/* Copyright (C) 2018  Curtis McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <complex.h>
#include <err.h>
#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>

#include "gfx/gfx.h"

static double absSq(double complex z) {
    return creal(z) * creal(z) + cimag(z) * cimag(z);
}

static uint32_t depth = 50;

static uint32_t mandelbrot(double complex c) {
    double complex z = 0;
    for (uint32_t i = 0; i < depth; ++i) {
        if (absSq(z) > 4.0) return i;
        z = z * z + c;
    }
    return 0;
}

static uint32_t color(uint32_t n) {
    uint32_t gray = (double)n / (double)depth * 255.0;
    return gray << 16 | gray << 8 | gray;
}

static double complex translate = -0.75;
static double complex transform = 2.5;

void draw(uint32_t *buf, size_t width, size_t height) {
    double yRatio = (height > width) ? (double)height / (double)width : 1.0;
    double xRatio = (width > height) ? (double)width / (double)height : 1.0;
    for (size_t y = 0; y < height; ++y) {
        for (size_t x = 0; x < width; ++x) {
            double zx = ((double)x / (double)width - 0.5) * xRatio;
            double zy = ((double)y / (double)height - 0.5) * yRatio;
            uint32_t n = mandelbrot((zx + zy * I) * transform + translate);
            buf[y * width + x] = color(n);
        }
    }
}

static double translateStep = 1.0 / 128.0;
static double rotateStep = 1.0 / 128.0;
static double scaleStep = 1.0 / 32.0;

bool input(char in) {
    const double PI = acos(-1.0);
    switch (in) {
        case 'q': return false;
        break; case '.': depth++;
        break; case ',': if (depth) depth--;
        break; case 'l': translate += translateStep * transform;
        break; case 'h': translate -= translateStep * transform;
        break; case 'j': translate += translateStep * I * transform;
        break; case 'k': translate -= translateStep * I * transform;
        break; case 'u': transform *= cexp(rotateStep * PI * I);
        break; case 'i': transform /= cexp(rotateStep * PI * I);
        break; case '+': transform *= 1.0 - scaleStep;
        break; case '-': transform /= 1.0 - scaleStep;
    }
    return true;
}

const char *status(void) {
    static char buf[256];
    snprintf(
        buf, sizeof(buf),
        "brot -i %u -t %g%+gi -f %g%+gi",
        depth,
        creal(translate), cimag(translate),
        creal(transform), cimag(transform)
    );
    return buf;
}

static double complex parseComplex(const char *str) {
    double real = 0.0, imag = 0.0;
    real = strtod(str, (char **)&str);
    if (str[0] == 'i') {
        imag = real;
        real = 0.0;
    } else if (str[0]) {
        imag = strtod(str, NULL);
    }
    return real + imag * I;
}

int init(int argc, char *argv[]) {
    int opt;
    while (0 < (opt = getopt(argc, argv, "f:i:t:"))) {
        switch (opt) {
            case 'f': transform = parseComplex(optarg); break;
            case 'i': depth = strtoul(optarg, NULL, 0); break;
            case 't': translate = parseComplex(optarg); break;
            default: return EX_USAGE;
        }
    }
    return EX_OK;
}