p);
    if (bc || !get_word(&p, word)) /* just a year */
    {
	year = n;
	to = DATETIME_YEAR;
	goto set;
    }
    to = DATETIME_DAY; /* must be at least: day Mon year [bc] */
    day = n;
    if (!which_month(word, &month))
	return 0;
    if (!get_int(&p, &year, &ndigits))
	return 0;
    if(is_bc(&p))
	bc = 1;

/* now for the time */
    if (!get_int (&p, &hour, &ndigits))
	goto set;
    to=DATETIME_HOUR;
    if (*p != ':')
	goto set;
    p++;
    if (!get_int (&p, &minute, &ndigits))
	return 0;
    if (ndigits != 2)
	return 0;
    to=DATETIME_MINUTE;
    if (*p != ':')
	goto timezone;
    p++;
    if (!get_double (&p, &second, &ndigits, &fracsec))
	return 0;
    if (ndigits != 2)
	return 0;
    to=DATETIME_SECOND;

timezone:
    if (!get_word(&p, word))
	goto set;
    if (!scan_tz (word, &tz))
	return 0;
    have_tz = 1;

set:
    if (more(&p)) /* make sure there isn't anything else */
	return 0;
    if (datetime_set_type (dt, DATETIME_ABSOLUTE, DATETIME_YEAR, to, fracsec))
	return 0;
    for (n = DATETIME_YEAR; n <= to; n++)
    {
	switch (n)
	{
	case DATETIME_YEAR:   if(datetime_set_year(dt, year)) return 0; break;
	case DATETIME_MONTH:  if(datetime_set_month(dt, month)) return 0; break;
	case DATETIME_DAY:    if(datetime_set_day(dt, day)) return 0; break;
	case DATETIME_HOUR:   if(datetime_set_hour(dt, hour)) return 0; break;
	case DATETIME_MINUTE: if(datetime_set_minute(dt, minute)) return 0; break;
	case DATETIME_SECOND: if(datetime_set_second(dt, second)) return 0; break;
	}
    }
    if (bc)
	datetime_set_negative(dt);
    if (have_tz && datetime_set_timezone(dt, tz))
	return 0;

    return 1;
}


static int scan_relative (DateTime *dt, const char *buf)
{
    const char *p;
    double x;
    int ndigits, ndecimal;
    int pos;
    int neg = 0;
    int year = 0, month = 0, day = 0, hour = 0, minute = 0, fracsec = 0;
    double second = 0.0;
    int from = DATETIME_SECOND + 1, to = DATETIME_YEAR - 1;

    p = buf;
    neg = minus_sign(&p);
    if (!more(&p)) return 0;

    while (relative_term (&p, &x, &ndigits, &ndecimal, &pos))
    {
	if (from > pos)
	    from = pos;
	if (to < pos)
	    to = pos;

	if (pos != DATETIME_SECOND && ndecimal != 0)
	    return 0;

	switch (pos)
	{
	case DATETIME_YEAR: year = (int) x; break;
	case DATETIME_MONTH: month = (int) x; break;
	case DATETIME_DAY: day = (int) x;; break;
	case DATETIME_HOUR: hour = (int) x; break;
	case DATETIME_MINUTE: minute = (int) x; break;
	case DATETIME_SECOND: second = x; fracsec = ndecimal; break;
	}

    }

    if (more(&p)) /* make sure there isn't anything else */
	return 0;
    if (datetime_set_type (dt, DATETIME_RELATIVE, from, to, fracsec))
	return 0;
    for (pos = from; pos <= to; pos++)
    {
	switch (pos)
	{
	case DATETIME_YEAR:   if(datetime_set_year(dt, year)) return 0; break;
	case DATETIME_MONTH:  if(datetime_set_month(dt, month)) return 0; break;
	case DATETIME_DAY:    if(datetime_set_day(dt, day)) return 0; break;
	case DATETIME_HOUR:   if(datetime_set_hour(dt, hour)) return 0; break;
	case DATETIME_MINUTE: if(datetime_set_minute(dt, minute)) return 0; break;
	case DATETIME_SECOND: if(datetime_set_second(dt, second)) return 0; break;
	}
    }
    if (neg)
	datetime_set_negative(dt);

    return 1;
}

static int is_space(char c)
{
    return (c == ' ' || c == '\t' || c == '\n');
}

static int is_digit(char c)
{
    return (c >= '0' && c <= '9');
}

static void skip_space(const char **s)
{
    while (is_space(**s))
	(*s)++;
}

static int get_int ( const char **s, int *n, int *ndigits)
{
    const char *p;

