#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#define ASCII_ZERO 48
#define ASCII_NINE 57
#define MIN_CONTRAST 0.5
    //html = _dec_colors.sub(lambda match: _dec_spans[int(match.group(1))], qstr)
    // this is an extremely fancy if not confusing way to say
    // the single number that isn't an x, right after a ^
    // is an index to an array of strings.
    //html = _hex_colors.sub(hex_repl, html)
    // the next 3 letters after after ^x is digits for rgb
    // the verdict is:
    // regex is not needed
    // do the hex replacement first, then do the dec replacement

    // instead of concatenating strings, they will be printed in parts.

// can either be RGB or HLS
struct Rgb {
    int r, g, b;
};

struct Hls {
    int h;
    float l, s;
};

void cvt_rgb(struct Rgb *dest, const struct Hls const *src) {
    if ((0 > src -> h || src -> h > 360) || 
       (0 > src -> s && src -> s > 1) ||
       (0 > src -> l && src -> l > 1)) {
        return;
    }
    float hue = src -> h;
    float r, g, b;
    float chroma = (1 - fabs(2 * (src -> l) - 1)) * (src -> s);
    float x = chroma * (1 - fabs((int)(hue/60) % 2 - 1));
    float m = (src -> l) - chroma/2;
    if (0 <= hue && hue < 60) {
        r = chroma;
        g = x;
        b = 0;
    } else if (60 <= hue && hue < 120) {
        r = x;
        g = chroma;
        b = 0;
    } else if (120 <= hue && hue < 180) {
        r = 0;
        g = chroma;
        b = x;
    } else if (180 <= hue && hue < 240) {
        r = 0;
        g = x;
        b = chroma;
    } else if (240 <= hue && hue < 300) {
        r = x;
        g = 0;
        b = chroma;
    } else if (300 <= hue && hue < 360) {
        r = chroma;
        g = 0;
        b = x;
    } else {
        r = 0;
        g = 0;
        b = 0;
    }
    dest -> r = (r + m) * 255;
    dest -> g = (g + m) * 255;
    dest -> b = (b + m) * 255;
}

void cvt_hls(struct Hls *dest, const struct Rgb const *src) {
    if (src == NULL || dest == NULL) {
        return;
    }
    float r = src -> r / 255.0f;
    float g = src -> g / 255.0f;
    float b = src -> b / 255.0f;
    float min = fmin(fmin(r, g), b);
    float max = fmax(fmax(r, g), b);
    dest -> l = (max + min)/2; //bi-hexcone model.
    if (max == min) { // neutral color.
        dest -> h = 0; // undefined.
        dest -> s = 0.0f;
    } else {
        float chroma = max - min;
        dest -> s = (dest -> l > 0.5) ? (chroma/(2 - max - min)) : (chroma/(max + min));
        //piecewise function..
        float hue;
        if (max == r) {
            hue = (int)((g - b)/chroma) + (g < b ? 6 : 0); // % 6 will break magenta (255, 0, 255)
        } else if (max == g) {
            hue = ((b - r)/chroma) + 2.0f;
        } else {
            hue = ((r - g)/chroma) + 4.0f;
        }
        dest -> h = (int)(hue * 60);
    }
}

void dec(const int d) {
    switch(d) {
        case 0:
            printf("<span style='color:rgb(128,128,128)'>");
            break;
        case 1:
            printf("<span style='color:rgb(255,0,0)'>");
            break;
        case 2:
            printf("<span style='color:rgb(51,255,0)'>");
            break;
        case 3:
            printf("<span style='color:rgb(255,255,0)'>");
            break;
        case 4:
            printf("<span style='color:rgb(51,102,255)'>");
            break;
        case 5:
            printf("<span style='color:rgb(51,255,255)'>");
            break;
        case 6:
            printf("<span style='color:rgb(255,51,102)'>");
            break;
        case 7:
            printf("<span style='color:rgb(255,255,255)'>");
            break;
        case 8:
            printf("<span style='color:rgb(153,153,153)'>");
            break;
        case 9:
            printf("<span style='color:rgb(128,128,128)'>");
            break;
    }
}

