/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */

/*
 * Author :
 *  Damon Chaplin <damon@ximian.com>
 *
 * Copyright 2001, Ximian, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 */

/*
 * Lays out events for the Week & Month views of the calendar. It is also
 * used for printing.
 */

#include <config.h>

#include "e-week-view-layout.h"


static void e_week_view_layout_event	(EWeekViewEvent	*event,
					 guint8		*grid,
					 GArray		*spans,
					 GArray		*old_spans,
					 gboolean	 multi_week_view,
					 gint		 weeks_shown,
					 gboolean	 compress_weekend,
					 gint		 start_weekday,
					 time_t		*day_starts,
					 gint		*rows_per_day);
static gint e_week_view_find_day	(time_t		 time_to_find,
					 gboolean	 include_midnight_in_prev_day,
					 gint		 days_shown,
					 time_t		*day_starts);
static gint e_week_view_find_span_end	(gboolean	 multi_week_view,
					 gboolean	 compress_weekend,
					 gint		 display_start_day,
					 gint		 day);


GArray*
e_week_view_layout_events	(GArray		*events,
				 GArray		*old_spans,
				 gboolean	 multi_week_view,
				 gint		 weeks_shown,
				 gboolean	 compress_weekend,
				 gint		 start_weekday,
				 time_t		*day_starts,
				 gint		*rows_per_day)
{
	EWeekViewEvent *event;
	EWeekViewEventSpan *span;
	gint num_days, day, event_num, span_num;
	guint8 *grid;
	GArray *spans;

	/* This is a temporary 2-d grid which is used to place events.
	   Each element is 0 if the position is empty, or 1 if occupied.
	   We allocate the maximum size possible here, assuming that each
	   event will need its own row. */
	grid = g_new0 (guint8, E_WEEK_VIEW_MAX_ROWS_PER_CELL * 7
		       * E_WEEK_VIEW_MAX_WEEKS);

	/* We create a new array of spans, which will replace the old one. */
	spans = g_array_new (FALSE, FALSE, sizeof (EWeekViewEventSpan));

	/* Clear the number of rows used per day. */
	num_days = multi_week_view ? weeks_shown * 7 : 7;
	for (day = 0; day < num_days; day++) {
		rows_per_day[day] = 0;
	}

	/* Iterate over the events, finding which weeks they cover, and putting
	   them in the first free row available. */
	for (event_num = 0; event_num < events->len; event_num++) {
		event = &g_array_index (events, EWeekViewEvent, event_num);
		e_week_view_layout_event (event, grid, spans, old_spans,
					  multi_week_view,
					  weeks_shown, compress_weekend,
					  start_weekday, day_starts,
					  rows_per_day);
	}

	/* Free the grid. */
	g_free (grid);

	/* Destroy the old spans array, destroying any unused canvas items. */
	if (old_spans) {
		for (span_num = 0; span_num < old_spans->len; span_num++) {
			span = &g_array_index (old_spans, EWeekViewEventSpan,
					       span_num);
			if (span->background_item)
				gtk_object_destroy (GTK_OBJECT (span->background_item));
			if (span->text_item)
				gtk_object_destroy (GTK_OBJECT (span->text_item));
		}
		g_array_free (old_spans, TRUE);
	}

	return spans;
}


static void
e_week_view_layout_event	(EWeekViewEvent	*event,
				 guint8		*grid,
				 GArray		*spans,
				 GArray		*old_spans,
				 gboolean	 multi_week_view,
				 gint		 weeks_shown,
				 gboolean	 compress_weekend,
				 gint		 start_weekday,
				 time_t		*day_starts,
				 gint		*rows_per_day)
{
	gint start_day, end_day, span_start_day, span_end_day, rows_per_cell;
	gint free_row, row, day, span_num, spans_index, num_spans, days_shown;
	EWeekViewEventSpan span, *old_span;

	days_shown = multi_week_view ? weeks_shown * 7 : 7;
	start_day = e_week_view_find_day (event->start, FALSE, days_shown,
					  day_starts);
	end_day = e_week_view_find_day (event->end, TRUE, days_shown,
					day_starts);
	start_day = CLAMP (start_day, 0, days_shown - 1);
	end_day = CLAMP (end_day, 0, days_shown - 1);

