// Build & run: c++ -std=c++17 test/round_rect_test.cpp -o /tmp/round_rect_test && /tmp/round_rect_test
#include "../src/gfx/round_rect.h"

#include <cassert>
#include <cstdio>

using namespace gfx;

static float cornerCoverage(int w, int h, float radius, int column, int row) {
  float halfWidth = w * 0.5f, halfHeight = h * 0.5f;
  return coverage(roundRectDistance(column + 0.5f - halfWidth, row + 0.5f - halfHeight,
                                    halfWidth, halfHeight, radius));
}

int main() {
  const int w = 296, h = 24;
  const float radius = 6;

  // A straight edge is pixel aligned, so it must be fully lit; a fringe there would
  // show up as a washed-out border down the sides of every button.
  assert(cornerCoverage(w, h, radius, 0, h / 2) == 1.0f);
  assert(cornerCoverage(w, h, radius, w - 1, h / 2) == 1.0f);
  assert(cornerCoverage(w, h, radius, w / 2, 0) == 1.0f);

  // Well inside is solid, well outside the corner is empty.
  assert(cornerCoverage(w, h, radius, w / 2, h / 2) == 1.0f);
  assert(cornerCoverage(w, h, radius, 0, 0) == 0.0f);

  // The corner is a real arc: partial pixels exist, and coverage grows monotonically
  // along the diagonal instead of stepping like the old integer inset did.
  bool sawPartial = false;
  float previous = -1.0f;
  for (int i = 0; i < (int)radius; i++) {
    float value = cornerCoverage(w, h, radius, i, i);
    if (value > 0.0f && value < 1.0f) sawPartial = true;
    assert(value >= previous);
    previous = value;
  }
  assert(sawPartial && "an anti-aliased corner must produce partial coverage");

  // The arc must stay within the radius: the pixel just past it is already solid.
  assert(cornerCoverage(w, h, radius, (int)radius, (int)radius) == 1.0f);

  // Symmetry across both axes, so no corner is fatter than another.
  for (int row = 0; row < (int)radius; row++) {
    for (int column = 0; column < (int)radius; column++) {
      float topLeft = cornerCoverage(w, h, radius, column, row);
      assert(topLeft == cornerCoverage(w, h, radius, w - 1 - column, row));
      assert(topLeft == cornerCoverage(w, h, radius, column, h - 1 - row));
      assert(topLeft == cornerCoverage(w, h, radius, w - 1 - column, h - 1 - row));
    }
  }

  // radius 0 keeps square corners fully lit, which is what the mono theme pins.
  assert(cornerCoverage(w, h, 0, 0, 0) == 1.0f);

  // Blending endpoints must be exact, or repeated repaints would drift the colour.
  const uint16_t black = 0x0000, white = 0xFFFF;
  assert(blend565(black, white, 0.0f) == black);
  assert(blend565(black, white, 1.0f) == white);
  uint16_t half = blend565(black, white, 0.5f);
  assert(half > black && half < white);
  assert(blend565(white, white, 0.5f) == white);

  // A gradient must reach both stops exactly, so a button's edges match its theme.
  assert(lerp565(black, white, 0, h - 1) == black);
  assert(lerp565(black, white, h - 1, h - 1) == white);
  assert(lerp565(black, white, 1, 0) == black);  // degenerate height must not divide by zero

  printf("ok\n");
  return 0;
}