/* ============================================================
 * Diablo2D — fov.js : raycast visibility & fog of war
 * ============================================================ */
'use strict';
window.D2 = window.D2 || {};
(function (D2) {

  const RAY_COUNT = 160;

  /**
   * Update world.visible / world.explored from (cx, cy) within radius.
   * world must expose: w, h, transparent(x,y), visible(Uint8), explored(Uint8)
   */
  function compute(world, cx, cy, radius) {
    const { w, h } = world;
    world.visible.fill(0);
    const r2 = radius * radius;

    const mark = (x, y) => {
      if (x < 0 || y < 0 || x >= w || y >= h) return;
      const i = y * w + x;
      world.visible[i] = 1;
      world.explored[i] = 1;
    };

    mark(cx, cy);

    for (let i = 0; i < RAY_COUNT; i++) {
      const ang = (i / RAY_COUNT) * Math.PI * 2;
      const dx = Math.cos(ang), dy = Math.sin(ang);
      let x = cx + 0.5, y = cy + 0.5;
      for (let d = 0; d < radius; d += 0.5) {
        x += dx * 0.5; y += dy * 0.5;
        const tx = x | 0, ty = y | 0;
        if (tx < 0 || ty < 0 || tx >= w || ty >= h) break;
        const ddx = x - cx - 0.5, ddy = y - cy - 0.5;
        if (ddx * ddx + ddy * ddy > r2) break;
        mark(tx, ty);
        if (!world.transparent(tx, ty)) break;
      }
    }
  }

  D2.fov = { compute };
})(window.D2);