#if 0
	g_print ("In e_week_view_layout_event Start:%i End: %i\n",
		 start_day, end_day);
#endif

	/* Iterate through each of the spans of the event, where each span
	   is a sequence of 1 or more days displayed next to each other. */
	span_start_day = start_day;
	rows_per_cell = E_WEEK_VIEW_MAX_ROWS_PER_CELL;
	span_num = 0;
	spans_index = spans->len;
	num_spans = 0;
	while (span_start_day <= end_day) {
		span_end_day = e_week_view_find_span_end (multi_week_view,
							  compress_weekend,
							  start_weekday,
							  span_start_day);
		span_end_day = MIN (span_end_day, end_day);
#if 0
		g_print ("  Span start:%i end:%i\n", span_start_day,
			 span_end_day);
#endif
		/* Try each row until we find a free one or we fall off the
		   bottom of the available rows. */
		row = 0;
		free_row = -1;
		while (free_row == -1 && row < rows_per_cell) {
			free_row = row;
			for (day = span_start_day; day <= span_end_day;
			     day++) {
				if (grid[day * rows_per_cell + row]) {
					free_row = -1;
					break;
				}
			}
			row++;
		};

		if (free_row != -1) {
			/* Mark the cells as full. */
			for (day = span_start_day; day <= span_end_day;
			     day++) {
				grid[day * rows_per_cell + free_row] = 1;
				rows_per_day[day] = MAX (rows_per_day[day],
							 free_row + 1);
			}
#if 0
			g_print ("  Span start:%i end:%i row:%i\n",
				 span_start_day, span_end_day, free_row);
#endif
			/* Add the span to the array, and try to reuse any
			   canvas items from the old spans. */
			span.start_day = span_start_day;
			span.num_days = span_end_day - span_start_day + 1;
			span.row = free_row;
			span.background_item = NULL;
			span.text_item = NULL;
			if (event->num_spans > span_num) {
				old_span = &g_array_index (old_spans, EWeekViewEventSpan, event->spans_index + span_num);
				span.background_item = old_span->background_item;
				span.text_item = old_span->text_item;
				old_span->background_item = NULL;
				old_span->text_item = NULL;
			}

			g_array_append_val (spans, span);
			num_spans++;
		}

		span_start_day = span_end_day + 1;
		span_num++;
	}

	/* Set the event's spans. */
	event->spans_index = spans_index;
	event->num_spans = num_spans;
}


/* Finds the day containing the given time.
   If include_midnight_in_prev_day is TRUE then if the time exactly
   matches the start of a day the previous day is returned. This is useful
   when calculating the end day of an event. */
static gint
e_week_view_find_day		(time_t		 time_to_find,
				 gboolean	 include_midnight_in_prev_day,
				 gint		 days_shown,
				 time_t		*day_starts)
{
	gint day;

	if (time_to_find < day_starts[0])
		return -1;
	if (time_to_find > day_starts[days_shown])
		return days_shown;

	for (day = 1; day <= days_shown; day++) {
		if (time_to_find <= day_starts[day]) {
			if (time_to_find == day_starts[day]
			    && !include_midnight_in_prev_day)
				return day;
			return day - 1;
		}
	}

	g_assert_not_reached ();
	return days_shown;
}


/* This returns the last possible day in the same span as the given day.
   A span is all the days which are displayed next to each other from left to
   right. In the week view all spans are only 1 day, since Tuesday is below
   Monday rather than beside it etc. In the month view, if the weekends are not
   compressed then each week is a span, otherwise we have to break a span up
   on Saturday, use a separate span for Sunday, and start again on Monday. */
static gint
e_week_view_find_span_end	(gboolean	 multi_week_view,
				 gboolean	 compress_weekend,
				 gint		 display_start_day,
				 gint		 day)
{
	gint week, col, sat_col, end_col;

	if (multi_week_view) {
		week = day / 7;
		col = day % 7;

		/* We default to the last column in the row. */
		end_col = 6;

