/* im_linreg.c
 *
 * Copyright: 2006, The Nottingham Trent University
 *
 * Author: Tom Vajzovic
 *
 * Written on: 2006-12-26
 *
 * 12/5/09
 *	- make x_anal() static, fix some signed/unsigned warnings
 * 3/9/09
 * 	- gtkdoc comment
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	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 Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /* HAVE_CONFIG_H */
#include <glib/gi18n-lib.h>

#include <stdlib.h>
#include <math.h>
#include <vips/vips.h>
#include <vips/vips7compat.h>

typedef struct {

	unsigned int n;
	double *xs;
	double *difs;
	double mean;
	double nsig2;
	double err_term;

} x_set;

#define LINREG_SEQ(TYPE) \
	typedef struct { \
		REGION **regs; \
		TYPE **ptrs; \
		size_t *skips; \
	} linreg_seq_##TYPE

LINREG_SEQ(gint8);
LINREG_SEQ(guint8);
LINREG_SEQ(gint16);
LINREG_SEQ(guint16);
LINREG_SEQ(gint32);
LINREG_SEQ(guint32);
LINREG_SEQ(float);
LINREG_SEQ(double);

static x_set *x_anal(IMAGE *im, double *xs, unsigned int n);

#define LINREG_START_DECL(TYPE) static void *linreg_start_##TYPE(IMAGE *, void *, void *);
#define LINREG_GEN_DECL(TYPE) static int linreg_gen_##TYPE(REGION *, void *, void *, void *);
#define LINREG_STOP_DECL(TYPE) static int linreg_stop_##TYPE(void *, void *, void *);
#define INCR_ALL_DECL(TYPE) static void incr_all_##TYPE(TYPE **ptrs, unsigned int n)
#define SKIP_ALL_DECL(TYPE) static void skip_all_##TYPE(TYPE **ptrs, size_t *skips, unsigned int n)

LINREG_START_DECL(gint8);
LINREG_START_DECL(guint8);
LINREG_START_DECL(gint16);
LINREG_START_DECL(guint16);
LINREG_START_DECL(gint32);
LINREG_START_DECL(guint32);
LINREG_START_DECL(float);
LINREG_START_DECL(double);

LINREG_GEN_DECL(gint8);
LINREG_GEN_DECL(guint8);
LINREG_GEN_DECL(gint16);
LINREG_GEN_DECL(guint16);
LINREG_GEN_DECL(gint32);
LINREG_GEN_DECL(guint32);
LINREG_GEN_DECL(float);
LINREG_GEN_DECL(double);

LINREG_STOP_DECL(gint8);
LINREG_STOP_DECL(guint8);
LINREG_STOP_DECL(gint16);
LINREG_STOP_DECL(guint16);
LINREG_STOP_DECL(gint32);
LINREG_STOP_DECL(guint32);
LINREG_STOP_DECL(float);
LINREG_STOP_DECL(double);

INCR_ALL_DECL(gint8);
INCR_ALL_DECL(guint8);
INCR_ALL_DECL(gint16);
INCR_ALL_DECL(guint16);
INCR_ALL_DECL(gint32);
INCR_ALL_DECL(guint32);
INCR_ALL_DECL(float);
INCR_ALL_DECL(double);

SKIP_ALL_DECL(gint8);
SKIP_ALL_DECL(guint8);
SKIP_ALL_DECL(gint16);
SKIP_ALL_DECL(guint16);
SKIP_ALL_DECL(gint32);
SKIP_ALL_DECL(guint32);
SKIP_ALL_DECL(float);
SKIP_ALL_DECL(double);

/**
 * im_linreg:
 * @ins: NULL-terminated array of input images
 * @out: results of analysis
 * @xs:	X position of each image (pixel value is Y)
 *
 * Function to find perform pixelwise linear regression on an array of
 * single band images. The output is a seven-band douuble image
 *
 * TODO: figure out how this works and fix up these docs!
 */
int
im_linreg(IMAGE **ins, IMAGE *out, double *xs)
{
#define FUNCTION_NAME "im_linreg"
	int n;
	x_set *x_vals;

	if (im_poutcheck(out))
		return -1;

	for (n = 0; ins[n]; ++n) {
		/*
			if (!isfinite(xs[n])) {
			  im_error(FUNCTION_NAME, "invalid argument");
			  return -1;
			}
		*/
		if (im_pincheck(ins[n]))
			return -1;

