#include "const.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

Chunk *chunks = NULL;
int lastI = 0;
int seed = 69420;
int prevExists = 0;
double interpolate(double a0, double a1, double w) {
  return (a1 - a0) * (3.0 - w * 2.0) * w * w + a0;
}

int hash_combine(int a, int b) { return b + 0x9e3779b9 + (a << 6) + (a >> 2); }

Vertex2 perlin_grad(int x, int y) {
  int x_hash = hash_combine(x, seed);
  int y_hash = hash_combine(seed, y);

  double random = hash_combine(x_hash, y_hash) * (M_PI / ~(~0u >> 1));
  Vertex2 out = {cos(random), sin(random)};
  return out;
}

double perlin_dot(double ix, double iy, double x, double y) {
  Vertex2 grad = perlin_grad(ix, iy);

  double dx = x - (double)ix;
  double dy = y - (double)iy;
  return (dx * grad.pos[0] + dy * grad.pos[1]);
}

double perlin_calc(double x, double y, double s) {
  x /= s;
  y /= s;

  int x0 = (int)floor(x);
  int x1 = x0 + 1;
  int y0 = (int)floor(y);
  int y1 = y0 + 1;

  float sx = x - (float)x0;
  float sy = y - (float)y0;

  float n0, n1, ix0, ix1, value;

  n0 = perlin_dot(x0, y0, x, y);
  n1 = perlin_dot(x1, y0, x, y);
  ix0 = interpolate(n0, n1, sx);

  n0 = perlin_dot(x0, y1, x, y);
  n1 = perlin_dot(x1, y1, x, y);
  ix1 = interpolate(n0, n1, sx);

  value = interpolate(ix0, ix1, sy);

  return value;
}

Chunk fetch_chunk(int x, int y, int z, int ci, int h, int r_order) {

  Chunk *chunks2 = chunks; // &chunks[CBUF_ALL * ci];

  Chunk chunk;

  if (x < 0 || y < 0 || z < 0) {
    chunk.exists = 0;
    return chunk;
  }

  int cbuf2 = CHUNK_ALL; // CBUF_ALL * (CHUNK_DIAMETER_H + (MAX_R * 2));

  int i, j;
  int r = (h == 0);

  h = h * 16;

  for (j = 0; j < (r ? 16 : 1) && h; j++) {
    i = (j + h + cbuf2) % cbuf2;
    chunk = chunks2[i];
    if (chunk.x == x && chunk.y == y && chunk.z == z && chunk.exists != 0) {

      chunk.exists = i / 16;
      if (chunk.exists == 0)
        chunk.exists = 1;
      return chunk;
    }
  }

  // printf("fail\n");
  for (j = 0; j < cbuf2; j += 16) {
    i = (j + h + cbuf2) % cbuf2;
    chunk = chunks2[i];
    if (chunk.exists == 0) {
      break;
    }
  }

  char fname[1024];
  snprintf(fname, 1023, "./db/chunk_%i_%i_%i.dat", x, y, z);

  FILE *fp = fopen(fname, "rb+");

  int code = (fp) ? fread(&chunk, sizeof(Chunk), 1, fp) : 0;
  if (code != 0) {
    fclose(fp);
    fp = 0;
    if (chunk.exists != 0) {
      chunk.exists = i / 16;
      if (chunk.exists == 0)
        chunk.exists = 1;
      return chunk;
    }
  }
  if (!fp) {
    fp = fopen(fname, "wb");
  }

  lastI = i;

  chunk.exists = i / 16;
  if (chunk.exists == 0)
    chunk.exists = 1;
  chunk.x = x;
  chunk.y = y;
  chunk.z = z;

  int c = 0;

  for (int x2 = 0; x2 < CHUNK_LENGTH; x2++) {
    int x3 = x2 + x * CHUNK_LENGTH;
    for (int z2 = 0; z2 < CHUNK_LENGTH; z2++) {
      int z3 = z2 + z * CHUNK_LENGTH;
      double hp = perlin_calc(x3, z3, 128.0);
      hp = ((hp > 0.0) ? -1.0 : 1.0) * (pow(fabs(hp), 0.7));
      hp *= 32.0;
      int h = hp + 32;

      for (int y2 = 0; y2 < CHUNK_LENGTH; y2++) {
        int y3 = y2 + y * CHUNK_LENGTH;
        chunk.blocks[c] = (y3 < h) ? (((int)((hp + 64.0) * 2.98) % 3) + 1) : 0;
        c++;
      }
    }
  }

  chunks2[i] = chunk;

  if (!fp) {
    return chunk;
  }

  fwrite(&chunk, sizeof(Chunk), 1, fp);
  fclose(fp);

  return chunk;
}

void purge_chunks(int ci) {
  /*
  free(chunks);
  chunks = calloc(CBUF_ALL, sizeof(Chunk));
  */
  if (chunks == NULL) {
    chunks = calloc(CHUNK_ALL, sizeof(Chunk));
  }
  // memset(chunks, 0, sizeof(Chunk) *CHUNK_ALL);
}

int cube_exists(int x, int y, int z, Chunk dat, int ci, int r_order) {
  if (x < 0 || y < 0 || z < 0)
    return 0;

  if (dat.exists == 0 || dat.x != (x / CHUNK_LENGTH) ||
      dat.y != (y / CHUNK_LENGTH) || dat.z != (z / CHUNK_LENGTH)) {
    dat = fetch_chunk((x / CHUNK_LENGTH), (y / CHUNK_LENGTH),
                      (z / CHUNK_LENGTH), ci, dat.exists, r_order);
    prevExists = dat.exists;
  }

  int h = dat.blocks[(y % CHUNK_LENGTH) + (z % CHUNK_LENGTH) * CHUNK_LENGTH +
                     (x % CHUNK_LENGTH) * CHUNK_LENGTH * CHUNK_LENGTH];

  return h;
}