// Scene1 effect shader - ShaderToy conversion (raymarching cube & sphere)
// Source: Saturday cubism experiment by skal

#include "common_uniforms"
#include "math/color"
#include "math/utils"
#include "math/sdf_shapes"
#include "render/raymarching"

@group(0) @binding(0) var<uniform> uniforms: CommonUniforms;

const PI: f32 = 3.141592654;
const TAU: f32 = 6.283185307;

// Colors (precomputed HSV conversions)
const skyCol = vec3<f32>(0.176, 0.235, 0.25); // HSV(0.57, 0.90, 0.25)
const skylineCol = vec3<f32>(0.5, 0.125, 0.025); // HSV(0.02, 0.95, 0.5)
const sunCol = vec3<f32>(0.5, 0.163, 0.025); // HSV(0.07, 0.95, 0.5)
const diffCol1 = vec3<f32>(0.4, 1.0, 1.0); // HSV(0.60, 0.90, 1.0)
const diffCol2 = vec3<f32>(0.325, 1.0, 0.975); // HSV(0.55, 0.90, 1.0)

// Lighting (normalized manually)
const sunDir1 = vec3<f32>(0.0, 0.04997, -0.99875); // normalize(0, 0.05, -1)
const lightPos1 = vec3<f32>(10.0, 10.0, 10.0);
const lightPos2 = vec3<f32>(-10.0, 10.0, -10.0);

fn rayPlane(ro: vec3<f32>, rd: vec3<f32>, plane: vec4<f32>) -> f32 {
  return -(dot(ro, plane.xyz) + plane.w) / dot(rd, plane.xyz);
}

var<private> g_rot0: mat2x2<f32>;

fn render0(ro: vec3<f32>, rd: vec3<f32>) -> vec3<f32> {
  var col = vec3<f32>(0.0);
  var sf = 1.0001 - max(dot(sunDir1, rd), 0.0);
  col += skyCol * pow((1.0 - abs(rd.y)), 8.0);
  col += clamp(vec3<f32>(mix(0.0025, 0.125, tanh_approx(0.005 / sf)) / abs(rd.y)) * skylineCol, vec3<f32>(0.0), vec3<f32>(10.0));
  sf *= sf;
  col += sunCol * 0.00005 / sf;

  let tp1 = rayPlane(ro, rd, vec4<f32>(0.0, -1.0, 0.0, 6.0));
  if (tp1 > 0.0) {
    let pos = ro + tp1 * rd;
    let pp = pos.xz;
    let db = sdBox2D(pp, vec2<f32>(5.0, 9.0)) - 3.0;
    col += vec3<f32>(4.0) * skyCol * rd.y * rd.y * smoothstep(0.25, 0.0, db);
    col += vec3<f32>(0.8) * skyCol * exp(-0.5 * max(db, 0.0));
  }

  return clamp(col, vec3<f32>(0.0), vec3<f32>(10.0));
}

fn df(p_in: vec3<f32>) -> f32 {
  var p = p_in;
  p.x = p_in.x * g_rot0[0][0] + p_in.z * g_rot0[0][1];
  p.z = p_in.x * g_rot0[1][0] + p_in.z * g_rot0[1][1];

  // Cube
  var pc = p;
  pc -= vec3<f32>(-1.9, 0.0, 0.0);
  let dCube = sdBox(pc, vec3<f32>(1.6));

  // Sphere
  var ps = p;
  ps -= vec3<f32>(1.3, 0.0, 0.0);
  let dSphere = sdSphere(ps, 1.2);

  // Ground plane
  let dPlane = p.y + 1.0;

  // Union
  var d = min(dCube, dSphere);
  d = min(d, dPlane);

  return d;
}

fn boxCol(col: vec3<f32>, nsp: vec3<f32>, rd: vec3<f32>, nnor: vec3<f32>, nrcol: vec3<f32>, nshd1: f32, nshd2: f32) -> vec3<f32> {
  var nfre = 1.0 + dot(rd, nnor);
  nfre *= nfre;

  let nld1 = normalize(lightPos1 - nsp);
  let nld2 = normalize(lightPos2 - nsp);

  var ndif1 = max(dot(nld1, nnor), 0.0);
  ndif1 *= ndif1;

  var ndif2 = max(dot(nld2, nnor), 0.0);
  ndif2 *= ndif2;

  var scol = vec3<f32>(0.0);
  let rf = smoothstep(1.0, 0.9, nfre);
  scol += diffCol1 * ndif1 * nshd1;
  scol += diffCol2 * ndif2 * nshd2;
  scol += 0.1 * (skyCol + skylineCol);
  scol += nrcol * 0.75 * mix(vec3<f32>(0.25), vec3<f32>(0.5, 0.5, 1.0), nfre);

  return mix(col, scol, rf * smoothstep(90.0, 20.0, dot(nsp, nsp)));
}

fn render1(ro: vec3<f32>, rd: vec3<f32>) -> vec3<f32> {
  let skyCol_local = render0(ro, rd);
  var col = skyCol_local;

  let nt = rayMarch(ro, rd, 0.0);
  if (nt < MAX_RAY_LENGTH) {
    let nsp = ro + rd * nt;
    let nnor = normal(nsp);

    let nref = reflect(rd, nnor);
    let nrt = rayMarch(nsp, nref, 0.2);
    var nrcol = render0(nsp, nref);

    if (nrt < MAX_RAY_LENGTH) {
      let nrsp = nsp + nref * nrt;
      let nrnor = normal(nrsp);
      let nrref = reflect(nref, nrnor);
      nrcol = boxCol(nrcol, nrsp, nref, nrnor, render0(nrsp, nrref), 1.0, 1.0);
    }

    let nshd1 = mix(0.0, 1.0, shadow(nsp, normalize(lightPos1 - nsp), 0.1, distance(lightPos1, nsp)));
    let nshd2 = mix(0.0, 1.0, shadow(nsp, normalize(lightPos2 - nsp), 0.1, distance(lightPos2, nsp)));

    col = boxCol(col, nsp, rd, nnor, nrcol, nshd1, nshd2);
  }

  return col;
}

fn effect(p: vec2<f32>) -> vec3<f32> {
  g_rot0 = rot(-0.2 * uniforms.time);

  let fov = tan(TAU / 6.0);
  let ro = vec3<f32>(0.0, 2.5, 5.0);
  let la = vec3<f32>(0.0, 0.0, 0.0);
  let up = vec3<f32>(0.1, 1.0, 0.0);

  let ww = normalize(la - ro);
  let uu = normalize(cross(up, ww));
  let vv = cross(ww, uu);
  let rd = normalize(-p.x * uu + p.y * vv + fov * ww);

  return render1(ro, rd);
}

#include "render/fullscreen_vs"

@fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
  // Flip Y to match ShaderToy convention (origin at bottom-left)
  let flipped = vec2<f32>(p.x, uniforms.resolution.y - p.y);
  let q = flipped / uniforms.resolution;
  var coord = -1.0 + 2.0 * q;
  coord.x *= uniforms.resolution.x / uniforms.resolution.y;
  var col = effect(coord);
  col = aces_approx(col);
  col = sRGB(col);
  return vec4<f32>(col, 1.0);
}