#include "calendar.h"

#include "err.h"
#include "opt.h"

#include <errno.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>

#define ERRP(...) \
	do { \
		fprintf(stderr, "err: %zu:%zu: ", s->last_line, s->last_col); \
		fprintf(stderr, __VA_ARGS__); \
		fprintf(stderr, "\n"); \
	} while (0)

struct state_s {
	bool err_flag;
	size_t line, col;
	size_t last_line, last_col;
	struct entry_interval_s cur_warn;
	struct entry_interval_s cur_stay;
	bool cur_urgent;
	bool cur_local;
	FILE *f;
	struct calendar_s *cal;
};

enum cmd_type_e {
	CMD_TYPE_WARN,
	CMD_TYPE_URGENT,
	CMD_TYPE_LOCAL,
	CMD_TYPE_STAY,
};

struct cmd_s {
	enum cmd_type_e type;
	struct entry_interval_s iv;
	bool b;
};

struct pos_s {
	size_t line, col;
};

static struct pos_s sub_get_pos(struct state_s *s)
{
	struct pos_s p = {
		.line = s->line,
		.col = s->col
	};

	return p;
}

static void sub_set_pos(struct state_s *s, struct pos_s p)
{
	s->last_line = p.line;
	s->last_col = p.col;
}

static void sub_eat_spaces(struct state_s *s)
{
	int c;

	while (true) {
		c = getc(s->f);

		if (c == '\n') {
			s->col = 1;
			s->line++;
			continue;
		}

		if (!isspace(c)) {
			ungetc(c, s->f);
			break;
		}

		s->col++;

	}
}

static void sub_eat_comment(struct state_s *s)
{
	int c;

	while (true) {
		c = getc(s->f);

		if (c == '\n' || c == EOF)
			break;
	}

	s->col = 1;
	s->line++;
}

static struct entry_interval_s sub_get_interval(struct state_s *s)
{
	struct entry_interval_s iv = { 0 };
	int r, count;
	long l;
	bool ready = false;

	sub_set_pos(s, sub_get_pos(s));

	while (true) {
		errno = 0;
		r = fscanf(s->f, "%ld%n", &l, &count);

		/* read err */
		if (errno) {
			ERRP("invalid time interval");
			s->err_flag = true;
			return iv;
		}

		/* no int found */
		if (r == 0) {
			/* err if digit */
			r = getc(s->f);
			if (isdigit(r)) {
				ERRP("expected time interval");
				s->err_flag = true;
				return iv;
			}
			ungetc(r, s->f);

			/* err if empty so far */
			if (ready == false) {
				ERRP("expected time interval");
				s->err_flag = true;
			}

			/* done */
			return iv;
		}

		/* range err interval */
		if (l <= 0) {
			ERRP("invalid time interval");
			s->err_flag = true;
			return iv;
		}

		if (l > INT_MAX - 365) {
			ERRP("time interval too large");
			s->err_flag = true;
			return iv;
		}

		s->col += count;

		switch (getc(s->f)) {
		case 'y':
			if (iv.year != 0) {
				ERRP("duplicate year entry in time interval");
				s->err_flag = true;
				return iv;
			}
			iv.year = l;
			break;

		case 'm':
			if (iv.month != 0) {
				ERRP("duplicate month entry in time interval");
				s->err_flag = true;
				return iv;
			}
			iv.month = l;
			break;

		case 'd':
			if (iv.day != 0) {
				ERRP("duplicate day entry in time interval");
				s->err_flag = true;
				return iv;
			}
			iv.day = l;
			break;

		case 'H':
			if (iv.hour != 0) {
				ERRP("duplicate hour entry in time interval");
				s->err_flag = true;
				return iv;
			}
			iv.hour = l;
			break;

		case 'M':
			if (iv.minute != 0) {
				ERRP("duplicate minute entry in time interval");
				s->err_flag = true;
				return iv;
			}
			iv.minute = l;
			break;

		case 'S':
			if (iv.second != 0) {
				ERRP("duplicate second entry in time interval");
				s->err_flag = true;
				return iv;
			}
			iv.second = l;
			break;

		default:
			ERRP("invalid time interval");
			s->err_flag = true;
			return iv;
		}

		s->col++;
		ready = true;

		sub_eat_spaces(s);
	}
}

static time_t sub_get_date(struct state_s *s)
{
	int r, count;
	long l;
	int i;
	char c;
	time_t rt = 0;
	struct tm ttmp;
	struct tm t = {
		.tm_year = 2000,
		.tm_mday = 1,
		.tm_isdst = -1,
	};
	bool seen = false;

	sub_set_pos(s, sub_get_pos(s));

	for (i = 0; i < 6; i++) {
		c = getc(s->f);
		if (c == '_') {
			count = 1;
			switch (i) {
			/* year */
			case 0:
				l = 2000;
				break;
			case 1:
			case 2:
				l = 1;
				break;
			default:
				l = 0;
				break;
			}
			goto skip_num;
		}
		ungetc(c, s->f);

		errno = 0;
		r = fscanf(s->f, "%ld%n", &l, &count);