		if (1 != ins[n]->Bands) {
			im_error(FUNCTION_NAME, "image is not single band");
			return -1;
		}
		if (ins[n]->Coding) {
			im_error(FUNCTION_NAME, "image is not uncoded");
			return -1;
		}
		if (n) {
			if (ins[n]->BandFmt != ins[0]->BandFmt) {
				im_error(FUNCTION_NAME, "image band formats differ");
				return -1;
			}
		}
		else {
			if (vips_band_format_iscomplex(ins[0]->BandFmt)) {
				im_error(FUNCTION_NAME, "image has non-scalar band format");
				return -1;
			}
		}
		if (n &&
			(ins[n]->Xsize != ins[0]->Xsize ||
				ins[n]->Ysize != ins[0]->Ysize)) {
			im_error(FUNCTION_NAME, "image sizes differ");
			return -1;
		}
	}
	if (n < 3) {
		im_error(FUNCTION_NAME, "not enough input images");
		return -1;
	}
	if (im_cp_desc_array(out, ins))
		return -1;

	out->Bands = 7;
	out->BandFmt = IM_BANDFMT_DOUBLE;
	out->Type = 0;

	if (im_demand_hint_array(out, IM_THINSTRIP, ins))
		return -1;

	x_vals = x_anal(out, xs, n);

	if (!x_vals)
		return -1;

	switch (ins[0]->BandFmt) {
#define LINREG_RET(TYPE) return im_generate(out, linreg_start_##TYPE, linreg_gen_##TYPE, linreg_stop_##TYPE, ins, x_vals)

	case IM_BANDFMT_CHAR:
		LINREG_RET(gint8);

	case IM_BANDFMT_UCHAR:
		LINREG_RET(guint8);

	case IM_BANDFMT_SHORT:
		LINREG_RET(gint16);

	case IM_BANDFMT_USHORT:
		LINREG_RET(guint16);

	case IM_BANDFMT_INT:
		LINREG_RET(gint32);

	case IM_BANDFMT_UINT:
		LINREG_RET(guint32);

	case IM_BANDFMT_FLOAT:
		LINREG_RET(float);

	case IM_BANDFMT_DOUBLE:
		LINREG_RET(double);

	default: /* keep -Wall happy */
		return -1;
	}
#undef FUNCTION_NAME
}

static x_set *
x_anal(IMAGE *im, double *xs, unsigned int n)
{
	unsigned int i;

	x_set *x_vals = IM_NEW(im, x_set);

	if (!x_vals)
		return NULL;

	x_vals->xs = IM_ARRAY(im, 2 * n, double);

	if (!x_vals->xs)
		return NULL;

	x_vals->difs = x_vals->xs + n;
	x_vals->n = n;
	x_vals->mean = 0.0;

	for (i = 0; i < n; ++i) {
		x_vals->xs[i] = xs[i];
		x_vals->mean += xs[i];
	}
	x_vals->mean /= n;
	x_vals->nsig2 = 0.0;

	for (i = 0; i < n; ++i) {
		x_vals->difs[i] = xs[i] - x_vals->mean;
		x_vals->nsig2 += x_vals->difs[i] * x_vals->difs[i];
	}
	x_vals->err_term = (1.0 / (double) n) + ((x_vals->mean * x_vals->mean) / x_vals->nsig2);

	return x_vals;
}

#define LINREG_START_DEFN(TYPE) \
	static void *linreg_start_##TYPE(IMAGE *out, void *a, void *b) \
	{ \
		IMAGE **ins = (IMAGE **) a; \
		x_set *x_vals = (x_set *) b; \
		linreg_seq_##TYPE *seq = IM_NEW(out, linreg_seq_##TYPE); \
\
		if (!seq) \
			return NULL; \
\
		seq->regs = im_start_many(NULL, ins, NULL); \
		seq->ptrs = IM_ARRAY(out, x_vals->n, TYPE *); \
		seq->skips = IM_ARRAY(out, x_vals->n, size_t); \
\
		if (!seq->ptrs || !seq->regs || !seq->skips) { \
			linreg_stop_##TYPE(seq, NULL, NULL); \
			return NULL; \
		} \
		return (void *) seq; \
	}

#define N ((double) n)
#define y(a) ((double) (*seq->ptrs[(a)]))
#define x(a) ((double) (x_vals->xs[(a)]))
#define xd(a) ((double) (x_vals->difs[(a)]))
#define Sxd2 (x_vals->nsig2)
#define mean_x (x_vals->mean)
#define mean_y (out[0])
#define dev_y (out[1])
#define y_x0 (out[2])
#define d_y_x0 (out[3])
#define dy_dx (out[4])
#define d_dy_dx (out[5])
#define R (out[6])