		/* If the weekend is compressed we must end any spans on
		   Saturday and Sunday. */
		if (compress_weekend) {
			sat_col = (5 + 7 - display_start_day) % 7;
			if (col <= sat_col)
				end_col = sat_col;
			else if (col == sat_col + 1)
				end_col = sat_col + 1;
		}

		return week * 7 + end_col;
	} else {
		return day;
	}
}


void
e_week_view_layout_get_day_position	(gint		 day,
					 gboolean	 multi_week_view,
					 gint		 weeks_shown,
					 gint		 display_start_day,
					 gboolean	 compress_weekend,
					 gint		*day_x,
					 gint		*day_y,
					 gint		*rows)
{
	gint week, day_of_week, row, col, weekend_col, box, weekend_box;

	*day_x = *day_y = *rows = 0;
	g_return_if_fail (day >= 0);

	if (multi_week_view) {
		g_return_if_fail (day < weeks_shown * 7);

		week = day / 7;
		col = day % 7;
		day_of_week = (display_start_day + day) % 7;
		if (compress_weekend && day_of_week >= 5) {
			/* In the compressed view Saturday is above Sunday and
			   both have just one row as opposed to 2 for all the
			   other days. */
			if (day_of_week == 5) {
				*day_y = week * 2;
				*rows = 1;
			} else {
				*day_y = week * 2 + 1;
				*rows = 1;
				col--;
			}
			/* Both Saturday and Sunday are in the same column. */
			*day_x = col;
		} else {
			/* If the weekend is compressed and the day is after
			   the weekend we have to move back a column. */
			if (compress_weekend) {
				/* Calculate where the weekend column is.
				   Note that 5 is Saturday. */
				weekend_col = (5 + 7 - display_start_day) % 7;
				if (col > weekend_col)
					col--;
			}

			*day_y = week * 2;
			*rows = 2;
			*day_x = col;
		}
	} else {
		g_return_if_fail (day < 7);

		/* Calculate which box to place the day in, from 0-5.
		   Note that in the week view the weekends are always
		   compressed and share a box. */
		box = day;
		day_of_week = (display_start_day + day) % 7;
		weekend_box = (5 + 7 - display_start_day) % 7;
		if (box > weekend_box)
			box--;

		if (box < 3)
			*day_x = 0;
		else
			*day_x = 1;

		row = (box % 3) * 2;
		if (day_of_week < 5) {
			*day_y = row;
			*rows = 2;
		} else if (day_of_week == 5) {
			/* Saturday. */
			*day_y = row;
			*rows = 1;

		} else {
			/* Sunday. */
			*day_y = row + 1;
			*rows = 1;
		}
	}
}


/* Returns TRUE if the event span is visible or FALSE if it isn't.
   It also returns the number of days of the span that are visible.
   Usually this can easily be determined by the start & end days and row of
   the span, which are set in e_week_view_layout_event(). Though we need a
   special case for the weekends when they are compressed, since the span may
   not fit. */
gboolean
e_week_view_layout_get_span_position	(EWeekViewEvent *event,
					 EWeekViewEventSpan *span,
					 gint		 rows_per_cell,
					 gint		 rows_per_compressed_cell,
					 gint		 display_start_day,
					 gboolean	 multi_week_view,
					 gboolean	 compress_weekend,
					 gint		*span_num_days)
{
	gint end_day_of_week;

	if (span->row >= rows_per_cell)
		return FALSE;

	end_day_of_week = (display_start_day + span->start_day
			   + span->num_days - 1) % 7;
	*span_num_days = span->num_days;
	/* Check if the row will not be visible in compressed cells. */
	if (span->row >= rows_per_compressed_cell) {
		if (multi_week_view) {
			if (compress_weekend) {
				/* If it ends on a Saturday and is 1 day long
				   we skip it, else we shorten it. If it ends
				   on a Sunday it must be 1 day long and we
				   skip it. */
				if (end_day_of_week == 5) {	   /* Sat */
					if (*span_num_days == 1) {
						return FALSE;
					} else {
						(*span_num_days)--;
					}
				} else if (end_day_of_week == 6) { /* Sun */
					return FALSE;
				}
			}
		} else {
			/* All spans are 1 day long in the week view, so we
			   just skip it. */
			if (end_day_of_week > 4)
				return FALSE;
		}
	}

	return TRUE;
}