		/* read err */
		if (errno) {
			ERRP("invalid date");
			s->err_flag = true;
			return rt;
		}

		/* no int found */
		if (r == 0) {
			if (seen)
				ERRP("invalid date");
			else
				ERRP("expected date");
			s->err_flag = true;
			return rt;
		}

		seen = true;

		/* range err interval */
		if (l < 0) {
			ERRP("invalid date");
			s->err_flag = true;
			return rt;
		}

		if (l > INT_MAX) {
			ERRP("invalid date");
			s->err_flag = true;
			return rt;
		}

skip_num:

		switch (i) {
		case 0:
			t.tm_year = l - 1900;
			break;
		case 1:
			t.tm_mon = l - 1;
			break;
		case 2:
			t.tm_mday = l;
			break;
		case 3:
			t.tm_hour = l;
			break;
		case 4:
			t.tm_min = l;
			break;
		case 5:
			t.tm_sec = l;
			break;
		}

		s->col += count;

		if (i < 2) {
			c = getc(s->f);

			if (c != '-') {
				ungetc(c, s->f);
				goto validate;
			}
		s->col++;

		} else if (i == 2) {
			sub_eat_spaces(s);
			c = getc(s->f);
			ungetc(c, s->f);
			if (!isdigit(c) && c != '_')
				goto validate;
		} else if (i < 5) {
			c = getc(s->f);

			if (c != ':') {
				ungetc(c, s->f);
				goto validate;
			}
		}
	}

validate:
	ttmp = t;

	/* NOTE: timegm is non-POSIX, but commonplace */
	if (s->cur_local)
		rt = mktime(&t);
	else
		rt = timegm(&t);

	if (rt == -1) {
		ERRP("invalid date");
		s->err_flag = true;
	}

	if (s->cur_local)
		t = *localtime(&rt);
	else
		t = *gmtime(&rt);

	if (
		ttmp.tm_year != t.tm_year ||
		ttmp.tm_mon  != t.tm_mon ||
		ttmp.tm_mday != t.tm_mday ||
		ttmp.tm_hour != t.tm_hour ||
		ttmp.tm_min  != t.tm_min ||
		ttmp.tm_sec  != t.tm_sec
	) {
		ERRP("invalid date");
		s->err_flag = true;
	}

	return rt;
}

static inline struct cmd_s sub_get_cmd_warn(struct state_s *s)
{
	struct cmd_s cmd = {
		.type = CMD_TYPE_WARN
	};

	cmd.iv = sub_get_interval(s);

	return cmd;
}

static inline struct cmd_s sub_get_cmd_stay(struct state_s *s)
{
	struct cmd_s cmd = {
		.type = CMD_TYPE_STAY
	};

	cmd.iv = sub_get_interval(s);

	return cmd;
}

static bool sub_get_bool(struct state_s *s)
{
	bool r = false;

	sub_set_pos(s, sub_get_pos(s));

	switch (tolower(getc(s->f))) {
	case 't':
		if (
			tolower(getc(s->f)) == 'r' &&
			tolower(getc(s->f)) == 'u' &&
			tolower(getc(s->f)) == 'e'
		) {
			r = true;
			s->col += 4;
		} else {
			s->err_flag = true;
		}
		break;

	case 'y':
		if (
			tolower(getc(s->f)) == 'e' &&
			tolower(getc(s->f)) == 's'
		) {
			r = true;
			s->col += 3;
		} else {
			s->err_flag = true;
		}
		break;

	case 'n':
		if (
			tolower(getc(s->f)) == 'o'
		) {
			s->col += 2;
		} else {
			s->err_flag = true;
		}
		break;

	case 'f':
		if (
			tolower(getc(s->f)) == 'a' &&
			tolower(getc(s->f)) == 'l' &&
			tolower(getc(s->f)) == 's' &&
			tolower(getc(s->f)) == 'e'
		) {
			s->col += 5;
		} else {
			s->err_flag = true;
		}
		break;

