toastsim/src/sim/roasting.ts

import { Field } from '../core/field';
import { Rng, valueNoise2D } from '../core/rng';
import { type HeatSource, setKnob, heatStep, applyToHeatMap } from './heatsource';

/**
 * Roasting tomatoes — the oven is the toaster, generalized.
 *
 * It is the same browning Field the toast has always used, pointed at tomato
 * halves on a tray instead of a slice in a slot. The math is toastStep's twin:
 * moisture has to boil off before the surface can colour, and tomatoes are
 * basically water balloons, so they stall a long time and then go fast — the
 * "leave them in, nothing's happening, leave them in, they're gone" of a real
 * oven.
 *
 * Two things are the tomato's and not the toast's:
 *   blister  — past 0.6 the skin blisters and speckles (a different colour ramp
 *              and a speckle mask in the scene; here it's just a fraction the
 *              judge rewards — blistered is the target, not black).
 *   collapse — past ~0.9 the half slumps into sauce. The moisture it was holding
 *              becomes mess the moment you handle it, and it soaks the toast
 *              faster (the assembly reads collapseFrac into the sog clock).
 *
 * Pure — Field + Rng, no three.js — so the harness roasts headless and reads the
 * exact same numbers the judge will.
 */

/** Blistered skin begins here — the target window's floor. */
export const BLISTER_AT = 0.6;
/** Past this the half has collapsed into sauce. */
export const COLLAPSE_AT = 0.9;

/** Roasts a touch slower than toast browns: the oven is gentler than the coils,
 *  and the wet flesh drinks the first stretch of heat. Measured headless at power
 *  6: the halves stall wet until ~26s (mean ~0.56, barely blistered), the blister
 *  window opens ~28–36s (mean ~0.61→0.79, fully blistered, none slumped), and past
 *  ~40s they collapse to sauce — "nothing's happening, nothing's happening, gone". */
const RATE = 0.042;

export interface RoastSession {
  /** 0 raw .. 1 blackened. Blister past 0.6, collapse past 0.9. */
  roast: Field;
  /** Moisture that must cook off first — tomatoes carry a lot of it. */
  dry: Field;
  /** 1 where a tomato half sits on the tray; every stat is masked by this. */
  mask: Field;
  /** Where the oven puts its heat — hotter in the middle, like a real element. */
  heat: Float32Array;
  seconds: number;
  power: number;
  /** Optional fuel character (gas oven vs electric fan). When absent, the oven
   *  behaves EXACTLY as it always has — the knob maps straight to power. */
  src?: HeatSource;
}

export interface RoastResult {
  /** Mean roast over the tomatoes. */
  mean: number;
  /** Evenness — a rack that roasted unevenly reads here. */
  stdev: number;
  /** Fraction blistered (past 0.6) — the good bit. */
  blisterFrac: number;
  /** Fraction collapsed into sauce (past 0.9) — the overdone bit. */
  collapseFrac: number;
}

const N = 96;

/**
 * A tray of `halves` tomato halves. They sit in a row; the mask is a set of
 * discs so the stats are over the tomatoes, not the empty tray between them.
 */
export function newRoastSession(halves = 4, seed = 20260718, power = 6, src?: HeatSource): RoastSession {
  const roast = new Field(N);
  const dry = new Field(N);
  const mask = new Field(N);
  const rng = new Rng(seed);

  // Lay the halves out across the tray as discs.
  const r = 0.5 / halves; // disc radius in UV, so they tile the width
  for (let h = 0; h < halves; h++) {
    const cu = (h + 0.5) / halves;
    const cv = 0.5;
    stampDisc(mask, cu, cv, r * 0.82);
  }

  // The oven's heat: hotter toward the centre/back, gently blotched, so an even
  // roast is a real (if mild) skill — the tuning keeps it forgiving.
  const bias = valueNoise2D(rng, N, N, 3);
  const heat = new Float32Array(N * N);
  for (let y = 0; y < N; y++) {
    for (let x = 0; x < N; x++) {
      const u = x / (N - 1);
      const v = y / (N - 1);
      // Radial: the middle of the tray runs hotter than the corners.
      const dc = Math.hypot(u - 0.5, v - 0.5);
      const centre = 1 - 0.18 * Math.min(1, dc / 0.6);
      const blot = 0.9 + 0.2 * bias[y * N + x];
      heat[y * N + x] = centre * blot;
    }
  }
  // A fuel character reshapes the heat map (gas oven top-hot & blotchy vs fan
  // even) — normalized over the mask so equal cook time gives equal MEAN, and
  // the fuel shows up as evenness (stdev), not as a head start. Omit src and the
  // heat map above is untouched: the oven is byte-for-byte its old self.
  if (src) applyToHeatMap(heat, N, src, new Rng(seed ^ 0x5f), mask);
  return { roast, dry, mask, heat, seconds: 0, power, src };
}

function stampDisc(mask: Field, cu: number, cv: number, r: number): void {
  const n = mask.n;
  for (let y = 0; y < n; y++) {
    for (let x = 0; x < n; x++) {
      const u = x / (n - 1);
      const v = y / (n - 1);
      if (Math.hypot(u - cu, v - cv) <= r) mask.data[y * n + x] = 1;
    }
  }
}

/**
 * Advance the roast one tick. The twin of toastStep: dryness climbs first, and
 * only a dried surface colours at full rate. `power` 1..10 is the oven dial.
 */
export function roastStep(s: RoastSession, dt: number): void {
  // The knob commands a target; the fuel decides how fast the heat obeys. With
  // no source this is `s.power` unchanged — the whole retrofit is invisible.
  let effective = s.power;
  if (s.src) {
    setKnob(s.src, s.power);
    heatStep(s.src, dt);
    effective = s.src.output;
  }
  const p = Math.max(0, Math.min(10, effective)) / 10;
  const r = s.roast.data;
  const d = s.dry.data;
  const m = s.mask.data;
  // Tomatoes hold a lot of water — a high cap means a long stall then a rush.
  const moistureCap = 2.4;
  for (let i = 0; i < r.length; i++) {
    if (m[i] < 0.5) continue;
    const h = s.heat[i] * p;
    if (h <= 0) continue;
    d[i] = Math.min(1, d[i] + (h * dt) / moistureCap);
    const rate = RATE * h * (0.2 + 0.8 * d[i]);
    r[i] = Math.min(1.1, r[i] + rate * dt);
  }
  s.seconds += dt;
}

export function roastResult(s: RoastSession): RoastResult {
  const st = s.roast.stats(s.mask);
  return {
    mean: st.mean,
    stdev: st.stdev,
    blisterFrac: s.roast.fraction(s.mask, (v) => v >= BLISTER_AT && v < COLLAPSE_AT),
    collapseFrac: s.roast.fraction(s.mask, (v) => v >= COLLAPSE_AT),
  };
}

/** The live-readout word for the oven, in the judge's own thresholds. */
export function roastWord(r: RoastResult): string {
  if (r.collapseFrac > 0.4) return 'collapsing to sauce';
  if (r.mean < 0.28) return 'still raw';
  if (r.mean < BLISTER_AT) return 'softening';
  if (r.blisterFrac > 0.25) return 'blistered';
  return 'coming along';
}