// Terrain that stands in the room rather than lying on its floor: bushes
// filling a square to half height, the killer ooze as a translucent cube
// of jello, dust billowing, dimensional warps throwing light. Each is a
// paintable sprite at public/terrain3d/<name>.png (transparent PNG, any
// size); the bakes below stand in until painted.

export const TERRAIN3D = ["thornbush", "rosebush", "jello", "dust", "warpglow", "safe"] as const;

const baked = new Map<string, HTMLCanvasElement>();
export function terrainFallback(name: string): HTMLCanvasElement {
  let t = baked.get(name);
  if (t) return t;
  t = document.createElement("canvas");
  t.width = 128;
  t.height = 64;
  const c = t.getContext("2d")!;
  const h2 = (a: number, b: number) => {
    const n = Math.sin(a * 127.1 + b * 311.7) * 43758.5453;
    return n - Math.floor(n);
  };
  if (name === "thornbush" || name === "rosebush") {
    // A hedge of tangles wall to wall; roses get their blooms.
    for (let i = 0; i < 40; i++) {
      const x = h2(i, 1) * 128, y = 16 + h2(i, 3) * 46, r = 6 + h2(i, 5) * 9;
      const g = 60 + (h2(i, 7) * 50 | 0);
      c.fillStyle = `rgba(${g * 0.35 | 0},${g},${g * 0.3 | 0},0.9)`;
      c.beginPath();
      c.arc(x, y, r, 0, Math.PI * 2);
      c.fill();
    }
    c.strokeStyle = "rgba(30,40,18,0.7)";
    for (let i = 0; i < 14; i++) {
      c.beginPath();
      c.moveTo(h2(i, 11) * 128, 18 + h2(i, 13) * 40);
      c.lineTo(h2(i, 11) * 128 + 10 - h2(i, 17) * 20, 8 + h2(i, 19) * 40);
      c.stroke();
    }
    if (name === "rosebush") {
      for (let i = 0; i < 9; i++) {
        c.fillStyle = "rgba(210,40,70,0.95)";
        c.beginPath();
        c.arc(6 + h2(i, 23) * 116, 14 + h2(i, 29) * 40, 3.5, 0, Math.PI * 2);
        c.fill();
      }
    }
  } else if (name === "jello") {
    // The gelatinous whole of the killer ooze, drawn as one cube face
    // with a paler top edge — the renderer's alpha keeps it see-through.
    t.height = 128;
    const g2 = t.getContext("2d")!;
    g2.fillStyle = "rgba(90,190,70,0.85)";
    g2.fillRect(4, 12, 120, 112);
    g2.fillStyle = "rgba(170,240,140,0.9)";
    g2.fillRect(4, 12, 120, 10);
    g2.fillStyle = "rgba(230,255,210,0.5)";
    g2.fillRect(16, 30, 22, 12);
    for (let i = 0; i < 8; i++) {
      g2.fillStyle = "rgba(40,120,30,0.5)";
      g2.beginPath();
      g2.arc(16 + h2(i, 31) * 96, 40 + h2(i, 37) * 72, 3 + h2(i, 41) * 3, 0, Math.PI * 2);
      g2.fill();
    }
  } else if (name === "dust") {
    t.height = 128;
    const g2 = t.getContext("2d")!;
    for (let i = 0; i < 26; i++) {
      const a = 0.12 + h2(i, 43) * 0.16;
      g2.fillStyle = `rgba(200,190,170,${a})`;
      g2.beginPath();
      g2.arc(14 + h2(i, 47) * 100, 14 + h2(i, 53) * 100, 12 + h2(i, 59) * 16, 0, Math.PI * 2);
      g2.fill();
    }
  } else if (name === "safe") {
    // A squat iron strongbox with its combination dial.
    t.width = 128;
    t.height = 128;
    const g2 = t.getContext("2d")!;
    g2.fillStyle = "#3c3f46";
    g2.fillRect(14, 34, 100, 90);
    g2.fillStyle = "#54585f";
    g2.fillRect(20, 40, 88, 78);
    g2.strokeStyle = "#23252a";
    g2.lineWidth = 4;
    g2.strokeRect(16, 36, 96, 86);
    g2.fillStyle = "#8b8f96";
    g2.beginPath();
    g2.arc(64, 78, 16, 0, Math.PI * 2);
    g2.fill();
    g2.fillStyle = "#2a2c31";
    g2.beginPath();
    g2.arc(64, 78, 10, 0, Math.PI * 2);
    g2.fill();
    g2.fillStyle = "#8b8f96";
    g2.fillRect(96, 66, 8, 24);
  } else {
    // warpglow: a pillar of violet light, brightest at its core.
    t.width = 64;
    t.height = 128;
    const g2 = t.getContext("2d")!;
    const grad = g2.createLinearGradient(0, 0, 64, 0);
    grad.addColorStop(0, "rgba(140,80,220,0)");
    grad.addColorStop(0.5, "rgba(200,160,255,0.75)");
    grad.addColorStop(1, "rgba(140,80,220,0)");
    g2.fillStyle = grad;
    g2.fillRect(0, 0, 64, 128);
  }
  baked.set(name, t);
  return t;
}