void hex(const char *str) {
    const char h1[2] = {str[0], '\0'};
    const char h2[2] = {str[1], '\0'};
    const char h3[2] = {str[2], '\0'};
    struct Rgb nrgb;
    nrgb.r = strtol(h1, NULL, 16);
    nrgb.g = strtol(h2, NULL, 16);
    nrgb.b = strtol(h3, NULL, 16);
    struct Hls nhls;
    cvt_hls(&nhls, &nrgb);
    if (nhls.l < MIN_CONTRAST) {
        nhls.l = MIN_CONTRAST;
        cvt_rgb(&nrgb, &nhls);
    }
    printf("<span style=\"color:rgb(%d,%d,%d)\">", nrgb.r, nrgb.g, nrgb.b);
}

void b(char * const str) {
#define IS_DIGIT(x) (x >= ASCII_ZERO && x <= ASCII_NINE)
    char *token = strtok(str, "^");
    char c;
    while (token) {
        c = token[0];
        if (IS_DIGIT(c)) {
            dec(c - ASCII_ZERO);
            printf("%s", token + 1);
        } else if (c == 'x' && strlen(token) > 4) {
            hex(token + 1); //exclude x
            printf("%s", token + 4);
        } else {
            printf("%s", token);
        }
        token = strtok(NULL, "^");
    }
    printf("</span>");
}

// O(n)
void a(const char* str) {
    //find instance of ^^
    //replace with ^
    //concatenate with rest of the string
    char *copy;
    copy = calloc(strlen(str) + 1, sizeof(char));
    strcpy(copy, str);
    char *pos = copy;
    while (pos = strstr(pos, "^^")) {
        strcpy(pos, (pos + 1));
    }
    b(copy);
    free(copy);
}

void testconversion(int r, int g, int b) {
    struct Rgb x;
    x.r = r;
    x.g = g;
    x.b = b;
    struct Hls y;
    cvt_hls(&y, &x);
    printf("%d %f %f\n", y.h, y.s, y.l);
}

void testconvhls(int h, float s, float l) {
    struct Hls x;
    x.h = h;
    x.s = s;
    x.l = l;
    struct Rgb y;
    cvt_rgb(&y, &x);
    printf("%d %d %d\n", y.r, y.g, y.b);
}

int main() {
/*     a("^xf00Unregistered Player^7");
    a("^9[^1S^9]^x469Kom^0ier^7");
    a("^9sjn^5|^9F^5e^9tus^7");
    a("^0[^7>>^0]^xaefdizzy^7"); */
/*     testconversion(10, 15, 12);
    testconversion(5, 5, 5);
    testconversion(3, 15, 10);
    testconversion(7, 8, 9);
    testconvhls(144, 0.20, 0.5);
    testconvhls(0, 0, 0.2);
    testconvhls(154, 0.67, 0.035);
    testconvhls(210, 0.125, 0.03);
    testconvhls(60, 1, 0.25);
    testconvhls(180, 1, 0.25);
    testconvhls(240, 1, 0.25); */
    testconversion(0, 0, 0);
    testconversion(255, 255, 255);
    testconversion(255, 0, 0);
    testconversion(0, 255, 0);
    testconversion(0, 0, 255);
    testconversion(255, 255, 0);
    testconversion(0, 255, 255);
    testconversion(255, 0, 255);
    testconversion(192, 192, 192);
    testconversion(128, 128, 128);
    testconversion(128, 0, 0);
    testconversion(128, 128, 0);
    testconversion(0, 128, 0);
    testconversion(128, 0, 128);
    testconversion(128, 0, 128);
    testconversion(0, 128, 128);
    testconversion(0, 0, 128);
}