	case 'o':
			switch (tolower(getc(s->f))) {
			case 'n':
				r = true;
				s->col += 2;
				break;
			case 'f':
				if (tolower(getc(s->f)) == 'f') {
					s->col += 3;
				} else {
					s->err_flag = true;
				}
				break;
			default:
				s->err_flag = true;
				break;
			}
			break;

	default:
			s->err_flag = true;
			break;
	}

	if (s->err_flag)
		ERRP("invalid boolean");

	return r;
}

static inline struct cmd_s sub_get_cmd_urgent(struct state_s *s)
{
	struct cmd_s cmd = {
		.type = CMD_TYPE_URGENT
	};

	cmd.b = sub_get_bool(s);

	return cmd;
}

static inline struct cmd_s sub_get_cmd_local(struct state_s *s)
{
	struct cmd_s cmd = {
		.type = CMD_TYPE_LOCAL
	};

	cmd.b = sub_get_bool(s);

	return cmd;
}

static inline struct cmd_s sub_get_cmd(struct state_s *s)
{
	struct cmd_s cmd = { 0 };
	struct pos_s p = {
		.line = s->line,
		.col = s->col - 1,
	};

	sub_set_pos(s, p);

	switch (getc(s->f)) {
	case 'w':
		if (
			getc(s->f) == 'a' &&
			getc(s->f) == 'r' &&
			getc(s->f) == 'n'
		) {
			s->col += 4;
			sub_eat_spaces(s);
			return sub_get_cmd_warn(s);
		}
		break;

	case 'u':
		if (
			getc(s->f) == 'r' &&
			getc(s->f) == 'g' &&
			getc(s->f) == 'e' &&
			getc(s->f) == 'n' &&
			getc(s->f) == 't'
		) {
			s->col += 6;
			sub_eat_spaces(s);
			return sub_get_cmd_urgent(s);
		}
		break;

	case 'l':
		if (
			getc(s->f) == 'o' &&
			getc(s->f) == 'c' &&
			getc(s->f) == 'a' &&
			getc(s->f) == 'l'
		) {
			s->col += 5;
			sub_eat_spaces(s);
			return sub_get_cmd_local(s);
		}
		break;

	case 's':
		if (
			getc(s->f) == 't' &&
			getc(s->f) == 'a' &&
			getc(s->f) == 'y'
		) {
			s->col += 4;
			sub_eat_spaces(s);
			return sub_get_cmd_stay(s);
		}
		break;
	}

	ERRP("unknown command");
	s->err_flag = true;
	return cmd;
}

static char* sub_get_msg(struct state_s *s)
{
	const size_t step_size = 64;
	size_t count = 0, width = 0;
	char *msg = NULL;
	char c;

	while ( (c = getc(s->f)) != '\n' && c != EOF) {
		s->col++;
		if (count == width || count + 1 == width) {
			width += step_size;
			msg = realloc(msg, width * sizeof(*msg));

			if (msg == NULL) {
				ERRM("failed to allocate memory");
				s->err_flag = true;
				return NULL;
			}
		}

		if (c == opt_line_delim() || c == opt_col_delim()) {
			sub_set_pos(s, sub_get_pos(s));
			ERRP("message may not contain line or column delimiter characters");
			s->err_flag = true;
			free(msg);
			return NULL;
		}

		msg[count] = c;
		count++;
	}

	msg[count] = '\0';
	s->col = 0;
	s->line++;

	return msg;
}

static inline struct entry_s sub_get_entry_on(struct state_s *s)
{
	struct entry_s e = {
		.type = ENTRY_TYPE_ON,
		.urgent = s->cur_urgent,
		.local = s->cur_local,
		.warn = s->cur_warn,
		.stay = s->cur_stay,
	};
	time_t rt;
	int c;

	rt = sub_get_date(s);
	if (s->err_flag)
		return e;

	e.start = rt;

	sub_eat_spaces(s);

	c = getc(s->f);

	if (c != ',') {
		ungetc(c, s->f);
		return e;
	}

	s->col++;

	sub_eat_spaces(s);
	e.msg = sub_get_msg(s);
	return e;
}

static inline struct entry_s sub_get_entry_every(struct state_s *s)
{
	struct entry_s e = {
		.type = ENTRY_TYPE_EVERY,
		.urgent = s->cur_urgent,
		.local = s->cur_local,
		.warn = s->cur_warn,
		.stay = s->cur_stay,
	};
	bool from_seen = false, to_seen = false;
	char c;
	struct pos_s p = {
		.line = s->last_line,
		.col = s->last_col,
	};

	e.every = sub_get_interval(s);

	if (s->err_flag)
		return e;

