/* vim: set sw=8: -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * gog-logfit.c :  
 *
 * Copyright (C) 2005 Jean Brefort (jean.brefort@normalesup.org)
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */

#include <goffice/goffice-config.h>
#include <goffice/app/module-plugin-defs.h>
#include "gog-logfit.h"
#include <goffice/data/go-data.h>
#include <goffice/graph/gog-series-impl.h>
#include <goffice/utils/go-math.h>
#include <goffice/utils/go-rangefunc.h>
#include <glib/gi18n-lib.h>

#include <gsf/gsf-impl-utils.h>

GOFFICE_PLUGIN_MODULE_HEADER;

static void
gog_log_fit_curve_update (GogObject *obj)
{
	GogRegCurve *rc = GOG_REG_CURVE (obj);
	GogSeries *series = GOG_SERIES (obj->parent);
	double const *y_vals, *x_vals = NULL;
	double *tx_vals, *ty_vals, x, y;
	int i, used, tmp, nb;
	double xmin, xmax;

	g_return_if_fail (gog_series_is_valid (GOG_SERIES (series)));

	y_vals = go_data_vector_get_values (
		GO_DATA_VECTOR (series->values[1].data));
	nb = go_data_vector_get_len (
		GO_DATA_VECTOR (series->values[1].data));
	if (series->values[0].data) {
		x_vals = go_data_vector_get_values (
			GO_DATA_VECTOR (series->values[0].data));
		tmp = go_data_vector_get_len (
			GO_DATA_VECTOR (series->values[0].data));
		if (nb > tmp)
			nb = tmp;
	}
	gog_reg_curve_get_bounds (rc, &xmin, &xmax);
	tx_vals = g_new (double, nb);
	ty_vals = g_new (double, nb);
	for (i = 0, used = 0; i < nb; i++) {
		x = (x_vals)? x_vals[i]: i;
		y = y_vals[i];
		if (!go_finite (x) || !go_finite (y)) {
			if (rc->skip_invalid)
				continue;
			used = 0;
			break;
		}
		if (x < xmin || x > xmax)
			continue;
		tx_vals[used] = x;
		ty_vals[used] = y;
		used++;
	}
	if (used > 4) {
		RegressionResult res = go_logarithmic_fit (tx_vals, ty_vals,
								used, rc->a);
		if (res == REG_ok) {
			go_range_devsq (ty_vals, used, &x);
			rc->R2 = (x - rc->a[4]) / x;
		} else for (nb = 0; nb < 5; nb++)
			rc->a[nb] = go_nan;
	} else {
		rc->R2 = go_nan;
		for (nb = 0; nb < 5; nb++)
			rc->a[nb] = go_nan;
	}
	g_free (tx_vals);
	g_free (ty_vals);
	if (rc->equation) {
		g_free (rc->equation);
		rc->equation = NULL;
	}
	gog_object_emit_changed (GOG_OBJECT (obj), FALSE);
}

static double
gog_log_fit_curve_get_value_at (GogRegCurve *curve, double x)
{
	return (curve->a[0] > 0.)?
		curve->a[1] + curve->a[2] * log (x - curve->a[3]):
		curve->a[1] + curve->a[2] * log (curve->a[3] - x);
}

static gchar const*
gog_log_fit_curve_get_equation (GogRegCurve *curve)
{
	if (!curve->equation) {
		if (curve->a[0] > 0.) {
			if (curve->a[2] > 0.)
				curve->equation = (curve->a[3] > 0.)?
					g_strdup_printf ("y = %g + %g * ln (x - %g)", curve->a[1], curve->a[2], curve->a[3]):
					g_strdup_printf ("y = %g + %g * ln (x + %g)", curve->a[1], curve->a[2], -curve->a[3]);
			else
				curve->equation = (curve->a[3] > 0.)?
					g_strdup_printf ("y = %g - %g * ln (x - %g)", curve->a[1], -curve->a[2], curve->a[3]):
					g_strdup_printf ("y = %g - %g * ln (x + %g)", curve->a[1], -curve->a[2], -curve->a[3]);
		} else {
			if (curve->a[2] > 0.)
				curve->equation = g_strdup_printf ("y = %g + %g * ln (%g - x)", curve->a[1], curve->a[2], curve->a[3]);
			else
				curve->equation = g_strdup_printf ("y = %g - %g * ln (%g - x)", curve->a[1], -curve->a[2], curve->a[3]);
		}
	}
	return curve->equation;
}

static char const *
gog_log_fit_curve_type_name (G_GNUC_UNUSED GogObject const *item)
{
	/* xgettext : the base for how to name scatter plot objects
	 * eg The 2nd plot in a chart will be called
	 * 	Log fit2 */
	return N_("Log fit");
}


static void
gog_log_fit_curve_class_init (GogRegCurveClass *reg_curve_klass)
{
	GogObjectClass *gog_object_klass = (GogObjectClass *) reg_curve_klass;

	gog_object_klass->update = gog_log_fit_curve_update;
	gog_object_klass->type_name	= gog_log_fit_curve_type_name;

	reg_curve_klass->get_value_at = gog_log_fit_curve_get_value_at;
	reg_curve_klass->get_equation = gog_log_fit_curve_get_equation;
}

static void
gog_log_fit_curve_init (GogRegCurve *model)
{
	int i;
	model->a = g_new (double, 5);
	model->R2 = go_nan;
	for (i = 0; i < 5; i++)
		model->a[i] = go_nan;
}

GSF_DYNAMIC_CLASS (GogLogFitCurve, gog_log_fit_curve,
	gog_log_fit_curve_class_init, gog_log_fit_curve_init,
	GOG_REG_CURVE_TYPE)

/* Plugin initialization */

G_MODULE_EXPORT void
go_plugin_init (GOPlugin *plugin, GOCmdContext *cc)
{
	GTypeModule *module = go_plugin_get_type_module (plugin);
	gog_log_fit_curve_register_type (module);
}

G_MODULE_EXPORT void
go_plugin_shutdown (GOPlugin *plugin, GOCmdContext *cc)
{
}