    *n = 0;
    skip_space(s);
    p = *s;
    for (*ndigits = 0; is_digit(*p); (*ndigits)++)
    {
	*n *= 10;
	*n += *p - '0';
	p++;
    }
    if (*ndigits > 0)
	*s = p;
    return (*ndigits > 0);
}

static int get_double (
    const char **s,
    double *x,
    int *ndigits, /* number of digits before decimal */
    int *ndecimal) /* number of decimal places */
{
    char buf[1024];
    char *b;
    const char *p;

    skip_space (s);

    p = *s;
    *ndecimal = 0;
    b = buf;

    for (*ndigits = 0; is_digit(*p); (*ndigits)++)
	*b++ = *p++;
    if (*p == '.')
    {
	*b++ = *p++;
	while (is_digit(*p))
	{
	    *b++ = *p++;
	    (*ndecimal)++;
	}
    }
    *b = 0;
    if (sscanf (buf, "%lf", x) != 1)
	return 0;
    *s = p;
    return 1;
}


/* if pos is non-zero, *(p-1) must be legal */
/*
static int
is_wordend (pos, p)
    int pos;
    char *p;
{
    int d1, d0;

    if ('\0'==(*p)) return (1);
    if (is_space(*p)) return (1);
    if (pos){
	d0 = is_digit(*(p-1));
	d1 = is_digit(*p);
	return(d0 != d1);
    }
    return (0);

}
*/

/* get a word (between white space) and convert to lowercase */
static int get_word (const char **s, char *word)
{
    const char *p;
    int any;

    skip_space(s);
    p = *s;
    for (any = 0; *p && !is_space(*p); any = 1)
	*word++ = lowercase(*p++);
    *word = 0;
    *s = p;
    return any;
}

static char lowercase (char c)
{
    if (c >= 'A' && c <= 'Z')
	c += 'a' - 'A';
    return c;
}

static int which_month (const char *name, int *n)
{
    int i;

    for (i = 0; i < 12; i++)
	if (strcmp(name, month_names[i]) == 0)
	{
	    *n = i + 1;
	    return 1;
	}
    return 0;
}

static int is_bc (const char **s)
{
    const char *p;
    char word[1024];

    p = *s;
    if (!get_word(&p, word))
	return 0;
    if (strcmp("bc",word) != 0)
	return 0;
    *s = p;
    return 1;
}

static int scan_tz (const char *word, int *tz)
{
    int neg = 0;

    if (word[0] == '+')
	neg = 0;
    else if (word[0] == '-')
	neg = 1;
    else
	return 0;

    if (!is_digit(word[1])) return 0;
    if (!is_digit(word[2])) return 0;
    if (!is_digit(word[3])) return 0;
    if (!is_digit(word[4])) return 0;

    *tz = (word[1] - '0') * 600 + (word[2] - '0') * 60 +
	  (word[3] - '0') * 10  + (word[4] - '0');
    if (neg)
	*tz = -(*tz);
    return 1;
}

/* returns
    0 not a recognized term
    1 valid term, but perhaps illiegal value
*/
static int relative_term(
    const char **s,
    double *x,
    int *ndigits,int *ndecimal,
    int *pos)
{
    char word[1024];
    const char *p;

    p = *s;
    if (!get_double (&p, x, ndigits, ndecimal) || !get_word (&p, word))
	return 0;

    if (strcmp(word,"year")==0 || strcmp(word,"years")==0)
	*pos = DATETIME_YEAR;
    else if (strcmp(word,"month")==0 || strcmp(word,"months")==0 ||
	     strcmp(word,"mon") == 0)
	*pos = DATETIME_MONTH;
    else if (strcmp(word,"day")==0 || strcmp(word,"days")==0)
	*pos = DATETIME_DAY;
    else if (strcmp(word,"hour")==0 || strcmp(word,"hours")==0)
	*pos = DATETIME_HOUR;
    else if (strcmp(word,"minute")==0 || strcmp(word,"minutes")==0 ||
	     strcmp(word,"min") == 0)
	*pos = DATETIME_MINUTE;
    else if (strcmp(word,"second")==0 || strcmp(word,"seconds")==0 ||
	     strcmp(word,"sec") == 0)
	*pos = DATETIME_SECOND;
    else
	return 0;
    *s = p;
    return 1;
}

static int minus_sign(const char **s)
{
    skip_space(s);
    if (**s == '-')
    {
	(*s)++;
	return 1;
    }
    return 0;
}

static int is_relative(const char *buf)
{
    int n;
    double x;
    const char *p;

    p = buf;
    (void)minus_sign(&p);
    return relative_term (&p, &x, &n, &n, &n) != 0;
}

static int more (const char **s)
{
    skip_space(s);
    return **s != 0;
}
