import { ColorAdjustments } from '../types';

// Tone-domain adjustments (Fuji-style Dynamic Range + Highlight/Shadow).
// SkSL runtime effect over a child image shader, driven by luma so hue is
// preserved (single multiplicative factor per pixel).
//
// Soft-knee masks keep the knobs independent, like camera tone curves:
//   hl affects ONLY the bright end (knee 0.80..1.00),
//   sh affects ONLY the dark end   (knee 0.00..0.30),
// leaving the whole 0.30..0.80 mid/upper band untouched. Earlier knees
// (0.40..0.95 / 0.05..0.55, then 0.55..1.0 / 0.0..0.45, then 0.70..1.0) still
// reached mid/upper grays, so HL read as a global gray/brightness change
// instead of isolating the bright end — on-device testing confirmed it.
//
// HL is multiplicative on BOTH signs so +/− act on the same region:
// + scales 0.85+ up toward white (natural clip at 1.0), − scales them down.
// A + additive lift using (1-t) dies at t→1.0 and never touched the specular
// end — that asymmetry made +HL look like a mid-tone push, not a highlight
// change. (SH keeps its original form; additive + worked there.)
//
// dr  - DR strength 0..1: lifts shadows slightly and rolls highlights
//       (Fuji extended DR); 0/auto/DR100 = no extra curve.
// hl  - highlight -1..1: + lifts toward white, - rolls the bright side down.
// sh  - shadow    -1..1: + lifts the dark side, - deepens it.
// vib - vibrance -1..1: chroma-masked saturation. It rides along in this shader
//       (rather than the colour matrix) because it needs per-pixel chroma:
//       already-vivid pixels move least, so skins/skies deepen without the neon
//       clip a plain Saturation boost causes. All-zero still = no pass.
export const TONE_SKSL = `
uniform shader src;
uniform float dr;
uniform float hl;
uniform float sh;
uniform float vib;
vec4 main(vec2 xy) {
  vec4 c = src.eval(xy);
  float t = clamp(dot(c.rgb, vec3(0.2126, 0.7152, 0.0722)), 0.0, 1.0);
  float hlMask = smoothstep(0.80, 1.0, t);
  float shMask = 1.0 - smoothstep(0.0, 0.30, t);
  // NOTE: never name a local 'out' — it is a reserved SkSL qualifier.
  float o = t;
  // Highlight: bright end only, multiplicative on both signs (symmetric region).
  if (hl >= 0.0) {
    o *= 1.0 + hl * 0.30 * hlMask;
  } else {
    o *= 1.0 + hl * 0.45 * hlMask;
  }
  // Shadow: dark end only.
  if (sh >= 0.0) {
    o += sh * 0.80 * shMask * (1.0 - t);
  } else {
    o *= 1.0 + sh * 0.80 * shMask;
  }
  // Dynamic range: gentle shadow lift + highlight roll (protect brights).
  o += dr * 0.12 * shMask * (1.0 - t);
  o -= dr * 0.18 * hlMask * t;
  float f = clamp(o / max(t, 0.0004), 0.0, 4.0);
  vec3 rgb = clamp(c.rgb * f, 0.0, 1.0);
  // Vibrance: push the LESS-saturated pixels harder than the vivid ones.
  float l2 = dot(rgb, vec3(0.2126, 0.7152, 0.0722));
  float mx = max(max(rgb.r, rgb.g), rgb.b);
  float mn = min(min(rgb.r, rgb.g), rgb.b);
  float chroma = mx > 0.0001 ? (mx - mn) / mx : 0.0;
  float kv = 1.0 + vib * 0.75 * (1.0 - chroma);
  return vec4(clamp(mix(vec3(l2), rgb, kv), 0.0, 1.0), c.a);
}
`;

export interface ToneUniforms {
  // All zero → no tone adjustment needed (caller can skip the shader pass).
  dr: number; // 0..1
  hl: number; // -1..1 (adjustments.highlight / 10)
  sh: number; // -1..1 (adjustments.shadow / 10)
  vib: number; // -1..1 (adjustments.vibrance / 10)
}

export function getToneUniforms(adj: ColorAdjustments): ToneUniforms {
  const drRaw = adj.dynamicRange ?? 'auto';
  const dr = drRaw === 'auto' || drRaw === 100 ? 0 : (drRaw - 100) / 300;
  const hl = Math.max(-1, Math.min(1, (adj.highlight ?? 0) / 10));
  const sh = Math.max(-1, Math.min(1, (adj.shadow ?? 0) / 10));
  const vib = Math.max(-1, Math.min(1, (adj.vibrance ?? 0) / 10));
  return { dr, hl, sh, vib };
}

export function toneIsActive(u: ToneUniforms): boolean {
  return u.dr !== 0 || u.hl !== 0 || u.sh !== 0 || u.vib !== 0;
}