#define LINREG_GEN_DEFN(TYPE) \
	static int linreg_gen_##TYPE(REGION *to_make, void *vseq, void *unrequired, void *b) \
	{ \
		linreg_seq_##TYPE *seq = (linreg_seq_##TYPE *) vseq; \
		x_set *x_vals = (x_set *) b; \
		unsigned int n = x_vals->n; \
		double *out = (double *) IM_REGION_ADDR_TOPLEFT(to_make); \
		size_t out_skip = IM_REGION_LSKIP(to_make) / sizeof(double); \
		double *out_end = out + out_skip * to_make->valid.height; \
		double *out_stop; \
		size_t out_n = IM_REGION_N_ELEMENTS(to_make); \
		unsigned int i; \
\
		out_skip -= out_n; \
\
		if (im_prepare_many(seq->regs, &to_make->valid)) \
			return -1; \
\
		for (i = 0; i < n; ++i) { \
			seq->ptrs[i] = (TYPE *) IM_REGION_ADDR(seq->regs[i], to_make->valid.left, to_make->valid.top); \
			seq->skips[i] = (IM_REGION_LSKIP(seq->regs[i]) / sizeof(TYPE)) - IM_REGION_N_ELEMENTS(seq->regs[i]); \
		} \
\
		for (; out < out_end; out += out_skip, skip_all_##TYPE(seq->ptrs, seq->skips, n)) \
			for (out_stop = out + out_n; out < out_stop; out += 7, incr_all_##TYPE(seq->ptrs, n)) { \
				double Sy = 0.0; \
				double Sxd_y = 0.0; \
				double Syd2 = 0.0; \
				double Sxd_yd = 0.0; \
				double Se2 = 0.0; \
\
				for (i = 0; i < n; ++i) { \
					Sy += y(i); \
					Sxd_y += xd(i) * y(i); \
				} \
				mean_y = Sy / N; \
				dy_dx = Sxd_y / Sxd2; \
				y_x0 = mean_y - dy_dx * mean_x; \
\
				for (i = 0; i < n; ++i) { \
					double yd = y(i) - mean_y; \
					double e = y(i) - dy_dx * x(i) - y_x0; \
					Syd2 += yd * yd; \
					Sxd_yd += xd(i) * yd; \
					Se2 += e * e; \
				} \
				dev_y = sqrt(Syd2 / N); \
				Se2 /= (N - 2.0); \
				d_dy_dx = sqrt(Se2 / Sxd2); \
				d_y_x0 = sqrt(Se2 * x_vals->err_term); \
				R = Sxd_yd / sqrt(Sxd2 * Syd2); \
			} \
		return 0; \
	}

#define LINREG_STOP_DEFN(TYPE) \
	static int linreg_stop_##TYPE(void *vseq, void *a, void *b) \
	{ \
		linreg_seq_##TYPE *seq = (linreg_seq_##TYPE *) vseq; \
		if (seq->regs) \
			im_stop_many(seq->regs, NULL, NULL); \
		return 0; \
	}

#define INCR_ALL_DEFN(TYPE) \
	static void incr_all_##TYPE(TYPE **ptrs, unsigned int n) \
	{ \
		TYPE **stop = ptrs + n; \
		for (; ptrs < stop; ++ptrs) \
			++*ptrs; \
	}

#define SKIP_ALL_DEFN(TYPE) \
	static void skip_all_##TYPE(TYPE **ptrs, size_t *skips, unsigned int n) \
	{ \
		TYPE **stop = ptrs + n; \
		for (; ptrs < stop; ++ptrs, ++skips) \
			*ptrs += *skips; \
	}

LINREG_START_DEFN(gint8);
LINREG_START_DEFN(guint8);
LINREG_START_DEFN(gint16);
LINREG_START_DEFN(guint16);
LINREG_START_DEFN(gint32);
LINREG_START_DEFN(guint32);
LINREG_START_DEFN(float);
LINREG_START_DEFN(double);

LINREG_GEN_DEFN(gint8);
LINREG_GEN_DEFN(guint8);
LINREG_GEN_DEFN(gint16);
LINREG_GEN_DEFN(guint16);
LINREG_GEN_DEFN(gint32);
LINREG_GEN_DEFN(guint32);
LINREG_GEN_DEFN(float);
LINREG_GEN_DEFN(double);

LINREG_STOP_DEFN(gint8);
LINREG_STOP_DEFN(guint8);
LINREG_STOP_DEFN(gint16);
LINREG_STOP_DEFN(guint16);
LINREG_STOP_DEFN(gint32);
LINREG_STOP_DEFN(guint32);
LINREG_STOP_DEFN(float);
LINREG_STOP_DEFN(double);

INCR_ALL_DEFN(gint8);
INCR_ALL_DEFN(guint8);
INCR_ALL_DEFN(gint16);
INCR_ALL_DEFN(guint16);
INCR_ALL_DEFN(gint32);
INCR_ALL_DEFN(guint32);
INCR_ALL_DEFN(float);
INCR_ALL_DEFN(double);

SKIP_ALL_DEFN(gint8);
SKIP_ALL_DEFN(guint8);
SKIP_ALL_DEFN(gint16);
SKIP_ALL_DEFN(guint16);
SKIP_ALL_DEFN(gint32);
SKIP_ALL_DEFN(guint32);
SKIP_ALL_DEFN(float);
SKIP_ALL_DEFN(double);