	while (true) {
		sub_eat_spaces(s);
		sub_set_pos(s, p);

		switch (c = getc(s->f)) {
		case 'f':
			if (
				getc(s->f) == 'r' &&
				getc(s->f) == 'o' &&
				getc(s->f) == 'm'
			) {
				if (from_seen) {
					ERRP("invalid calendar entry");
					s->err_flag = true;
					return e;
				}
				from_seen = true;

				s->col += 4;
				sub_eat_spaces(s);
				e.start = sub_get_date(s);

				if (s->err_flag)
					return e;

				break;
			}

		case 't':
			if (
				getc(s->f) == 'o'
			) {
				if (to_seen) {
					ERRP("invalid calendar entry");
					s->err_flag = true;
					return e;
				}
				to_seen = true;

				s->col += 2;
				sub_eat_spaces(s);
				e.end = sub_get_date(s);
				e.has_end = true;

				if (s->err_flag)
					return e;

				break;
			}

		default:
			goto done;
		}
	}

done:
	if (!from_seen) {
		ERRP("invalid calendar entry");
		s->err_flag = true;
	}

	ungetc(c, s->f);

	sub_eat_spaces(s);

	c = getc(s->f);

	if (c != ',') {
		ungetc(c, s->f);
		return e;
	}

	s->col++;

	sub_eat_spaces(s);
	e.msg = sub_get_msg(s);
	return e;
}

static inline struct entry_s sub_get_entry(struct state_s *s)
{
	struct entry_s e = { 0 };

	switch (getc(s->f)) {
	case 'o':
		if (
			getc(s->f) == 'n'
		) {
			s->col += 2;
			sub_eat_spaces(s);
			return sub_get_entry_on(s);
		}
		break;

	case 'e':
		if (
			getc(s->f) == 'v' &&
			getc(s->f) == 'e' &&
			getc(s->f) == 'r' &&
			getc(s->f) == 'y'
		) {
			s->col += 5;
			sub_eat_spaces(s);
			return sub_get_entry_every(s);
		}
		break;
	}

	ERRP("invalid calendar entry");
	s->err_flag = true;

	return e;
}

static inline void sub_cal_push(struct state_s *s, struct calendar_s *cal,
	struct entry_s *e)
{
	const size_t step_size = 64;

	if (cal->count == cal->width) {
		cal->width += step_size;
		cal->entries = realloc(cal->entries, cal->width * sizeof(*e));

		if (cal->entries == NULL) {
			ERRM("failed to allocate memory");
			s->err_flag = true;
			return;
		}
	}

	cal->entries[cal->count] = *e;
	cal->count++;
}

struct calendar_s calendar_parse(FILE *f)
{
	struct calendar_s cal = {
		.count = 0,
		.err_flag = false,
	};
	struct state_s s = {
		.err_flag = false,
		.line = 1,
		.col = 1,
		.cur_warn = {
			.day = 1,
		},
		.cur_stay = {
			.day = 1,
		},
		.cur_urgent = false,
		.cur_local = true,
		.f = f,
		.cal = &cal,
	};
	int c;
	struct cmd_s cmd;
	struct entry_s e;

	while (true) {
		sub_eat_spaces(&s);
		sub_set_pos(&s, sub_get_pos(&s));

		c = getc(f);
		if (c == EOF)
			break;

		if (c == '#') {
			sub_eat_comment(&s);
			continue;
		}

		if (c == '.') {
			s.col++;
			cmd = sub_get_cmd(&s);

			if (s.err_flag) {
				calendar_wipe(&cal);
				cal.err_flag = true;
				return cal;
			}

			switch (cmd.type) {
			case CMD_TYPE_WARN:
				s.cur_warn = cmd.iv;
				break;
			case CMD_TYPE_URGENT:
				s.cur_urgent = cmd.b;
				break;
			case CMD_TYPE_LOCAL:
				s.cur_local = cmd.b;
				break;
			case CMD_TYPE_STAY:
				s.cur_stay = cmd.iv;
				break;
			}

			continue;
		}

		ungetc(c, f);

		e = sub_get_entry(&s);
		if (s.err_flag) {
			calendar_wipe(&cal);
			cal.err_flag = true;
			return cal;
		}
		sub_cal_push(&s, &cal, &e);
	}

	return cal;
}

void calendar_wipe(struct calendar_s *cal)
{
	size_t i;

	if (cal->entries == NULL)
		return;

	for (i = 0; i < cal->count; i++) {
		if (cal->entries[i].msg != NULL)
			free(cal->entries[i].msg);
	}

	free(cal->entries);
	cal->entries = NULL;
}