#include <sys/time.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <gd.h>
#include <gdfontl.h>

/*
  This code is only a C implementation (with some minor modifications) of this captcha generator :
  http://logz.org/captchaz/

  Copyright   November 2012    Grégory Soutadé
  Copyright   July 2007        Loz

  LICENCE : Copyleft, Licence Art Libre (http://artlibre.org/licence/lal)

  Modifications : 
  * Group letters 
  * Add another layer for letter rendering (more confusing)
  * Change start, not appropriate for big fonts
  * Change min/max font size

  You need libgd2-xpm-dev package

  It's recommanded the included font "scrawl.ttf"
 */

#define MAX(a, b) (((a) >= (b)) ? (a) : (b))

// If not defined
/* int overflow2(int a, int b) */
/* { */
/* 	if(a < 0 || b < 0) { */
/* 		fprintf(stderr, "gd warning: one parameter to a memory allocation multiplication is negative, failing operation gracefully\n"); */
/* 		return 1; */
/* 	} */
/* 	if(b == 0) */
/* 		return 0; */
/* 	if(a > 0xFFFFFFFF / b) { */
/* 		fprintf(stderr, "gd warning: product of memory allocation multiplication would exceed INT_MAX, failing operation gracefully\n"); */
/* 		return 1; */
/* 	} */
/* 	return 0; */
/* } */

static int my_rand(int min, int max)
{
    int val;
    struct timeval tv;
    static unsigned int seed = 0;
    int interval;

    if (seed == 0)
    {
        gettimeofday(&tv, NULL);
        seed = tv.tv_usec;
    }
    
    val = rand_r(&seed);
    
    if (min < 0)
    {
        if (max < 0)
            interval = -(min-max);
        else
            interval = max-min;
    }
    else
        interval = max-min;

    val = (int)(((double)val/(double)RAND_MAX)*(double)(interval));

    val += min;

    /* printf("rand [%d..%d] %d\n", min, max, val); */

    return val;
}

static inline int random_color(gdImagePtr im, int a, int b) {
    return gdImageColorAllocate(im, my_rand(a,b), my_rand(a,b), my_rand(a,b));
}

static int generate_captcha(int width, int height, int inverse, char* font, char* phrase, char* out)
{
    gdImagePtr im;
    int R, c1, c2;
    int wd, x, y, w1, w2, limit, n, p, r, g, b;
    int size, half, len;
    double rotation;
    char letter[2] = {0, 0};
    int brect[8];
    char* error;
    const double rad = 3.14/(double)180;

// initialize in-memory image with gd library
    im = gdImageCreateTrueColor(width, height);

    R = (inverse) ? 0xFF : 0x00;

    gdImageFilledRectangle(im, 0, 0, width, height, random_color(im, 222^R, 255^R));

    c1 = my_rand(150^R, 185^R);
    c2 = my_rand(195^R, 230^R);

// encolour bg
    wd=20; x=0;
    while (x < width)
    {
        gdImageFilledRectangle(im, x, 0, x+wd, height, random_color(im, 222^R, 255^R));
        x += wd;
        wd += MAX(10, my_rand(0, 20) - 10);
    }

    // make interesting background I, lines
    wd=4; w1=0; w2=0;
    for(x=0; x<width; x+=wd)
    {
        if (x < width)
            gdImageLine(im, x+w1, 0, x+w2, height-1, random_color(im, c1, c2));

        if (x < height)
            gdImageLine(im, 0, x-w2, width-1, x-w1, random_color(im, c1, c2));
        
        wd += my_rand(0, 8)-4;
        if (wd < 1) wd = 2;
        w1 += my_rand(0, 8)-4;
        w2 += my_rand(0, 8)-4;
        
        if ((x > height) && (x > height)) // ???
            break;
    }

    // more disturbing II, random letters
    limit = my_rand(30, 90);
    for(n=0; n<limit; n++)
    {
        letter[0] = my_rand(31, 125); // only one letter
        size = my_rand(5, height/2);
        half = size / 2;
        x = my_rand(-half, width+half);
        y = my_rand(half, height);
        rotation = my_rand(60, 300);
        c1 = random_color(im, 130^R, 240^R);
        error = gdImageStringFT(im, brect, c1, font, size, rotation, x, y, letter);
        if (error)
        {
            fprintf(stderr, "%s, font is %s\n", error, font);
            return 1;
        }
    }

    // add the real text to it
    len = strlen(phrase);
    w1 = 10;
    w2 = width / (height/4); // Change start, not appropriate for big fonts
    x = w2;

    for(p=0; p<len; p++)
    {
        letter[0] = phrase[p];
        size = my_rand(height/4, height/3); // Change min/max font size
        half = size / 2;
        rotation = (double)my_rand(-33, 33)*rad;
        y = my_rand(size+3, height-3);
        /* x = w1 + w2*p; */
        w1 += my_rand(-width/90, width/40);
        r = my_rand(30, 99) ; g = my_rand(30, 99) ; b = my_rand(30, 99);
        c1 = gdImageColorAllocate(im, r*1^R, g*1^R, b*1^R);
        c2 = gdImageColorAllocate(im, r*2^R, g*2^R, b*2^R);
        gdImageStringFT(im, brect, c2, font, size, rotation, x+1, y, letter);
        gdImageStringFT(im, brect, c1, font, size, rotation, x, y-1, letter);
        // Add another layer
        gdImageStringFT(im, brect, c1, font, size, rotation, x+2, y+2, letter);
        // Group letters
        x += size;
    }

    FILE* f= fopen(out, "wb");
    
    if (!f)
    {
        fprintf(stderr, "Error opening %s\n", out);
        return 1;
    }

    gdImagePng(im, f);
    fclose(f);

    gdImageDestroy(im);

    return 0;
}

static void usage()
{
    printf("gcpatchaz is a command line captcha generator\n\n");
    printf("usage : gcpatchaz [options]\n");
    printf("\t-w WIDTH\n");
    printf("\t-h HEIGHT\n");
    printf("\t-o OUT.PNG\n");
    printf("\t-f FONT\n");
    printf("\t-s STRING\n");    
    printf("\t-i : inverse\n");    
    printf("\t-h : help\n");
}

int main(int argc, char** argv)
{
    int opt;
    int width=180, height=40;
    char* out = "captcha.png", *font = "ttf-japanese-gothic.ttf", *string = NULL;
    int inverse= 0;
    int i, res;

    while ((opt = getopt(argc, argv, "w:H:o:f:s:ih")) != -1)
    {
        switch(opt)
        {
        case 'w': width = atoi(optarg); break;
        case 'H': height = atoi(optarg); break;
        case 'o': out = optarg; break;
        case 'f': font = optarg; break;
        case 's': string = strdup(optarg); break;
        case 'i': inverse = 1; break;
        case 'h':
            usage();
            return 0;
        default:
            usage();
            return 1;
        }
    }

    if (string == NULL)
    {
        string = malloc(6);
        for(i=0; i<5; i++)
        {
            string[i] = my_rand(65, 90);
        }
        string[i] = 0;
    }

    res = generate_captcha(width, height, inverse, font, string, out);

    if (res == 0)
        printf("Captcha generated for text \"%s\"\n", string);

    free(string);

    return 0;
}