/* -*- 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 Day & Work-Week views of the calendar. It is also
 * used for printing.
 */

#include <config.h>

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

static void e_day_view_layout_long_event (EDayViewEvent	  *event,
					  guint8	  *grid,
					  gint		   days_shown,
					  time_t	  *day_starts,
					  gint		  *rows_in_top_display);

static void e_day_view_layout_day_event (EDayViewEvent    *event,
					 guint8	          *grid,
					 guint16	  *group_starts,
					 gint8	          *cols_per_row,
					 gint	           rows,
					 gint	           mins_per_row);
static void e_day_view_expand_day_event (EDayViewEvent    *event,
					 guint8	          *grid,
					 gint8	          *cols_per_row,
					 gint	           mins_per_row);
static void e_day_view_recalc_cols_per_row (gint           rows,
					    gint8	  *cols_per_row,
					    guint16       *group_starts);


void
e_day_view_layout_long_events (GArray	   *events,
			       gint	   days_shown,
			       time_t	  *day_starts,
			       gint	   *rows_in_top_display)
{
	EDayViewEvent *event;
	gint event_num;
	guint8 *grid;

	/* 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, events->len * E_DAY_VIEW_MAX_DAYS);

	/* Reset the number of rows in the top display to 0. It will be
	   updated as events are layed out below. */
	*rows_in_top_display = 0;

	/* Iterate over the events, finding which days 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, EDayViewEvent, event_num);
		e_day_view_layout_long_event (event, grid,
					      days_shown, day_starts,
					      rows_in_top_display);
	}

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


static void
e_day_view_layout_long_event (EDayViewEvent *event,
			      guint8	   *grid,
			      gint	    days_shown,
			      time_t	   *day_starts,		
			      gint	   *rows_in_top_display)
{
	gint start_day, end_day, free_row, day, row;

	event->num_columns = 0;

	if (!e_day_view_find_long_event_days (event,
					      days_shown, day_starts,
					      &start_day, &end_day))
		return;

	/* Try each row until we find a free one. */
	row = 0;
	do {
		free_row = row;
		for (day = start_day; day <= end_day; day++) {
			if (grid[row * E_DAY_VIEW_MAX_DAYS + day]) {
				free_row = -1;
				break;
			}
		}
		row++;
	} while (free_row == -1);

	event->start_row_or_col = free_row;
	event->num_columns = 1;

	/* Mark the cells as full. */
	for (day = start_day; day <= end_day; day++) {
		grid[free_row * E_DAY_VIEW_MAX_DAYS + day] = 1;
	}

	/* Update the number of rows in the top canvas if necessary. */
	*rows_in_top_display = MAX (*rows_in_top_display, free_row + 1);
}


void
e_day_view_layout_day_events (GArray	   *events,
			      gint	    rows,
			      gint	    mins_per_row,
			      gint8	   *cols_per_row)
{
	EDayViewEvent *event;
	gint row, event_num;
	guint8 *grid;

	/* This is a temporary array which keeps track of rows which are
	   connected. When an appointment spans multiple rows then the number
	   of columns in each of these rows must be the same (i.e. the maximum
	   of all of them). Each element in the array corresponds to one row
	   and contains the index of the first row in the group of connected
	   rows. */
	guint16 group_starts[12 * 24];

	/* Reset the cols_per_row array, and initialize the connected rows so
	   that all rows are not connected - each row is the start of a new
	   group. */
	for (row = 0; row < rows; row++) {
		cols_per_row[row] = 0;
		group_starts[row] = row;
	}

	/* 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. */
	grid = g_new0 (guint8, rows * E_DAY_VIEW_MAX_COLUMNS);


	/* Iterate over the events, finding which rows they cover, and putting
	   them in the first free column available. Increment the number of
	   events in each of the rows it covers, and make sure they are all
	   in one group. */
	for (event_num = 0; event_num < events->len; event_num++) {
		event = &g_array_index (events, EDayViewEvent, event_num);

		e_day_view_layout_day_event (event, grid, group_starts,
					     cols_per_row, rows, mins_per_row);
	}

	/* Recalculate the number of columns needed in each row. */
	e_day_view_recalc_cols_per_row (rows, cols_per_row, group_starts);

	/* Iterate over the events again, trying to expand events horizontally
	   if there is enough space. */
	for (event_num = 0; event_num < events->len; event_num++) {
		event = &g_array_index (events, EDayViewEvent, event_num);
		e_day_view_expand_day_event (event, grid, cols_per_row,
					     mins_per_row);
	}

