// Copyright 2012-2019 David Robillard <d@drobilla.net>
// SPDX-License-Identifier: ISC

#ifndef EXAMPLES_DEMO_UTILS_H
#define EXAMPLES_DEMO_UTILS_H

#include <pugl/pugl.h>

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

typedef struct {
  double lastReportTime;
} PuglFpsPrinter;

typedef float vec4[4];
typedef vec4  mat4[4];

static inline void
mat4Identity(mat4 m)
{
  for (int c = 0; c < 4; ++c) {
    for (int r = 0; r < 4; ++r) {
      m[c][r] = c == r ? 1.0f : 0.0f;
    }
  }
}

static inline void
mat4Translate(mat4 m, const float x, const float y, const float z)
{
  m[3][0] = x;
  m[3][1] = y;
  m[3][2] = z;
}

static inline void
mat4Mul(mat4 m, mat4 a, mat4 b)
{
  for (int c = 0; c < 4; ++c) {
    for (int r = 0; r < 4; ++r) {
      m[c][r] = 0.0f;
      for (int k = 0; k < 4; ++k) {
        m[c][r] += a[k][r] * b[c][k];
      }
    }
  }
}

static inline void
mat4Ortho(mat4        m,
          const float l,
          const float r,
          const float b,
          const float t,
          const float n,
          const float f)
{
  m[0][0] = 2.0f / (r - l);
  m[0][1] = m[0][2] = m[0][3] = 0.0f;

  m[1][1] = 2.0f / (t - b);
  m[1][0] = m[1][2] = m[1][3] = 0.0f;

  m[2][2] = -2.0f / (f - n);
  m[2][0] = m[2][1] = m[2][3] = 0.0f;

  m[3][0] = -(r + l) / (r - l);
  m[3][1] = -(t + b) / (t - b);
  m[3][2] = -(f + n) / (f - n);
  m[3][3] = 1.0f;
}

/// Calculate a projection matrix for a given perspective
static inline void
perspective(float* m, float fov, float aspect, float zNear, float zFar)
{
  const float h     = tanf(fov);
  const float w     = h / aspect;
  const float depth = zNear - zFar;
  const float q     = (zFar + zNear) / depth;
  const float qn    = 2 * zFar * zNear / depth;

  // clang-format off
  m[0]  = w;  m[1]  = 0;  m[2]  = 0;   m[3]  = 0;
  m[4]  = 0;  m[5]  = h;  m[6]  = 0;   m[7]  = 0;
  m[8]  = 0;  m[9]  = 0;  m[10] = q;   m[11] = -1;
  m[12] = 0;  m[13] = 0;  m[14] = qn;  m[15] = 0;
  // clang-format on
}

static inline void
puglPrintFps(const PuglWorld* world,
             PuglFpsPrinter*  printer,
             unsigned* const  framesDrawn)
{
  const double thisTime = puglGetTime(world);
  if (thisTime > printer->lastReportTime + 5.0) {
    const double elapsed = (thisTime - printer->lastReportTime);
    const double fps     = *framesDrawn / elapsed;
    fprintf(stderr,
            "FPS: %.2f (%u frames / %.2f seconds)\n",
            fps,
            *framesDrawn,
            elapsed);

    printer->lastReportTime = thisTime;
    *framesDrawn            = 0;
  }
}

#endif // EXAMPLES_DEMO_UTILS_H
