#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <math.h>

#include <gsl/gsl_spline.h>

#include "pnm.h"

typedef struct {
	int n;
	short value[1];
} table_t;

static int
pam_transform(FILE *in_fp, FILE *out_fp,
	const struct pnm *in_pnm, table_t **tables);

static table_t*
buildCurve(const char *ctrl_points, int resolution);

#define RED 0x1
#define GREEN 0x2
#define BLUE 0x4

int
main(int argc, char **argv) {
	int c, i;
	char *curve = NULL;
	struct pnm in_pnm;
	int channels = 0;
	table_t *gTable[3];

	while ((c = getopt(argc, argv, "rgbC:h")) != EOF) {
		switch (c) {  
			case 'r':
				channels |= RED;
				break;
			case 'g':
				channels |= GREEN;
				break;
			case 'b':
				channels |= BLUE;
				break;
			case 'C':
				curve = optarg;
				break;

			default:
				break;
		}
	}

	if (readPnmHeader(stdin, &in_pnm) != 0) {
		exit(1);
	}

	if (in_pnm.maxval == 255) {
	} else if (in_pnm.maxval == 65535) {
	} else {
		fprintf(stderr, "unsupported PNM maxval %d\n", in_pnm.maxval);
		exit(1);
	}

	if (curve) {
		table_t *table;

		if (channels == 0) channels = RED | GREEN | BLUE;

		table = buildCurve(curve, 256);
	
		gTable[0] = channels & RED?table:NULL;	
		gTable[1] = channels & GREEN?table:NULL;	
		gTable[2] = channels & BLUE?table:NULL;	

	}

	writePnmHeader(stdout, &in_pnm);

	pam_transform(stdin, stdout, &in_pnm, gTable);

	return 0;
}

static int
pam_transform(FILE *in_fp, FILE *out_fp,
	const struct pnm *in_pnm, table_t **tables) {
	int row, col;
	int nbytes = in_pnm->maxval == 65535?2:1;
	char *buf = malloc(in_pnm->width * nbytes * 3);

	for (row = 0; row < in_pnm->height; row++) {
		fread(buf, in_pnm->width, nbytes * 3, in_fp);

		for (i = 0; i < in_pnm->width; i++) {
			for (c = 0; c < in_pnm->depth; c++) {
				if (tables[c]) {
					int val = (unsigned char) buf[(i * in_pnm->depth + c) * nbytes];	
					if (nbytes == 2) {
						val = (val << 8) |
							(uchar) buf[(i * in_pnm->depth + c) * nbytes + 1];
					}

					bud

				}
			}
		}

		fwrite(buf, in_pnm->width, nbytes * 3, out_fp);
	}

	free(buf);
	return 0;
}

#define MAX_CTRL 256

static table_t*
buildCurve(const char *ctrl_points, int resolution) {
	table_t *table;
	char *pstr, *buf = strdup(ctrl_points);
	int i, n = 0;
	double X[MAX_CTRL], Y[MAX_CTRL];
	gsl_interp_accel *acc;
	gsl_spline *spline;

	while (pstr = strsep(&buf, ",")) {
		if (n == MAX_CTRL) {
			fprintf(stderr, "Maximum number of control points (%d) reached.\n",
				MAX_CTRL);
			break;
		}

		if (sscanf(pstr, "%lf:%lf", &X[n], &Y[n]) != 2 ||
			X[n] < 0.0 || X[n] > 1.0 || Y[n] < 0.0 || Y[n] > 1.0) {
			fprintf(stderr, "Could not parse control point %s.\n", pstr);
			free(buf);
			return NULL;
		}

		n++;
	}

	free(buf);

	table = (table_t*) malloc(sizeof(table_t) + resolution * sizeof(short));
	table->n = resolution;

	acc = gsl_interp_accel_alloc();
	spline = gsl_spline_alloc(gsl_interp_cspline, n);
	gsl_spline_init (spline, X, Y, n);

	for (i = 0; i < resolution; i++) {
		double _x = (double) i / (resolution - 1);
		double _y = gsl_spline_eval(spline, _x, acc);
        double dval = _y * 65535.0 + .5;
        if (dval > 65535.) dval = 65535.0;
        if (dval < 0) dval = 0;

        table->value[i] = (short) floor(dval);
	}

	gsl_spline_free(spline);
	gsl_interp_accel_free(acc);
	
	return table;
}