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


/* Finds the first free position to place the event in.
   Increments the number of events in each of the rows it covers, and makes
   sure they are all in one group. */
static void
e_day_view_layout_day_event (EDayViewEvent *event,
			     guint8	   *grid,
			     guint16	   *group_starts,
			     gint8	   *cols_per_row,
			     gint	    rows,
			     gint	    mins_per_row)
{
	gint start_row, end_row, free_col, col, row, group_start;

	start_row = event->start_minute / mins_per_row;
	end_row = (event->end_minute - 1) / mins_per_row;
	if (end_row < start_row)
		end_row = start_row;

	event->num_columns = 0;

	/* If the event can't currently be seen, just return. */
	if (start_row >= rows || end_row < 0)
		return;

	/* Make sure we don't go outside the visible times. */
	start_row = CLAMP (start_row, 0, rows - 1);
	end_row = CLAMP (end_row, 0, rows - 1);

	/* Try each column until we find a free one. */
	for (col = 0; col < E_DAY_VIEW_MAX_COLUMNS; col++) {
		free_col = col;
		for (row = start_row; row <= end_row; row++) {
			if (grid[row * E_DAY_VIEW_MAX_COLUMNS + col]) {
				free_col = -1;
				break;
			}
		}

		if (free_col != -1)
			break;
	}

	/* If we can't find space for the event, just return. */
	if (free_col == -1)
		return;

	/* The event is assigned 1 col initially, but may be expanded later. */
	event->start_row_or_col = free_col;
	event->num_columns = 1;

	/* Determine the start index of the group. */
	group_start = group_starts[start_row];

	/* Increment number of events in each of the rows the event covers.
	   We use the cols_per_row array for this. It will be sorted out after
	   all the events have been layed out. Also make sure all the rows that
	   the event covers are in one group. */
	for (row = start_row; row <= end_row; row++) {
		grid[row * E_DAY_VIEW_MAX_COLUMNS + free_col] = 1;
		cols_per_row[row]++;
		group_starts[row] = group_start;
	}

	/* If any following rows should be in the same group, add them. */
	for (row = end_row + 1; row < rows; row++) {
		if (group_starts[row] > end_row)
			break;
		group_starts[row] = group_start;
	}
}


/* For each group of rows, find the max number of events in all the
   rows, and set the number of cols in each of the rows to that. */
static void
e_day_view_recalc_cols_per_row (gint      rows,
				gint8	 *cols_per_row,
				guint16  *group_starts)
{
	gint start_row = 0, row, next_start_row, max_events;

	while (start_row < rows) {
		max_events = 0;
		for (row = start_row; row < rows && group_starts[row] == start_row; row++)
			max_events = MAX (max_events, cols_per_row[row]);

		next_start_row = row;

		for (row = start_row; row < next_start_row; row++)
			cols_per_row[row] = max_events;

		start_row = next_start_row;
	}
}


/* Expands the event horizontally to fill any free space. */
static void
e_day_view_expand_day_event (EDayViewEvent *event,
			     guint8	   *grid,
			     gint8	   *cols_per_row,
			     gint	    mins_per_row)
{
	gint start_row, end_row, col, row;
	gboolean clashed;

	start_row = event->start_minute / mins_per_row;
	end_row = (event->end_minute - 1) / mins_per_row;
	if (end_row < start_row)
		end_row = start_row;

	/* Try each column until we find a free one. */
	clashed = FALSE;
	for (col = event->start_row_or_col + 1; col < cols_per_row[start_row]; col++) {
		for (row = start_row; row <= end_row; row++) {
			if (grid[row * E_DAY_VIEW_MAX_COLUMNS + col]) {
				clashed = TRUE;
				break;
			}
		}

		if (clashed)
			break;

		event->num_columns++;
	}
}


/* Find the start and end days for the event. */
gboolean
e_day_view_find_long_event_days (EDayViewEvent	*event,
				 gint		 days_shown,
				 time_t		*day_starts,		
				 gint		*start_day_return,
				 gint		*end_day_return)
{
	gint day, start_day, end_day;

	start_day = -1;
	end_day = -1;

	for (day = 0; day < days_shown; day++) {
		if (start_day == -1
		    && event->start < day_starts[day + 1])
			start_day = day;
		if (event->end > day_starts[day])
			end_day = day;
	}

	/* Sanity check. */
	if (start_day < 0 || start_day >= days_shown
	    || end_day < 0 || end_day >= days_shown
	    || end_day < start_day) {
		g_warning ("Invalid date range for event");
		return FALSE;
	}

	*start_day_return = start_day;
	*end_day_return = end_day;

	return TRUE;
}